DNS Extensions R. Arends Internet-Draft Telematica Instituut Expires: April 26, 2004 M. Larson VeriSign R. Austein ISC D. Massey USC/ISI S. Rose NIST October 27, 2003 Protocol Modifications for the DNS Security Extensions draft-ietf-dnsext-dnssec-protocol-03 Status of this Memo This document is an Internet-Draft and is in full conformance with all provisions of Section 10 of RFC2026. Internet-Drafts are working documents of the Internet Engineering Task Force (IETF), its areas, and its working groups. Note that other groups may also distribute working documents as Internet-Drafts. Internet-Drafts are draft documents valid for a maximum of six months and may be updated, replaced, or obsoleted by other documents at any time. It is inappropriate to use Internet-Drafts as reference material or to cite them other than as "work in progress." The list of current Internet-Drafts can be accessed at http:// www.ietf.org/ietf/1id-abstracts.txt. The list of Internet-Draft Shadow Directories can be accessed at http://www.ietf.org/shadow.html. This Internet-Draft will expire on April 26, 2004. Copyright Notice Copyright (C) The Internet Society (2003). All Rights Reserved. Abstract This document is part of a family of documents which describe the DNS Security Extensions (DNSSEC). The DNS Security Extensions are a collection of new resource records and protocol modifications which add data origin authentication and data integrity to the DNS. This document describes the DNSSEC protocol modifications. This document Arends, et al. Expires April 26, 2004 [Page 1] Internet-Draft DNSSEC Protocol Modifications October 2003 defines the concept of a signed zone, along with the requirements for serving and resolving using DNSSEC. These techniques allow a security-aware resolver to authenticate both DNS resource records and authoritative DNS error indications. This document obsoletes RFC 2535 and incorporates changes from all updates to RFC 2535. Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 4 1.1 Background and Related Documents . . . . . . . . . . . . . . 4 1.2 Reserved Words . . . . . . . . . . . . . . . . . . . . . . . 4 1.3 Editors' Notes . . . . . . . . . . . . . . . . . . . . . . . 4 1.3.1 Open Technical Issues . . . . . . . . . . . . . . . . . . . 4 1.3.2 Technical Changes or Corrections . . . . . . . . . . . . . . 4 1.3.3 Typos and Minor Corrections . . . . . . . . . . . . . . . . 5 2. Zone Signing . . . . . . . . . . . . . . . . . . . . . . . . 6 2.1 Including DNSKEY RRs in a Zone . . . . . . . . . . . . . . . 6 2.2 Including RRSIG RRs in a Zone . . . . . . . . . . . . . . . 6 2.3 Including NSEC RRs in a Zone . . . . . . . . . . . . . . . . 8 2.4 Including DS RRs in a Zone . . . . . . . . . . . . . . . . . 8 2.5 Changes to the CNAME Resource Record. . . . . . . . . . . . 8 2.6 Example of a Secure Zone . . . . . . . . . . . . . . . . . . 8 3. Serving . . . . . . . . . . . . . . . . . . . . . . . . . . 9 3.1 Authoritative Name Servers . . . . . . . . . . . . . . . . . 9 3.1.1 Including RRSIG RRs in a Response . . . . . . . . . . . . . 10 3.1.2 Including DNSKEY RRs In a Response . . . . . . . . . . . . . 10 3.1.3 Including NSEC RRs In a Response . . . . . . . . . . . . . . 11 3.1.4 Including DS RRs In a Response . . . . . . . . . . . . . . . 13 3.1.5 Responding to Queries for Type AXFR or IXFR . . . . . . . . 14 3.1.6 The AD and CD Bits in an Authoritative Response . . . . . . 15 3.2 Recursive Name Servers . . . . . . . . . . . . . . . . . . . 16 3.2.1 The DO bit . . . . . . . . . . . . . . . . . . . . . . . . . 16 3.2.2 The CD bit . . . . . . . . . . . . . . . . . . . . . . . . . 17 3.2.3 The AD bit . . . . . . . . . . . . . . . . . . . . . . . . . 18 3.3 Example DNSSEC Responses . . . . . . . . . . . . . . . . . . 18 4. Resolving . . . . . . . . . . . . . . . . . . . . . . . . . 19 4.1 Rate Limiting . . . . . . . . . . . . . . . . . . . . . . . 21 4.2 Stub resolvers . . . . . . . . . . . . . . . . . . . . . . . 21 5. Authenticating DNS Responses . . . . . . . . . . . . . . . . 23 5.1 Special Considerations for Islands of Security . . . . . . . 24 5.2 Authenticating Referrals . . . . . . . . . . . . . . . . . . 24 5.3 Authenticating an RRset Using an RRSIG RR . . . . . . . . . 