draft-ietf-nsis-rsvp-sec-properties-02.txt   draft-ietf-nsis-rsvp-sec-properties-03.txt 
NSIS NSIS
Internet Draft Hannes Tschofenig Internet Draft Hannes Tschofenig
Document: Siemens Siemens
draft-ietf-nsis-rsvp-sec-properties-02.txt Richard Graveman
Expires: December 2003 June 2003 RFG Security
Document:
draft-ietf-nsis-rsvp-sec-properties-03.txt
Expires: April 2002 October 2003
RSVP Security Properties RSVP Security Properties
<draft-ietf-nsis-rsvp-sec-properties-02.txt> <draft-ietf-nsis-rsvp-sec-properties-03.txt>
Status of this Memo Status of this Memo
This document is an Internet-Draft and is in full conformance This document is an Internet-Draft and is in full conformance
with all provisions of Section 10 of RFC2026. with all provisions of Section 10 of RFC2026.
Internet-Drafts are working documents of the Internet Engineering Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF), its areas, and its working groups. Note that Task Force (IETF), its areas, and its working groups. Note that
other groups may also distribute working documents as Internet- other groups may also distribute working documents as Internet-
Drafts. Drafts.
skipping to change at page 1, line 35 skipping to change at page 1, line 38
material or to cite them other than as "work in progress". material or to cite them other than as "work in progress".
The list of current Internet-Drafts can be accessed at The list of current Internet-Drafts can be accessed at
http://www.ietf.org/ietf/1id-abstracts.txt http://www.ietf.org/ietf/1id-abstracts.txt
The list of Internet-Draft Shadow Directories can be accessed at The list of Internet-Draft Shadow Directories can be accessed at
http://www.ietf.org/shadow.html. http://www.ietf.org/shadow.html.
Abstract Abstract
This document summarizes the security properties of RSVP. The goal of This document summarizes the security properties of RSVP. The goal of
this analysis is to benefit from previous work done with RSVP and to this analysis is to benefit from previous work done on RSVP and to
capture the knowledge about past activities. capture knowledge about past activities.
Table of Contents Table of Contents
1. Introduction...................................................2 1. Introduction...................................................2
2. Terminology and Architectural Assumptions......................3 2. Terminology and Architectural Assumptions......................3
3. Overview.......................................................5 3. Overview.......................................................5
3.1 The RSVP INTEGRITY Object..................................5 3.1 The RSVP INTEGRITY Object..................................5
3.2 Security Associations......................................6 3.2 Security Associations......................................7
3.3 RSVP Key Management Assumptions............................7 3.3 RSVP Key Management Assumptions............................8
3.4 Identity Representation....................................7 3.4 Identity Representation....................................8
3.5 RSVP Integrity Handshake..................................12 3.5 RSVP Integrity Handshake..................................12
4. Detailed Security Property Discussion.........................13 4. Detailed Security Property Discussion.........................13
4.1 Discussed Network Topology................................13 4.1 Network Topology..........................................13
4.2 Host/Router...............................................13 4.2 Host/Router...............................................14
4.3 User to PEP/PDP...........................................17 4.3 User to PEP/PDP...........................................18
4.4 Communication between RSVP aware routers..................25 4.4 Communication between RSVP-Aware Routers..................26
5. Miscellaneous Issues..........................................26 5. Miscellaneous Issues..........................................27
5.1 First Hop Issue...........................................26 5.1 First Hop Issue...........................................28
5.2 Next-Hop Problem..........................................27 5.2 Next-Hop Problem..........................................28
5.3 Last-Hop Issue............................................29 5.3 Last-Hop Issue............................................31
5.4 RSVP and IPsec protected data traffic.....................30 5.4 RSVP and IPsec protected data traffic.....................32
5.5 End-to-End Security Issues and RSVP.......................32 5.5 End-to-End Security Issues and RSVP.......................34
5.6 IPsec protection of RSVP signaling messages...............32 5.6 IPsec protection of RSVP signaling messages...............34
5.7 Authorization.............................................33 5.7 Authorization.............................................35
6. Conclusions...................................................34 6. Conclusions...................................................36
7. Security Considerations.......................................35 7. Security Considerations.......................................37
8. IANA considerations...........................................35 8. IANA considerations...........................................37
9. Acknowledgments...............................................35 9. Acknowledgments...............................................37
10. Normative References.........................................38 10. Normative References.........................................40
11. Informative References.......................................39 11. Informative References.......................................41
Author's Contact Information.....................................42 Author's Contact Information.....................................44
Full Copyright Statement.........................................42 Full Copyright Statement.........................................44
Acknowledgement..................................................45
1. Introduction 1. Introduction
As the work of the NSIS working group has begun there are also As the work of the NSIS working group has begun, there are also
concerns about security and its implication for the design of a concerns about security and its implications for the design of a
signaling protocol. In order to understand the security properties signaling protocol. In order to understand the security properties
and available options of RSVP a number of documents have to be read. and available options of RSVP a number of documents have to be read.
This document summarize the security properties of RSVP and is part This document summarizes the security properties of RSVP and is part
of the overall process of analyzing other signaling protocols and to of the overall process of analyzing other signaling protocols and
learn from their design considerations. This document should also learning from their design considerations. This document should also
provide a starting point for further discussions. provide a starting point for further discussions.
The content of this document is organized as follows: The content of this document is organized as follows:
Section 3 provides an overview of the security mechanisms provided by Section 3 provides an overview of the security mechanisms provided by
RSVP including the INTEGRITY object, a description of the identity RSVP including the INTEGRITY object, a description of the identity
representation within the POLICY_DATA object (i.e. user representation within the POLICY_DATA object (i.e., user
authentication) and the RSVP Integrity Handshake mechanism. authentication), and the RSVP Integrity Handshake mechanism.
RSVP Security Properties June 2003
Section 4 provides a more detailed discussion of the used mechanism Section 4 provides a more detailed discussion of the mechanisms used
and tries to describe the mechanisms provided in detail. and tries to describe in detail the mechanisms provided.
Finally a number of miscellaneous issues are described which address Finally a number of miscellaneous issues are described, which address
first-hop, next-hop and last-hop issues. Furthermore the problem of first-hop, next-hop, and last-hop issues. Furthermore the problem of
IPsec security protection of data traffic and RSVP signaling message IPsec security protection of data traffic and RSVP signaling messages
is discussed. is discussed.
2. Terminology and Architectural Assumptions 2. Terminology and Architectural Assumptions
This section describes some important terms and explains some This section describes some important terms and explains some
architectural assumptions: architectural assumptions:
- Chain-of-Trust - Chain-of-Trust
The security mechanisms supported by RSVP [RFC2747] heavily relies on The security mechanisms supported by RSVP [RFC2747] heavily rely on
optional hop-by-hop protection using the built-in INTEGRITY object. optional hop-by-hop protection using the built-in INTEGRITY object.
Hop-by-hop security with the INTEGRITY object inside the RSVP message Hop-by-hop security with the INTEGRITY object inside the RSVP message
thereby refers to the protection between RSVP supporting network thereby refers to the protection between RSVP-supporting network
elements. Additionally there is the notion of policy aware network elements. Additionally, there is the notion of policy-aware network
elements that additionally understand the POLICY_DATA element within elements that understand the POLICY_DATA element within the RSVP
the RSVP message. Since this element also includes an INTEGRITY message. Because this element also includes an INTEGRITY object,
object there is an additional hop-by-hop security mechanism that there is an additional hop-by-hop security mechanism that provides
provides security between policy aware nodes. Policy ignorant nodes security between policy-aware nodes. Policy-ignorant nodes are not
are not affected by the inclusion of this object in the POLICY_DATA affected by the inclusion of this object in the POLICY_DATA element,
element since they do not try to interpret it. because they do not try to interpret it.
To protect signaling messages that are possibly modified by each RSVP To protect signaling messages that are possibly modified by each RSVP
router along the path it must be assumed that each incoming request router along the path, it must be assumed that each incoming request
is authenticated, integrity and replay protected. This provides is authenticated, integrity protected, and replay protected. This
protection against unauthorized nodes injecting bogus messages. provides protection against unauthorized nodes' injecting bogus
Furthermore each RSVP-router is assumed to behave in the expected messages. Furthermore, each RSVP-router is assumed to behave in the
manner. Outgoing messages transmitted to the next hop network element expected manner. Outgoing messages transmitted to the next hop
experience protection according RSVP security processing. network element receive protection according RSVP security
processing.
Using the above described mechanisms a chain-of-trust is created Using the above described mechanisms, a chain-of-trust is created
whereby a signaling message transmitted by router A via router B and whereby a signaling message transmitted by router A via router B and
received by router C is supposed to be secure if router A and B and received by router C is supposed to be secure if routers A and B and
router B and C share a security association and all routers behave routers B and C share security associations and all routers behave as
expectedly. Hence router C trusts router A although router C does not expected. Hence router C trusts router A although router C does not
have a direct security association with router A. We can therefore have a direct security association with router A. We can therefore
conclude that the protection achieved with this hop-by-hop security conclude that the protection achieved with this hop-by-hop security
for the chain-of-trust is as good as the weakest link in the chain. for the chain-of-trust is no better than the weakest link in the
chain.
If one router is malicious (for example because an adversary has If one router is malicious (for example because an adversary has
control over this router) then it can arbitrarily modify messages and control over this router), then it can arbitrarily modify messages,
cause unexpected behavior and mount a number of attacks not only cause unexpected behavior, and mount a number of attacks not limited
restricted to QoS signaling. Additionally it must be mentioned that only to QoS signaling. Additionally, it must be mentioned that some
protocols demand more protection than others (which depends in part
RSVP Security Properties June 2003 on which nodes are executing these protocols). For example, edge
some protocols demand more protection than others (this depends
between which nodes these protocols are executed). For example edge
devices, where end-users are attached, may more likely be attacked in devices, where end-users are attached, may more likely be attacked in
comparison to the more secure core network of a service provider. In comparison with the more secure core network of a service provider.
some cases a network service provider may choose not to use the RSVP In some cases a network service provider may choose not to use the
provided security mechanisms inside the core network because a RSVP-provided security mechanisms inside the core network because a
different security protection is deployed. different security protection is deployed.
Section 6 of [RFC2750] mentions the term chain-of-trust in the Section 6 of [RFC2750] mentions the term chain-of-trust in the
context of RSVP integrity protection. In Section 6 of [HH01] the same context of RSVP integrity protection. In Section 6 of [HH01] the same
term is used in the context of user authentication with the INTEGRITY term is used in the context of user authentication with the INTEGRITY
object inside the POLICY_DATA element. Unfortunately the term is not object inside the POLICY_DATA element. Unfortunately the term is not
explained in detail and the assumption is not clearly specified. explained in detail and the assumptions behind it are not clearly
specified.
- Host and User Authentication - Host and User Authentication
The presence of the RSVP protection and a separate user identity The presence of RSVP protection and a separate user identity
representation leads to the fact that both user- and the host- representation leads to the fact that both user-identity and host-
identities are used for RSVP protection. Therefore user and host identity are used for RSVP protection. Therefore, user-based security
based security is investigated separately because of the different and host-based security are covered separately, because of the
authentication mechanisms provided. To avoid confusion about the different authentication mechanisms provided. To avoid confusion
different concepts Section 3.4 will describe the concept of user about the different concepts, Section 3.4 describes the concept of
authentication in more detail. user authentication in more detail.
- Key Management - Key Management
For most of the security associations required for the protection of It is assumed that most of the security associations required for the
RSVP signaling messages it is assumed that they are already available protection of RSVP signaling messages are already available, and
and hence key management was done in advance. There is however an hence key management was done in advance. There is, however, an
exception with the support for Kerberos. Using Kerberos an entity is exception with respect to support for Kerberos. Using Kerberos, an
able to distribute a session key used for RSVP signaling protection. entity is able to distribute a session key used for RSVP signaling
protection.
- RSVP INTEGRITY and POLICY_DATA INTEGRITY Object
RSVP uses the INTEGRITY object in two places of the message. The
first usage is in the RSVP message itself and covers the entire RSVP
message as defined in [RFC2747] whereas the latter is included in the
POLICY_DATA object and defined in [RFC2750]. In order to
differentiate the two objects regarding their scope of protection the
two terms RSVP INTEGRITY and POLICY_DATA INTEGRITY object are used.
The data structure of the two objects however is the same.
- Hop vs. Peer
In the past there was considerable discussion about the terminology - RSVP INTEGRITY and POLICY_DATA INTEGRITY Objects
of a nodes that are addressed by RSVP. In particular two favorites
have used: hop and peer. This document uses the term hop which is
different to an IP hop. Two neighboring RSVP nodes communicating with
RSVP Security Properties June 2003 RSVP uses an INTEGRITY object in two places in a message. The first
is in the RSVP message itself and covers the entire RSVP message as
defined in [RFC2747]. The second is included in the POLICY_DATA
object and defined in [RFC2750]. To differentiate the two objects
regarding their scope of protection, the two terms RSVP INTEGRITY and
POLICY_DATA INTEGRITY object are used, respectively. The data
structure of the two objects, however, is the same.
each other are not necessarily neighboring IP nodes (i.e. one IP hop - Hop versus Peer
away). In the past, the terminology for nodes addressed by RSVP has been
discussed considerably. In particular, two favorite terms have been
used: hop and peer. This document uses the term hop, which is
different from an IP hop. Two neighboring RSVP nodes communicating
with each other are not necessarily neighboring IP nodes (i.e., they
may be more than one IP hop away).
3. Overview 3. Overview
This section describes the security mechanisms provided by RSVP. This section describes the security mechanisms provided by RSVP.
Although the usage of IPsec is mentioned in Section 10 of [RFC2747] Although use of IPsec is mentioned in Section 10 of [RFC2747], the
the security mechanisms primarily envisioned for RSVP are described. security mechanisms primarily envisioned for RSVP are described.
3.1 The RSVP INTEGRITY Object 3.1 The RSVP INTEGRITY Object
The RSVP INTEGRITY object is the major component of the RSVP security The RSVP INTEGRITY object is the major component of RSVP security
protection. This object is used to provide integrity and replay protection. This object is used to provide integrity and replay
protect the content of the signaling message between two RSVP protection for the content of the signaling message between two RSVP
participating router. Furthermore the RSVP INTEGRITY object provides participating routers. Furthermore, the RSVP INTEGRITY object
data origin authentication. The attributes of the object are briefly provides data origin authentication. The attributes of the object are
described: briefly described:
- Flags field - Flags field
The Handshake Flag is the only defined flag and is used to The Handshake Flag is the only defined flag. It is used to
synchronize sequence numbers if the communication gets out-of-sync synchronize sequence numbers if the communication gets out of sync
(i.e. for a restarting host to recover the most recent sequence (e.g., it allows a restarting host to recover the most recent
number). Setting this flag to one indicates that the sender is sequence number). Setting this flag to one indicates that the sender
willing to respond to an Integrity Challenge message. This flag can is willing to respond to an Integrity Challenge message. This flag
therefore be seen as a capability negotiation transmitted within each can therefore be seen as a negotiation capability transmitted within
INTEGRITY object. each INTEGRITY object.
- Key Identifier - Key Identifier
The Key Identifier selects the key used for verification of the Keyed The Key Identifier selects the key used for verification of the Keyed
Message Digest field and hence must be unique for the sender. Its Message Digest field and, hence, must be unique for the sender. It
length is fixed with 48-bit. The generation of this Key Identifier has a fixed 48-bit length. The generation of this Key Identifier
field is mostly a decision of the local host. [RFC2747] describes field is mostly a decision of the local host. [RFC2747] describes
this field as a combination of an address, the sending interface and this field as a combination of an address, sending interface, and key
a key number. We assume that the Key Identifier is simply a (keyed) number. We assume that the Key Identifier is simply a (keyed) hash
hash value computed over a number of fields with the requirement to value computed over a number of fields with the requirement to be
be unique if more than one security association is used in parallel unique if more than one security association is used in parallel
between two hosts (i.e. as it is the case with security association between two hosts (e.g., as is the case with security associations
that have overlapping lifetimes). A receiving system uniquely having overlapping lifetimes). A receiving system uniquely identifies
identifies a security association based on the Key Identifier and the a security association based on the Key Identifier and the sender's
sender's IP address. The sender's IP address may be obtained from the IP address. The sender's IP address may be obtained from the RSVP_HOP
RSVP_HOP object or from the source IP address of the packet if the object or from the source IP address of the packet if the RSVP_HOP
RSVP_HOP object is not present. The sender uses the outgoing object is not present. The sender uses the outgoing interface to
interface to determine which security association to use. The term determine which security association to use. The term outgoing
outgoing interface might be confusing. The sender selects the interface may be confusing. The sender selects the security
security association based on the receiver's IP address (of the next association based on the receiver's IP address (i.e., the address of
RSVP capable router). To determine which node is the next capable the next RSVP-capable router). The process of determining which node
is the next RSVP-capable router is not further specified and is
RSVP Security Properties June 2003 likely to be statically configured.
RSVP router is not further specified and is likely to be statically
configured.
- Sequence Number - Sequence Number
The sequence number used by the INTEGRITY object is 64-bits in length The sequence number used by the INTEGRITY object is 64 bits in
and the starting value can be selected arbitrarily. The length of the length, and the starting value can be selected arbitrarily. The
sequence number field was chosen to avoid exhaustion during the length of the sequence number field was chosen to avoid exhaustion
lifetime of a security association as stated in Section 3 of during the lifetime of a security association as stated in Section 3
[RFC2747]. In order for the receiver to distinguish between a new and of [RFC2747]. In order for the receiver to distinguish between a new
a replayed sequence number each value must be monotonically and a replayed message, the sequence number must be monotonically
increasing modulo 2^64. We assume that the first sequence number seen incremented modulo 2^64 for each message. We assume that the first
(i.e. the starting sequence number) is stored somewhere. The modulo- sequence number seen (i.e., the starting sequence number) is stored
operation is required because the starting sequence number may be an somewhere. The modulo-operation is required because the starting
arbitrary number. The receiver therefore only accepts packets with a sequence number may be an arbitrary number. The receiver therefore
sequence number larger (modulo 2^64) than the previous packet. As only accepts packets with a sequence number larger (modulo 2^64) than
explained in [RFC2747] this process is started by handshaking and the previous packet. As explained in [RFC2747] this process is
agreeing on an initial sequence number. If no such handshaking is started by handshaking and agreeing on an initial sequence number. If
available then the initial sequence number must be part of the no such handshaking is available then the initial sequence number
establishment of the security association. must be part of the establishment of the security association.
The generation and storage of sequence numbers is an important step The generation and storage of sequence numbers is an important step
in preventing replay attacks and is largely determined by the in preventing replay attacks and is largely determined by the
capabilities of the system in presence of system crashes, failures capabilities of the system in presence of system crashes, failures
and restarts. Section 3 of [RFC2747] explains some of the most and restarts. Section 3 of [RFC2747] explains some of the most
important considerations. important considerations. However, the description of how the
receiver distinguishes proper from improper sequence numbers is
incomplete--it implicitly assumes that gaps large enough to cause the
sequence number to wrap around cannot occur.
If delivery in order were guaranteed, the following procedure would
work: The receiver keeps track of the first sequence number received,
INIT-SEQ, and most recent sequence number received, LAST-SEQ, for
each key identifier in a security association. When the first message
is received, set INIT-SEQ = LAST-SEQ = value received and accept.
When a subsequent message is received, if its sequence number is
strictly between LAST-SEQ and INIT-SEQ, modulo 2^64, accept and
update LAST-SEQ with the value just received. If it is between INIT-
SEQ and LAST-SEQ, inclusive, modulo 2^64, reject and leave the value
of LAST-SEQ unchanged. Because delivery in order is not guaranteed,
the above rules need to be combined with a method of allowing a fixed
sized window in the neighborhood of LAST-SEQ for out-of-order
delivery, for example, as described in Appendix C of [RFC2401].
