rfc4025.txt

非常好的dns解析软件


RFC 4025          Storing IPsec Keying Material in DNS     February 2005


   An example of a node, 192.0.2.38, that has delegated authority to the
   node 192.0.2.3.

   38.2.0.192.in-addr.arpa. 7200 IN     IPSECKEY ( 10 1 2
                    192.0.2.3
                    AQNRU3mG7TVTO2BkR47usntb102uFJtugbo6BSGvgqt4AQ== )

   An example of a node, 192.0.1.38 that has delegated authority to the
   node with the identity "mygateway.example.com".

   38.1.0.192.in-addr.arpa. 7200 IN     IPSECKEY ( 10 3 2
                    mygateway.example.com.
                    AQNRU3mG7TVTO2BkR47usntb102uFJtugbo6BSGvgqt4AQ== )

   An example of a node, 2001:0DB8:0200:1:210:f3ff:fe03:4d0, that has
   delegated authority to the node 2001:0DB8:c000:0200:2::1

   $ORIGIN 1.0.0.0.0.0.2.8.B.D.0.1.0.0.2.ip6.arpa.
   0.d.4.0.3.0.e.f.f.f.3.f.0.1.2.0 7200 IN     IPSECKEY ( 10 2 2
                    2001:0DB8:0:8002::2000:1
                    AQNRU3mG7TVTO2BkR47usntb102uFJtugbo6BSGvgqt4AQ== )

4.  Security Considerations

   This entire memo pertains to the provision of public keying material
   for use by key management protocols such as ISAKMP/IKE (RFC 2407)
   [7].

   The IPSECKEY resource record contains information that SHOULD be
   communicated to the end client in an integral fashion; i.e., free
   from modification.  The form of this channel is up to the consumer of
   the data; there must be a trust relationship between the end consumer
   of this resource record and the server.  This relationship may be
   end-to-end DNSSEC validation, a TSIG or SIG(0) channel to another
   secure source, a secure local channel on the host, or some
   combination of the above.

   The keying material provided by the IPSECKEY resource record is not
   sensitive to passive attacks.  The keying material may be freely
   disclosed to any party without any impact on the security properties
   of the resulting IPsec session.  IPsec and IKE provide defense
   against both active and passive attacks.

   Any derivative specification that makes use of this resource record
   MUST carefully document its trust model and why the trust model of
   DNSSEC is appropriate, if that is the secure channel used.





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   An active attack on the DNS that caused the wrong IP address to be
   retrieved (via forged address), and therefore the wrong QNAME to be
   queried, would also result in a man-in-the-middle attack.  This
   situation is independent of whether the IPSECKEY RR is used.

4.1.  Active Attacks Against Unsecured IPSECKEY Resource Records

   This section deals with active attacks against the DNS.  These
   attacks require that DNS requests and responses be intercepted and
   changed.  DNSSEC is designed to defend against attacks of this kind.
   This section deals with the situation in which DNSSEC is not
   available.  This is not the recommended deployment scenario.

4.1.1.  Active Attacks Against IPSECKEY Keying Materials

   The first kind of active attack is when the attacker replaces the
   keying material with either a key under its control or with garbage.

   The gateway field is either untouched or is null.  The IKE
   negotiation will therefore occur with the original end-system.  For
   this attack to succeed, the attacker must perform a man-in-the-middle
   attack on the IKE negotiation.  This attack requires that the
   attacker be able to intercept and modify packets on the forwarding
   path for the IKE and data packets.

   If the attacker is not able to perform this man-in-the-middle attack
   on the IKE negotiation, then a denial of service will result, as the
   IKE negotiation will fail.

   If the attacker is not only able to mount active attacks against DNS
   but also in a position to perform a man-in-the-middle attack on IKE
   and IPsec negotiations, then the attacker will be able to compromise
   the resulting IPsec channel.  Note that an attacker must be able to
   perform active DNS attacks on both sides of the IKE negotiation for
   this to succeed.

4.1.2.  Active Attacks Against IPSECKEY Gateway Material

   The second kind of active attack is one in which the attacker
   replaces the gateway address to point to a node under the attacker's
   control.  The attacker then either replaces the public key or removes
   it.  If the public key were removed, then the attacker could provide
   an accurate public key of its own in a second record.

   This second form creates a simple man-in-the-middle attacks since the
   attacker can then create a second tunnel to the real destination.
   Note that, as before, this requires that the attacker also mount an
   active attack against the responder.



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RFC 4025          Storing IPsec Keying Material in DNS     February 2005


   Note that the man-in-the-middle cannot just forward cleartext packets
   to the original destination.  While the destination may be willing to
   speak in the clear, replying to the original sender, the sender will
   already have created a policy expecting ciphertext.  Thus, the
   attacker will need to intercept traffic in both directions.  In some
   cases, the attacker may be able to accomplish the full intercept by
   use of Network Address/Port Translation (NAT/NAPT) technology.