25 5.3.1 Checking the RRSIG RR Validity . . . . . . . . . . . . . . . 26 5.3.2 Reconstructing the Signed Data . . . . . . . . . . . . . . . 27 5.3.3 Checking the Signature . . . . . . . . . . . . . . . . . . . 28 5.3.4 Authenticating A Wildcard Expanded RRset Positive Arends, et al. Expires April 26, 2004 [Page 2] Internet-Draft DNSSEC Protocol Modifications October 2003 Response . . . . . . . . . . . . . . . . . . . . . . . . . . 29 5.4 Authenticated Denial of Existence . . . . . . . . . . . . . 29 6. IANA Considerations . . . . . . . . . . . . . . . . . . . . 31 7. Security Considerations . . . . . . . . . . . . . . . . . . 32 8. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 33 Normative References . . . . . . . . . . . . . . . . . . . . 34 Informative References . . . . . . . . . . . . . . . . . . . 35 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . 35 A. Signed Zone Example . . . . . . . . . . . . . . . . . . . . 37 B. Example Responses . . . . . . . . . . . . . . . . . . . . . 43 B.1 Answer . . . . . . . . . . . . . . . . . . . . . . . . . . . 43 B.2 Name Error . . . . . . . . . . . . . . . . . . . . . . . . . 44 B.3 No Data Error . . . . . . . . . . . . . . . . . . . . . . . 45 B.4 Referral to Signed Zone . . . . . . . . . . . . . . . . . . 46 B.5 Referral to Unsigned Zone . . . . . . . . . . . . . . . . . 47 B.6 Wildcard Expansion . . . . . . . . . . . . . . . . . . . . . 47 B.7 Wildcard No Data Error . . . . . . . . . . . . . . . . . . . 48 B.8 DS Child Zone No Data Error . . . . . . . . . . . . . . . . 49 C. Authentication Examples . . . . . . . . . . . . . . . . . . 51 C.1 Authenticating An Answer . . . . . . . . . . . . . . . . . . 51 C.1.1 Authenticating the example DNSKEY RR . . . . . . . . . . . . 51 C.2 Name Error . . . . . . . . . . . . . . . . . . . . . . . . . 52 C.3 No Data Error . . . . . . . . . . . . . . . . . . . . . . . 52 C.4 Referral to Signed Zone . . . . . . . . . . . . . . . . . . 52 C.5 Referral to Unsigned Zone . . . . . . . . . . . . . . . . . 52 C.6 Wildcard Expansion . . . . . . . . . . . . . . . . . . . . . 53 C.7 Wildcard No Data Error . . . . . . . . . . . . . . . . . . . 53 C.8 DS Child Zone No Data Error . . . . . . . . . . . . . . . . 53 Intellectual Property and Copyright Statements . . . . . . . 54 Arends, et al. Expires April 26, 2004 [Page 3] Internet-Draft DNSSEC Protocol Modifications October 2003 1. Introduction The DNS Security Extensions (DNSSEC) are a collection of new resource records and protocol modifications which add data origin authentication and data integrity to the DNS. This document defines the DNSSEC protocol modifications. Section 2 of this document defines the concept of a signed zone and lists the requirements for zone signing. Section 3 describes the modifications to authoritative name server behavior necessary to handle signed zones. Section 4 describes the behavior of entities which include security-aware resolver functions. Finally, Section 5 defines how to use DNSSEC RRs to authenticate a response. 1.1 Background and Related Documents The reader is assumed to be familiar with the basic DNS concepts described in RFC1034 [RFC1034] and RFC1035 [RFC1035]. This document is part of a family of documents which define DNSSEC. An introduction to DNSSEC and definition of common terms can be found in [I-D.ietf-dnsext-dnssec-intro]. A definition of the DNSSEC resource records can be found in [I-D.ietf-dnsext-dnssec-records]. 1.2 Reserved Words 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. [RFC2119]. 1.3 Editors' Notes 1.3.1 Open Technical Issues 1.3.2 Technical Changes or Corrections Please report technical corrections to dnssec-editors@east.isi.edu. To assist the editors, please indicate the text in error and point out the RFC that defines the correct behavior. For a technical change where no RFC that defines the correct behavior, or if there's more than one applicable RFC and the definitions conflict, please post the issue to namedroppers. An example correction to dnssec-editors might be: Page X says "DNSSEC RRs SHOULD be automatically returned in responses." This was true in RFC 2535, but RFC 3225 (Section 3, 3rd paragraph) says the DNSSEC RR types MUST NOT be included in responses unless the resolver indicated support