- Keyed Message Digest - Keyed Message Digest
The Keyed Message Digest is an RSVP built-in security mechanism used The Keyed Message Digest is a security mechanism built into RSVP and
to provide integrity protection of the signaling messages. Prior to used to provide integrity protection of a signaling message
computing the value for the Keyed Message Digest field the Keyed (including its sequence number). Prior to computing the value for the
Message Digest field itself must be set to zero and a keyed hash Keyed Message Digest field, the Keyed Message Digest field itself
computed over the entire RSVP packet. The Keyed Message Digest field must be set to zero and a keyed hash computed over the entire RSVP
is variable in length but must be a multiple of four octets. If HMAC- packet. The Keyed Message Digest field is variable in length but must
MD5 is used then the output value is 16 bytes long. The keyed hash be a multiple of four octets. If HMAC-MD5 is used, then the output
function HMAC-MD5 [RFC2104] is required for a RSVP implementation as value is 16 bytes long. The keyed hash function HMAC-MD5 [RFC2104] is
noted in Section 1 of [RFC2747]. Hash algorithms other than MD5 required for a RSVP implementation as noted in Section 1 of
[RFC1321] like SHA [SHA] may also be supported. [RFC2747]. Hash algorithms other than MD5 [RFC1321] like SHA-1 [SHA]
may also be supported.
The key used for computing this Keyed Message Digest may be obtained The key used for computing this Keyed Message Digest may be obtained
from the pre-shared secret which is either manually distributed or from the pre-shared secret, which is either manually distributed or
the result of a key management protocol. No key management protocol, the result of a key management protocol. No key management protocol,
however, is specified to create the desired security associations. however, is specified to create the desired security associations.
Also, no guidelines for key length are given. It should be
recommended that HMAC-MD5 keys be 128 bits and SHA-1 key 160 bits, as
in IPsec AH [RFC2402]and ESP [RFC2406].
3.2 Security Associations 3.2 Security Associations
Different attributes are stored for security associations of sending Different attributes are stored for security associations of sending
and receiving systems (i.e. unidirectional security associations). and receiving systems (i.e., unidirectional security associations).
RSVP Security Properties June 2003
The sending system needs to maintain the following attributes in such The sending system needs to maintain the following attributes in such
a security association [RFC2747]: a security association [RFC2747]:
- Authentication algorithm and algorithm mode - Authentication algorithm and algorithm mode
- Key - Key
- Key Lifetime - Key Lifetime
- Sending Interface - Sending Interface
- Latest sequence number (sent with this key identifier) - Latest sequence number (sent with this key identifier)
The receiving system has to store the following fields: The receiving system has to store the following fields:
skipping to change at page 7, line 29 skipping to change at page 8, line 4
- Key - Key
- Key Lifetime - Key Lifetime
- Source address of the sending system - Source address of the sending system
- List of last n sequence numbers (received with this key identifier) - List of last n sequence numbers (received with this key identifier)
Note that the security associations need to have additional fields to Note that the security associations need to have additional fields to
indicate their state. It is necessary to have an overlapping lifetime indicate their state. It is necessary to have an overlapping lifetime
of security associations to avoid interrupting an ongoing of security associations to avoid interrupting an ongoing
communication because of expired security associations. During such a communication because of expired security associations. During such a
period of overlapping lifetime it is necessary to authenticate either period of overlapping lifetime it is necessary to authenticate either
one or both active keys. As mentioned in [RFC2747] a sender and a one or both active keys. As mentioned in [RFC2747], a sender and a
receiver might have multiple active keys simultaneously. receiver may have multiple active keys simultaneously.
If more than one algorithm is supported then the algorithm used must If more than one algorithm is supported then the algorithm used must
be specified for a security association. be specified for a security association.
3.3 RSVP Key Management Assumptions 3.3 RSVP Key Management Assumptions
[RFC2205] assumes that security associations are already available. [RFC2205] assumes that security associations are already available.
Manual key distribution must be provided by an implementation as An implementation must provide manual key distribution as noted in
noted in Section 5.2 of [RFC2747]. Manual key distribution however Section 5.2 of [RFC2747]. Manual key distribution, however, has
has different requirements to a key storage - - a simple plaintext different requirements for key storage-ûa simple plaintext ASCII file
ASCII file may be sufficient in some cases. If multiple security may be sufficient in some cases. If multiple security associations
associations with different lifetimes should be supported at the same with different lifetimes need to be supported at the same time, then
time then a key engine would be more appropriate. Further security a key engine would be more appropriate. Further security requirements
requirements listed in Section 5.2 of [RFC2747] are the following: listed in Section 5.2 of [RFC2747] are the following:
- The manual deletion of security associations must be supported. - The manual deletion of security associations must be supported.
- The key storage should persist a system restart. - The key storage should persist a system restart.
- Each key must be assigned a specific lifetime and a specific Key - Each key must be assigned a specific lifetime and a specific Key
Identifier. Identifier.
3.4 Identity Representation 3.4 Identity Representation
In addition to host-based authentication with the INTEGRITY object In addition to host-based authentication with the INTEGRITY object
inside the RSVP message user-based authentication is available as inside the RSVP message, user-based authentication is available as
introduced with [RFC2750]. Section 2 of [RFC3182] stated that introduced in [RFC2750]. Section 2 of [RFC3182] states that
RSVP Security Properties June 2003
"Providing policy based admission control mechanism based on user "Providing policy based admission control mechanism based on user
identities or application is one of the prime requirements." To identities or application is one of the prime requirements." To
identify the user or the application, a policy element called identify the user or the application, a policy element called
AUTH_DATA, which is contained in the POLICY_DATA object, is created AUTH_DATA, which is contained in the POLICY_DATA object, is created
by the RSVP daemon at the userÆs host and transmitted inside the RSVP by the RSVP daemon at the user's host and transmitted inside the RSVP
message. The structure of the POLICY_DATA element is described in message. The structure of the POLICY_DATA element is described in
[RFC2750]. Network nodes like the PDP then use the information [RFC2750]. Network nodes like the policy decision point (PDP) then
contained in the AUTH_DATA element to authenticate the user and to use the information contained in the AUTH_DATA element to
allow policy-based admission control to be executed. As mentioned in authenticate the user and to allow policy-based admission control to
[RFC3182] the policy element is processed and the policy decision be executed. As mentioned in [RFC3182], the policy element is
point replaces the old element with a new one for forwarding to the processed and the PDP replaces the old element with a new one for
next hop router. forwarding to the next hop router.
A detailed description of the POLICY_DATA element can be found in A detailed description of the POLICY_DATA element can be found in
[RFC2750]. The attributes contained in the authentication data policy [RFC2750]. The attributes contained in the authentication data policy
element AUTH_DATA, which is defined in [RFC3182], are briefly element AUTH_DATA, which is defined in [RFC3182], are briefly
explained in this Section. Figure 1 shows the abstract structure of explained in this Section. Figure 1 shows the abstract structure of
the RSVP message with its security relevant objects and the scope of the RSVP message with its security-relevant objects and the scope of
protection. The RSVP INTEGRITY object (outer object) covers the protection. The RSVP INTEGRITY object (outer object) covers the
entire RSVP message whereas the POLICY_DATA INTEGRITY object only entire RSVP message, whereas the POLICY_DATA INTEGRITY object only
covers objects within the POLICY_DATA element. covers objects within the POLICY_DATA element.
+--------------------------------------------------------+ +--------------------------------------------------------+
| RSVP Message | | RSVP Message |
+--------------------------------------------------------+ +--------------------------------------------------------+
| INTEGRITY +-------------------------------------------+| | INTEGRITY +-------------------------------------------+|
| Object |POLICY_DATA Object || | Object |POLICY_DATA Object ||
| +-------------------------------------------+| | +-------------------------------------------+|
| | INTEGRITY +------------------------------+|| | | INTEGRITY +------------------------------+||
| | Object | AUTH_DATA Object ||| | | Object | AUTH_DATA Object |||
| | +------------------------------+|| | | +------------------------------+||
| | | Various Authentication ||| | | | Various Authentication |||
| | | Attributes ||| | | | Attributes |||
| | +------------------------------+|| | | +------------------------------+||
| +-------------------------------------------+| | +-------------------------------------------+|
+--------------------------------------------------------+ +--------------------------------------------------------+
Figure 1: Security relevant Objects and Elements within the RSVP Figure 1: Security Relevant Objects and Elements within the RSVP
message Message
The AUTH_DATA object contains information for identifying users and The AUTH_DATA object contains information for identifying users and
applications together with credentials for those identities. The main applications together with credentials for those identities. The main
purpose of those identities seems to be the usage for policy based purpose of these identities seems to be usage for policy-based
admission control and not for authentication and key management. As admission control and not authentication and key management. As noted
noted in Section 6.1 of [RFC3182] an RSVP may contain more than one in Section 6.1 of [RFC3182], an RSVP message may contain more than
POLICY_DATA object and each of them may contain more than one one POLICY_DATA object and each of them may contain more than one
AUTH_DATA object. As indicated in the Figure above and in [RFC3182] AUTH_DATA object. As indicated in Figure 1 and in [RFC3182], one
one AUTH_DATA object contains more than one authentication attribute. AUTH_DATA object may contain more than one authentication attribute.
A typical configuration for a Kerberos-based user authentication A typical configuration for Kerberos-based user authentication
RSVP Security Properties June 2003
includes at least the Policy Locator and an attribute containing the includes at least the Policy Locator and an attribute containing the
Kerberos session ticket. Kerberos session ticket.
Successful user authentication is the basis for executing policy- Successful user authentication is the basis for executing policy-
based admission control. Additionally other information such as time- based admission control. Additionally, other information such as
of-day, application type, location information, group membership etc. time-of-day, application type, location information, group
may be relevant for a policy. membership, etc. may be relevant to implement an access control
policy.
The following attributes are defined for the usage in the AUTH_DATA The following attributes are defined for the usage in the AUTH_DATA
object: object:
a) Policy Locator a) Policy Locator
The policy locator string that is a X.500 distinguished name (DN) The policy locator string that is an X.500 distinguished name (DN)
used to locate the user and/or application specific policy used to locate user or application specific policy information. The
information. The following types of X.500 DNs are listed: following types of X.500 DNs are listed:
- ASCII_DN - ASCII_DN
- UNICODE_DN - UNICODE_DN
- ASCII_DN_ENCRYPT - ASCII_DN_ENCRYPT
- UNICODE_DN_ENCRYPT - UNICODE_DN_ENCRYPT
The first two types are the ASCII and the Unicode representation of The first two types are the ASCII and the Unicode representation of
the user or application DN identity. The two "encrypted" the user or application DN identity. The two "encrypted"
distinguished name types are either encrypted with the Kerberos distinguished name types are either encrypted with the Kerberos
session key or with the private key of the userÆs digital certificate session key or with the private key of the user's digital certificate
(i.e. digitally signed). The term encrypted together with a digital (i.e., digitally signed). The term encrypted together with a digital
signature is easy to misconceive. If user identity confidentiality signature is easy to misconceive. If user identity confidentiality is
shall be provided then the policy locator has to be encrypted with provided, then the policy locator has to be encrypted with the public
the public key of the recipient. How to obtain this public key is not key of the recipient. How to obtain this public key is not described
described in the document. Such an issue may be specified in a in the document. Such an issue may be specified in a concrete
concrete architecture where RSVP is used. architecture where RSVP is used.
b) Credentials b) Credentials
Two cryptographic credentials are currently defined for a user: Two cryptographic credentials are currently defined for a user:
Authentication with Kerberos V5 [RFC1510], and authentication with Authentication with Kerberos V5 [RFC1510], and authentication with
the help of digital signatures based on X.509 [RFC2495] and PGP the help of digital signatures based on X.509 [RFC2495] and PGP
[RFC2440]. The following list contains all defined credential types [RFC2440]. The following list contains all defined credential types
currently available and defined in [RFC3182]: currently available and defined in [RFC3182]:
RSVP Security Properties June 2003
+--------------+--------------------------------+ +--------------+--------------------------------+
| Credential | Description | | Credential | Description |
| Type | | | Type | |
+===============================================| +===============================================|
| ASCII_ID | User or application identity | | ASCII_ID | User or application identity |
| | encoded as an ASCII string | | | encoded as an ASCII string |
+--------------+--------------------------------+ +--------------+--------------------------------+
| UNICODE_ID | User or application identity | | UNICODE_ID | User or application identity |
| | encoded as an Unicode string | | | encoded as a Unicode string |
+--------------+--------------------------------+ +--------------+--------------------------------+
| KERBEROS_TKT | Kerberos V5 session ticket | | KERBEROS_TKT | Kerberos V5 session ticket |
+--------------+--------------------------------+ +--------------+--------------------------------+
| X509_V3_CERT | X.509 V3 certificate | | X509_V3_CERT | X.509 V3 certificate |
+--------------+--------------------------------+ +--------------+--------------------------------+
| PGP_CERT | PGP certificate | | PGP_CERT | PGP certificate |
+--------------+--------------------------------+ +--------------+--------------------------------+
Table 1: Credentials Supported in RSVP Table 1: Credentials Supported in RSVP
The first two credentials only contain a plaintext string and The first two credentials contain only a plaintext string, and
therefore they do not provide cryptographic user authentication. therefore they do not provide cryptographic user authentication.
These plaintext strings may be used to identify applications, which These plaintext strings may be used to identify applications, which
are included for policy-based admission control. Note that these are included for policy-based admission control. Note that these
plain-text identifiers may, however, be protected if either the RSVP plain-text identifiers may, however, be protected if either the RSVP
INTEGRITY and/or the INTEGRITY object of the POLICY_DATA element is INTEGRITY or the INTEGRITY object of the POLICY_DATA element is
present. Note that the two INTEGRITY objects can terminate at present. Note that the two INTEGRITY objects can terminate at
different entities depending on the network structure. The digital different entities depending on the network structure. The digital
signature may also provide protection of application identifiers. A signature may also provide protection of application identifiers. A
protected application identity (and the entire content of the protected application identity (and the entire content of the
POLICY_DATA element) cannot be modified as long as no policy ignorant POLICY_DATA element) cannot be modified as long as no policy ignorant
nodes are used in between. nodes are encountered in between.
A Kerberos session ticket, as previously mentioned, is the ticket of A Kerberos session ticket, as previously mentioned, is the ticket of
a Kerberos AP_REQ message [RFC1510] without the Authenticator. a Kerberos AP_REQ message [RFC1510] without the Authenticator.
Normally, the AP_REQ message is used by a client to authenticate to a Normally, the AP_REQ message is used by a client to authenticate to a
server. The INTEGRITY object (e.g. of the POLICY_DATA element) server. The INTEGRITY object (e.g., of the POLICY_DATA element)
provides the functionality of the Kerberos Authenticator, namely provides the functionality of the Kerberos Authenticator, namely
replay protection and shows that the user was able to retrieve the protecting against replay and showing that the user was able to
session key following the Kerberos protocol. This is, however, only retrieve the session key following the Kerberos protocol. This is,
the case if the Kerberos session was used for the keyed message however, only the case if the Kerberos session was used for the keyed
digest field of the INTEGRITY object. Section 7 of [RFC2747] message digest field of the INTEGRITY object. Section 7 of [RFC2747]
discusses some issues for establishment of keys for the INTEGRITY discusses some issues for establishment of keys for the INTEGRITY
object. The establishment of the security association for the RSVP object. The establishment of the security association for the RSVP
INTEGRITY object with the inclusion of the Kerberos Ticket within the INTEGRITY object with the inclusion of the Kerberos Ticket within the
AUTH_DATA element may be complicated by the fact that the ticket can AUTH_DATA element may be complicated by the fact that the ticket can
be decrypted by node B whereas the RSVP INTEGRITY object terminates be decrypted by node B whereas the RSVP INTEGRITY object terminates
at a different host C. The Kerberos session ticket contains, among at a different host C. The Kerberos session ticket contains, among
many other fields, the session key. The Policy Locator may also be many other fields, the session key. The Policy Locator may also be
RSVP Security Properties June 2003
encrypted with the same session key. The protocol steps that need to encrypted with the same session key. The protocol steps that need to
be executed to obtain such a Kerberos service ticket are not be executed to obtain such a Kerberos service ticket are not
described in [RFC3182] and may involve several roundtrips depending described in [RFC3182] and may involve several roundtrips depending
on many Kerberos related factors. The Kerberos ticket does not need on many Kerberos-related factors. The Kerberos ticket does not need
to be included in every RSVP message as an optimisation as described to be included in every RSVP message as an optimization, as described
in Section 7.1 of [RFC2747]. Thus the receiver must store the in Section 7.1 of [RFC2747]. Thus the receiver must store the
received service ticket. If the lifetime of the ticket is expired received service ticket. If the lifetime of the ticket has expired,
then a new service ticket must be sent. If the receiver lost his then a new service ticket must be sent. If the receiver lost its
state information (because of a crash or restart) then he may state information (because of a crash or restart) then it may
transmit an Integrity Challenge message to force the sender to re- transmit an Integrity Challenge message to force the sender to re-
transmit a new service ticket. transmit a new service ticket.
If either the X.509 V3 or the PGP certificate is included in the If either the X.509 V3 or the PGP certificate is included in the
policy element then a digital signature must be added. The digital policy element, then a digital signature must be added. The digital
signature computed over the entire AUTH_DATA object provides signature computed over the entire AUTH_DATA object provides
authentication and integrity protection. The SubType of the digital authentication and integrity protection. The SubType of the digital
signature authentication attribute is set to zero before computing signature authentication attribute is set to zero before computing
the digital signature. Whether or not a guarantee of freshness with the digital signature. Whether or not a guarantee of freshness with
the replay protection (either timestamps or sequence numbers) is replay protection (either timestamps or sequence numbers) is provided
provided by the digital signature is an open issue as discussed in by the digital signature is an open issue as discussed in Section
Section 4.3. 4.3.
c) Digital Signature c) Digital Signature
The digital signature computed over the data of the AUTH_DATA object The digital signature computed over the data of the AUTH_DATA object
must be the last attribute. The algorithm used to compute the digital must be the last attribute. The algorithm used to compute the digital
signature depends on the authentication mode listed in the signature depends on the authentication mode listed in the
credential. This is only partially true since for example PGP again credential. This is only partially true, because, for example, PGP
allows different algorithms to be used for computing a digital again allows different algorithms to be used for computing a digital
signature. The algorithm identifier used for computing the digital signature. The algorithm identifier used for computing the digital
signature is not included in the certificate itself. The algorithm signature is not included in the certificate itself. The algorithm
identifier included in the certificate only serves the purpose to identifier included in the certificate only serves the purpose of
allow the verification of the signature computed by the certificate allowing the verification of the signature computed by the
authority (except for the case of self-signed certificates). certificate authority (except for the case of self-signed
certificates).
d) Policy Error Object d) Policy Error Object
The Policy Error Object is used in the case of a failure of the The Policy Error Object is used in the case of a failure of policy-
policy based admission control or other credential verification. based admission control or other credential verification. Currently
Currently available error messages allow to notify if the credentials available error messages allow notification if the credentials are
are expired (EXPIRED_CREDENTIALS), if the authorization process expired (EXPIRED_CREDENTIALS), if the authorization process
disallowed the resource request (INSUFFICIENT_PRIVILEGES) and if the disallowed the resource request (INSUFFICIENT_PRIVILEGES), or if the
given set of credentials is not supported given set of credentials is not supported
(UNSUPPORTED_CREDENTIAL_TYPE). The latter error message returned by (UNSUPPORTED_CREDENTIAL_TYPE). The last error message returned by the
the network allows the user's host to discover the type of network allows the user's host to discover the type of credentials
credentials supported. Particularly for mobile environments this supported. Particularly for mobile environments this might be quite
might be quite inefficient. Furthermore it is unlikely that a user inefficient. Furthermore, it is unlikely that a user supports
supports different types of credentials. The purpose of the error different types of credentials. The purpose of the error message
IDENTITY_CHANGED is unclear. Also, the protection of the error
RSVP Security Properties June 2003
message IDENTITY_CHANGED is unclear. The protection of the error
message is not discussed in [RFC3182]. message is not discussed in [RFC3182].
