draft-ietf-ipsecme-ikev2-null-auth-03.txt   draft-ietf-ipsecme-ikev2-null-auth-04.txt 
Network Working Group V. Smyslov Network Working Group V. Smyslov
Internet-Draft ELVIS-PLUS Internet-Draft ELVIS-PLUS
Intended status: Standards Track P. Wouters Intended status: Standards Track P. Wouters
Expires: August 1, 2015 Red Hat Expires: August 24, 2015 Red Hat
January 28, 2015 February 20, 2015
The NULL Authentication Method in IKEv2 Protocol The NULL Authentication Method in IKEv2 Protocol
draft-ietf-ipsecme-ikev2-null-auth-03 draft-ietf-ipsecme-ikev2-null-auth-04
Abstract Abstract
This document specifies the NULL Authentication method and the This document specifies the NULL Authentication method and the
ID_NULL Identification Payload ID Type for the IKEv2 Protocol. This ID_NULL Identification Payload ID Type for the IKEv2 Protocol. This
allows two IKE peers to establish single-side authenticated or mutual allows two IKE peers to establish single-side authenticated or mutual
unauthenticated IKE sessions for those use cases where a peer is unauthenticated IKE sessions for those use cases where a peer is
unwilling or unable to authenticate or identify itself. This ensures unwilling or unable to authenticate or identify itself. This ensures
IKEv2 can be used for Opportunistic Security (also known as IKEv2 can be used for Opportunistic Security (also known as
Opportunistic Encryption) to defend against Pervasive Monitoring Opportunistic Encryption) to defend against Pervasive Monitoring
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Internet-Drafts are working documents of the Internet Engineering Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute Task Force (IETF). Note that other groups may also distribute
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time. It is inappropriate to use Internet-Drafts as reference time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress." material or to cite them other than as "work in progress."
This Internet-Draft will expire on August 1, 2015. This Internet-Draft will expire on August 24, 2015.
Copyright Notice Copyright Notice
Copyright (c) 2015 IETF Trust and the persons identified as the Copyright (c) 2015 IETF Trust and the persons identified as the
document authors. All rights reserved. document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents Provisions Relating to IETF Documents
(http://trustee.ietf.org/license-info) in effect on the date of (http://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents publication of this document. Please review these documents
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authentication of the initiator. authentication of the initiator.
o Two peers without any trust relationship wish to defend against o Two peers without any trust relationship wish to defend against
widespread pervasive monitoring attacks as described in [RFC7258]. widespread pervasive monitoring attacks as described in [RFC7258].
Without a trust relationship, the peers cannot authenticate each Without a trust relationship, the peers cannot authenticate each
other. Opportunistic Security [RFC7435] states that other. Opportunistic Security [RFC7435] states that
unauthenticated encrypted communication is preferred over unauthenticated encrypted communication is preferred over
cleartext communication. The peers want to use IKE to setup an cleartext communication. The peers want to use IKE to setup an
unauthenticated encrypted connection, that gives them protection unauthenticated encrypted connection, that gives them protection
against pervasive monitoring attacks. An attacker that is able against pervasive monitoring attacks. An attacker that is able
and willing to send packets can still launch an Man-in-the-Middle and willing to send packets can still launch a Man-in-the-Middle
attack to obtain access to the decrypted communication. This case attack to obtain access to the decrypted communication. This case
uses a fully unauthenticated key exchange. uses a fully unauthenticated key exchange.
To meet these needs this document introduces the NULL Authentication To meet these needs this document introduces the NULL Authentication
method, and the ID_NULL ID type. This allows an IKE peer to method, and the ID_NULL ID type. This allows an IKE peer to
explicitly indicate that it is unwilling or unable to certify its explicitly indicate that it is unwilling or unable to certify its
identity. identity.
