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Versions: (draft-stillman-rserpool-threats) 00 01 02 03 04 05 06 07 08 09 10 11 12 13 14 15 RFC 5355

Network Working Group                                   M. Stillman, Ed.
Internet-Draft                                                     Nokia
Intended status: Informational                                  R. Gopal
Expires: April 26, 2008                            Nokia Research Center
                                                              E. Guttman
                                                        Sun Microsystems
                                                             M. Holdrege
                                                           Strix Systems
                                                             S. Sengodan
                                                   Nokia Research Center
                                                        October 24, 2007


Threats Introduced by RSerPool and Requirements for Security in Response
                               to Threats
                   draft-ietf-rserpool-threats-09.txt

Status of this Memo

   By submitting this Internet-Draft, each author represents that any
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   This Internet-Draft will expire on April 26, 2008.

Copyright Notice

   Copyright (C) The IETF Trust (2007).






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Abstract

   Rserpool is an architecture and set of protocols for the management
   and access to server pools supporting highly reliable applications
   and for client access mechanisms to a server pool.  This Internet
   draft describes security threats to the Rserpool architecture and
   presents requirements for security to thwart these threats.


Table of Contents

   1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  3
     1.1.  Definitions  . . . . . . . . . . . . . . . . . . . . . . .  3
   2.  Threats  . . . . . . . . . . . . . . . . . . . . . . . . . . .  4
     2.1.  PE Registration/Deregistration flooding --
           non-existent PE  . . . . . . . . . . . . . . . . . . . . .  4
     2.2.  PE Registration/Deregistration flooding --
           unauthorized PE  . . . . . . . . . . . . . . . . . . . . .  4
     2.3.  PE Registration/Deregistration spoofing  . . . . . . . . .  5
     2.4.  PE Registration/Deregistration unauthorized  . . . . . . .  5
     2.5.  Malicious ENRP server joins the group of legitimate
           ENRP servers . . . . . . . . . . . . . . . . . . . . . . .  6
     2.6.  Registration/deregistration with malicious ENRP server . .  6
     2.7.  Malicious ENRP Handlespace Resolution  . . . . . . . . . .  6
     2.8.  Malicious node performs a replay attack  . . . . . . . . .  7
     2.9.  Re-establishing PU-PE security during failover . . . . . .  7
     2.10. Integrity  . . . . . . . . . . . . . . . . . . . . . . . .  8
     2.11. Data Confidentiality . . . . . . . . . . . . . . . . . . .  8
     2.12. ENRP Server Discovery  . . . . . . . . . . . . . . . . . .  9
     2.13. Flood of endpoint unreachable messages from the PU to
           the ENRP server  . . . . . . . . . . . . . . . . . . . . .  9
     2.14. Flood of endpoint keep alive messages from the ENRP
           server to a PE . . . . . . . . . . . . . . . . . . . . . . 10
   3.  Security Considerations  . . . . . . . . . . . . . . . . . . . 10
     3.1.  Security of the ENRP Database  . . . . . . . . . . . . . . 12
     3.2.  Cookie mechanism security  . . . . . . . . . . . . . . . . 12
   4.  IANA Considerations  . . . . . . . . . . . . . . . . . . . . . 13
   5.  References . . . . . . . . . . . . . . . . . . . . . . . . . . 13
     5.1.  Normative References . . . . . . . . . . . . . . . . . . . 13
     5.2.  Informative References . . . . . . . . . . . . . . . . . . 13
   Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 13
   Intellectual Property and Copyright Statements . . . . . . . . . . 15









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1.  Introduction

   RSerPool provides a session layer for robustness.  The session layer
   function may redirect communication transparently to upper layers.
   This alters the direct one-to-one association between communicating
   endpoints which typically exists between clients and servers.  In
   particular, secure operation of protocols often relies on assumptions
   at different layers regarding the identity of the communicating party
   and the continuity of the communication between endpoints.  Further,
   the operation of RSerPool itself has security implications and risks.
   The session layer operates dynamically which imposes additional
   concerns for the overall security of the end-to-end application.
   This document explores the security implications of RSerPool, both
   due to its own functions and due to its being interposed between
   applications and transport interfaces.