for DNSSEC. Arends, et al. Expires April 26, 2004 [Page 4] Internet-Draft DNSSEC Protocol Modifications October 2003 1.3.3 Typos and Minor Corrections Please report any typos corrections to dnssec-editors@east.isi.edu. To assist the editors, please provide enough context for us to find the incorrect text quickly. An example message to dnssec-editors might be: page X says "the DNSSEC standard has been in development for over 1 years". It should read "over 10 years". Arends, et al. Expires April 26, 2004 [Page 5] Internet-Draft DNSSEC Protocol Modifications October 2003 2. Zone Signing DNSSEC is built around the concept of signed zones. A signed zone includes DNSKEY, RRSIG, NSEC and (optionally) DS records according to the rules specified in Section 2.1, Section 2.2, Section 2.3 and Section 2.4, respectively. Any zone which does not include these records according to the rules in this section MUST be considered unsigned for the purposes of the DNS security extensions. DNSSEC requires a change to the definition of the CNAME resource record. Section 2.5 changes the CNAME RR to allow RRSIG and NSEC RRs to appear at the same owner name as a CNAME RR. Section 2.6 shows a sample signed zone. 2.1 Including DNSKEY RRs in a Zone To sign a zone, the zone's administrator generates one or more public/private key pairs and uses the private key(s) to sign authoritative RRsets in the zone. For each private key used to create RRSIG RRs, there SHOULD be a corresponding zone DNSKEY RR stored in the zone. A zone key DNSKEY RR has the Zone Key bit of the flags RDATA field set to one -- see Section 2.1.1 of [I-D.ietf-dnsext-dnssec-records]. Public keys associated with other DNS operations MAY be stored in DNSKEY RRs that are not marked as zone keys. If the zone is delegated and does not wish to act as an island of security, the zone MUST have at least one DNSKEY RR at the apex to act as a secure entry point into the zone. This DNSKEY would then be used to generate a DS RR at the delegating parent (see [I-D.ietf-dnsext-dnssec-records]). This DNSKEY RR SHOULD be either a zone key or a DNSKEY signing key (see [I-D.ietf-dnsext-dnssec-intro] for definition). DNSKEY RRs MUST NOT appear at delegation points. 2.2 Including RRSIG RRs in a Zone For each authoritative RRset in a signed zone (which excludes both NS RRsets at delegation points and glue RRsets), there MUST be at least one RRSIG record that meets all of the following requirements: o The RRSIG owner name is equal to the RRset owner name; o The RRSIG class is equal to the RRset class; o The RRSIG Type Covered field is equal to the RRset type; Arends, et al. Expires April 26, 2004 [Page 6] Internet-Draft DNSSEC Protocol Modifications October 2003 o The RRSIG Original TTL field is equal to the TTL of the RRset; o The RRSIG RR's TTL is equal to the TTL of the RRset; o The RRSIG Labels field is equal to the number of labels in the RRset owner name, not counting the null root label and not counting the wildcard label if the owner name is a wildcard; o The RRSIG Signer's Name field is equal to the name of the zone containing the RRset; and o The RRSIG Algorithm, Signer's Name, and Key Tag fields identify a zone key DNSKEY record at the zone apex. The process for constructing the RRSIG RR for a given RRset is described in [I-D.ietf-dnsext-dnssec-records]. An RRset MAY have multiple RRSIG RRs associated with it. An RRSIG RR itself MUST NOT be signed, since signing an RRSIG RR would add no value and would create an infinite loop in the signing process. The NS RRset which appears at the zone apex name MUST be signed, but the NS RRsets which appear at delegation points (that is, the NS RRsets in the parent zone which delegate the name to the child zone's name servers) MUST NOT be signed. Glue address RRsets associated with delegations MUST NOT be signed. There MUST be an RRSIG for each RRset generated using at least one DNSKEY of each algorithm in the parent zone's DS RRset and each additional algorithm, if any, in the apex DNSKEY RRset. The apex DNSKEY RRset itself MUST be signed by each algorithm appearing in the DS RRset. The difference between the set of owner names which require RRSIG records and the set of owner names which require NSEC records is subtle