1.1. Conventions Used in This Document 1.1. Conventions Used in This Document
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2.2. Identification Payload 2.2. Identification Payload
When a remote peer is not authenticated, any ID presented in the When a remote peer is not authenticated, any ID presented in the
Identification Data field of the ID payload cannot be validated. To Identification Data field of the ID payload cannot be validated. To
avoid the need of sending a bogus ID Type with placeholder data, this avoid the need of sending a bogus ID Type with placeholder data, this
specification defines a new ID Type, ID_NULL. The Identification specification defines a new ID Type, ID_NULL. The Identification
Data field of the ID payload for this ID Type MUST be empty. Data field of the ID payload for this ID Type MUST be empty.
If NULL Authentication is in use and an anonymity is a concern then If NULL Authentication is in use and an anonymity is a concern then
ID_NULL SHOULD be used in Identification payload. In some cases ID_NULL SHOULD be used in the Identification payload. Some examples
there may be good reasons to use non-null identities (and ID Types of acceptable cases to use a non-null identity type and value with
other than ID_NULL) with NULL Authentication. The identities may be NULL Authentication are logging, troubleshooting or in scenarios
used for logging, troubleshooting or in scenarios when authentication where authentication takes place out of band after the IKE SA is
takes place out of band after the IKE SA is created (like in created (like in [AUTOVPN]). The content of the Identification
[AUTOVPN]). In any case, when NULL Authentication is employed, the payload MUST NOT be used for any trust and policy checking in
content of Identification payload MUST NOT be used for any trust and IKE_AUTH exchange when NULL Authentication is employed (see Section
policy checking in IKE_AUTH exchange. 2.4 for details).
ID_NULL is primarily intended to be used with the NULL ID_NULL is primarily intended to be used with NULL Authentication but
Authentication, but it MAY also be used in other situations, when the could be used in other situations where the content of the
content of Identification payload does not matter. For example, Identification Payload is not used. For example, ID_NULL could be
ID_NULL can be used when authentication is performed via raw public used when authentication is performed via raw public keys and the
keys and the identities are these keys themselves. Another example identities are the keys themselves. These alternative uses of
is EAP authentication when the client identity in ID payload is not ID_NULL should be described in their own respective documents.
used.
The IKEv2 Identification Payload ID Type for ID_NULL is 13. The IKEv2 Identification Payload ID Type for ID_NULL is 13.
2.3. INITIAL_CONTACT Notification 2.3. INITIAL_CONTACT Notification
The identity of a peer using NULL Authentication cannot be used to The identity of a peer using NULL Authentication cannot be used to
distinguish from IKE SAs created by other peers using the NULL find existing IKE SAs created by the same peer, as the peer identity
Authentication method. For that reason the INITIAL_CONTACT is not authenticated. For that reason the INITIAL_CONTACT
notifications MUST be ignored for IKE SAs using NULL Authentication. notifications MUST NOT be used to delete any other IKE SAs based on
the same peer identity without additional verification that the
existing IKE SAs with matching identity are actually stale.
The standard IKE Liveness Check procedure, decribed in Section 2.4 of The standard IKE Liveness Check procedure, described in Section 2.4
[RFC7296], can be used to detect stale IKE SAs created by peers using of [RFC7296], can be used to detect stale IKE SAs created by peers
NULL Authentication. Inactive unauthenticated IKE SAs should be using NULL Authentication. Inactive unauthenticated IKE SAs should
checked periodically. Additionally, the event of creating a new be checked periodically. Additionally, the event of creating a new
unauthenticated IKE SA can be used to trigger an out-of-order check unauthenticated IKE SA can be used to trigger an out-of-order check
on existing unauthenticated IKE SAs, possibly limited to identical or on existing unauthenticated IKE SAs, possibly limited to identical or
close-by IP addresses or to identical identities of the just created close-by IP addresses or to identical identities of the just created
IKE SA. IKE SA.
Implementations should weight the resource consumption of sending Implementations should weight the resource consumption of sending
Liveness Checks against the memory usage of possible orphaned IKE Liveness Checks against the memory usage of possible orphaned IKE
SAs. Implementations may choose to handle situations with thousands SAs. Implementations may choose to handle situations with thousands
of unauthenticated IKE SAs differently from situations with very few of unauthenticated IKE SAs differently from situations with very few
such SAs. such SAs.