1.1.  Definitions

   This document uses the following terms:

   Endpoint Name Resolution Protocol (ENRP):
      Within the operational scope of Rserpool, ENRP defines the
      procedures and message formats of a distributed fault-tolerant
      registry service for storing, bookkeeping, retrieving, and
      distributing pool operation and membership information.

   Aggregate Server Access Protocol (ASAP):
      A session layer protocol which uses ENRP to provide a high
      availability handlespace.  ASAP is responsible for the abstraction
      of the underlying transport technologies, load distribution
      management,fault management, as well as the presentation to the
      upper layer (i.e., the ASAP user) a unified primitive interface.

   Operational scope:
      The part of the network visible to pool users by a specific
      instance of the reliable server pooling protocols.

   Pool (or server pool):
      A collection of servers providing the same application
      functionality.

   Pool handle:
      A logical pointer to a pool.  Each server pool will be
      identifiable in the operational scope of the system by a unique
      pool handle.






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   ENRP handlespace (or handlespace):
      A cohesive structure of pool names and relations that may be
      queried by an internal or external agent.

   Pool element (PE):  A server entity having registered to a pool.

   Pool user (PU):  A server pool user.


2.  Threats

2.1.  PE Registration/Deregistration flooding -- non-existent PE

2.1.1.  Threat

   A malicious node could send a stream of false registrations/
   deregistrations on behalf of non-existent PEs to ENRP servers at a
   very rapid rate and thereby create unnecessary state in an ENRP
   server.

2.1.2.  Effect

   Corrupting the pool registrar database and/or disabling the Rserpool
   discovery and database function.  This represents a denial of service
   attack as the PU would potentially get an IP address of a non-
   existent PE in response to an ENRP query.

2.1.3.  Requirement

   An ENRP server that receives a registration/deregistration should not
   create or update state information until it has authenticated the PE.

2.2.  PE Registration/Deregistration flooding -- unauthorized PE

2.2.1.  Threat

   A malicious node or PE could send a stream of registrations/
   deregistrations that are unauthorized to register/deregister - to
   ENRP servers at a very rapid rate and thereby create unnecessary
   state in an ENRP server.

2.2.2.  Effect

   Corrupting the pool registrar database and/or disabling the Rserpool
   discovery and database function.  This represents a denial of service
   attack as the PU would potentially get an IP address of a rogue PE in
   response to an ENRP query which might not provide the actual service.
   If it does provide the service, this would be a man in the middle



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   attack to allow them to collect data.  This could also prevent
   legitimate PEs from registering.

2.2.3.  Requirement

   An ENRP server that receives a registration/deregistration should not
   create or update state information until the authorization of the
   registering/de-registering entity is verified.

2.3.  PE Registration/Deregistration spoofing

2.3.1.  Threat

   A malicious node could send false registrations/deregistrations to
   ENRP servers concerning a legitimate PE thereby creating false state
   information in the ENRP servers.

2.3.2.  Effect

   Misinformation in the ENRP server concerning a PE would get
   propagated to other ENRP servers thereby corrupting the ENRP
   database.  DDoS, by adding a PE that is a target for DDoS attack for
   some popular high volume service the attacker can register a PE that
   a lot of PUs will try to connect to.  This allows man in the middle
   or masquerade attacks on the service provided by the legitimate PEs.
   If a hacker registers its server address as a PE and handles the
   requests he can eavesdrop on service data.

2.3.3.  Requirement

   An ENRP server that receives a registration/deregistration should not
   create or update state information until it has authenticated the PE.

2.4.  PE Registration/Deregistration unauthorized

2.4.1.  Threat

   A PE who is not authorized to join a pool could send registrations/
   deregistrations to ENRP servers thereby creating false state
   information in the ENRP servers.

2.4.2.  Effect

   Misinformation in the ENRP server concerning a PE would get
   propagated to other ENRP servers thereby corrupting the ENRP
   database.  This allows man in the middle or masquerade attacks on the
   service provided by the legitimate PEs.  If a hacker registers its
   server address as a PE and handles the requests he can eavesdrop on



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   service data.

2.4.3.  Requirement

   An ENRP server that receives a registration/deregistration should not
   create or update state information until it has authorized the
   requesting entity.