and worth highlighting. RRSIG records are present at the owner names of all authoritative RRsets. NSEC records are present at the owner names of all names for which the signed zone is authoritative and also at the owner names of delegations from the signed zone to its children. Neither NSEC nor RRSIG records are present (in the parent zone) at the owner names of glue address RRsets. Note, however, that this distinction is for the most part only visible during the zone signing process, because NSEC RRsets are authoritative data, and are therefore signed, thus any owner name which has an NSEC RRset will have RRSIG RRs as well in the signed zone. Arends, et al. Expires April 26, 2004 [Page 7] Internet-Draft DNSSEC Protocol Modifications October 2003 2.3 Including NSEC RRs in a Zone Each owner name in the zone MUST have an NSEC resource record, except for the owner names of any glue address RRsets. The process for constructing the NSEC RR for a given name is described in [I-D.ietf-dnsext-dnssec-records]. The type bitmap of every NSEC resource record in a signed zone MUST indicate the presence of both the NSEC record itself and its corresponding RRSIG record. 2.4 Including DS RRs in a Zone The DS resource record establishes authentication chains between DNS zones. A DS RRset SHOULD be present at a delegation point when the child zone is signed. The DS RRset MAY contain multiple records, each referencing a key used by the child zone to sign its apex DNSKEY RRset. All DS RRsets in a zone MUST be signed and DS RRsets MUST NOT appear at non-delegation points nor at a zone's apex. A DS RR SHOULD point to a DNSKEY RR which is present in the child's apex DNSKEY RRset, and the child's apex DNSKEY RRset SHOULD be signed by the corresponding private key. The TTL of a DS RRset SHOULD match the TTL of the corresponding NS RRset. Construction of a DS RR requires knowledge of the corresponding DNSKEY RR in the child zone, which implies communication between the child and parent zones. This communication is an operational matter not covered by this document. 2.5 Changes to the CNAME Resource Record. If a CNAME RRset is present at a name in a signed zone, appropriate RRSIG and NSEC RRsets are REQUIRED at that name. Other types MUST NOT be present at that name. This is a modification to the original CNAME definition given in [RFC1034]. The original definition of the CNAME RR did not allow any other types to coexist with a CNAME record, but a signed zone requires NSEC and RRSIG RRs for every authoritative name. To resolve this conflict, this specification modifies the definition of the CNAME resource record to allow it to coexist with NSEC and RRSIG RRs. 2.6 Example of a Secure Zone Appendix A shows a complete example of a small signed zone. Arends, et al. Expires April 26, 2004 [Page 8] Internet-Draft DNSSEC Protocol Modifications October 2003 3. Serving This section describes the behavior of entities which include security-aware name functions. In many cases such functions will be part of a security-aware recursive name server, but a security-aware authoritative name server has some of the same requirements as a security-aware recursive name server does. Functions specific to security-aware recursive name servers are described in Section 3.2; functions specific to authoritative servers are described in Section 3.1. The terms "SNAME", "SCLASS", and "STYPE" in the following discussion are as used in [RFC1034]. A security-aware name server MUST support the EDNS0 [RFC2671] message size extension, MUST support a message size of at least 1220 octets, and SHOULD support a message size of 4000 octets [RFC3226]. A security-aware name server which receives a DNS query which does not include the EDNS OPT pseudo-RR or which has the DO bit set to zero MUST treat the RRSIG, DNSKEY, and NSEC RRs as it would any other RRset, and MUST NOT perform any of the additional processing described below. Since the DS RR type has the peculiar property of only existing in the parent zone at delegation points, DS RRs always require some special processing, as described in Section 3.1.4.1. DNSSEC allocates two new bits in the DNS message header: the CD (Checking Disabled) bit and the AD (Authentic Data) bit. The CD bit is controlled