3.5 RSVP Integrity Handshake 3.5 RSVP Integrity Handshake
The Integrity Handshake is a protocol that was designed to allow a The Integrity Handshake protocol was designed to allow a crashed or
crashed or restarted host to obtain the latest valid challenge value restarted host to obtain the latest valid challenge value stored at
stored at the receiving host. Due to the absent key management it the receiving host. Due to the absence of key management, it must be
must be guaranteed that two messages do not use the same sequence guaranteed that two messages do not use the same sequence number with
number with the same key. A host stores the latest sequence number of the same key. A host stores the latest sequence number of a
a cryptographically verified message. An adversary can replay cryptographically verified message. An adversary can replay
eavesdropped packets if the crashed host has lost its sequence eavesdropped packets if the crashed host has lost its sequence
numbers. A signaling message from the real sender with a new sequence numbers. A signaling message from the real sender with a new sequence
number would therefore allow the crashed host to update the sequence number would therefore allow the crashed host to update the sequence
number field and prevent further replays. Hence if there is a steady number field and prevent further replays. Hence, if there is a steady
flow of RSVP protected messages between the two hosts an attacker may flow of RSVP protected messages between the two hosts, an attacker
find it difficult to inject old messages since new authenticated may find it difficult to inject old messages, because new,
messages with high sequence numbers arrive and get stored authenticated messages with higher sequence numbers arrive and get
immediately. stored immediately.
The following description explains the details of the RSVP Integrity The following description explains the details of a RSVP Integrity
Handshake that is started by Node A after recovering from a Handshake that is started by Node A after recovering from a
synchronization failure: synchronization failure:
Integrity Challenge Integrity Challenge
(1) Message (including (1) Message (including
+----------+ a Cookie) +----------+ +----------+ a Cookie) +----------+
| |-------------------------->| | | |-------------------------->| |
| Node A | | Node B | | Node A | | Node B |
| |<--------------------------| | | |<--------------------------| |
+----------+ Integrity Response +----------+ +----------+ Integrity Response +----------+
(2) Message (including (2) Message (including
the Cookie and the the Cookie and the
INTEGRITY object) INTEGRITY object)
Figure 2: RSVP Integrity Handshake Figure 2: RSVP Integrity Handshake
The details of the messages are described below: The details of the messages are as follows:
CHALLENGE= (Key Identifier, Challenge Cookie) CHALLENGE:=(Key Identifier, Challenge Cookie)
Integrity Challenge Message:=(Common Header, CHALLENGE) Integrity Challenge Message:=(Common Header, CHALLENGE)
Integrity Response Message:=(Common Header, INTEGRITY, CHALLENGE) Integrity Response Message:=(Common Header, INTEGRITY, CHALLENGE)
The "Challenge Cookie" is suggested to be a MD5 hash of a local The "Challenge Cookie" is suggested to be a MD5 hash of a local
secret and a timestamp [RFC2747]. secret and a timestamp [RFC2747].
The Integrity Challenge message is not protected with an INTEGRITY The Integrity Challenge message is not protected with an INTEGRITY
object as show in the protocol flow above. As explained in Section 10 object as shown in the protocol flow above. As explained in Section
10 of [RFC2747] this was done to avoid problems in situations where
RSVP Security Properties June 2003 both communicating parties do not have a valid starting sequence
number.
of [RFC2747] this was done to avoid problems in situations where both
communication parties do not have a valid starting sequence number.
It is recommended to use the RSVP Integrity Handshake protocol Using the RSVP Integrity Handshake protocol is recommended although
although it is not mandatory (since it may not be needed in all it is not mandatory (since it may not be needed in all network
network environments). environments).
4. Detailed Security Property Discussion 4. Detailed Security Property Discussion
The purpose of this section is to describe the security protection of The purpose of this section is to describe the protection of the
the RSVP provided mechanisms individually for authentication, RSVP-provided mechanisms individually for authentication,
authorization, integrity and replay protection, user identity authorization, integrity and replay protection, user identity
confidentiality, confidentiality of the signaling messages. confidentiality, and confidentiality of the signaling messages.
4.1 Discussed Network Topology 4.1 Network Topology
The main purpose of this paragraph is to show the basic interface of The main purpose of this paragraph is to show the basic interfaces in
a simple RSVP network architecture. The architecture below assumes a simple RSVP network architecture. The architecture below assumes
that there is only a very single domain and that two routers are RSVP that there is only a single domain and that two routers are RSVP and
and policy aware. These assumptions are relaxed in the individual policy aware. These assumptions are relaxed in the individual
paragraphs as necessary. Layer 2 devices between the clients and paragraphs as necessary. Layer 2 devices between the clients and
their corresponding first hop routers are not shown. Other network their corresponding first hop routers are not shown. Other network
elements like a Kerberos Key Distribution Center and for example an elements like a Kerberos Key Distribution Center and for example a
LDAP server where the PDP retrieves his policies are also omitted. LDAP server, from which the PDP retrieves its policies are also
The security of various interfaces to the individual servers (KDC, omitted. The security of various interfaces to the individual servers
PDP, etc.) depends very much on the security policy of a specific (KDC, PDP, etc.) depends very much on the security policy of a
network service provider. specific network service provider.
+--------+ +--------+
|Policy | |Policy |
|Decision| |Decision|
+----+Point +---+ +----+Point +---+
| +--------+ | | +--------+ |
| | | |
| | | |
| | | |
+------+ +-+----+ +---+--+ +------+ +------+ +-+----+ +---+--+ +------+
|Client| |Router| |Router| |Client| |Client| |Router| |Router| |Client|
| A +-------+ 1 +--------+ 2 +----------+ B | | A +-------+ 1 +--------+ 2 +----------+ B |
+------+ +------+ +------+ +------+ +------+ +------+ +------+ +------+
Figure 3: Simple RSVP Architecture Figure 3: Simple RSVP Architecture
4.2 Host/Router 4.2 Host/Router
When talking about authentication in RSVP it is very important to When considering authentication in RSVP it is important to make a
make a distinction between user and host authentication of the distinction between user and host authentication of the signaling
messages. By using the RSVP INTEGRITY object the host is
RSVP Security Properties June 2003
signaling messages. By using the RSVP INTEGRITY object the host is
authenticated while credentials inside the AUTH_DATA object can be authenticated while credentials inside the AUTH_DATA object can be
used to authenticate the user. In this section the focus is on host used to authenticate the user. In this section the focus is on host
authentication whereas the next section covers user authentication. authentication whereas the next section covers user authentication.
a) Authentication a) Authentication
We use the term host authentication above since the selection of the The term host authentication is used above, because the selection of
security association is bound to the hostÆs IP address as mentioned the security association is bound to the host's IP address as
in Section 3.1 and 3.2. Depending on the key management protocol used mentioned in Sections 3.1 and 3.2. Depending on the key management
to create this security association and the identity used it is also protocol used to create this security association and the identity
possible to bind a user identity to this security association. Since used, it is also possible to bind a user identity to this security
the key management protocol is not specified it is difficult to association. Because the key management protocol is not specified, it
evaluate this part and hence we speak about data origin is difficult to evaluate this part and hence we speak about data
authentication based on the hostÆs identity for RSVP INTEGRITY origin authentication based on the host's identity for RSVP INTEGRITY
objects. The fact that the host identity is used for selecting the objects. The fact that the host identity is used for selecting the
security association has already been described in Section 3.1. security association has already been described in Section 3.1.
Data origin authentication is provided with the keyed hash value Data origin authentication is provided with the keyed hash value
computed over the entire RSVP message excluding the keyed message computed over the entire RSVP message excluding the keyed message
digest field itself. The security association used between the userÆs digest field itself. The security association used between the user's
host and the first-hop router is, as previously mentioned, not host and the first-hop router is, as previously mentioned, not
established by RSVP and must therefore be available before the established by RSVP and must therefore be available before signaling
signaling is started. is started.
- Kerberos for the RSVP INTEGRITY object - Kerberos for the RSVP INTEGRITY object
As described in Section 7 of [RFC2747] Kerberos may be used to create As described in Section 7 of [RFC2747], Kerberos may be used to
the key for the RSVP INTEGRITY object. How to learn the principal create the key for the RSVP INTEGRITY object. How to learn the
name (and realm information) of the other node is outside the scope principal name (and realm information) of the other node is outside
of [RFC2747]. Section 4.2.1 of [RFC2747] states that the required the scope of [RFC2747]. Section 4.2.1 of [RFC2747] states that the
identities can be obtained statically or dynamically via a directory required identities can be obtained statically or dynamically via a
service or DHCP. [HA01] describes a way to distribute principal and directory service or DHCP. [HA01] describes a way to distribute
realm information via DNS which can be used for this purpose principal and realm information via DNS, which can be used for this
(assuming that the FQDN or the IP address of the other node is known purpose (assuming that the FQDN or the IP address of the other node
for which this information is desired). It is only required to for which this information is desired is known). All that is required
encapsulate the Kerberos ticket inside the policy element. It is is to encapsulate the Kerberos ticket inside the policy element. It
furthermore mentioned that Kerberos tickets with expired lifetime is furthermore mentioned that Kerberos tickets with expired lifetime
must not be used and the initiator is responsible for requesting and must not be used and the initiator is responsible for requesting and
exchanging a new service ticket before expiration. exchanging a new service ticket before expiration.
RSVP multicast processing in combination with Kerberos requires RSVP multicast processing in combination with Kerberos requires
additional thoughts: additional considerations:
Section 7 of [RFC2747] states that in the multicast case all Section 7 of [RFC2747] states that in the multicast case all
receivers must share a single key with the Kerberos Authentication receivers must share a single key with the Kerberos Authentication
Server i.e. a single principal used for all receivers). From a Server, i.e., a single principal used for all receivers). From a
personal discussion with Rodney Hess it seems that there is currently personal discussion with Rodney Hess it seems that there is currently
RSVP Security Properties June 2003
no other solution available in the context of Kerberos. Multicast no other solution available in the context of Kerberos. Multicast
handling therefore leaves some questions open in this context. handling therefore leaves some open questions in this context.
In case that one entity crashed the established security association In the case where one entity crashed, the established security
is lost and therefore the other node must retransmit the service association is lost and therefore the other node must retransmit the
ticket. The crashed entity can use an Integrity Challenge message to service ticket. The crashed entity can use an Integrity Challenge
request a new Kerberos ticket to be retransmitted by the other node. message to request a new Kerberos ticket to be retransmitted by the
If a node receives such a request then a reply message must be other node. If a node receives such a request, then a reply message
returned. must be returned.
b) Integrity Protection b) Integrity Protection
Integrity protection between the userÆs host and the first hop router Integrity protection between the user's host and the first hop router
is based on the RSVP INTEGRITY object. HMAC-MD5 is the preferred is based on the RSVP INTEGRITY object. HMAC-MD5 is preferred,
although other keyed hash functions may also be used within the RSVP although other keyed hash functions may also be used within the RSVP
INTEGRITY object. In any case both communicating entities must have a INTEGRITY object. In any case, both communicating entities must have
security association which indicates the algorithm to use. This may a security association that indicates the algorithm to use. This may,
be however difficult since there is no negotiation protocol defined however, be difficult, because no negotiation protocol is defined to
to agree on a specific algorithm. Hence it is very likely that HMAC- agree on a specific algorithm. Hence, if RSVP is used in a mobile
MD5 is the only usable algorithm for the RSVP INTEGRITY object if environment, it is likely that HMAC-MD5 is the only usable algorithm
RSVP is used in a mobile environment and only in local environments for the RSVP INTEGRITY object. Only in local environments may it be
it may be useful to switch to a different keyed hash algorithm. The useful to switch to a different keyed hash algorithm. The other
other possible alternative is that every implementation must support possible alternative is that every implementation must support the
the most important keyed hash algorithms for example MD5, SHA-1, most important keyed hash algorithms for example MD5, SHA-1, RIPEMD-
RIPEMD-160 etc. HMAC-MD5 was mainly chosen because of the performance 160, etc. HMAC-MD5 was mainly chosen because of its performance
characteristics. The weaknesses of MD5 [DBP96] are known and characteristics. The weaknesses of MD5 [DBP96] are known and
described in [Dob96]. Other algorithms like SHA-1 [SHA] and RIPEMD- described in [Dob96]. Other algorithms like SHA-1 [SHA] and RIPEMD-
160 [DBP96] provide better security properties. 160 [DBP96] have stronger security properties.
c) Replay Protection c) Replay Protection
The main mechanism used for replay protection in RSVP is based on The main mechanism used for replay protection in RSVP is based on
sequence numbers whereby the sequence number is included in the RSVP sequence numbers, whereby the sequence number is included in the RSVP
INTEGRITY object. The properties of this sequence number mechanism INTEGRITY object. The properties of this sequence number mechanism
are described in Section 3.1. The fact that the receiver stores a are described in Section 3.1. The fact that the receiver stores a
list of sequence numbers is an indicator for a window mechanism. This list of sequence numbers is an indicator for a window mechanism. This
somehow conflicts with the requirement that the receiver only has to somehow conflicts with the requirement that the receiver only has to
store the highest number given in Section 3 of [RFC2747]. We assume store the highest number given in Section 3 of [RFC2747]. We assume
that this is a typo. Section 4.1 of [RFC2747] gives a few comments that this is a typo. Section 4.1 of [RFC2747] gives a few comments
about the out-of-order delivery and the ability of an implementation about the out-of-order delivery and the ability of an implementation
to specify the replay window. to specify the replay window. Appendix C of [RFC2401] describes a
window mechanism for handling out-of-sequence delivery.
- Integrity Handshake - Integrity Handshake
The mechanism of the Integrity Handshake is explained in Section 3.5. The mechanism of the Integrity Handshake is explained in Section 3.5.
The Cookie value is suggested to be hash of a local secret and a The Cookie value is suggested to be hash of a local secret and a
timestamp. The Cookie value is not verified by the receiver. The timestamp. The Cookie value is not verified by the receiver. The
mechanism used by the Integrity Handshake is a simple mechanism used by the Integrity Handshake is a simple
Challenge/Response message which assumes that the key shared between Challenge/Response message, which assumes that the key shared between
the two hosts survives the crash. If, however, the security
RSVP Security Properties June 2003 association is dynamically created, then this assumption may not be
true.
the two hosts survives the crash. If the security association is
however dynamically created then this assumption may not be true.
In Section 10 of [RFC2747] the authors note that an adversary can In Section 10 of [RFC2747] the authors note that an adversary can
create faked Integrity Handshake message including challenge cookies. create a faked Integrity Handshake message including challenge
Subsequently he would store the received response. Later he tries to cookies. Subsequently it could store the received response and later
replay these responses while a responder recovers from a crash or try to replay these responses while a responder recovers from a crash
restart. If this replayed Integrity Response value is valid and has a or restart. If this replayed Integrity Response value is valid and
lower sequence number than actually used then this value is stored at has a lower sequence number than actually used, then this value is
the recovering host. In order for this attack to be successful the stored at the recovering host. In order for this attack to be
adversary must either have collected a large number of successful the adversary must either have collected a large number of
challenge/response value pairs or the adversary "discovered" the challenge/response value pairs or have "discovered" the cookie
cookie generation mechanism (for example by knowing the local generation mechanism (for example by knowing the local secret). The
secret). The collection of Challenge/Response pairs is even more collection of Challenge/Response pairs is even more difficult,
difficult since they depend on the Cookie value, on sequence number because they depend on the Cookie value, the sequence number included
included in the response message and on the shared key which is used in the response message, and the shared key used by the INTEGRITY
by the INTEGRITY object. object.
d) Confidentiality d) Confidentiality
Confidentiality is not considered to be a security requirement for Confidentiality is not considered to be a security requirement for
RSVP. Hence it is not supported by RSVP. RSVP. Hence it is not supported by RSVP, except as described in
paragraph d) of Section 4.3. This assumption may not hold, however,
for enterprises or carriers who want to protect, in addition to
users' identities, also billing data, network usage patterns, or
network configurations from eavesdropping and traffic analysis.
Confidentiality may also help make certain other attacks more
difficult. For example, the PathErr attack described in Section 5.2
is harder to carry out if the attacker cannot observe the Path
message to which the PathErr corresponds.
e) Authorization e) Authorization
The task of authorization consists of two subcategories: Network The task of authorization consists of two subcategories: network
access authorization and RSVP request authorization. Access access authorization and RSVP request authorization. Access
authorization is provided when a node is authenticated to the network authorization is provided when a node is authenticated to the
e.g. using EAP [RFC2284] in combination with AAA protocols (for network, e.g., using EAP [RFC2284] in combination with AAA protocols
example using RADIUS [RFC2865] or DIAMETER [CA+02]). Issues related (for example using RADIUS [RFC2865] or DIAMETER [CA+02]). Issues
to network access authentication and authorization are outside the related to network access authentication and authorization are
scope of RSVP. outside the scope of RSVP.
The second authorization refers to RSVP itself. Depending on the The second authorization refers to RSVP itself. Depending on the
network configuration network configuration:
- the router either forwards the received RSVP request to the policy - the router either forwards the received RSVP request to the policy
decision point e.g. by using COPS (see [RFC2748] and [RFC2749]) and decision point, e.g., by using COPS (see [RFC2748] and [RFC2749]),
to request admission control procedure to be executed or to request that an admission control procedure be executed or
- the router supports the functionality of a PDP and therefore there - the router supports the functionality of a PDP and therefore there
is no need to forward the request or is no need to forward the request or
- the router may already be configured with the appropriate policy - the router may already be configured with the appropriate policy
information to decide locally whether to grant this request or not. information to decide locally whether to grant this request or not.
Based on the result of the admission control the request may be Based on the result of the admission control, the request may be
granted or rejected. Information about the resource requesting entity granted or rejected. Information about the resource-requesting entity
must be available to provide policy-based admission control. must be available to provide policy-based admission control.
f) Performance f) Performance
RSVP Security Properties June 2003
The computation of the keyed message digest for a RSVP INTEGRITY The computation of the keyed message digest for a RSVP INTEGRITY
object does not represent a performance problem. The protection of object does not represent a performance problem. The protection of
signaling messages is usually not a problem since these messages are signaling messages is usually not a problem, because these messages
transmitted at a low rate. Even a high number of messages does not are transmitted at a low rate. Even a high volume of messages does
cause performance problems for a RSVP routers due to the efficiency not cause performance problems for a RSVP routers due to the
of the keyed message digest routine. efficiency of the keyed message digest routine.