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Section 4.4.3 of [RFC4301] defines the Peer Authorization Database Section 4.4.3 of [RFC4301] defines the Peer Authorization Database
(PAD), which provides the link between Security Policy Database (SPD) (PAD), which provides the link between Security Policy Database (SPD)
and the IKEv2. The PAD contains an ordered list of records, with and the IKEv2. The PAD contains an ordered list of records, with
peers' identities along with corresponding authentication data and peers' identities along with corresponding authentication data and
Child SA authorization data. When the IKE SA is being established Child SA authorization data. When the IKE SA is being established
the PAD is consulted to determine how the peer should be the PAD is consulted to determine how the peer should be
authenticated and what Child SAs it is authorized to create. authenticated and what Child SAs it is authorized to create.
When using NULL Authentication, the peer identity is not When using NULL Authentication, the peer identity is not
authenticated and cannot be used. If ID_NULL is used with NULL authenticated and cannot be trusted. If ID_NULL is used with NULL
Authentication, there is no ID at all. The processing of PAD Authentication, there is no ID at all. The processing of PAD
described in Section 4.4.3.4 of [RFC4301] must be updated. described in Section 4.4.3.4 of [RFC4301] must be updated.
If NULL Authentication is supported and allowed, then a special entry The NULL authentication needs to be added as one of supported
MUST be included in the PAD. This entry MUST contain no authentication methods. This method does not have any authentication
authentication data. It MAY contain a set of constraints for data. To add support for ID_NULL, it needs to be included into the
creating Child SAs as described in Section 4.4.3 of [RFC4301]. When list of ID types, specified in Section 4.4.3.1 of [RFC4301]. The
a peer uses NULL Authentication, regular matching rules for the PAD matching rule for ID_NULL is just whether this type is used, i.e. no
MUST be ignored and this special entry MUST be selected regardless of actual ID matching is done, as ID_NULL contains no identity data.
the peer identity. Likewise, if a peer uses any other authentication
method, then this special entry MUST NOT be selected regardless of
the peer identity and the regular search of the PAD described in
Section 4.4.3.4 of [RFC4301] MUST be performed.
Implementations SHOULD allow to be configured so, that when a peer Section 4.4.3.3 of the [RFC4301] describes how the IKE ID is matched
requests NULL Authentication, then regular PAD entries are searched against the SPD entries. When using the NULL authentication method
before selecting the special entry, to ensure that there is no entry, those matching rules MUST include matching of a new flag in the SPD
containing peer's IP address. In this case implementations MUST entry specifying whether unauthenticated users are allowed to use
reject the IKE_AUTH exchange by sending an AUTHENTICATION_FAILED that entry. I.e. each SPD entry needs to be augmented to have flag
notification if such an entry is found. specifying whether it can be used with NULL authentication or not,
and only those rules explictly having that flag turned on can be used
with unauthenticated connections.
2.5. Traffic Selectors 2.5. Traffic Selectors
Traffic Selectors and narrowing allow two IKE peers to mutually agree Traffic Selectors and narrowing allow two IKE peers to mutually agree
on a traffic range for an IPsec SA. An unauthenticated peer must not on a traffic range for an IPsec SA. An unauthenticated peer must not
be allowed to use this mechanism to steal traffic that an IKE peer be allowed to use this mechanism to steal traffic that an IKE peer
intended to be for another host. This is especially problematic when intended to be for another host. This is especially problematic when
supporting anonymous IKE peers behind NAT, as such IKE peers build an supporting anonymous IKE peers behind NAT, as such IKE peers build an
IPsec SA using their pre-NAT IP address that are different from the IPsec SA using their pre-NAT IP address that are different from the
source IP of their IKE packets. A rogue IKE peer could use malicious source IP of their IKE packets. A rogue IKE peer could use malicious
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internal NAT and connection tracking. internal NAT and connection tracking.