by resolvers; a security-aware name server MUST copy the CD bit from a query into the corresponding response. The AD bit is controlled by name servers; a security-aware name server MUST ignore the setting of the AD bit in queries. See Section 3.1.6, Section 3.2.2, Section 3.2.3, Section 4, and Section 4.2 for details on the behavior of these bits. 3.1 Authoritative Name Servers Upon receiving a relevant query which has the EDNS [RFC2671] OPT pseudo-RR DO bit [RFC3225] set to one, a security-aware authoritative name server for a signed zone MUST include additional RRSIG, NSEC, and DS RRs according to the following rules: o RRSIG RRs which can be used to authenticate a response MUST be included in the response according to the rules in Section 3.1.1; o NSEC RRs which can be used to provide authenticated denial of existence MUST be included in the response automatically according to the rules in Section 3.1.3; Arends, et al. Expires April 26, 2004 [Page 9] Internet-Draft DNSSEC Protocol Modifications October 2003 o Either a DS RRset or an NSEC RR proving that no DS RRs exist MUST be included in referrals automatically according to the rules in Section 3.1.4. DNSSEC does not change the DNS zone transfer protocol. Section 3.1.5 discusses zone transfer requirements. 3.1.1 Including RRSIG RRs in a Response When responding to a query which has the DO bit set to one, a security-aware authoritative name server SHOULD attempt to send RRSIG RRs which a security-aware resolver can use to authenticate the RRsets in the response. Inclusion of RRSIG RRs in a response is subject to the following rules: o When placing a signed RRset in the Answer section, the name server MUST also place its RRSIG RRs in the Answer section. The RRSIG RRs have a higher priority for inclusion than any other RRsets which may need to be included. If space does not permit inclusion of these RRSIG RRs, the name server MUST set the TC bit. o When placing a signed RRset in the Authority section, the name server MUST also place its RRSIG RRs in the Authority section. The RRSIG RRs have a higher priority for inclusion than any other RRsets that may need to be included. If space does not permit inclusion of these RRSIG RRs, the name server MUST set the TC bit. o When placing a signed RRset in the Additional section, the name server MUST also place its RRSIG RRs in the Additional section. If space does not permit inclusion of these RRSIG RRs, the name server MUST NOT set the TC bit solely because these RRSIG RRs didn't fit. 3.1.2 Including DNSKEY RRs In a Response When responding to a query which has the DO bit set to one and which requests the SOA or NS RRs at the apex of a signed zone, a security-aware authoritative name server for that zone MAY return the zone apex DNSKEY RRset in the Additional section. In this situation, the DNSKEY RRset and associated RRSIG RRs have lower priority than any other information that would be placed in the additional section. The name server SHOULD NOT include the DNSKEY RRset unless there is enough space in the response message for both the DNSKEY RRset and its associated RRSIG RR(s). If there is not enough space to include these DNSKEY and RRSIG RRs, the name server MUST omit them and MUST NOT set the TC bit solely because these RRs didn't fit (see Section 3.1.1). Arends, et al. Expires April 26, 2004 [Page 10] Internet-Draft DNSSEC Protocol Modifications October 2003 3.1.3 Including NSEC RRs In a Response When responding to a query which has the DO bit set to one, a security-aware authoritative name server for a signed zone MUST include NSEC RRs in each of the following cases: No Data: The zone contains RRsets which exactly match , but does not contain any RRsets which exactly match . Name Error: The zone does not contain any RRsets which match either exactly or via wildcard name expansion. Wildcard Answer: The zone does not contain any RRsets which exactly match but does contain an RRset which matches via wildcard name expansion. Wildcard No Data: The zone does not contain any RRsets which exactly match , does contain one or more RRsets which matches via wildcard name expansion, but does not contain any RRsets which match via wildcard name expansion. In each of these cases, the name server