Dynamic key management, which is computationally more demanding, is Dynamic key management, which is computationally more demanding, is
more important for scalability. Since RSVP does not specify a more important for scalability. Because RSVP does not specify a
particular key exchange protocol to be used it is difficult to particular key exchange protocol, it is difficult to estimate the
estimate the effort to create the required security associations. effort to create the required security associations. Furthermore, the
Furthermore the number of key exchanges to be triggered depends on number of key exchanges to be triggered depends on security policy
security policy issues like lifetime of a security association, issues like lifetime of a security association, required security
required security properties of the key exchange protocol, properties of the key exchange protocol, authentication mode used by
authentication mode used by the key exchange protocol etc. In a the key exchange protocol, etc. In a stationary environment with a
stationary environment with a single administrative domain the manual single administrative domain, manual security association
security association distribution may be acceptable and provides the establishment may be acceptable and may provide the best performance
best performance characteristics. In a mobile environment asymmetric characteristics. In a mobile environment, asymmetric authentication
authentication methods are likely to be used with a key exchange methods are likely to be used with a key exchange protocol, and some
protocol and some sort of certificate verification needs to be sort of public key or certificate verification needs to be supported.
supported.
4.3 User to PEP/PDP 4.3 User to PEP/PDP
As noted in the previous section both user and host based As noted in the previous section, both user-based and host-based
authentication is supported by RSVP. Using RSVP, a user may authentication are supported by RSVP. Using RSVP, a user may
authenticate to the first hop router or to the PDP as specified in authenticate to the first hop router or to the PDP as specified in
[RFC2747] depending on the infrastructure provided by the network [RFC2747], depending on the infrastructure provided by the network
domain or on the architecture used (e.g. the integration of RSVP and domain or the architecture used (e.g., the integration of RSVP and
Kerberos V5 into the Windows 2000 Operating System [MADS01]). Another Kerberos V5 into the Windows 2000 Operating System [MADS01]). Another
architecture where RSVP is tightly integrated is the one specified by architecture in which RSVP is tightly integrated is the one specified
the PacketCable organization. The interested reader is referred to by the PacketCable organization. The interested reader is referred to
[PKTSEC] for a discussion of their security architecture. [PKTSEC] for a discussion of their security architecture.
a) Authentication a) Authentication
When a user sends a RSVP PATH or RESV message then this message may When a user sends a RSVP PATH or RESV message, this message may
include some information to authenticate the user. [RFC3182] include some information to authenticate the user. [RFC3182]
describes how user and application information is embedded into the describes how user and application information is embedded into the
RSVP message (AUTH_DATA object) and how to protect it. A router RSVP message (AUTH_DATA object) and how to protect it. A router
receiving such a message can use this information to authenticate the receiving such a message can use this information to authenticate the
client and forward the user/application information to the policy client and forward the user or application information to the policy
decision point (PDP). Optionally the PDP itself can authenticate the decision point (PDP). Optionally the PDP itself can authenticate the
user, which is described in the next section. In order to be able to user, which is described in the next section. To be able to
authenticate the user, to verify the integrity and to check for authenticate the user, to verify the integrity, and to check for
replays the entire POLICY_DATA element has to be forwarded from the replays, the entire POLICY_DATA element has to be forwarded from the
router to the PDP e.g. by including the element into a COPS message. router to the PDP, e.g., by including the element into a COPS
message. It is assumed, although not clearly specified in [RFC3182],
RSVP Security Properties June 2003 that the INTEGRITY object within the POLICY_DATA element is sent to
the PDP along with all other attributes.
It is assumed that the INTEGRITY object within the POLICY_DATA
element is sent to the PDP along with all other attributes although
not clearly specified in [RFC3182].
Certificate Verification Certificate Verification
Using the policy element as described in [RFC3182] it is not possible Using the policy element as described in [RFC3182] it is not possible
to provide a certificate revocation list or other information to to provide a certificate revocation list or other information to
proof the validity of the certificate inside the policy element. A prove the validity of the certificate inside the policy element. A
specific mechanism for certificate verification is not discussed in specific mechanism for certificate verification is not discussed in
[RFC3182] and hence a number of them can be used for this purpose. [RFC3182] and hence a number of them can be used for this purpose.
For certificate verification the network element (a router or the For certificate verification, the network element (a router or the
policy decision point), which has to authenticate the user, could policy decision point), which has to authenticate the user, could
frequently download certificate revocation lists or should use a frequently download certificate revocation lists or use a protocol
protocol like the Online Certificate Status Protocol (OCSP) [RFC2560] like the Online Certificate Status Protocol (OCSP) [RFC2560] and the
and the Simple Certificate Validation Protocol (SCVP) [MHHF01] to Simple Certificate Validation Protocol (SCVP) [MHHF01] to determine
determine the current status of a digital certificate. the current status of a digital certificate.
User Authentication to the PDP User Authentication to the PDP
This alternative authentication procedure uses the PDP to This alternative authentication procedure uses the PDP to
authenticate the user instead of the first hop router. In Section authenticate the user instead of the first hop router. In Section
4.2.1 in [RFC3182] the choice is given for the user to either obtain 4.2.1 of [RFC3182] the choice is given for the user to obtain a
a session ticket for the next hop router or for the PDP. As noted in session ticket either for the next hop router or for the PDP. As
the same Section the identity of the PDP or the next hop router is noted in the same Section, the identity of the PDP or the next hop
statically configured or dynamically retrieved. Subsequently user router is statically configured or dynamically retrieved.
authentication to the PDP is considered. Subsequently, user authentication to the PDP is considered.
Kerberos-based Authentication to the PDP Kerberos-based Authentication to the PDP
If Kerberos is used to authenticate the user then first a session If Kerberos is used to authenticate the user, then a session ticket
ticket for the PDP needs to be requested. If the user roams between for the PDP needs to be requested first. A user who roams between
different routers in the same administrative domain then he does not different routers in the same administrative domain does not need to
need to request a new service ticket since the PDP is likely to be request a new service ticket, because the PDP is likely to be used by
used by most or all first-hop routers within the same administrative most or all first-hop routers within the same administrative domain.
domain. This is different if a session ticket for a router has to be This is different from the case in which a session ticket for a
obtained and authentication to a router is required. The router router has to be obtained and authentication to a router is required.
therefore plays a passive role of forwarding the request only to the The router therefore plays a passive role of forwarding the request
PDP and executing the policy decision returned by the PDP. only to the PDP and executing the policy decision returned by the
PDP.
Appendix B describes one example of user-to-PDP authentication. Appendix B describes one example of user-to-PDP authentication.
User authentication with the policy element only provides unilateral User authentication with the policy element only provides unilateral
authentication where the client authenticates to the router or to the authentication whereby the client authenticates to the router or to
PDP. If a RSVP message is sent to the userÆs host and public keyed the PDP. If a RSVP message is sent to the user's host and public key
based authentication is used then the message does not contain a based authentication is used, then the message does not contain a
certificate and digital signature. Hence no mutual authentication can certificate and digital signature. Hence no mutual authentication can
be assumed. In case of Kerberos mutual authentication may be be assumed. In case of Kerberos, mutual authentication may be
accomplished if the PDP or the router transmits a policy element with accomplished if the PDP or the router transmits a policy element with
RSVP Security Properties June 2003
an INTEGRITY object computed with the session key retrieved from the an INTEGRITY object computed with the session key retrieved from the
Kerberos ticket or if the Kerberos ticket included in the policy Kerberos ticket or if the Kerberos ticket included in the policy
element is also used for the RSVP INTEGRITY object as described in element is also used for the RSVP INTEGRITY object as described in
Section 4.2. This procedure only works if a previous message was Section 4.2. This procedure only works if a previous message was
transmitted from the end host to the network and such key is already transmitted from the end host to the network and such key is already
established. [RFC3182] does not discuss this issue and therefore established. [RFC3182] does not discuss this issue and therefore
there is no particular requirement dealing with transmitting network there is no particular requirement dealing with transmitting network-
specific credentials back to the end-user's host. specific credentials back to the end-user's host.
b) Integrity Protection b) Integrity Protection
The integrity protection of the RSVP message and the POLICY_DATA Integrity protection is applied separately to the RSVP message and
element are protected separately as shown in Figure 1. In case of a the POLICY_DATA element as shown in Figure 1. In case of a policy-
policy ignorant node along the path the RSVP INTEGRITY object and the ignorant node along the path, the RSVP INTEGRITY object and the
INTEGRITY object inside the policy element terminate at different INTEGRITY object inside the policy element terminate at different
nodes. Basically the same is true for the credentials of the user if nodes. Basically, the same is true for the user credentials if they
they are verified at the policy decision point instead of the first are verified at the policy decision point instead of the first hop
hop router. router.
- Kerberos - Kerberos
If Kerberos is used to authenticate the user to the first hop router If Kerberos is used to authenticate the user to the first hop router,
then the session key included in the Kerberos ticket may be used to then the session key included in the Kerberos ticket may be used to
compute the INTEGRITY object of the policy element. It is the keyed compute the INTEGRITY object of the policy element. It is the keyed
message digest that provides the authentication. The existence of the message digest that provides the authentication. The existence of the
Kerberos service ticket inside the AUTH_DATA object does not provide Kerberos service ticket inside the AUTH_DATA object does not provide
authentication and a guarantee of freshness for the receiving host. authentication and a guarantee of freshness for the receiving host.
Authentication and guarantee of freshness is provided by the keyed Authentication and guarantee of freshness are provided by the keyed
hash value of the INTEGRITY object inside the POLICY_DATA element. hash value of the INTEGRITY object inside the POLICY_DATA element.
The user thereby shows that he actively participated in the Kerberos This shows that the user actively participated in the Kerberos
protocol and that he was able to obtain the session key to compute protocol and was able to obtain the session key to compute the keyed
the keyed message digest. The Authenticator used in the Kerberos V5 message digest. The Authenticator used in the Kerberos V5 protocol
protocol provides similar functionality but replay protection is provides similar functionality, but replay protection is based on
based on timestamps (or based on sequence number if the optional seq- timestamps (or on a sequence number if the optional seq-number field
number field inside the Authenticator is used for KRB_PRIV/KRB_SAFE inside the Authenticator is used for KRB_PRIV/KRB_SAFE messages as
messages as described in Section 5.3.2 of [RFC1510]). described in Section 5.3.2 of [RFC1510]).
- Digital Signature - Digital Signature
If public key based authentication is provided then user If public key based authentication is provided, then user
authentication is accomplished with the digital signature. As authentication is accomplished with a digital signature. As explained
explained in Section 3.3.3 of [RFC3182] the DIGITAL_SIGNATURE in Section 3.3.3 of [RFC3182], the DIGITAL_SIGNATURE attribute must
attribute must be the last attribute in the AUTH_DATA object and the be the last attribute in the AUTH_DATA object, and the digital
digital signature covers the entire AUTH_DATA object. Which hash signature covers the entire AUTH_DATA object. Which hash algorithm
algorithm and public key algorithm is used for the digital signature and public key algorithm are used for the digital signature
computation is described in [RFC2440] in case of PGP. In case of computation is described in [RFC2440] in the case of PGP. In the case
X.509 credentials the situation is more complex since different of X.509 credentials the situation is more complex, because different
mechanisms like CMS [RFC2630] or PKCS#7 [RFC2315] may be used for the mechanisms like CMS [RFC2630] or PKCS#7 [RFC2315] may be used for
RSVP Security Properties June 2003
digitally signing the message element. X.509 only provides the digitally signing the message element. X.509 only provides the
standard for the certificate layout which seems to provide standard for the certificate layout, which seems to provide
insufficient information for this purpose. Therefore X.509 insufficient information for this purpose. Therefore, X.509
certificates are supported for example by CMS and PKCS#7. [RFC3182], certificates are supported for example by CMS and PKCS#7. [RFC3182],
however, does not make any statements about the usage of CMS and however, does not make any statements about the usage of CMS and
PKCS#7. Currently there is no support for CMS or PKCS#7 described in PKCS#7. Currently there is no support for CMS or PKCS#7 described in
[RFC3182], which provides more than only public key based [RFC3182], which provides more than just public key based
authentication (e.g. CRL distribution, key transport, key agreement, authentication (e.g., CRL distribution, key transport, key agreement,
etc.). Furthermore the usage of PGP in RSVP is vague since there are etc.). Furthermore, the use of PGP in RSVP is vaguely defined,
different versions of PGP (including OpenPGP [RFC2440]) and there has because there are different versions of PGP (including OpenPGP
been no indication which version should be used. [RFC2440]), and no indication is given as to which should be used.
Supporting public key based mechanisms in RSVP might increase the Supporting public key based mechanisms in RSVP might increase the
risks of denial of service attacks. Additionally the large risks of denial of service attacks. Additionally, the large
processing, memory and bandwidth utilization should be considered. processing, memory, and bandwidth utilization should be considered.
Fragmentation might also be an issue here. Fragmentation might also be an issue here.
If the INTEGRITY object is not included in the POLICY_DATA element or If the INTEGRITY object is not included in the POLICY_DATA element or
not sent to the PDP then we have to make the following observation: not sent to the PDP, then we have to make the following observations:
a) For the digital signature case only the replay protection provided a) For the digital signature case, only the replay protection
by the digital signature algorithm can be used. It is however not provided by the digital signature algorithm can be used. It is not
clear whether this usage was anticipated or not. Hence we might clear, however, whether this usage was anticipated or not. Hence,
assume that the replay protection is based on the availability of we might assume that replay protection is based on the
RSVP INTEGRITY object used with a security association that is availability of the RSVP INTEGRITY object used with a security
established by other means. association that is established by other means.
b) Including only the Kerberos session ticket is insufficient since b) Including only the Kerberos session ticket is insufficient,
freshness is not provided (since the Kerberos Authenticator is because freshness is not provided (since the Kerberos
missing). Obviously there is no guarantee that the user actually Authenticator is missing). Obviously there is no guarantee that
followed the Kerberos protocol and was able to decrypt the received the user actually followed the Kerberos protocol and was able to
TGS_REP (or in rare cases the AS_REP if a session ticket is requested decrypt the received TGS_REP (or in rare cases the AS_REP if a
with the initial AS_REQ). session ticket is requested with the initial AS_REQ).
c) Replay Protection c) Replay Protection
Figure 4 shows the interfaces relevant for replay protection of Figure 4 shows the interfaces relevant for replay protection of
signaling messages in a more complicated architecture. The client signaling messages in a more complicated architecture. In this case,
therefore uses the policy data element with PEP2 since PEP1 is not the client uses the policy data element with PEP2, because PEP1 is
policy aware. The interfaces between the client and the PEP1 and not policy aware. The interfaces between the client and PEP1 and
between the PEP1 and PEP2 are protected with the RSVP INTEGRITY between PEP1 and PEP2 are protected with the RSVP INTEGRITY object.
object. The link between the PEP2 and the PDP is protected for The link between the PEP2 and the PDP is protected, for example, by
example by using the COPS built-in INTEGRITY object. The dotted line using the COPS built-in INTEGRITY object. The dotted line between the
between the Client and the PDP indicates the protection provided by Client and the PDP indicates the protection provided by the AUTH_DATA
the AUTH_DATA element which has no RSVP INTEGRITY object included. element, which has no RSVP INTEGRITY object included.
RSVP Security Properties June 2003
AUTH_DATA +----+ AUTH_DATA +----+
+- - - - - - - - - - - - - - - - - - - - - - - - - -+PDP +-+ +- - - - - - - - - - - - - - - - - - - - - - - - - -+PDP +-+
+----+ | +----+ |
| | | |
| |
| COPS | | COPS |
INTEGRITY| INTEGRITY|
| | | |
| |
skipping to change at page 21, line 28 skipping to change at page 22, line 26
|Client+-------------------+PEP1+----------------------+PEP2+-+ |Client+-------------------+PEP1+----------------------+PEP2+-+
+--+---+ +----+ +-+--+ +--+---+ +----+ +-+--+
| | | |
+-----------------------------------------------------+ +-----------------------------------------------------+
POLICY_DATA INTEGRITY POLICY_DATA INTEGRITY
Figure 4: Replay Protection Figure 4: Replay Protection
Host authentication with the RSVP INTEGRITY object and user Host authentication with the RSVP INTEGRITY object and user
authentication with the INTEGRITY object inside the POLICY_DATA authentication with the INTEGRITY object inside the POLICY_DATA
element both use the same replay mechanism. The length of the element both use the same anti-replay mechanism. The length of the
Sequence Number field, sequence number rollover and the Integrity Sequence Number field, sequence number rollover, and the Integrity
Handshake is already explained in Section 3.1. Handshake have already been explained in Section 3.1.
Section 9 in [RFC3182] states "RSVP INTEGRITY object is used to Section 9 of [RFC3182] states: "RSVP INTEGRITY object is used to
protect the policy object containing user identity information from protect the policy object containing user identity information from
security (replay) attacks.". Using public key based authentication security (replay) attacks." When using public key based
RSVP based replay protection is not supported since the digital authentication, RSVP based replay protection is not supported,
signature does not cover the POLICY_DATA INTEGRITY object with its because the digital signature does not cover the POLICY_DATA
Sequence Number field. The digital signature covers the entire INTEGRITY object with its Sequence Number field. The digital
AUTH_DATA object only. signature covers only the entire AUTH_DATA object.
The usage of public key cryptography within the AUTH_DATA object The use of public key cryptography within the AUTH_DATA object
complicates replay protection. Digital signature computation with PGP complicates replay protection. Digital signature computation with PGP
is described in [PGP] and in [RFC2440]. The data structure preceding is described in [PGP] and in [RFC2440]. The data structure preceding
the signed message digest includes information about the message the signed message digest includes information about the message
digest algorithm used and a 32-bit timestamp when the signature was digest algorithm used and a 32-bit timestamp of when the signature
created ("Signature creation time"). The timestamp is included in the was created ("Signature creation time"). The timestamp is included in
computation of the message digest. The IETF standardized OpenPGP the computation of the message digest. The IETF standardized OpenPGP
version [RFC2440] contains more information and describes the version [RFC2440] contains more information and describes the
different hash algorithms (MD2, MD5, SHA-1, RIPEMD-160) provided. different hash algorithms (MD2, MD5, SHA-1, RIPEMD-160) supported.
[RFC3182] does not make any statements whether the "Signature [RFC3182] does not make any statements as to whether the "Signature
creation time" field is used for replay protection. Using timestamps creation time" field is used for replay protection. Using timestamps
for replay protection requires different synchronization mechanisms for replay protection requires different synchronization mechanisms
in case of clock-screws. Traditionally "loosely" synchronized clocks in the case of clock-skew. Traditionally, these cases assume "loosely
are assumed in those cases but also requires specifying a replay- synchronized" clocks but also require specifying a replay-window.
window.
RSVP Security Properties June 2003
If the "Signature creation time" is not used for replay protection If the "Signature creation time" is not used for replay protection,
then a malicious policy ignorant node can use this weakness to then a malicious, policy-ignorant node can use this weakness to
replace the AUTH_DATA object without destroying the digital replace the AUTH_DATA object without destroying the digital
signature. It is therefore assumed that replay protection of the user signature. If this was not simply an oversight, it is therefore
credentials is not considered as an important security requirement assumed that replay protection of the user credentials was not
since the hop-by-hop processing of the RSVP message protects the considered an important security requirement, because the hop-by-hop
message against modification by an adversary between two processing of the RSVP message protects the message against
communicating nodes. modification by an adversary between two communicating nodes.
The lifetime of the Kerberos ticket is based on the fields starttime The lifetime of the Kerberos ticket is based on the fields starttime
and endtime of the EncTicketPart structure of the ticket as described and endtime of the EncTicketPart structure in the ticket, as
in Section 5.3.1 of [RFC1510]. Since the ticket is created by the KDC described in Section 5.3.1 of [RFC1510]. Because the ticket is
located at the network of the verifying entity it is not difficult to created by the KDC located at the network of the verifying entity, it
have the clocks roughly synchronized for the purpose of lifetime is not difficult to have the clocks roughly synchronized for the
verification. Additional information about clock-synchronization and purpose of lifetime verification. Additional information about clock-
Kerberos can be found at [DG96]. synchronization and Kerberos can be found in [DG96].