Implementations MAY force unauthenticated IKE peers to single host- Implementations MAY force unauthenticated IKE peers to single host-
to-host IPsec SAs. When using IPv6 it is not always possible, so in to-host IPsec SAs. When using IPv6 it is not always possible, so in
this case implementations MUST be able to assign full /64 address this case implementations MUST be able to assign full /64 address
block to the peer as described in [RFC5739], even if it is not block to the peer as described in [RFC5739], even if it is not
authenticated. authenticated.
3. Security Considerations 3. Security Considerations
If authenticated IKE sessions are possible between the peers, then If authenticated IKE sessions are possible for a certain traffic
unauthenticated IKE SHOULD NOT be used, unless implementations make selector range between the peers, then unauthenticated IKE SHOULD NOT
sure to keep authenticated and unauthenticated IKE sessions separate, be used for that traffic selector range. When mixing authenticated
and has policy rules to specify when to use which IKE session. See and unauthenticated IKE with the same peer, policy rules should
[RFC7435] for details. ensure the highest level of security will be used to protect the
communication between the two peers. See [RFC7435] for details.
If both peers use NULL Authentication, the entire key exchange If both peers use NULL Authentication, the entire key exchange
becomes unauthenticated. This makes the IKE session vulnerable to becomes unauthenticated. This makes the IKE session vulnerable to
active Man-in-the-Middle Attacks. active Man-in-the-Middle Attacks.
Using an ID Type other than ID_NULL with the NULL Authentication Using an ID Type other than ID_NULL with the NULL Authentication
Method may compromise the client's anonimity in case of an active Method may compromise the client's anonymity in case of an active
MITM attack. MITM attack.
IKE implementations without NULL Authentication have always performed IKE implementations without NULL Authentication have always performed
mutual authentication and were not designed for use with mutual authentication and were not designed for use with
unauthenticated IKE peers. Implementations might have made unauthenticated IKE peers. Implementations might have made
assumptions that are no longer valid. Furthermore, the host itself assumptions that are no longer valid. Furthermore, the host itself
might have made trust assumptions or may not be aware of the network might have made trust assumptions or may not be aware of the network
topology changes that resulted from IPsec SAs from unauthenticated topology changes that resulted from IPsec SAs from unauthenticated
IKE peers. IKE peers.
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peer. peer.
3.4. Networking topology changes 3.4. Networking topology changes
When a host relies on packet filters or firewall software to protect When a host relies on packet filters or firewall software to protect
itself, establishing an IKE SA and installing an IPsec SA might itself, establishing an IKE SA and installing an IPsec SA might
accidentally circumvent these packet filters and firewall accidentally circumvent these packet filters and firewall
restrictions, as the encrypted ESP (protocol 50) or ESPinUDP (UDP restrictions, as the encrypted ESP (protocol 50) or ESPinUDP (UDP
port 4500) packets do not match the packet filters defined. IKE port 4500) packets do not match the packet filters defined. IKE
peers supporting unauthenticated IKE MUST pass all decrypted traffic peers supporting unauthenticated IKE MUST pass all decrypted traffic
through the same packet filters and security mechanisms as plaintext through the same packet filters and security mechanisms as incoming
traffic. plaintext traffic.
4. Acknowledgments 4. Acknowledgments
The authors would like to thank Yaron Sheffer and Tero Kivinen for The authors would like to thank Yaron Sheffer and Tero Kivinen for
their reviews and valuable comments. their reviews, valuable comments and contributed text.
5. IANA Considerations 5. IANA Considerations
This document defines a new entry in the "IKEv2 Authentication This document defines a new entry in the "IKEv2 Authentication
Method" registry: Method" registry:
13 NULL Authentication 13 NULL Authentication
This document also defines a new entry in the "IKEv2 Identification This document also defines a new entry in the "IKEv2 Identification
Payload ID Types" registry: Payload ID Types" registry:
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