includes NSEC RRs in the response to prove that an exact match for was not present in the zone and that the response which the name server is returning is correct given the data which are in the zone. 3.1.3.1 Including NSEC RRs: No Data Response If the zone contains RRsets matching but contains no RRset matching , then the name server MUST include the NSEC RR for along with its associated RRSIG RR(s) in the Authority section of the response (see Section 3.1.1). If space does not permit inclusion of the NSEC RR or its associated RRSIG RR(s), the name server MUST set the TC bit (see Section 3.1.1). Since the search name exists, wildcard name expansion does not apply to this query, and a single signed NSEC RR suffices to prove the requested RR type does not exist. 3.1.3.2 Including NSEC RRs: Name Error Response If the zone does not contain any RRsets matching either exactly or via wildcard name expansion, then the name server MUST include the following NSEC RRs in the Authority section, along with their associated RRSIG RRs: Arends, et al. Expires April 26, 2004 [Page 11] Internet-Draft DNSSEC Protocol Modifications October 2003 o An NSEC RR proving that there is no exact match for ; and o An NSEC RR proving that the zone contains no RRsets which would match via wildcard name expansion. In some cases a single NSEC RR may prove both of these points, in which case the name server SHOULD only include the NSEC RR and its RRSIG RR(s) once in the Authority section. If space does not permit inclusion of these NSEC and RRSIG RRs, the name server MUST set the TC bit (see Section 3.1.1). 3.1.3.3 Including NSEC RRs: Wildcard Answer Response If the zone does not contain any RRsets which exactly match but does contain an RRset which matches via wildcard name expansion, the name server MUST include the wildcard-expanded answer and the corresponding wildcard-expanded RRSIG RRs in the Answer section, and MUST include in the Authority section an NSEC RR and associated RRSIG RR(s) proving that the zone does not contain a closer match for . If space does not permit inclusion of these answer, NSEC and RRSIG RRs, the name server MUST set the TC bit (see Section 3.1.1). 3.1.3.4 Including NSEC RRs: Wildcard No Data Response This case is a combination of the previous cases. The zone does not contain an exact match for , and while the zone does contain RRsets which match via wildcard name expansion, none of those RRsets match STYPE. The name server MUST include the following NSEC RRs in the Authority section, along with their associated RRSIG RRs: o An NSEC RR proving that there are no RRsets matching STYPE at the wildcard owner name which matched via wildcard expansion; and o An NSEC RR proving that there are no RRsets in the zone which would have been a closer match for . In some cases a single NSEC RR may prove both of these points, in which case the name server SHOULD only include the NSEC RR and its RRSIG RR(s) once in the Authority section. If space does not permit inclusion of these NSEC and RRSIG RRs, the name server MUST set the TC bit (see Section 3.1.1). Arends, et al. Expires April 26, 2004 [Page 12] Internet-Draft DNSSEC Protocol Modifications October 2003 3.1.3.5 Finding The Right NSEC RRs As explained above, there are several situations in which a security-aware authoritative name server needs to locate an NSEC RR which proves that a particular SNAME does not exist. Locating such an NSEC RR within an authoritative zone is relatively simple, at least in concept. The following discussion assumes that the name server is authoritative for the zone which would have held the nonexistent SNAME. The algorithm below is written for clarity, not efficiency. To find the NSEC which proves that name N does not exist in the zone Z which would have held it, construct sequence S consisting of every name in Z, sorted into canonical order. Find the name M which would have immediately preceded N in S if N had existed. M is the owner name of the NSEC RR which proves that N does not exist. The algorithm for finding the NSEC RR which proves that a given name is not covered by any applicable wildcard is similar, but requires an extra step. More precisely, the algorithm for finding the NSEC proving that the applicable wildcard name does not exist is precisely the same as the algorithm for finding the NSEC RR which proves that any other name does not exist: the part that's missing is how to determine the name of the nonexistent applicable wildcard. In practice, this is easy, because the authoritative name server has already checked for the presence of precisely this wildcard name as part of step (1)(c) of the normal lookup algorithm described in Section 4.3.2 of [RFC1034]. 