If the lifetime of the Kerberos ticket expires then a new ticket must If the lifetime of the Kerberos ticket expires, then a new ticket
be requested and used. Rekeying is implemented with this procedure. must be requested and used. Rekeying is implemented with this
procedure.
d) (User Identity) Confidentiality d) (User Identity) Confidentiality
This section discusses privacy protection of identity information This section discusses privacy protection of identity information
transmitted inside the policy element. Especially user identity transmitted inside the policy element. User identity confidentiality
confidentiality is of interest because there is no built-in RSVP is of particular interest because there is no built-in RSVP mechanism
mechanism for encrypting the POLICY_DATA object or the AUTH_DATA for encrypting the POLICY_DATA object or the AUTH_DATA elements.
elements. Encryption of one of the attributes inside the AUTH_DATA Encryption of one of the attributes inside the AUTH_DATA element, the
element - of the POLICY_LOCATOR attribute is discussed. POLICY_LOCATOR attribute, is discussed.
To protect the users privacy it is important not to reveal the users To protect the user's privacy it is important not to reveal the
identity to an adversary located between the userÆs host and the user's identity to an adversary located between the user's host and
first-hop router (e.g. on a wireless link). User identities should the first-hop router (e.g., on a wireless link). User identities
furthermore not be transmitted outside the domain of the visited should furthermore not be transmitted outside the domain of the
network provider i.e. the user identity information inside the policy visited network provider, i.e., the user identity information inside
data element should be removed or modified by the PDP to prevent the policy data element should be removed or modified by the PDP to
revealing information to other (non-authorized) entities along the prevent revealing its contents to other (non-authorized) entities
signaling path. It is not possible (with the offered mechanisms) to along the signaling path. It is not possible (with the offered
hide the user identity in such a way that it is not visible to the mechanisms) to hide the user's identity in such a way that it is not
first policy aware RSVP node (or to the attached network in general). visible to the first policy-aware RSVP node (or to the attached
network in general).
The ASCII or Unicode distinguished name of user or application inside The ASCII or Unicode distinguished name of user or application inside
the POLICY_LOCATOR attribute of the AUTH_DATA element may be the POLICY_LOCATOR attribute of the AUTH_DATA element may be
encrypted as specified in Section 3.3.1 of [RFC3182]. The user (or encrypted as specified in Section 3.3.1 of [RFC3182]. The user (or
application) identity is then encrypted with either the Kerberos application) identity is then encrypted with either the Kerberos
session key or with the private key in case of public key based session key or with the private key in case of public key based
authentication. Since the private key is used we usually speak of a authentication. When the private key is used, we usually speak of a
digital signature which can be verified by everyone possessing the digital signature that can be verified by everyone possessing the
public key. Since the certificate with the public key is included in public key. Because the certificate with the public key is included
in the message itself, decryption is no obstacle. Furthermore, the
RSVP Security Properties June 2003 included certificate together with the additional (unencrypted)
information in the RSVP message provides enough identity information
the message itself this is no obstacle. Furthermore the included for an eavesdropper. Hence, the possibility of encrypting the policy
certificate provides enough identity information for an eavesdropper locator in case of public key based authentication is problematic. To
together with the additional (unencrypted) information provided in encrypt the identities using asymmetric cryptography, the user's host
the RSVP message. Hence the possibility of encrypting the policy must be able somehow to retrieve the public key of the entity
locator in case of public key based authentication is less obvious. verifying the policy element (i.e., the first policy aware router or
To encrypt the identities using asymmetric cryptography the userÆs the PDP). Then, this public key could be used to encrypt a symmetric
host must be able to somehow retrieve the public key of the entity key, which in turn encrypts the user's identity and certificate, as
verifying the policy element (i.e. the first policy aware router or is done, e.g., by PGP. Currently no such mechanism is defined in
the PDP). Currently no such mechanism is defined in [RFC3182]. [RFC3182].
The algorithm used to encrypt the POLICY_LOCATOR with the Kerberos The algorithm used to encrypt the POLICY_LOCATOR with the Kerberos
session key is assumed to be the same as the one used for encrypting session key is assumed to be the same as the one used for encrypting
the service ticket. The information about the used algorithm is the service ticket. The information about the algorithm used is
available in the etype field of the EncryptedData ASN.1 encoded available in the etype field of the EncryptedData ASN.1 encoded
message part. Section 6.3 of [RFC1510] lists the supported message part. Section 6.3 of [RFC1510] lists the supported
algorithms. [Rae01] defines new encryption algorithms (Rijndael, algorithms. [Rae01] defines new encryption algorithms (Rijndael,
Serpent, and Twofish). Serpent, and Twofish).
Evaluating user identity confidentiality requires also looking at Evaluating user identity confidentiality requires also looking at
protocols executed outside of RSVP (for example to look at the protocols executed outside of RSVP (for example, the Kerberos
Kerberos protocol). The ticket included in the CREDENTIAL attribute protocol). The ticket included in the CREDENTIAL attribute may
may provide user identity protection by not including the optional provide user identity protection by not including the optional cname
cname attribute inside the unencrypted part of the Ticket. Since the attribute inside the unencrypted part of the Ticket. Because the
Authenticator is not transmitted with the RSVP message the cname and Authenticator is not transmitted with the RSVP message, the cname and
the crealm of the unencrypted part of the Authenticator are not the crealm of the unencrypted part of the Authenticator are not
revealed. In order for the user to request the Kerberos session revealed. In order for the user to request the Kerberos session
ticket, for inclusion in the CREDENTIAL attribute, the Kerberos ticket for inclusion in the CREDENTIAL attribute, the Kerberos
protocol exchange must be executed. Then the Authenticator sent with protocol exchange must be executed. Then the Authenticator sent with
the TGS_REQ reveals the identity of the user. The AS_REQ must also the TGS_REQ reveals the identity of the user. The AS_REQ must also
include the user identity to allow the Kerberos Authentication Server include the user's identity to allow the Kerberos Authentication
to respond with an AS_REP message that is encrypted with the user's Server to respond with an AS_REP message that is encrypted with the
secret key. Using Kerberos, it is therefore only possible not to user's secret key. Using Kerberos, it is therefore only possible to
reveal content of the encrypted policy locator, which is only useful hide the content of the encrypted policy locator, which is only
if this value differs from the Kerberos principal name. Hence using useful if this value differs from the Kerberos principal name. Hence
Kerberos it is not "entirely" possible to provide user identity using Kerberos it is not "entirely" possible to provide user identity
confidentiality. confidentiality.
It is important to note that information stored in the policy element It is important to note that information stored in the policy element
may be changed by a policy aware router or by the policy decision may be changed by a policy-aware router or by the policy decision
point. Which parts are changed depends upon whether multicast or point. Which parts are changed depends upon whether multicast or
unicast is used, how the policy server reacts, where the user is unicast is used, how the policy server reacts, where the user is
authenticated and whether he needs to be re-authenticated in other authenticated, whether the user needs to be re-authenticated in other
network nodes etc. Hence user and application specific information network nodes, etc. Hence, user and application specific information
can leak after the messages leave the first hop within the network can leak after the messages leave the first hop within the network
where the user's host is attached. As mentioned at the beginning of where the user's host is attached. As mentioned at the beginning of
this Section this information leakage is assumed to be intentional. this section, this information leakage is assumed to be intentional.
e) Authorization e) Authorization
RSVP Security Properties June 2003 In addition to the description of the authorization steps of the
Host-to-Router interface, user-based authorization is performed with
Additional to the description of the authorization steps of the the policy element providing user credentials. The inclusion of user
Host/Router interface, user based authorization is added with the and application specific information enables policy-based admission
policy element providing user credentials. The inclusion of user and
application specific information enables policy-based admission
control with special user policies that are likely to be stored at a control with special user policies that are likely to be stored at a
dedicated server. Hence a Policy Decision Point can query for example dedicated server. Hence a Policy Decision Point can query, for
a LDAP server for a service level agreement stating the amount of example, a LDAP server for a service level agreement stating the
resources a certain user is allowed to request. Additional to the amount of resources a certain user is allowed to request. In addition
user identity information group membership and other non-security to the user identity information, group membership and other non-
related information may contribute to the evaluation of the final security-related information may contribute to the evaluation of the
policy decision. If the user is not registered to the currently final policy decision. If the user is not registered to the currently
attached domain then there is the question of how much information attached domain, then there is the question of how much information
the home domain of the user is willing to exchange. This also impacts the home domain of the user is willing to exchange. This also impacts
the user's privacy policy. In general the user may not want to the user's privacy policy. In general, the user may not want to
distribute much of his policy information. Furthermore the missing distribute much of this policy information. Furthermore, the lack of
standardized authorization data format may create interoperability a standardized authorization data format may create interoperability
problems when exchanging policy information. Hence we can assume that problems when exchanging policy information. Hence, we can assume
the policy decision point may use information from an initial that the policy decision point may use information from an initial
authentication and key agreement protocol which may already required authentication and key agreement protocol, which may have already
cross-realm communication with the user's home domain to only assume required cross-realm communication with the user's home domain if
that the home domain knows the user and that the user is entitled to only to assume that the home domain knows the user and that the user
roam and to be able to forward accounting messages to this domain. is entitled to roam and to be able to forward accounting messages to
This represents the traditional subscriber based accounting scenario. this domain. This represents the traditional subscriber-based
Non-traditional or alternative means of access might be deployed in accounting scenario. Non-traditional or alternative means of access
the near future that do not require the any type of inter-domain might be deployed in the near future that do not require any type of
communication. inter-domain communication.
Additional discussions are required to determine the expected Additional discussions are required to determine the expected
authorization procedures. [TB+03a] and [TB+03b] discuss authorization authorization procedures. [TB+03a] and [TB+03b] discuss authorization
issues for QoS signaling protocols. Furthermore a number of mobililty issues for QoS signaling protocols. Furthermore, a number of
implications for the policy handling in RSVP are described in mobililty implications for policy handling in RSVP are described in
[Tho02]. [Tho02].
f) Performance f) Performance
If Kerberos is used for user authentication then a Kerberos ticket If Kerberos is used for user authentication, then a Kerberos ticket
must be included in the CREDENTIAL Section of the AUTH_DATA element. must be included in the CREDENTIAL Section of the AUTH_DATA element.
The Kerberos ticket has a size larger than 500 bytes but only needs The Kerberos ticket has a size larger than 500 bytes but only needs
to be sent once since a performance optimization allows the session to be sent once, because a performance optimization allows the
key to be cached as noted in Section 7.1 of [RFC2747]. It is assumed session key to be cached as noted in Section 7.1 of [RFC2747]. It is
that subsequent RSVP messages only include the POLICY_DATA INTEGRITY assumed that subsequent RSVP messages only include the POLICY_DATA
object with a keyed message digest that uses the Kerberos session INTEGRITY object with a keyed message digest that uses the Kerberos
key. This however assumes that the security association required for session key. This, however, assumes that the security association
the POLICY_DATA INTEGRITY object is created after (or modified) to required for the POLICY_DATA INTEGRITY object is created (or
allow the selection of the correct key. Otherwise it difficult to say modified) to allow the selection of the correct key. Otherwise, it
which identifier is used to index the security association. difficult to say which identifier is used to index the security
association.
RSVP Security Properties June 2003
When Kerberos is used as an authentication system then, from a When Kerberos is used as an authentication system then, from a
performance perspective, then the message exchange to obtain the performance perspective, the message exchange to obtain the session
session key needs to be considered although the exchange only needs key needs to be considered, although the exchange only needs to be
to be done once in a long time frame depending on the lifetime of the done once in the lifetime of the session ticket. This is particularly
session ticket. This is particularly true in a mobile environment true in a mobile environment with a fast roaming user's host.
with a fast roaming user's host.
Public key based authentication usually provides the best scalability Public key based authentication usually provides the best scalability
characteristics for key distribution but the protocols are characteristics for key distribution, but the protocols are
performance demanding. A major disadvantage of the public key based performance demanding. A major disadvantage of the public key based
user authentication in RSVP is the non-existing possibility to derive user authentication in RSVP is the lack of a method to derive a
a session key. Hence every RSVP PATH or RESV message includes the session key. Hence every RSVP PATH or RESV message includes the
certificate and a digital signature, which is a huge performance and certificate and a digital signature, which is a huge performance and
bandwidth penalty. For a mobile environment with low performance bandwidth penalty. For a mobile environment with low power devices,
devices, high latency and low bandwidth links this seems to be less high latency, channel noise, and low bandwidth links, this seems to
encouraging. Note that a public key infrastructure is required to be less encouraging. Note that a public key infrastructure is
allow the PDP (or the first-hop router) to verify the digital required to allow the PDP (or the first-hop router) to verify the
signature and the certificate. To check for revoked certificates, digital signature and the certificate. To check for revoked
certificate revocation lists or protocols like the Online Certificate certificates, certificate revocation lists or protocols like the
Status Protocol [RFC2560] and the Simple Certificate Validation Online Certificate Status Protocol [RFC2560] and the Simple
Protocol [MHHF01]. Then the integrity of the AUTH_DATA object via the Certificate Validation Protocol [MHHF01] are needed. Then the
digital signature is verified. integrity of the AUTH_DATA object via the digital signature can be
verified.
4.4 Communication between RSVP aware routers 4.4 Communication between RSVP-Aware Routers
a) Authentication a) Authentication
RSVP signaling messages are data origin authenticated and protected RSVP signaling messages are data origin authenticated and protected
against modification and replay using the RSVP INTEGRITY object. The against modification and replay using the RSVP INTEGRITY object. The
RSVP message flow between routers is protected based on the chain of RSVP message flow between routers is protected based on the chain of
trust and hence each router only needs to have a security association trust and hence each router only needs to have a security association
with its neighboring routers. This assumption was made because of with its neighboring routers. This assumption was made because of
performance advantages and because of special security performance advantages and because of special security
characteristics of the core network where no user hosts are directly characteristics of the core network where no user hosts are directly
attached. In the core network the network structure does not change attached. In the core network the network structure does not change
frequently and the manual distribution of shared secrets for the RSVP frequently and the manual distribution of shared secrets for the RSVP
INTEGRITY object may be acceptable. The shared secrets may be either INTEGRITY object may be acceptable. The shared secrets may be either
manually configured or distributed by using network management manually configured or distributed by using appropriately secured
protocols like SNMP. network management protocols like SNMPv3.
Independent of the key distribution mechanism host authentication Independent of the key distribution mechanism, host authentication
with RSVP built-in mechanisms is accomplished with the keyed message with RSVP built-in mechanisms is accomplished with the keyed message
digest in the RSVP INTEGRITY object computed using the previously digest in the RSVP INTEGRITY object computed using the previously
exchanged symmetric key. exchanged symmetric key.
b) Integrity Protection b) Integrity Protection
Integrity protection is accomplished with the RSVP INTEGRITY object Integrity protection is accomplished with the RSVP INTEGRITY object
with the variable length Keyed Message Digest field. with the variable length Keyed Message Digest field.
RSVP Security Properties June 2003
c) Replay Protection c) Replay Protection
Replay protection with the RSVP INTEGRITY object is extensively Replay protection with the RSVP INTEGRITY object is extensively
described in previous sections. described in previous sections.
To enable crashed hosts to learn the latest sequence number used the To enable crashed hosts to learn the latest sequence number used, the
Integrity Handshake mechanism is used in RSVP. Integrity Handshake mechanism is provided in RSVP.
d) Confidentiality d) Confidentiality
Confidentiality is not provided by RSVP. Confidentiality is not provided by RSVP.
e) Authorization e) Authorization
Depending on the RSVP network QoS resource authorization at different Depending on the RSVP network, QoS resource authorization at
routers may need to contact the PDP again. Since the PDP is allowed different routers may need to contact the PDP again. Because the PDP
to modify the policy element, a token may be added to the policy is allowed to modify the policy element, a token may be added to the
element to increase the efficiency of the re-authorization procedure. policy element to increase the efficiency of the re-authorization
This token is used to refer to an already computed policy decision. procedure. This token is used to refer to an already computed policy
The communications interface from the PEP to the PDP must be properly decision. The communications interface from the PEP to the PDP must
secured. be properly secured.
f) Performance f) Performance
The performance characteristics the protection of the RSVP signaling The performance characteristics for the protection of the RSVP
messages is largely determined by the key exchange protocol since the signaling messages is largely determined by the key exchange
RSVP INTEGRITY object is only used to compute a keyed message digest protocol, because the RSVP INTEGRITY object is only used to compute a
of the transmitted signaling messages. keyed message digest of the transmitted signaling messages.
The security associations within the core network i.e. between The security associations within the core network, i.e., between
individual routers (in comparison to the security association between individual routers (in comparison with the security association
the userÆs host and the first-hop router or with the attached network between the user's host and the first-hop router or with the attached
in general) can be established more easily because of the strong network in general) can be established more easily because of the
trust assumptions. Furthermore it is possible to use security normally strong trust assumptions. Furthermore, it is possible to use
associations with an increased lifetime to avoid too frequent security associations with an increased lifetime to avoid frequent
rekeying. Hence there is less impact for the performance compared to rekeying. Hence, there is less impact on the performance compared
the user to network interface. The security association storage with the user-to-network interface. The security association storage
requirements are also less problematic. requirements are also less problematic.
5. Miscellaneous Issues 5. Miscellaneous Issues
This section describes a number of issues which illustrate some of This section describes a number of issues that illustrate some of the
the short-comings of RSVP with respect to security. shortcomings of RSVP with respect to security.
5.1 First Hop Issue 5.1 First Hop Issue
In case of end-to-end signaling an end host starts signaling to its In case of end-to-end signaling, an end host starts signaling to its
attached network. The first-hop communication is often more difficult attached network. The first-hop communication is often more difficult
to secure because of the different requirements and a missing trust
RSVP Security Properties June 2003
because of the different requirements and a missing trust
relationship. An end host must therefore obtain some information to relationship. An end host must therefore obtain some information to
start RSVP signaling: start RSVP signaling:
- Does this network support RSVP signaling? - Does this network support RSVP signaling?
- Which node supports RSVP signaling? - Which node supports RSVP signaling?
- To which node is authentication required? - To which node is authentication required?
- Which security mechanisms are used for authentication? - Which security mechanisms are used for authentication?
- Which algorithms have to be used? - Which algorithms have to be used?
- Where should the keys/security association come from? - Where should the keys and security association come from?
- Should a security association be established? - Should a security association be established?
RSVP, as specified today, is used as a building block. Hence these RSVP, as specified today, is used as a building block. Hence, these
questions have to be answered as part of overall architectural questions have to be answered as part of overall architectural
considerations. Without giving an answer to this question "ad-hoc" considerations. Without giving an answer to this question, ad hoc
RSVP communication by an end host roaming to an unknown network is RSVP communication by an end host roaming to an unknown network is
not possible. A negotiation of security mechanisms and algorithms is not possible. A negotiation of security mechanisms and algorithms is
not supported for RSVP. not supported for RSVP.
5.2 Next-Hop Problem 5.2 Next-Hop Problem
Throughout the document it was always assumed that the next RSVP node Throughout the document it was assumed that the next RSVP node along
along the path is always known. Knowing your next hop is important to the path is always known. Knowing your next hop is important to be
be able to select the correct key for the RSVP Integrity object to able to select the correct key for the RSVP Integrity object and to
provide proper protection. In case that an RSVP node assumes to know apply the proper protection. In case in which an RSVP node assumes it
which node is the next hop then the following protocol exchange can knows which node is the next hop the following protocol exchange can
occur: occur:
Integrity Integrity
(A<->C) +------+ (A<->C) +------+
(3) | RSVP | (3) | RSVP |
+------------->+ Node | +------------->+ Node |
| | B | | | B |
Integrity | +--+---+ Integrity | +--+---+
(A<->C) | | (A<->C) | |
+------+ (2) +--+----+ | +------+ (2) +--+----+ |
skipping to change at page 28, line 5 skipping to change at page 29, line 25
| A +<-----------+Network| (4) | A +<-----------+Network| (4)
+------+ (5) +--+----+ +------+ (5) +--+----+
Error . Error .