2.5.  Malicious ENRP server joins the group of legitimate ENRP servers

2.5.1.  Threat

   Malicious ENRP server joins the group of legitimate ENRP servers with
   the intent of propagating inaccurate updates to corrupt the ENRP
   database.

2.5.2.  Effect

   Inconsistent ENRP database state.

2.5.3.  Requirement

   Mutual authentication of ENRP servers.

2.6.  Registration/deregistration with malicious ENRP server

2.6.1.  Threat

   A PE unknowingly registers/deregisters with malicious ENRP server.

2.6.2.  Effect

   Registration might not be properly processed or ignored.  A rogue
   ENRP server has the ability to return any address to a user
   requesting service which could result in denial of service or
   connection to a rouge PE of the hackers choice for service.

2.6.3.  Requirement

   PE needs to authenticate the ENRP server.

2.7.  Malicious ENRP Handlespace Resolution

2.7.1.  Threat

   The ASAP protocol receives a handlespace resolution response from an
   ENRP server, but the ENRP server is malicious and returns random IP
   addresses or an inaccurate list in response to the pool handle.



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2.7.2.  Effect

   PU application communicates with the wrong PE or is unable to locate
   the PE since the response is incorrect in saying that a PE with that
   handle did not exist.  A rouge ENRP server has the ability to return
   any address to ASAP requesting an address list which could result in
   denial of service or connection to a rouge PE of the hackers choice
   for service.  From the PE, the hacker could eavesdrop or tamper with
   the application.

2.7.3.  Requirement

   ASAP needs to authenticate the ENRP server.

2.8.  Malicious node performs a replay attack

2.8.1.  Threat

   A malicious node could replay the entire message previously sent by a
   legitimate entity.  This could create false/unnecessary state in the
   ENRP servers when the replay is for registration/de-registration or
   update.

2.8.2.  Effect

   False/extra state is maintained by ENRP servers.  This would most
   likely be used as a denial of service attack if the replay is used to
   deregister all PEs.

2.8.3.  Requirement

   Care should be taken to prevent replay attacks.

2.9.  Re-establishing PU-PE security during failover

2.9.1.  Threat

   PU fails over from PE A to PE B. In the case that the PU had a
   trusted relationship with PE A, then the PU will likely not have the
   same relationship established with PE B.

2.9.2.  Effect

   If there was a trust relationship involving security context between
   PU and PE A, the equivalent trust relationship will not exist between
   PU and PE B. This will violate security policy.





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2.9.3.  Requirement

   Either notify the application when fail over occurs so the
   application can take appropriate action to establish a trusted
   relationship with PE B OR reestablish the security context
   transparently.

2.10.  Integrity

2.10.1.  Threat

   a.  ENRP response to pool handle resolution is corrupted during
       transmission

   b.  ENRP peer messages are corrupted during transmission

   c.  PE sends update for values and that information is corrupted
       during transmission

2.10.2.  Effect

   ASAP receives corrupt information for pool handle resolution which
   the PU believes to be accurate.

2.10.3.  Requirement

   Integrity mechanism needed.

2.11.  Data Confidentiality

2.11.1.  Threat

   An eavesdropper capable of snooping on fields within messages in
   transit, may be able to garner information such as
   topology/location/IP addresses etc. that may not be desirable to
   divulge.

2.11.2.  Effect

   Information that an administrator does not wish to divulge are
   divulged.  The hacker gains valuable information that can be used for
   financial gain or attacks on hosts.

2.11.3.  Requirement

   Provision for data confidentiality service.





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2.12.  ENRP Server Discovery

2.12.1.  Threats

   a.  Thwarting successful discovery: When a PE wishes to register with
       an ENRP server, it needs to discover an ENRP server.  An attacker
       could thwart the successful discovery of ENRP server(s) thereby
       inducing the PE to believe that no ENRP server is available.  For
       instance, the attacker could reduce the returned set of ENRP
       servers to null or a small set of inactive ENRP servers.

   b.  A similar thwarting scenario also applies when an ENRP server or
       ASAP on behalf of a PU needs to discover ENRP servers.

   c.  Spoofing successful discovery: An attacker could spoof the
       discovery by claiming to be a legitimate ENRP server.  When a PE
       wishes to register, it finds the spoofed ENRP server.

   d.  A similar spoofing scenario also applies when an ENRP server or
       ASAP on behalf of a PU needs to discover ENRP servers.

