rfc3445.txt

bind 9.3结合mysql数据库

Network Working Group                                          D. Massey
Request for Comments: 3445                                       USC/ISI
Updates: 2535                                                    S. Rose
Category: Standards Track                                           NIST
                                                           December 2002


           Limiting the Scope of the KEY Resource Record (RR)

Status of this Memo

   This document specifies an Internet standards track protocol for the
   Internet community, and requests discussion and suggestions for
   improvements.  Please refer to the current edition of the "Internet
   Official Protocol Standards" (STD 1) for the standardization state
   and status of this protocol.  Distribution of this memo is unlimited.

Copyright Notice

   Copyright (C) The Internet Society (2002).  All Rights Reserved.

Abstract

   This document limits the Domain Name System (DNS) KEY Resource Record
   (RR) to only keys used by the Domain Name System Security Extensions
   (DNSSEC).  The original KEY RR used sub-typing to store both DNSSEC
   keys and arbitrary application keys.  Storing both DNSSEC and
   application keys with the same record type is a mistake.  This
   document removes application keys from the KEY record by redefining
   the Protocol Octet field in the KEY RR Data.  As a result of removing
   application keys, all but one of the flags in the KEY record become
   unnecessary and are redefined.  Three existing application key sub-
   types are changed to reserved, but the format of the KEY record is
   not changed.  This document updates RFC 2535.

1. Introduction

   This document limits the scope of the KEY Resource Record (RR).  The
   KEY RR was defined in [3] and used resource record sub-typing to hold
   arbitrary public keys such as Email, IPSEC, DNSSEC, and TLS keys.
   This document eliminates the existing Email, IPSEC, and TLS sub-types
   and prohibits the introduction of new sub-types.  DNSSEC will be the
   only allowable sub-type for the KEY RR (hence sub-typing is
   essentially eliminated) and all but one of the KEY RR flags are also
   eliminated.






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RFC 3445         Limiting the KEY Resource Record (RR)     December 2002


   Section 2 presents the motivation for restricting the KEY record and
   Section 3 defines the revised KEY RR.  Sections 4 and 5 summarize the
   changes from RFC 2535 and discuss backwards compatibility.  It is
   important to note that this document restricts the use of the KEY RR
   and simplifies the flags, but does not change the definition or use
   of DNSSEC keys.

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
   document are to be interpreted as described in RFC 2119 [1].

2. Motivation for Restricting the KEY RR

   The KEY RR RDATA [3] consists of Flags, a Protocol Octet, an
   Algorithm type, and a Public Key.  The Protocol Octet identifies the
   KEY RR sub-type.  DNSSEC public keys are stored in the KEY RR using a
   Protocol Octet value of 3.  Email, IPSEC, and TLS keys were also
   stored in the KEY RR and used Protocol Octet values of 1,2, and 4
   (respectively).  Protocol Octet values 5-254 were available for
   assignment by IANA and values were requested (but not assigned) for
   applications such as SSH.

   Any use of sub-typing has inherent limitations.  A resolver can not
   specify the desired sub-type in a DNS query and most DNS operations
   apply only to resource records sets.  For example, a resolver can not
   directly request the DNSSEC subtype KEY RRs.  Instead, the resolver
   has to request all KEY RRs associated with a DNS name and then search
   the set for the desired DNSSEC sub-type.  DNSSEC signatures also
   apply to the set of all KEY RRs associated with the DNS name,
   regardless of sub-type.

   In the case of the KEY RR, the inherent sub-type limitations are
   exacerbated since the sub-type is used to distinguish between DNSSEC
   keys and application keys.  DNSSEC keys and application keys differ
   in virtually every respect and Section 2.1 discusses these
   differences in more detail.  Combining these very different types of
   keys into a single sub-typed resource record adds unnecessary
   complexity and increases the potential for implementation and
   deployment errors.  Limited experimental deployment has shown that
   application keys stored in KEY RRs are problematic.

   This document addresses these issues by removing all application keys
   from the KEY RR.  Note that the scope of this document is strictly
   limited to the KEY RR and this document does not endorse or restrict
   the storage of application keys in other, yet undefined, resource
   records.





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RFC 3445         Limiting the KEY Resource Record (RR)     December 2002


2.1 Differences Between DNSSEC and Application Keys

   DNSSEC keys are an essential part of the DNSSEC protocol and are used
   by both name servers and resolvers in order to perform DNS tasks.  A
   DNS zone key, used to sign and authenticate RR sets, is the most
   common example of a DNSSEC key.  SIG(0) [4] and TKEY [3]  also use
   DNSSEC keys.

   Application keys such as Email keys, IPSEC keys, and TLS keys are
   simply another type of data.  These keys have no special meaning to a
   name server or resolver.