(I am B) . +------+ (I am B) . +------+
. | RSVP | . | RSVP |
...............+ Node | ...............+ Node |
| C | | C |
+------+ +------+
Figure 5: Next-Hop Issue Figure 5: Next-Hop Issue
RSVP Security Properties June 2003 When RSVP node A in Figure 5 receives an incoming RSVP Path message,
standard RSVP message processing takes place. Node A then has to
When RSVP node A in Figure 5 receives an incoming RSVP Path message
then standard RSVP message processing takes place. Node A then has to
decide which key to select to protect the signaling message. We decide which key to select to protect the signaling message. We
assume that some mechanism which is not further specified is used to assume that some unspecified mechanism is used to make this decision.
make this decision. In this example node A assumes that the message In this example node A assumes that the message will travel to RSVP
will travel to RSVP node C. However because of some reasons (e.g. a node C. However, because of some reasons (e.g. a route change,
route change, inability to learn the next RSVP hop along the path, inability to learn the next RSVP hop along the path, etc.) the
etc.) the message travels to node B via a non-RSVP supporting router message travels to node B via a non-RSVP supporting router that
which cannot verify the integrity of the message (or cannot decrypt cannot verify the integrity of the message (or cannot decrypt the
the Kerberos service ticket). The processing failure causes a PathErr Kerberos service ticket). The processing failure causes a PathErr
message to be returned to the originating sender of the Path message. message to be returned to the originating sender of the Path message.
This error message also contains information about the node This error message also contains information about the node
recognizing the error. In many cases a security association might not recognizing the error. In many cases a security association might not
be available. Node A receiving the PathErr message might use the be available. Node A receiving the PathErr message might use the
information returned with the PathErr message to select a different information returned with the PathErr message to select a different
security association (or to establish one). security association (or to establish one).
Figure 5 describes a behavior which might help node A to learn that Figure 5 describes a behavior that might help node A learn that an
an error occured. However, the description of Section 4.2 of error occurred. However, the description of Section 4.2 of [RFC2747]
[RFC2747] describes in step (5) that a signaling message is silently describes in step (5) that a signaling message is silently discarded
discarded if the receiving host cannot properly verify the message: if the receiving host cannot properly verify the message: "If the
"If the calculated digest does not match the received digest, the calculated digest does not match the received digest, the message is
message is discarded without further processing." For RSVP Path alike discarded without further processing." For RSVP Path and similar
messages this functionality is not really helpful. messages this functionality is not really helpful.
The RSVP Path message therefore provides a number of functions: path The RSVP Path message therefore provides a number of functions: path
discovery, detecting route changes, learning of QoS capabilities discovery, detecting route changes, learning of QoS capabilities
along the path using the Adspec object, (with some interpretation) along the path using the Adspec object, (with some interpretation)
next-hop discovery and possibly security association establishment next-hop discovery, and possibly security association establishment
(for example in case of Kerberos). (for example, in the case of Kerberos).
From a security point of view there is a conflict between From a security point of view there is a conflict between
- Idempotent messages delivery and efficiency - Idempotent message delivery and efficiency
Especially the RSVP Path message performs a number of functions. The RSVP Path message especially performs a number of functions.
Supporting idempotent message delivery somehow contradicts with Supporting idempotent message delivery somehow contradicts with
security association establishment and efficient message delivery and security association establishment, efficient message delivery, and
size. For example a "real" idempotent signaling message would contain message size. For example, a "real" idempotent signaling message
enough information to perform security processing without depending would contain enough information to perform security processing
on a previously executed message exchange. Adding a Kerberos ticket without depending on a previously executed message exchange. Adding a
with every signaling message is, however, very inefficient. Using Kerberos ticket with every signaling message is, however,
public key based mechanisms is even more inefficient when included in inefficient. Using public key based mechanisms is even more
every signaling message. With public key based protection for inefficient when included in every signaling message. With public key
idempotent messages there is additionally a risk of introducing based protection for idempotent messages, there is additionally a
denial of service attacks. risk of introducing denial of service attacks.
- RSVP Path message functionality and next-hop discovery - RSVP Path message functionality and next-hop discovery
RSVP Security Properties June 2003
To protect an RSVP signaling message (and a RSVP Path message in To protect an RSVP signaling message (and a RSVP Path message in
particular) it is necessary to know the identity of the next RSVP particular) it is necessary to know the identity of the next RSVP-
aware node (and some other parameters). Without a mechanism for next- aware node (and some other parameters). Without a mechanism for next-
hop discovery an RSVP Path message is also responsible for this task. hop discovery, an RSVP Path message is also responsible for this
Without knowing the identity of the next hop the Kerberos principal task. Without knowing the identity of the next hop, the Kerberos
name is also unknown. The so-called Kerberos user-to-user principal name is also unknown. The so-called Kerberos user-to-user
authentication mechanism is not supported which would allow the authentication mechanism, which would allow the receiver to trigger
receiver to trigger the process of establishing Kerberos the process of establishing Kerberos authentication, is not
authentication is not supported. This issue will again be discussed supported. This issue will again be discussed in relationship with
in relationship with the last-hop problem. the last-hop problem.
It is fair to assume that a RSVP supporting node might not have a It is fair to assume that a RSVP-supporting node might not have
security association with all immediately neighboring RSVP nodes. security associations with all immediately neighboring RSVP nodes.
Especially for inter-domain signaling, IntServ over DiffServ or for Especially for inter-domain signaling, IntServ over DiffServ, or some
some new applications such as firewall signaling the next RSVP aware new applications such as firewall signaling, the next RSVP-aware node
node might not be known in advance. The number of next RSVP nodes might not be known in advance. The number of next RSVP nodes might be
might be considerably large if they are separated by a large number considerably large if they are separated by a large number of non-
of non-RSVP aware nodes. Hence a node transmitting a RSVP Path RSVP aware nodes. Hence, a node transmitting a RSVP Path message
message might experience difficulties to properly protect the message might experience difficulties in properly protecting the message if
if it serves as a mechanism to detect both the next RSVP node (i.e. it serves as a mechanism to detect both the next RSVP node (i.e.,
Router Alert Option added to the signaling message and addressed to Router Alert Option added to the signaling message and addressed to
the destination address) and to detect route changes. It is fair to the destination address) and to detect route changes. It is fair to
note that in an intra-domain case this might be possible due to note that in an intra-domain case with a dense distribution of RSVP
manual configuration in case of a dense distribution of RSVP nodes. nodes this might be possible with manual configuration.
There is nothing which prevents an adversary from continuously Nothing prevents an adversary from continuously flooding an RSVP node
flooding an RSVP node with bogus PathErr messages. It might be with bogus PathErr messages, although it might be possible to protect
possible to protect the PathErr message with an existing security the PathErr message with an existing, available security association.
association if available. A legitimate RSVP node would believe that a
change in the path took place. Hence this node would try to select a A legitimate RSVP node would believe that a change in the path took
different security association or try to create one with the place. Hence, this node might try to select a different security
indicated node. Hence an adversary can send a PathErr message at any association or try to create one with the indicated node. If an
time to confuse an RSVP node. If an adversary is located somewhere adversary is located somewhere along the path and either
along the path then it might also be possible to act as a man-in-the- authentication or authorization is not performed with the necessary
middle adversary if either authentication or authorization is not strength and accuracy, then it might also be possible to act as a
performed with the necessary accuracy. man-in-the-middle. One method of reducing susceptibility to this
attack is as follows: when a PathErr message is received from a node
with which no security association exists, attempt to establish a
security association and then repeat the action that led to the
PathErr message.
5.3 Last-Hop Issue 5.3 Last-Hop Issue
This section tries to address practical difficulties when This section tries to address practical difficulties when
authentication and key establishment is accomplished with a protocol authentication and key establishment are accomplished with a two-
which shows some asymmetry in message processing when executed party protocol that shows some asymmetry in message processing.
between two nodes. Kerberos is such a protocol and also the only Kerberos is such a protocol and also the only supported protocol that
supported protocol which provides dynamic session key establishment provides dynamic session key establishment for RSVP. For first-hop
for RSVP. For first-hop communication authentication is typically communication, authentication is typically done between a user and
done between a user and some network in the network (for example the some router (for example the access router). Especially in a mobile
access router). Especially in a mobile environment it is not feasible environment, it is not feasible to authenticate end hosts based on
to authenticate end hosts based on their IP or MAC address. To show their IP or MAC address. To illustrate this problem, the typical
processing steps for Kerberos are shown for first-hop communication:
RSVP Security Properties June 2003
the problem the typical processing steps for Kerberos are shown for
first-hop communication:
a) The end host A learns the identity (i.e. Kerberos principal name) a) The end host A learns the identity (i.e., Kerberos principal name)
of some entity B. This entity B is either the next RSVP node or a PDP of some entity B. This entity B is either the next RSVP node, a PDP,
or the next policy aware RSVP node. or the next policy-aware RSVP node.
b) Entity A then requests a ticket granting ticket for the network b) Entity A then requests a ticket granting ticket for the network
domain. This assumes that the identity of the network domain is domain. This assumes that the identity of the network domain is
known. known.
c) Entity A then requests a service ticket for entity B which was c) Entity A then requests a service ticket for entity B, whose name
learned in step (a). was learned in step (a).
d) Entity A includes the service ticket to the RSVP signaling message d) Entity A includes the service ticket with the RSVP signaling
(inside the policy object). The Kerberos session key is used to message (inside the policy object). The Kerberos session key is used
protect the entire RSVP signaling message. to protect the integrity of the entire RSVP signaling message.
For last-hop communication this processing step theoretically has to For last-hop communication this processing step theoretically has to
be reversed; entity A is then a node in the network (for example the be reversed; entity A is then a node in the network (for example the
access router) and entity B is the other end host. This assumes that access router) and entity B is the other end host (under the
RSVP signaling is accomplished between two end hosts and not between assumption that RSVP signaling is accomplished between two end hosts
an end host and a application server. The access router might however and not between an end host and a application server). The access
in step (a) not be able to learn the identity of the user's principal router might, however, in step (a) not be able to learn the user's
name since this information might not be available. Entity A could principal name, because this information might not be available.
reverse the process by triggering an IAKERB exchange. This would Entity A could reverse the process by triggering an IAKERB exchange.
cause entity B to request a service ticket for A as described above.
IAKERB is however not supported. This would cause entity B to request a service ticket for A as
described above. IAKERB is however not supported in RSVP.
5.4 RSVP and IPsec protected data traffic 5.4 RSVP and IPsec protected data traffic
QoS signaling requires flow information to be established at routers QoS signaling requires flow information to be established at routers
along a path. This flow identifier installed at each device tells the along a path. This flow identifier installed at each device tells the
router which data packets should experience QoS treatment. RSVP router which data packets should receive QoS treatment. RSVP
typically establishes a flow identifier based on the 5-tuple (source typically establishes a flow identifier based on the 5-tuple (source
IP address, destination IP address, transport protocol type, source IP address, destination IP address, transport protocol type, source
port and destination port). If this 5-tuple information is not port, and destination port). If this 5-tuple information is not
available then other identifiers have to be used. IPsec protected available, then other identifiers have to be used. IPsec-protected
data traffic is such an example where the transport protocol and the data traffic is such an example where the transport protocol and the
port numbers are not accessible. Hence the IPsec SPI is used as a port numbers are not accessible. Hence the IPsec SPI is used as a
substitute for them. RFC 2207 considers these IPsec implications for substitute for them. RFC 2207 considers these IPsec implications for
RSVP and is based on three assumptions: RSVP and is based on three assumptions:
a) An end host, which initiates the RSVP signaling message exchange, a) An end host, which initiates the RSVP signaling message exchange,
has to be able to retrieve the SPI for given flow. This requires some has to be able to retrieve the SPI for given flow. This requires some
interaction with the IPsec SADB and SPD. An application usually does interaction with the IPsec security association database (SAD) and
security policy database (SPD) [RFC2401]. An application usually does
not know the SPI of the protected flow and cannot provide the desired not know the SPI of the protected flow and cannot provide the desired
values. It can provide the signaling protocol daemon with flow values. It can provide the signaling protocol daemon with flow
identifiers. The signaling daemon would then need to query the IPsec identifiers. The signaling daemon would then need to query the SAD by
providing the flow identifiers as input parameters and the SPI as an
RSVP Security Properties June 2003 output parameter.
security association database by providing the flow identifiers as
input parameters and the SPI as an output parameter.
b) RFC 2207 assumes an end-to-end IPsec protection of the data b) RFC 2207 assumes end-to-end IPsec protection of the data traffic.
traffic. In IPsec is applied in a nested fashion then parts of the If IPsec is applied in a nested fashion, then parts of the path do
path do not experience QoS treatment. This problem can be treated as not experience QoS treatment. This can be treated as a tunneling
a tunneling problem but is initiated by the end host. A figure better problem, but it is initiated by the end host. A figure better
illustrates the problem in case of enforcing secure network access: illustrates the problem in the case of enforcing secure network
access:
+------+ +---------------+ +--------+ +------+ +------+ +---------------+ +--------+ +------+
| Host | | Security | | Router | | Host | | Host | | Security | | Router | | Host |
| A | | Gateway (SGW) | | Rx | | B | | A | | Gateway (SGW) | | Rx | | B |
+--+---+ +-------+-------+ +----+---+ +--+---+ +--+---+ +-------+-------+ +----+---+ +--+---+
| | | | | | | |
|IPsec-Data( | | | |IPsec-Data( | | |
| OuterSrc=A, | | | | OuterSrc=A, | | |
| OuterDst=SGW, | | | | OuterDst=SGW, | | |
| SPI=SPI1, | | | | SPI=SPI1, | | |
skipping to change at page 31, line 44 skipping to change at page 33, line 33
| | | SrcPort=Y, | | | | SrcPort=Y, |
| | | DstPort=Z) | | | | DstPort=Z) |
| | |---------------->| | | |---------------->|
| | | | | | | |
| | --Unprotected data traffic-> | | | --Unprotected data traffic-> |
| | | | | | | |
Figure 6: RSVP and IPsec protected data traffic Figure 6: RSVP and IPsec protected data traffic
Host A transmitting data traffic would either indicate a 3-tuple <A, Host A transmitting data traffic would either indicate a 3-tuple <A,
SGW, SPI1> or a 5-tuple <A, B, X, Y, Z>. In any case it is not SGW, SPI1> or a 5-tuple <A, B, X, Y, Z>. In any case it is not
possible to make a QoS reservation for the entire path. Similar possible to make a QoS reservation for the entire path. Two similar
examples are remote access using a VPN, protection of data traffic examples are remote access using a VPN and protection of data traffic
between the home agent (or a security gateway in the home network) between a home agent (or a security gateway in the home network) and
and the mobile node and other. With a nested application of IPsec a mobile node. With a nested application of IPsec (for example, IPsec
(for example IPsec between A and SGW and between A and B) the same between A and SGW and between A and B) the same problem occurs.
problem occurs.
One possible solution to this problem is to change the flow One possible solution to this problem is to change the flow
identifier along the path to capture the new flow identifier after an identifier along the path to capture the new flow identifier after an
IPsec endpoint. IPsec endpoint.
RSVP Security Properties June 2003 IPsec tunnels that neither start nor terminate at one of the
IPsec tunnels which neither start nor terminate at one of the
signaling end points (for example between two networks) should be signaling end points (for example between two networks) should be
addressed differently by recursively applying an RSVP signaling addressed differently by recursively applying an RSVP signaling
exchange for the IPsec tunnel. RSVP signaling within tunnels is exchange for the IPsec tunnel. RSVP signaling within tunnels is
addressed in [RFC2746]. addressed in [RFC2746].
c) It is assumed that SPIs do not change during the lifetime of the c) It is assumed that SPIs do not change during the lifetime of the
established QoS reservation. If a new IPsec SA is created then a new established QoS reservation. If a new IPsec SA is created, then a new
SPI is allocated for the security association. To reflect this change SPI is allocated for the security association. To reflect this
either a new reservation has to be established or the flow identifier change, either a new reservation has to be established or the flow
of the existing reservation has to be updated. Since IPsec SAs have a identifier of the existing reservation has to be updated. Because
longer lifetime this issue does not seem to be a major issue. IPsec IPsec SAs usually have a longer lifetime, this does not seem to be a
protection of SCTP data traffic might more often require an IPsec SA major issue. IPsec protection of SCTP data traffic might more often
(and an SPI) change to reflect added and removed IP addresses from an require an IPsec SA (and an SPI) change to reflect added and removed
SCTP association. IP addresses from an SCTP association.
5.5 End-to-End Security Issues and RSVP 5.5 End-to-End Security Issues and RSVP
End-to-end security for RSVP has not been discussed throughout the End-to-end security for RSVP has not been discussed throughout the
document. In this context end-to-end security refers to credentials document. In this context end-to-end security refers to credentials
transmitted between the two end hosts using RSVP. It is obvious that transmitted between the two end hosts using RSVP. It is obvious that
care must be taken to ensure that routers along the path are able to care must be taken to ensure that routers along the path are able to
process and modify the signaling messages according to the processing process and modify the signaling messages according to prescribed
procedure. Some objects however could be used for end-to-end processing procedures. Some objects or mechanisms, however, could be
protection. The main question however is what the benefit of such an used for end-to-end protection. The main question however is what the
end-to-end security is. First there is the question how to establish benefit of such an end-to-end security is. First, there is the
the required security association. Between two arbitrary hosts on the question of how to establish the required security association.
Internet this might turn out to be quite difficult. Furthermore it Between two arbitrary hosts on the Internet this might turn out to be
depends on an architecture where RSVP is deployed whether it is quite difficult. Furthermore, te usefulness of end-to-end security
useful to provide end-to-end security. If RSVP is only used to signal depends on the architecture in which RSVP is deployed. If RSVP is
QoS information into the network and other protocols have to be only used to signal QoS information into the network, and other
executed beforehand to negotiate the parameters and to decide which protocols have to be executed beforehand to negotiate the parameters
entity is charged for the QoS reservation then no end-to-end security and to decide which entity is charged for the QoS reservation, then
is likely to be required. Introducing end-to-end security to RSVP no end-to-end security is likely to be required. Introducing end-to-
would then cause problems with extensions like RSVP proxy [GD+02], end security to RSVP would then cause problems with extensions like
Localized RSVP [MS+02] and others which terminate RSVP signaling RSVP proxy [GD+02], Localized RSVP [MS+02], and others that terminate
somewhere along the path without reaching the destination end host. RSVP signaling somewhere along the path without reaching the
Such a behavior could then be interpreted as a man-in-the-middle destination end host. Such a behavior could then be interpreted as a
attack. man-in-the-middle attack.
5.6 IPsec protection of RSVP signaling messages 5.6 IPsec protection of RSVP signaling messages
In this document it was assumed that RSVP signaling messages can also It is assumed throughout that RSVP signaling messages can also be
be protected by IPsec [RFC2401] in a hop-by-hop fashion between two protected by IPsec [RFC2401] in a hop-by-hop fashion between two
adjacent RSVP nodes. RSVP uses a special processing of signaling adjacent RSVP nodes. RSVP, however, uses special processing of
messages which complicates IPsec protection. As we explain in this signaling messages, which complicates IPsec protection. As explained
section IPsec should only be used for protection of RSVP signaling in this section, IPsec should only be used for protection of RSVP
messages in a point-to-point communication environment (i.e. a RSVP signaling messages in a point-to-point communication environment
message can only reach one RSVP router and not possibly more than (i.e., a RSVP message can only reach one RSVP router and not possibly
more than one). This restriction is caused by the combination of
RSVP Security Properties June 2003 signaling message delivery and discovery into a single message.