3.1.4 Including DS RRs In a Response When responding to a query which has the DO bit set to one, a security-aware authoritative name server returning a referral includes DNSSEC data along with the NS RRset. If a DS RRset is present at the delegation point, the name server MUST return both the DS RRset and its associated RRSIG RR(s) along with the NS RRset. The name server MUST place the NS RRset before the DS RRset and its associated RRSIG RR(s). If no DS RRset is present at the delegation point, the name server MUST return both the NSEC RR which proves that the DS RRset is not present and the NSEC RR's associated RRSIG RR(s) along with the NS RRset. The name server MUST place the NS RRset before the NSEC RRset and its associated RRSIG RR(s). Including these DS, NSEC, and RRSIG RRs increases the size of referral messages, and may cause some or all glue RRs to be omitted. Arends, et al. Expires April 26, 2004 [Page 13] Internet-Draft DNSSEC Protocol Modifications October 2003 If space does not permit inclusion of the DS or NSEC RRset and associated RRSIG RRs, the name server MUST set the TC bit (see Section 3.1.1). 3.1.4.1 Responding to Queries for DS RRs The DS resource record type is unusual in that it appears only on the parent zone's side of a zone cut. For example, the DS RRset for the delegation of "foo.example" is stored in the "example" zone rather than in the "foo.example" zone. This requires special processing rules for both name servers and resolvers, since the name server for the child zone is authoritative for the name at the zone cut by the normal DNS rules but the child zone does not contain the DS RRset. A security-aware resolver will send queries to the parent zone when looking for a DS RRset at a delegation point, and thus will never trigger the corresponding special processing in a security-aware name server. The rest of this section describes how a security-aware recursive name server processes a misdirected DS query. The need for special processing by a security-aware name server only arises when: o the name server has received a query for the DS RRset at a zone cut; o the name server is authoritative for the child zone; o the name server is not authoritative for the parent zone; and o the name server does not offer recursion. In all other cases, the name server either has some way of obtaining the DS RRset or could not have been expected to have the DS RRset even by the pre-DNSSEC processing rules, so the name server can return either the DS RRset or an error response according to the normal processing rules. If all of the above conditions are met, however, the name server is authoritative for SNAME but cannot supply the requested RRset. In this case, the name server MUST return an authoritative "no data" response showing that the DS RRset does not exist in the child zone's apex. See Appendix B.8 for an example of such a response. 3.1.5 Responding to Queries for Type AXFR or IXFR DNSSEC does not change the DNS zone transfer process. A signed zone will contain RRSIG, DNSKEY, NSEC, and DS resource records, but these Arends, et al. Expires April 26, 2004 [Page 14] Internet-Draft DNSSEC Protocol Modifications October 2003 records have no special meaning with respect to a zone transfer operation, and these RRs are treated as any other resource record type. An authoritative name server is not required to verify that a zone is properly signed before sending or accepting a zone transfer. However, an authoritative name server MAY choose to reject the entire zone transfer if the zone fails meets any of the signing requirements described in Section 2. The primary objective of a zone transfer is to ensure that all authoritative name servers have identical copies of the zone. An authoritative name server which chooses to