2.12.2.  Effects

   a.  A PE that could have been in an application server pool does not
       become part of a pool.  The PE does not complete discovery
       operation.  This is a DOS attack.

   b.  An ENRP server that could have been in an ENRP server pool does
       not become part of a pool.  A PU is unable to utilize services of
       ENRP servers.

   c.  This malicious ENRP would either misrepresent, ignore or
       otherwise hide or distort information about the PE to subvert
       RSerPool operation.

   d.  Same as last.

2.12.3.  Requirement

   Provision for data confidentiality service.

2.13.  Flood of endpoint unreachable messages from the PU to the ENRP
       server

2.13.1.  Threat

   These messages are sent by ASAP to the ENRP server when it is unable
   to contact a PE.  There is the potential that a PU could flood the



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   ENRP server intentionally or unintentionally with these messages.

2.13.2.  Effect

   DOS attack on the ENRP server.

2.13.3.  Requirement

   Need to limit the number of endpoint unreachable messages sent to the
   ENRP server from the PU.

2.14.  Flood of endpoint keep alive messages from the ENRP server to a
       PE

2.14.1.  Threat

   These messages would be sent in response to a flood of endpoint
   unreachable messages from the PUs to the ENRP server.

2.14.2.  Effect

   Unintentional DOS attack on the PE.

2.14.3.  Requirement

   ENRP must limit the frequency of keep alive messages to a given PE to
   prevent overwhelming the PE.


3.  Security Considerations

   This informational document characterizes potential security threats
   targeting the Rserpool architecture.  The security mechanisms
   required to mitigate these threats are summarized for each
   architectural component.  It will be noted which mechanisms are
   required and which are optional.

   From the threats described in this document, the security services
   required for the RSerPool protocol suite are given in the following
   table.











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   +--------------+----------------------------------------------------+
   |    Threat    |           Security mechanism in response           |
   +--------------+----------------------------------------------------+
   |  Section 2.1 |          ENRP server authenticates the PE.         |
   |  Section 2.2 |          ENRP server authenticates the PE.         |
   |  Section 2.3 |          ENRP server authenticates the PE.         |
   |  Section 2.4 |          ENRP server authenticates the PE.         |
   |  Section 2.5 |         ENRP servers mutually authenticate.        |
   |  Section 2.6 |          PE authenticates the ENRP server.         |
   |  Section 2.7 |    The PU authenticates the ENRP server.  If the   |
   |              |   authentication fails, it looks for another ENRP  |
   |              |                       server.                      |
   |  Section 2.8 | Security protocol which has protection from replay |
   |              |                      attacks.                      |
   |  Section 2.9 |    Either notify the application when fail over    |
   |              |   occurs so the application can take appropriate   |
   |              | action to establish a trusted relationship with PE |
   |              |        B OR reestablish the security context       |
   |              |                   transparently.                   |
   | Section 2.10 |     Security protocol which supports integrity     |
   |              |                     protection.                    |
   | Section 2.12 |        Security protocol which supports data       |
   |              |                  confidentiality.                  |
   | Section 2.11 |    The PU authenticates the ENRP server.  If the   |
   |              |   authentication fails, it looks for another ENRP  |
   |              |                       server.                      |
   | Section 2.13 |      ASAP must control the number of endpoint      |
   |              |   unreachable messages transmitted from the PU to  |
   |              |                  the ENRP server.                  |
   | Section 2.14 |       ENRP server must control the number of       |
   |              |       Endpoint_KeepAlive messages to the PE.       |
   +--------------+----------------------------------------------------+

   The first four threats combined with the sixth threat result in a
   requirement for mutual authentication of the ENRP server and the PE.

   To summarize the first twelve threats require security mechanisms
   which support authentication, integrity, data confidentiality and
   protection from replay attacks.  For RSerPool we need to authenticate
   the following:

   o  PU -----> ENRP Server (PU authenticates the ENRP server)

   o  PE <----> ENRP Server (mutual authentication)

   o  ENRP server <-----> ENRP Server (mutual authentication)

   Summary by component:



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   RSerPool client --  mandatory to implement authentication of the ENRP
      server is required for accurate pool handle resolution.  This is
      to protect against threats from rogue ENRP servers.  In addition,
      confidentiality, integrity and preventing replay attack are also
      mandatory to implement to protect from eavesdropping and data
      corruption or false data transmission.  Confidentiality is
      mandatory to implement and is used when privacy is required.