Furthermore, end-to-end addressing complicates IPsec handling
one). This circumstance is caused by the combination of signaling considerably. This section describes at least some of these
message delivery and discovery into a single message. Furthermore the complications.
end-to-end addressing complicates IPsec handling considerably. This
section tries to describe these complications.
RSVP messages are transmitted as raw IP packets with protocol number RSVP messages are transmitted as raw IP packets with protocol number
46. It might be possible to encapsulate them in UDP as described in 46. It might be possible to encapsulate them in UDP as described in
Appendix C of [RFC2205]. Some RSVP messages (Path, PathTear, and Appendix C of [RFC2205]. Some RSVP messages (Path, PathTear, and
ResvConf) must have the Router Alert IP Option set in the IP header. ResvConf) must have the Router Alert IP Option set in the IP header.
These messages are addressed to the (unicast or multicast) These messages are addressed to the (unicast or multicast)
destination address and not to the next RSVP node along the path. destination address and not to the next RSVP node along the path.
Hence an IPsec traffic selector can only use these fields for IPsec Hence an IPsec traffic selector can only use these fields for IPsec
SA selection. If there is only a single path (and possibly every SA selection. If there is only a single path (and possibly all
traffic is protected) then there is no problem for IPsec protection traffic along it is protected) then there is no problem for IPsec
of signaling messages. This type of protection is not common and protection of signaling messages. This type of protection is not
might only be used to secure network access between an end host and common and might only be used to secure network access between an end
its first-hop router. Since the described RSVP messages are addressed host and its first-hop router. Because the described RSVP messages
to the destination address instead of the next RSVP node it is not are addressed to the destination address instead of the next RSVP
possible to use IPsec ESP [RFC2406] or AH [RFC2402] in transport node, it is not possible to use IPsec ESP [RFC2406] or AH [RFC2402]
mode - only IPsec in tunnel mode is possible. in transport mode--only IPsec in tunnel mode is possible.
If there is more than one possible path which an RSVP message can If there is more than one possible path an RSVP message can take,
take then the IPsec engine will experience difficulties to protect then the IPsec engine will experience difficulties protecting the
the message. Even if the RSVP daemon installs a traffic selector with message. Even if the RSVP daemon installs a traffic selector with the
the destination IP address then still there is no distinguishing destination IP address, still, no distinguishing element allows
element which allows to select the correct security association of selection of the correct security association for one of the possible
one of the possible RSVP nodes along. Even if it possible to apply RSVP nodes along the path. Even if it possible to apply IPsec
IPsec protection (in tunnel mode) for RSVP signaling messages by protection (in tunnel mode) for RSVP signaling messages by
incorporating some additional information then there is still the incorporating some additional information, there is still the
possibility that the tunneled messages do not recognize a path change possibility that the tunneled messages do not recognize a path change
in a non-RSVP router. Then the signaling messages would simply follow in a non-RSVP router. In this case the signaling messages would
different path than the data. simply follow a different path than the data.
RSVP messages like RESV can be protected by IPsec since they are RSVP messages like RESV can be protected by IPsec, because they
contain enough information to create IPsec traffic selectors which contain enough information to create IPsec traffic selectors allowing
allow a differentiation between different next RSVP nodes. A traffic differentiation between various next RSVP nodes. The traffic selector
selector would then contain the protocol number and the source / would then contain the protocol number and the source and destination
destination address pair of the two communicating RSVP nodes. address pair of the two communicating RSVP nodes.
The benefit of using IPsec is the available key management using One benefit of using IPsec is the availability of key management
either IKE [RFC2409], KINK [FH+01] or IKEv2 [IKEv2]. using either IKE [RFC2409], KINK [FH+01] or IKEv2 [IKEv2].
5.7 Authorization 5.7 Authorization
In [TB+03a] two trust models (NJ Turnpike and NJ Parkway model) and [TB+03a] describes two trust models (NJ Turnpike and NJ Parkway) and
two authorization models (per-session and per-channel financial two authorization models (per-session and per-channel financial
settlement). The NJ Turnpike model gives a justification for the hop- settlement). The NJ Turnpike model gives a justification for hop-by-
by-hop security protection. RSVP supports the NJ Parkway model and hop security protection. RSVP supports the NJ Parkway model and per-
per-channel financial settlement to some extend only. The channel financial settlement only to a certain extent. The
communication procedures defined for policy objects [Her95] can be
RSVP Security Properties June 2003
communication procedures defined for policy object [Her95] can be
improved to support the more efficient per-channel financial improved to support the more efficient per-channel financial
settlement by avoiding policy handling between inter-domain networks settlement model by avoiding policy handling between inter-domain
at a signaling message granularity. Additional information about networks at a signaling message granularity. Additional information
expected behavior of policy handling in RSVP can also be obtained in about expected behavior of policy handling in RSVP can also be
[Her96]. obtained from [Her96].
[TB+03b] and [Tho02] provide additional information on authorization. [TB+03b] and [Tho02] provide additional information on authorization.
6. Conclusions 6. Conclusions
RSVP was the first QoS signaling protocol which provided some RSVP was the first QoS signaling protocol that provided some security
security protection. Whether RSVP provides enough security protection protection. Whether RSVP provides enough security protection heavily
heavily depends on the environment where it is deployed. As RSVP is depends on the environment where it is deployed. RSVP as specified
specified today should be seen as a building block that has to be today should be seen as a building block that has to be adapted to a
adapted to a given architecture. given architecture.
This document aims to provide more insights into the security of This document aims to provide more insights into the security of
RSVP. It cannot not be interpreted as a pass or fail evaluation of RSVP. It cannot not be interpreted as a pass or fail evaluation of
the security provided by RSVP. the security provided by RSVP.
Certainly this document is not complete to describe all security Certainly this document is not a complete description of all security
issues related to RSVP. Some issues that require further issues related to RSVP. Some issues that require further
considerations are RSVP extensions (for example [RFC2207]), multicast consideration are RSVP extensions (for example [RFC2207]), multicast
issues and other security properties like traffic analysis etc. issues, and other security properties like traffic analysis.
Additionally the interaction with mobility protocols (micro- and Additionally, the interaction with mobility protocols (micro- and
macro-mobility) from a security point of view demands further macro-mobility) from a security point of view demands further
investigation. investigation.
What can be learned from a practical protocol experience and from the What can be learned from practical protocol experience and from the
increased awareness regarding security is that some of the available increased awareness regarding security is that some of the available
credential types have received more acceptance. Kerberos is such a credential types have received more acceptance than others. Kerberos
system which is integrated in many IETF protocols today. is a system that is integrated into many IETF protocols today.
Public key based authentication techniques are however still Public key based authentication techniques are however still
considered to be too heavy-weight (computationally and from a considered to be too heavy-weight (computationally and from a
bandwidth perspective) to be used for a per-flow signaling. The bandwidth perspective) to be used for per-flow signaling. The
increased focus on denial of service attacks additionally demands a increased focus on denial of service attacks put additional demands
closer look on public key based authentication. on the design of public key based authentication.
The following list briefly summarizes a few security or architectural The following list briefly summarizes a few security or architectural
issues which desire improvement: issues that deserve improvement:
* Discovery and signaling message delivery should be separated. * Discovery and signaling message delivery should be separated.
* For some applications and scenarios it cannot be assumed that * For some applications and scenarios it cannot be assumed that
neighboring RSVP aware nodes know each other. Hence some in-path neighboring RSVP-aware nodes know each other. Hence some in-path
discovery mechanism should be provided. discovery mechanism should be provided.
RSVP Security Properties June 2003
* Addressing for signaling messages should be done in a hop-by-hop * Addressing for signaling messages should be done in a hop-by-hop
fashion. fashion.
* Standard security protocols (IPsec, TLS or CMS) should be used * Standard security protocols (IPsec, TLS or CMS) should be used
whenever possible. Authentication and key exchange should separated whenever possible. Authentication and key exchange should be
from signaling message protection. In general it is necessary to separated from signaling message protection. In general, it is
provide key management to dynamically establish a security necessary to provide key management to establish security
association for signaling message protection. Relying on manually associations dynamically for signaling message protection. Relying
configured keys between neighboring RSVP nodes is insufficient. on manually configured keys between neighboring RSVP nodes is
insufficient. A separate, less frequently executed key management
and security association establishment protocol is a good place to
perform entity authentication, security service negotiation and
selection, and agreement on mechanisms, transforms, and options.
* The usage of public key cryptography for authorization tokens, * The use of public key cryptography in authorization tokens,
identity representation, selective object protection, etc. is likely identity representations, selective object protection, etc. is
to cause fragmentation and problems. likely to cause fragmentation, the need to protect against denial
of service attacks, and other problems.
* Public key authentication and user identity confidentiality * Public key authentication and user identity confidentiality
provided with RSVP require some improvement. provided with RSVP require some improvement.
* Public key based user authentication only provides entity * Public key based user authentication only provides entity
authentication. An additional security association is required to authentication. An additional security association is required to
protect the signaling message. protect signaling messages.
* Data origin authentication should not be provided by non-RSVP nodes * Data origin authentication should not be provided by non-RSVP nodes
(such as the PDP). Such a procedure could be accomplished by entity (such as the PDP). Such a procedure could be accomplished by entity
authentication during the authentication and key exchange phase. authentication during the authentication and key exchange phase.
* Authorization and charging should be better integrated in the base * Authorization and charging should be better integrated into the
protocol. base protocol.
* Selective message protection should be provided. A protected * Selective message protection should be provided. A protected
message should be recognizable from a flag in the header. message should be recognizable from a flag in the header.
* Confidentiality protection is missing and should therefore be added * Confidentiality protection is missing and should therefore be added
to the protocol. to the protocol. The general principle is that protocol designers
can seldom foresee all of the environments in which protocols will
be run, so they should allow users to select from a full range of
security services, as the needs of different user communities vary.
* Parameter and mechanism negotiation should be provided. * Parameter and mechanism negotiation should be provided.
7. Security Considerations 7. Security Considerations
This document discusses security properties of RSVP and as such, it This document discusses security properties of RSVP and, as such, it
is concerned entirely with security. is concerned entirely with security.
8. IANA considerations 8. IANA considerations
This document does not address any IANA considerations. This document does not address any IANA considerations.
9. Acknowledgments 9. Acknowledgments
I would like to thank Jorge Cuellar, Robert Hancock, Xiaoming Fu and We would like to thank Jorge Cuellar, Robert Hancock, Xiaoming Fu,
Guenther Schaefer for their valuable comments. Additionally I would Guenther Schaefer, Marc De Vuyst and Jukka Manner for their valuable
comments. Additionally, we would like to thank Robert and Jorge for
RSVP Security Properties June 2003 their time to discuss various issues with me.
like to thank Robert and Jorge for their time to discuss various Finally we would Allison Mankin and John Loughney for their comments.
issues with me. Furthermore I would like to thank Marc De Vuyst and
Jukka Manner for their comments to this draft.
Appendix A: Dictionary Attacks and Kerberos Appendix A: Dictionary Attacks and Kerberos
Kerberos might be used with RSVP as described in this document. Since Kerberos might be used with RSVP as described in this document.
dictionary attacks are often mentioned in relationship with Kerberos Because dictionary attacks are often mentioned in relationship with
a few issues are addressed. Kerberos, a few issues are addressed here.
The initial Kerberos AS_REQ request (without pre-authentication, The initial Kerberos AS_REQ request (without pre-authentication,
various extensions and without PKINIT) is unprotected. The response without various extensions, and without PKINIT) is unprotected. The
message AS_REP is encrypted with the client's long-term key. An response message AS_REP is encrypted with the client's long-term key.
adversary can take advantage of this fact by requesting AS_REP An adversary can take advantage of this fact by requesting AS_REP
messages to mount an off-line dictionary attack. Using pre- messages to mount an off-line dictionary attack. Pre-authentication
authentication ([Pat92]) can be used to reduce this problem. ([Pat92]) can be used to reduce this problem. However, pre-
However pre-authentication does not entirely prevent dictionary authentication does not entirely prevent dictionary attacks by an
attacks by an adversary since he can still eavesdrop Kerberos adversary who can still eavesdrop on Kerberos messages along the path
messages if being located at the path between the mobile node and the between a mobile node and a KDC. With mandatory pre-authentication
KDC. With mandatory pre-authentication for the initial request an for the initial request, an adversary cannot request a Ticket
adversary cannot request a Ticket Granting Ticket for an arbitrary Granting Ticket for an arbitrary user. On-line password guessing
user. On-line password guessing attacks are still possible by attacks are still possible by choosing a password (e.g., from a
choosing a password (e.g. from a dictionary) and then transmitting an dictionary) and then transmitting an initial request including a pre-
initial request including pre-authentication data field. An authentication data field. An unsuccessful authentication by the KDC
unsuccessful authentication by the KDC results in an error message results in an error message and the gives the adversary a hint to
and the gives the adversary a hint to try a new password and restart restart the protocol and try a new password.
the protocol again.
There are however some proposals that prevent dictionary attacks from There are, however, some proposals that prevent dictionary attacks.
happening. The use of Public Key Cryptography for initial The use of Public Key Cryptography for initial authentication [TN+01]
authentication [TN+01] (PKINIT) is one such solution. Other proposals (PKINIT) is one such solution. Other proposals use strong-password-
use strong-password based authenticated key agreement protocols to based authenticated key agreement protocols to protect the user's
protect the user's password during the initial Kerberos exchange. In password during the initial Kerberos exchange. [Wu99] discusses the
[Wu99] Tom Wu discusses the security of Kerberos and also discusses security of Kerberos and also discusses mechanisms to prevent
mechanisms to prevent dictionary attacks. dictionary attacks.
Appendix B: Example of User-to-PDP Authentication Appendix B: Example of User-to-PDP Authentication
The following Section describes an example of user-to-PDP The following Section describes an example of user-to-PDP
authentication. Note that the description below is not fully covered authentication. Note that the description below is not fully covered
by the RSVP specification and hence it should only be seen as an by the RSVP specification and hence it should only be seen as an
example. example.
Windows 2000, which integrates Kerberos into RSVP, uses a Windows 2000, which integrates Kerberos into RSVP, uses a
configuration with the user authentication to the PDP as described in configuration with the user authentication to the PDP as described in
[MADS01]. The steps for authenticating the user to the PDP in an [MADS01]. The steps for authenticating the user to the PDP in an
intra-realm scenario are the following: intra-realm scenario are the following:
RSVP Security Properties June 2003
- Windows 2000 requires the user to contact the KDC and to request a - Windows 2000 requires the user to contact the KDC and to request a
Kerberos service ticket for the PDP account AcsService in the local Kerberos service ticket for the PDP account AcsService in the local
realm. realm.
- This ticket is then embedded in the AUTH_DATA element and included - This ticket is then embedded into the AUTH_DATA element and
in either the PATH or the RESV message. In case of MicrosoftÆs included in either the PATH or the RESV message. In case of
implementation the user identity encoded as a distinguished name is Microsoft's implementation, the user identity encoded as a
encrypted with the session key provided with the Kerberos ticket. The distinguished name is encrypted with the session key provided with
Kerberos ticket is sent without the Kerberos authdata element that the Kerberos ticket. The Kerberos ticket is sent without the
contains authorization information as explained in [MADS01]. Kerberos authdata element that contains authorization information,
as explained in [MADS01].
- The RSVP message is then intercepted by the PEP who forwards it to - The RSVP message is then intercepted by the PEP, which forwards it
the PDP. [MADS01] does not state which protocol is used to forward to the PDP. [MADS01] does not state which protocol is used to
the RSVP message to the PDP. forward the RSVP message to the PDP.
- The PDP who finally receives the message decrypts the received - The PDP that finally receives the message decrypts the received
service ticket. The ticket contains the session key which was used by service ticket. The ticket contains the session key used by the
the user's host to user's host to
a) Encrypt the principal name inside the policy locator field of the a) Encrypt the principal name inside the policy locator field of
AUTH_DATA object and to the AUTH_DATA object and to
b) Create the integrity protected Keyed Message Digest field in the b) Create the integrity-protected Keyed Message Digest field in the
INTEGRITY object of the POLICY_DATA element. The protection described INTEGRITY object of the POLICY_DATA element. The protection
here is between the user's host and the PDP. The RSVP INTEGRITY described here is between the user's host and the PDP. The RSVP
object on the other hand is used to protect the path between the INTEGRITY object on the other hand is used to protect the path
users host and the first-hop router since the two message parts between the user's host and the first-hop router, because the
terminate at a different node and a different security association two message parts terminate at different nodes and different
must be used. The interface between the message intercepting first- security associations must be used. The interface between the
hop router and the PDP must be protected as well. message-intercepting, first-hop router and the PDP must be
c) The PDP does not maintain a user database and [MADS01] describes protected as well.
that the PDP may query the Active Directory (a LDAP based directory c) The PDP does not maintain a user database, and [MADS01]
service) for user policy information. describes how the PDP may query the Active Directory (a LDAP
based directory service) for user policy information.
Appendix C: Literature on RSVP Security Appendix C: Literature on RSVP Security
Very few documents address the security of RSVP signaling. This Few documents address the security of RSVP signaling. This section
section briefly describes some important documents. briefly describes some important documents.
Improvements to RSVP are proposed in [WW+99] to deal with insider Improvements to RSVP are proposed in [WW+99] to deal with insider
attacks. Insider attacks are caused by malicious RSVP routers attacks. Insider attacks are caused by malicious RSVP routers that
modifying RSVP signaling messages in such a way that they cause harm modify RSVP signaling messages in such a way that they cause harm to
to the nodes participating in the signaling message exchange. the nodes participating in the signaling message exchange.
As a solution non-mutuable RSVP objects are digitally signed by the As a solution, non-mutable RSVP objects are digitally signed by the
sender. This digital signature is added to the RSVP PATH message. sender. This digital signature is added to the RSVP PATH message.
Additionally the receiver attaches an object to the RSVP RESV message Additionally, the receiver attaches an object to the RSVP RESV
containing a "signed" history. This value allows intermediate RSVP message containing a "signed" history. This value allows intermediate
routers (together with the previously signed value) to detect a RSVP routers (by examining the previously signed value) to detect a
malicious RSVP node. malicious RSVP node.
RSVP Security Properties June 2003
A few issues are, however, left open in the document. Replay attacks A few issues are, however, left open in the document. Replay attacks
are not covered and it is therefore assumed that timestamp-based are not covered, and it is therefore assumed that timestamp-based
replay protection is used. In order to detect a malicious node it is replay protection is used. To detect a malicious node, it is
necessary that all routers along the path are able to verify the necessary that all routers along the path are able to verify the
digital signature. This requires a global public key infrastructure digital signature. This may require a global public key
and also a client-side PKI. Furthermore the computational infrastructure and also client-side certificates. Furthermore the
requirements to verify and compute digital signatures with each bandwidth and computational requirements to compute, transmit, and
signaling message might place a burden on a real-world deployment. verify digital signatures for each signaling message might place a
Authorization is not considered in the document which might have an burden on a real-world deployment.
influence on the implication of signaling message modification. Hence
the chain-of-trust relationship (or step towards a different Authorization is not considered in the document, which might have an
influence on the implications of signaling message modification.
Hence, the chain-of-trust relationship (or this step in a different
direction) should be considered in relationship with authorization. direction) should be considered in relationship with authorization.