   This attack is easier than the first one because the attacker does
   NOT need to be on the end-to-end forwarding path.  The attacker need
   only be able to modify DNS replies.  This can be done by packet
   modification, by various kinds of race attacks, or through methods
   that pollute DNS caches.

   If the end-to-end integrity of the IPSECKEY RR is suspect, the end
   client MUST restrict its use of the IPSECKEY RR to cases where the RR
   owner name matches the content of the gateway field.  As the RR owner
   name is assumed when the gateway field is null, a null gateway field
   is considered a match.

   Thus, any records obtained under unverified conditions (e.g., no
   DNSSEC or trusted path to source) that have a non-null gateway field
   MUST be ignored.

   This restriction eliminates attacks against the gateway field, which
   are considered much easier, as the attack does not need to be on the
   forwarding path.

   In the case of an IPSECKEY RR with a value of three in its gateway
   type field, the gateway field contains a domain name.  The subsequent
   query required to translate that name into an IP address or IPSECKEY
   RR will also be subject to man-in-the-middle attacks.  If the
   end-to-end integrity of this second query is suspect, then the
   provisions above also apply.  The IPSECKEY RR MUST be ignored
   whenever the resulting gateway does not match the QNAME of the
   original IPSECKEY RR query.

5.  IANA Considerations

   This document updates the IANA Registry for DNS Resource Record Types
   by assigning type 45 to the IPSECKEY record.

   This document creates two new IANA registries, both specific to the
   IPSECKEY Resource Record:

   This document creates an IANA registry for the algorithm type field.





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RFC 4025          Storing IPsec Keying Material in DNS     February 2005


   Values 0, 1, and 2 are defined in Section 2.4.  Algorithm numbers 3
   through 255 can be assigned by IETF Consensus (see RFC 2434 [5]).

   This document creates an IANA registry for the gateway type field.

   Values 0, 1, 2, and 3 are defined in Section 2.3.  Gateway type
   numbers 4 through 255 can be assigned by Standards Action (see RFC
   2434 [5]).

6.  Acknowledgements

   My thanks to Paul Hoffman, Sam Weiler, Jean-Jacques Puig, Rob
   Austein, and Olafur Gudmundsson, who reviewed this document
   carefully.  Additional thanks to Olafur Gurmundsson for a reference
   implementation.

7.  References

7.1.  Normative References

   [1]  Mockapetris, P., "Domain names - concepts and facilities", STD
        13, RFC 1034, November 1987.

   [2]  Mockapetris, P., "Domain names - implementation and
        specification", STD 13, RFC 1035, November 1987.

   [3]  Bradner, S., "Key words for use in RFCs to Indicate Requirement
        Levels", BCP 14, RFC 2119, March 1997.

   [4]  Eastlake 3rd, D. and C. Kaufman, "Domain Name System Security
        Extensions", RFC 2065, January 1997.

   [5]  Narten, T. and H. Alvestrand, "Guidelines for Writing an IANA
        Considerations Section in RFCs", BCP 26, RFC 2434, October 1998.

   [6]  Josefsson, S., "The Base16, Base32, and Base64 Data Encodings",
        RFC 3548, July 2003.

7.2.  Informative References

   [7]  Piper, D., "The Internet IP Security Domain of Interpretation
        for ISAKMP", RFC 2407, November 1998.

   [8]  Eastlake 3rd, D., "Domain Name System Security Extensions", RFC
        2535, March 1999.

   [9]  Eastlake 3rd, D., "DSA KEYs and SIGs in the Domain Name System
        (DNS)", RFC 2536, March 1999.



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RFC 4025          Storing IPsec Keying Material in DNS     February 2005


   [10] Eastlake 3rd, D., "RSA/SHA-1 SIGs and RSA KEYs in the Domain
        Name System (DNS)", RFC 3110, May 2001.

   [11] Massey, D. and S. Rose, "Limiting the Scope of the KEY Resource
        Record (RR)", RFC 3445, December 2002.

   [12] Thomson, S., Huitema, C., Ksinant, V., and M. Souissi, "DNS
        Extensions to Support IP Version 6", RFC 3596, October 2003.

Author's Address

   Michael C. Richardson
   Sandelman Software Works
   470 Dawson Avenue
   Ottawa, ON  K1Z 5V7
   CA

   EMail: [e-mail]
   URI:   http://www.sandelman.ottawa.on.ca/
































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RFC 4025          Storing IPsec Keying Material in DNS     February 2005


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