   The following table summarizes some of the differences between DNSSEC
   keys and application keys:

      1.  They serve different purposes.

      2.  They are managed by different administrators.

      3.  They are authenticated according to different rules.

      4.  Nameservers use different rules when including them in
          responses.

      5.  Resolvers process them in different ways.

      6.  Faults/key compromises have different consequences.

   1.  The purpose of a DNSSEC key is to sign resource records
   associated with a DNS zone (or generate DNS transaction signatures in
   the case of SIG(0)/TKEY).  But the purpose of an application key is
   specific to the application.  Application keys, such as PGP/email,
   IPSEC, TLS, and SSH keys, are not a mandatory part of any zone and
   the purpose and proper use of application keys is outside the scope
   of DNS.

   2.  DNSSEC keys are managed by DNS administrators, but application
   keys are managed by application administrators.  The DNS zone
   administrator determines the key lifetime, handles any suspected key
   compromises, and manages any DNSSEC key changes.  Likewise, the
   application administrator is responsible for the same functions for
   the application keys related to the application.  For example, a user
   typically manages her own PGP key and a server manages its own TLS
   key.  Application key management tasks are outside the scope of DNS
   administration.






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RFC 3445         Limiting the KEY Resource Record (RR)     December 2002


   3.  DNSSEC zone keys are used to authenticate application keys, but
   by definition, application keys are not allowed to authenticate DNS
   zone keys.  A DNS zone key is either configured as a trusted key or
   authenticated by constructing a chain of trust in the DNS hierarchy.
   To participate in the chain of trust, a DNS zone needs to exchange
   zone key information with its parent zone [3].  Application keys are
   not configured as trusted keys in the DNS and are never part of any
   DNS chain of trust.  Application key data is not needed by the parent
   and does not need to be exchanged with the parent zone for secure DNS
   resolution to work.  A resolver considers an application key RRset as
   authenticated DNS information if it has a valid signature from the
   local DNS zone keys, but applications could impose additional
   security requirements before the application key is accepted as
   authentic for use with the application.

   4.  It may be useful for nameservers to include DNS zone keys in the
   additional section of a response, but application keys are typically
   not useful unless they have been specifically requested.  For
   example, it could be useful to include the example.com zone key along
   with a response that contains the www.example.com A record and SIG
   record.  A secure resolver will need the example.com zone key in
   order to check the SIG and authenticate the www.example.com A record.
   It is typically not useful to include the IPSEC, email, and TLS keys
   along with the A record.  Note that by placing application keys in
   the KEY record, a resolver would need the IPSEC, email, TLS, and
   other key associated with example.com if the resolver intends to
   authenticate the example.com zone key (since signatures only apply to
   the entire KEY RR set).  Depending on the number of protocols
   involved, the KEY RR set could grow unwieldy for resolvers, and DNS
   administrators to manage.

   5.  DNS zone keys require special handling by resolvers, but
   application keys are treated the same as any other type of DNS data.
   The DNSSEC keys are of no value to end applications, unless the
   applications plan to do their own DNS authentication.  By definition,
   secure resolvers are not allowed to use application keys as part of
   the authentication process.  Application keys have no unique meaning
   to resolvers and are only useful to the application requesting the
   key.  Note that if sub-types are used to identify the application
   key, then either the interface to the resolver needs to specify the
   sub-type or the application needs to be able to accept all KEY RRs
   and pick out the desired sub-type.

   6.  A fault or compromise of a DNS zone key can lead to invalid or
   forged DNS data, but a fault or compromise of an application key
   should have no impact on other DNS data.  Incorrectly adding or
   changing a DNS zone key can invalidate all of the DNS data in the
   zone and in all of its subzones.  By using a compromised key, an



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RFC 3445         Limiting the KEY Resource Record (RR)     December 2002


   attacker can forge data from the effected zone and for any of its
   sub-zones.  A fault or compromise of an application key has
   implications for that application, but it should not have an impact
   on the DNS.  Note that application key faults and key compromises can
   have an impact on the entire DNS if the application key and DNS zone
   keys are both stored in the KEY RR.

   In summary, DNSSEC keys and application keys differ in most every
   respect.  DNSSEC keys are an essential part of the DNS infrastructure
   and require special handling by DNS administrators and DNS resolvers.
   Application keys are simply another type of data and have no special
   meaning to DNS administrators or resolvers.  These two different
   types of data do not belong in the same resource record.

3. Definition of the KEY RR

   The KEY RR uses type 25 and is used as resource record for storing
   DNSSEC keys.  The RDATA for a KEY RR consists of flags, a protocol
   octet, the algorithm number octet, and the public key itself.  The
   format is as follows:

   ---------------------------------------------------------------------


                        1 1 1 1 1 1 1 1 1 1 2 2 2 2 2 2 2 2 2 2 3 3
    0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |              flags            |   protocol    |   algorithm   |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                                                               /
   /                        public key                             /
   /                                                               /
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

                             KEY RR Format

   ---------------------------------------------------------------------

   In the flags field, all bits except bit 7 are reserved and MUST be
   zero.  If Bit 7 (Zone bit) is set to 1, then the KEY is a DNS Zone
   key.  If Bit 7 is set to 0, the KEY is not a zone key.  SIG(0)/TKEY
   are examples of DNSSEC keys that are not zone keys.

   The protocol field MUST be set to 3.

   The algorithm and public key fields are not changed.





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