In [TN00] the above described idea of detecting malicious RSVP nodes In [TN00], the above-described idea of detecting malicious RSVP nodes
is improved by addressing the performance aspects. The proposed is improved by addressing performance aspects. The proposed solution
solution is somewhat between hop-by-hop security and the above is somewhere between hop-by-hop security and the approach in [WW+99],
described approach by separating the end-to-end path into individual insofar as it separates the end-to-end path into individual networks.
networks. Furthermore some additional RSVP messages (i.e. feedback Furthermore, some additional RSVP messages (e.g., feedback messages)
messages) are introduced to implement a mechanism call "delayed are introduced to implement a mechanism called "delayed integrity
integrity checking". In [TN+01] the approach presented with [TN00] is checking." In [TN+01], the approach presented in [TN00] is enhanced.
enhanced.
10. Normative References 10. Normative References
[RFC3182] Yadav, S., Yavatkar, R., Pabbati, R., Ford, P., Moore, T., [RFC3182] Yadav, S., Yavatkar, R., Pabbati, R., Ford, P., Moore, T.,
Herzog, S., Hess, R.: "Identity Representation for RSVP", RFC 3182, Herzog, S., Hess, R.: "Identity Representation for RSVP", RFC 3182,
October, 2001. October, 2001.
[RFC2750] Herzog, S.: "RSVP Extensions for Policy Control", RFC [RFC2750] Herzog, S.: "RSVP Extensions for Policy Control", RFC 2750,
2750, January, 2000. January, 2000.
[RFC2747] Baker, F., Lindell, B., Talwar, M.: "RSVP Cryptographic [RFC2747] Baker, F., Lindell, B., Talwar, M.: "RSVP Cryptographic
Authentication", RC 2747, January, 2000. Authentication", RC 2747, January, 2000.
[RFC2748] Boyle, J., Cohen, R., Durham, D., Herzog, S., Rajan, R., [RFC2748] Boyle, J., Cohen, R., Durham, D., Herzog, S., Rajan, R.,
Sastry, A.: "The COPS(Common Open Policy Service) Protocol", RFC Sastry, A.: "The COPS(Common Open Policy Service) Protocol", RFC
2748, January, 2000. 2748, January, 2000.
[RFC2749] Boyle, J., Cohen, R., Durham, D., Herzog, S., Rajan, R., [RFC2749] Boyle, J., Cohen, R., Durham, D., Herzog, S., Rajan, R.,
Sastry, A.: "COPS usage for RSVP", RFC 2749, January, 2000. Sastry, A.: "COPS usage for RSVP", RFC 2749, January, 2000.
[RFC2207] Berger, L., OÆMalley, T.: "RSVP Extensions for IPSEC Data [RFC2207] Berger, L., OÆMalley, T.: "RSVP Extensions for IPSEC Data
Flows", RFC 2207, September 1997. Flows", RFC 2207, September 1997.
[RFC1321] Rivest, R.: "The MD5 Message-Digest Algorithm", RFC 1321, [RFC1321] Rivest, R.: "The MD5 Message-Digest Algorithm", RFC 1321,
April, 1992. April, 1992.
RSVP Security Properties June 2003
[RFC1510] Kohl, J., Neuman, C.: "The Kerberos Network Authentication [RFC1510] Kohl, J., Neuman, C.: "The Kerberos Network Authentication
Service (V5)", RFC 1510, September 1993. Service (V5)", RFC 1510, September 1993.
[RFC2104] Krawczyk, H., Bellare, M., Canetti, R.: "HMAC: Keyed- [RFC2104] Krawczyk, H., Bellare, M., Canetti, R.: "HMAC: Keyed-
Hashing for Message Authentication", RFC 2104, February, 1997. Hashing for Message Authentication", RFC 2104, February, 1997.
[RFC2205] Braden, R., Zhang, L., Berson, S., Herzog, S., Jamin, [RFC2205] Braden, R., Zhang, L., Berson, S., Herzog, S., Jamin, S.:
S.: "Resource ReSerVation Protocol (RSVP) - Version 1 Functional "Resource ReSerVation Protocol (RSVP) - Version 1 Functional
Specification", RFC 2205, September 1997. Specification", RFC 2205, September 1997.
11. Informative References 11. Informative References
[CA+02] Calhoun, P., Arkko, J., Guttman, E., Zorn, G., Loughney, [CA+02] Calhoun, P., Arkko, J., Guttman, E., Zorn, G., Loughney, J.:
J.: "DIAMETER Base Protocol", <draft-ietf-aaa-diameter-17.txt>, (work "DIAMETER Base Protocol", <draft-ietf-aaa-diameter-17.txt>, (work in
in progress), December, 2002. progress), December, 2002.
[DBP96] Dobbertin, H., Bosselaers, A., Preneel, B.: "RIPEMD-160: A [DBP96] Dobbertin, H., Bosselaers, A., Preneel, B.: "RIPEMD-160: A
strengthened version of RIPEMD", in "Fast Software Encryption, LNCS strengthened version of RIPEMD", in "Fast Software Encryption, LNCS
Vol 1039, pp. 71-82", 1996. Vol 1039, pp. 71-82", 1996.
[DG96] Davis, D., Geer, D.: "Kerberos With Clocks Adrift: [DG96] Davis, D., Geer, D.: "Kerberos With Clocks Adrift: History,
History, Protocols and Implementation", in "USENIX Computing Systems Protocols and Implementation", in "USENIX Computing Systems Volume 9
Volume 9 no. 1, Winter", 1996. no. 1, Winter", 1996.
[Dob96] Dobbertin, H.: "The Status of Md5 After a Recent Attack," [Dob96] Dobbertin, H.: "The Status of Md5 After a Recent Attack," RSA
RSA Laboratories' CryptoBytes, Volume 2, Number 2, 1996. Laboratories' CryptoBytes, Volume 2, Number 2, 1996.
[GD+02] Gai, S., Dutt, D., Elfassy, N., Bernet, Y.: "RSVP Proxy", [GD+02] Gai, S., Dutt, D., Elfassy, N., Bernet, Y.: "RSVP Proxy",
<draft-ietf-rsvp-proxy-03.txt>, (expired), March, 2002. <draft-ietf-rsvp-proxy-03.txt>, (expired), March, 2002.
[HA01] Hornstein, K., Altman, J.: "Distributing Kerberos KDC and [HA01] Hornstein, K., Altman, J.: "Distributing Kerberos KDC and
Realm Information with DNS", <draft-ietf-krb-wg-krb-dns-locate- Realm Information with DNS", <draft-ietf-krb-wg-krb-dns-locate-
03.txt>, (expired), July, 2002. 03.txt>, (expired), July, 2002.
[HH01] Hess, R., Herzog, S.: "RSVP Extensions for Policy [HH01] Hess, R., Herzog, S.: "RSVP Extensions for Policy Control",
Control", <draft-ietf-rap-new-rsvp-ext-00.txt>, (expired), June, <draft-ietf-rap-new-rsvp-ext-00.txt>, (expired), June, 2001.
2001.
[Jab96] Jablon, D.: "Strong password-only authenticated key [Jab96] Jablon, D.: "Strong password-only authenticated key
exchange", Computer Communication Review, 26(5), pp. 5-26, October, exchange", Computer Communication Review, 26(5), pp. 5-26, October,
1996. 1996.
[MADS01] "Microsoft Authorization Data Specification v. 1.0 for [MADS01] "Microsoft Authorization Data Specification v. 1.0 for
Microsoft Windows 2000 Operating Systems", April, 2000. Microsoft Windows 2000 Operating Systems", April, 2000.
[RFC2284] Blunk, L. and J. Vollbrecht, "PPP Extensible Authentication [RFC2284] Blunk, L. and J. Vollbrecht, "PPP Extensible Authentication
Protocol (EAP)", RFC 2284, March 1998. Protocol (EAP)", RFC 2284, March 1998.
RSVP Security Properties June 2003 [MHHF01] Malpani, A., Hoffman, P., Housley, R., Freeman, T.: "Simple
Certificate Validation Protocol (SCVP)", <draft-ietf-pkix-scvp-
[MHHF01] Malpani, A., Hoffman, P., Housley, R., Freeman, T.: 11.txt>, (work in progress), December, 2002.
"Simple Certificate Validation Protocol (SCVP)", <draft-ietf-pkix-
scvp-11.txt>, (work in progress), December, 2002.
[MS+02] Manner, J., Suihko, T., Kojo, M., Liljeberg, M., [MS+02] Manner, J., Suihko, T., Kojo, M., Liljeberg, M., Raatikainen,
Raatikainen, K.: "Localized RSVP", <draft-manner-lrsvp-00.txt>, K.: "Localized RSVP", <draft-manner-lrsvp-00.txt>, (expired), May,
(expired), May, 2002. 2002.
[Pat92] Pato, J., "Using Pre-Authentication to Avoid Password [Pat92] Pato, J., "Using Pre-Authentication to Avoid Password
Guessing Attacks", Open Software Foundation DCE Request for Comments Guessing Attacks", Open Software Foundation DCE Request for Comments
26, December, 1992. 26, December, 1992.
[PGP] "Specifications and standard documents", [PGP] "Specifications and standard documents",
http://www.pgpi.org/doc/specs/ (March, 2002). http://www.pgpi.org/doc/specs/ (March, 2002).
[PKTSEC] PacketCable Security Specification, PKT-SP-SEC-I01-991201, [PKTSEC] PacketCable Security Specification, PKT-SP-SEC-I01-991201,
Cable Television Laboratories, Inc., December 1, 1999, Cable Television Laboratories, Inc., December 1, 1999,
http://www.PacketCable.com/ (June, 2003). http://www.PacketCable.com/ (June, 2003).
[Rae01] Raeburn, K.: " Encryption and Checksum Specifications for [Rae01] Raeburn, K.: " Encryption and Checksum Specifications for
Kerberos 5", <draft-ietf-krb-wg-crypto-05.txt>, (work in progress), Kerberos 5", <draft-ietf-krb-wg-crypto-05.txt>, (work in progress),
June, 2003. June, 2003.
[RFC2315] Kaliski, B.: " PKCS #7: Cryptographic Message Syntax [RFC2315] Kaliski, B.: "PKCS #7: Cryptographic Message Syntax Version
Version 1.5", RFC 2315, March, 1998. 1.5", RFC 2315, March, 1998.
[RFC2440] Callas, J., Donnerhacke, L., Finney, H., Thayer, R.: [RFC2440] Callas, J., Donnerhacke, L., Finney, H., Thayer, R.:
"OpenPGP Message Format", RFC 2440, November, 1998. "OpenPGP Message Format", RFC 2440, November, 1998.
[RFC2495] Housley, R., Ford, W., Polk, W., Solo, D.: "Internet X.509 [RFC2495] Housley, R., Ford, W., Polk, W., Solo, D.: "Internet X.509
Public Key Infrastructure Certificate and CRL Profile", RFC 2459, Public Key Infrastructure Certificate and CRL Profile", RFC 2459,
January, 1999. January, 1999.
[RFC2560] Myers, M., Ankney, R., Malpani, A., Galperin, S., Adams, [RFC2560] Myers, M., Ankney, R., Malpani, A., Galperin, S., Adams,
C.: "X.509 Internet Public Key Infrastructure Online Certificate C.: "X.509 Internet Public Key Infrastructure Online Certificate
Status Protocol - - OCSP", RFC 2560, June, 1999. Status Protocol û OCSP", RFC 2560, June, 1999.
[RFC2630] Housley, R.: "Cryptographic Message Syntax", RFC 2630, [RFC2630] Housley, R.: "Cryptographic Message Syntax", RFC 2630,
June, 1999. June, 1999.
[RFC2865] Rigney, C., Willens, S., Rubens, A., Simpson, W.: "Remote [RFC2865] Rigney, C., Willens, S., Rubens, A., Simpson, W.: "Remote
Authentication Dial In User Service (RADIUS)", RFC 2865, June, 2000. Authentication Dial In User Service (RADIUS)", RFC 2865, June, 2000.
[SHA] NIST, FIPS PUB 180-1, "Secure Hash Standard", April, 1995. [SHA] NIST, FIPS PUB 180-1, "Secure Hash Standard", April, 1995.
[TN+01] Tung, B., Neuman, C., Hur, M., Medvinsky, A., Medvinsky, [TN+01] Tung, B., Neuman, C., Hur, M., Medvinsky, A., Medvinsky, S.,
S., Wray, J., Trostle, J.: "Public Key Cryptography for Initial Wray, J., Trostle, J.: "Public Key Cryptography for Initial
Authentication in Kerberos", <draft-ietf-cat-kerberos-pk-init- Authentication in Kerberos", <draft-ietf-cat-kerberos-pk-init-
16.txt>, (expired), October, 2001. 16.txt>, (expired), October, 2001.
RSVP Security Properties June 2003 [Wu99] Wu, T.: "A Real-World Analysis of Kerberos Password Security",
in "Proceedings of the 1999 Network and Distributed System Security",
[Wu99] Wu, T.: "A Real-World Analysis of Kerberos Password February, 1999.
Security", in "Proceedings of the 1999 Network and Distributed System
Security", February, 1999.
[TB+03a] H. Tschofenig, M. Buechli, S. Van den Bosch, H. [TB+03a] H. Tschofenig, M. Buechli, S. Van den Bosch, H. Schulzrinne:
Schulzrinne: "NSIS Authentication, Authorization and Accounting "NSIS Authentication, Authorization and Accounting Issues", <draft-
Issues", <draft-tschofenig-nsis-aaa-issues-01.txt>, (work in tschofenig-nsis-aaa-issues-01.txt>, (work in progress), March, 2003.
progress), March, 2003.
[TB+03b] H. Tschofenig, M. Buechli, S. Van den Bosch, H. [TB+03b] H. Tschofenig, M. Buechli, S. Van den Bosch, H. Schulzrinne,
Schulzrinne, T. Chen: "QoS NSLP Authorization Issues", <draft- T. Chen: "QoS NSLP Authorization Issues", <draft-tschofenig-nsis-qos-
tschofenig-nsis-qos-authz-issues-00.txt>, (work in progress), June, authz-issues-00.txt>, (work in progress), June, 2003.
2003.
[Her95] Herzog, S.: "Accounting and Access Control in RSVP", [Her95] Herzog, S.: "Accounting and Access Control in RSVP", <draft-
<draft-ietf-rsvp-lpm-arch-00.txt>, (expired), November, 1995. ietf-rsvp-lpm-arch-00.txt>, (expired), November, 1995.
[Her96] S. Herzog: "Accounting and Access Control for Multicast [Her96] S. Herzog: "Accounting and Access Control for Multicast
Distributions: Models and Mechanisms", PhD Dissertation, University Distributions: Models and Mechanisms", PhD Dissertation, University
of Southern California, June 1996, available at: of Southern California, June 1996, available at:
http://www.policyconsulting.com/publications/USC%20thesis.pdf, (June, http://www.policyconsulting.com/publications/USC%20thesis.pdf, (June,
2003). 2003).
[Tho02] M. Thomas: "Analysis of Mobile IP and RSVP Interactions", [Tho02] M. Thomas: "Analysis of Mobile IP and RSVP Interactions",
<draft-thomas-nsis-rsvp-analysis-00.txt>, (work in progress), October <draft-thomas-nsis-rsvp-analysis-00.txt>, (work in progress), October
2002. 2002.
[FH+01] Thomas, M., Vilhuber, J.: "Kerberized Internet Negotiation [FH+01] Thomas, M., Vilhuber, J.: "Kerberized Internet Negotiation of
of Keys (KINK)", <draft-ietf-kink-kink-05.txt>, (work in progress), Keys (KINK)", <draft-ietf-kink-kink-05.txt>, (work in progress),
January, 2003. January, 2003.
[RFC2402] Kent, S., Atkinson, R.: "IP Authentication Header", RFC [RFC2402] Kent, S., Atkinson, R.: "IP Authentication Header", RFC
2402, November, 1998. 2402, November, 1998.
[RFC2406] Kent, S., Atkinson, R.: "IP Encapsulating Security Payload [RFC2406] Kent, S., Atkinson, R.: "IP Encapsulating Security Payload
(ESP)", RFC 2406, November, 1998. (ESP)", RFC 2406, November, 1998.
[RFC2409] Harkins, D., Carrel, D.: "The Internet Key Exchange [RFC2409] Harkins, D., Carrel, D.: "The Internet Key Exchange (IKE)",
(IKE)", RFC 2409, November, 1998. RFC 2409, November, 1998.
[IKEv2] C. Kaufman: "Internet Key Exchange (IKEv2) Protocol", [IKEv2] C. Kaufman: "Internet Key Exchange (IKEv2) Protocol",
Internet Draft, <draft-ietf-ipsec-ikev2-08.txt>, (work in progress), Internet Draft, <draft-ietf-ipsec-ikev2-08.txt>, (work in progress),
June, 2003. June, 2003.
[WW+99] Wu, T., Wu, F. and Gong, F.: "Securing QoS: Threats to [WW+99] Wu, T., Wu, F. and Gong, F.: "Securing QoS: Threats to RSVP
RSVP Messages and Their Countermeasures", in "IEEE IWQoS, pp. 62-64, Messages and Their Countermeasures", in "IEEE IWQoS, pp. 62-64, 1999.
1999.
RSVP Security Properties June 2003
[TN00] Talwar, V. and Nahrstedt, K.: "Securing RSVP For Multimedia [TN00] Talwar, V. and Nahrstedt, K.: "Securing RSVP For Multimedia
Applications", in "Proceedings of ACM Multimedia (Multimedia Security Applications", in "Proceedings of ACM Multimedia (Multimedia Security
Workshop)", Los Angeles, November, 2000. Workshop)", Los Angeles, November, 2000.
[TN+01] Talwar, V., Nath, S., Nahrstedt, K.: "RSVP-SQoS : A Secure [TN+01] Talwar, V., Nath, S., Nahrstedt, K.: "RSVP-SQoS : A Secure
RSVP Protocol", in "International Conference on Multimedia and RSVP Protocol", in "International Conference on Multimedia and
Exposition", Tokyo , Japan, August 2001. Exposition", Tokyo , Japan, August 2001.
Author's Contact Information Author's Contact Information
Hannes Tschofenig Hannes Tschofenig
Siemens AG Siemens AG
Otto-Hahn-Ring 6 Otto-Hahn-Ring 6
81739 Munich 81739 Munich
Germany Germany
Email: Hannes.Tschofenig@siemens.com Email: Hannes.Tschofenig@siemens.com
Richard Graveman
RFG Security, LLC
15 Park Avenue
Morristown, NJ 07960 USA
email: rfg@acm.org
Full Copyright Statement Full Copyright Statement
Copyright (C) The Internet Society (2000). All Rights Reserved. Copyright (C) The Internet Society (2000). All Rights Reserved.
This document and translations of it may be copied and furnished to This document and translations of it may be copied and furnished to
others, and derivative works that comment on or otherwise explain it others, and derivative works that comment on or otherwise explain it
or assist in its implementation may be prepared, copied, published or assist in its implementation may be prepared, copied, published
and distributed, in whole or in part, without restriction of any and distributed, in whole or in part, without restriction of any
kind, provided that the above copyright notice and this paragraph are kind, provided that the above copyright notice and this paragraph are
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skipping to change at page 43, line 4 skipping to change at page 45, line 7
revoked by the Internet Society or its successors or assigns. revoked by the Internet Society or its successors or assigns.
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TASK FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING TASK FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING
BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION
HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF
MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE. MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.
Acknowledgement Acknowledgement
RSVP Security Properties June 2003
Funding for the RFC Editor function is currently provided by the Funding for the RFC Editor function is currently provided by the
Internet Society. Internet Society.
 End of changes. 

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