   PE to ENRP communications --  mandatory to implement mutual
      authentication, integrity and protection from replay attack is
      required for PE to ENRP communications.  This is to protect the
      integrity of the ENRP handle space database.  Confidentiality is
      mandatory to implement and is used when privacy is required.

   ENRP to ENRP communications --  mandatory to implement mutual
      authentication, integrity and protection from replay attack is
      required for ENRP to ENRP communications.  This is to protect the
      integrity of the ENRP handle space database.  Confidentiality is
      mandatory to implement and is used when privacy is required.

3.1.  Security of the ENRP Database

   Another consideration involves the security characteristics of the
   ENRP database.  Suppose that some of the PEs register with an ENRP
   server using security and some do not.  In this case, when a client
   requests handle space resolution information from ENRP, it would have
   to be informed which entries are "secure" and which are not.  This
   would not only complicate the protocol, but actually bring into
   question the security and integrity of such a database.  What can be
   asserted about the security of such a database is a very thorny
   question.  Due to these two facts it was decided that either the
   entire ENRP server database is secure, that is, it has registrations
   exclusively from PEs that have used security mechanisms or the entire
   database is insecure, that is, registrations are from PEs that have
   used no security mechanisms.  ENRP servers that support security are
   required to reject any PE server registration that does not use the
   security mechanisms.  Likewise, ENRP servers that support security
   should not accept updates from other ENRP servers that do not use
   security mechanisms.

3.2.  Cookie mechanism security

   The application layer is out of scope for RSerPool.  However, some
   questions have been raised about the security of the cookie mechanism
   which will be addressed.

   Cookies are passed via the ASAP control channel.  If TCP is selected
   as the transport, the data and control channel must always be



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   multiplexed.  Therefore, the cases:

   a.  control channel is secured; data channel is not

   b.  data channel is secured; control channel is not

   are not allowed.  It is even hard to understand what this really
   means from a security point of view.

   The multiplexing requirement results in the following cases:

   1.  the multiplexed control channel-data channel is secure OR

   2.  the multiplexed control channel-data channel is not secured

   This applies to cookies in the sense that if you choose to secure
   your control-data channel, then the cookies are secured.

   A second issue is that the PE could choose to sign and/or encrypt the
   cookie.  In this case, it must share keys and other information with
   other PEs.  This application level state sharing is out of scope of
   Rserpool.


4.  IANA Considerations

   This document introduces no additional considerations for IANA.


5.  References

5.1.  Normative References

   [1]  Lei, P., "An Overview of Reliable Server Pooling Protocols",
        draft-ietf-rserpool-overview-02 (work in progress), July 2007.

5.2.  Informative References

   [2]  Bradner, S., "The Internet Standards Process -- Revision 3",
        BCP 9, RFC 2026, October 1996.

   [3]  Schiller, J., "Strong Security Requirements for Internet
        Engineering Task Force Standard Protocols", BCP 61, RFC 3365,
        August 2002.







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Authors' Addresses

   Maureen Stillman (editor)
   Nokia
   35 Woodcrest Avenue
   Ithaca, NY  14850
   US

   Email: maureen.stillman@nokia.com


   Ram Gopal
   Nokia Research Center
   5 Wayside Road
   Burlington, MA  01803
   US

   Email: ram.gopal@nokia.com


   Erik Guttman
   Sun Microsystems
   Eichhoelzelstrasse 7
   74915 Waibstadt
   DE

   Email: Erik.Guttman@sun.com


   Matt Holdrege
   Strix Systems
   26610 Agoura Road
   Suite 110
   Calabasas, CA  91302
   US

   Email: matt@strixsystems.com


   Senthil Sengodan
   Nokia Research Center
   5 Wayside Road
   Burlington, MA  01803
   US

   Email: Senthil.sengodan@nokia.com





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Full Copyright Statement

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