perform its own zone validation MUST NOT selectively reject some RRs and accept others. DS RRsets appear only on the parental side of a zone cut and are authoritative data in the parent zone. As with any other authoritative RRset, the DS RRset MUST be included in zone transfers of the zone in which the RRset is authoritative data: in the case of the DS RRset, this is the parent zone. NSEC RRs appear in both the parent and child zones at a zone cut, and are authoritative data in both the parent and child zones. The parental and child NSEC RRs at a zone cut are never identical to each other, since the NSEC RR in the child zone's apex will always indicate the presence of the child zone's SOA RR while the parental NSEC RR at the zone cut will never indicate the presence of an SOA RR. As with any other authoritative RRs, NSEC RRs MUST be included in zone transfers of the zone in which they are authoritative data: the parental NSEC RR at a zone cut MUST be included zone transfers of the parent zone, while the NSEC at the zone apex of the child zone MUST be included in zone transfers of the child zone. RRSIG RRs appear in both the parent and child zones at a zone cut, and are authoritative in whichever zone contains the authoritative RRset for which the RRSIG RR provides the signature. That is, the RRSIG RR for a DS RRset or a parental NSEC RR at a zone cut will be authoritative in the parent zone, while the RRSIG for any RRset in the child zone's apex will be authoritative in the child zone. As with any other authoritative RRs, RRSIG RRs MUST be included in zone transfers of the zone in which they are authoritative data. 3.1.6 The AD and CD Bits in an Authoritative Response The CD and AD bits are designed to be used in communication between security-aware resolvers and security-aware recursive name servers. This bits are for the most part not relevant to query processing by security-aware authoritative name servers. Arends, et al. Expires April 26, 2004 [Page 15] Internet-Draft DNSSEC Protocol Modifications October 2003 Since a security-aware name server does not perform signature validation for authoritative data during query processing even when the CD bit is set to zero, a security-aware name server SHOULD ignore the setting of the CD bit when composing an authoritative response. A security-aware name server MUST NOT set the AD bit in a response unless the name server considers all RRsets in the Answer or Authority sections of the response to be authentic. A security-aware name server's local policy MAY consider data from an authoritative zone to be authentic without further validation, but the name server MUST NOT do so unless the name server obtained the authoritative zone via secure means (such as a secure zone transfer mechanism), and MUST NOT do so unless this behavior has been configured explicitly. A security-aware name server which supports recursion MUST follow the rules for the CD and AD bits given in Section 3.2 when generating a response that involves data obtained via recursion. 3.2 Recursive Name Servers As explained in [I-D.ietf-dnsext-dnssec-intro], a security-aware recursive name server is an entity which acts in both the security-aware name server and security-aware resolver roles. This section uses the terms "name server side" and "resolver side" to refer to the code within a security-aware recursive name server which implements the security-aware name server role and the code which implements the security-aware resolver role, respectively. A security-aware recursive name server MUST NOT attempt to answer a query by piecing together cached data it received in response to previous queries that requested different QNAMEs, QTYPEs, or QCLASSes. A security-aware recursive name server MUST NOT use NSEC RRs from one negative response to synthesize a response for a different query. A security-aware recursive name server MUST NOT use a previous wildcard expansion to generate a response to a different query. The resolver side MUST follow the usual rules for caching and negative caching which would apply to any security-aware resolver. 3.2.1 The DO bit The resolver side of a security-aware recursive name server MUST set the DO bit when sending requests, regardless of the state of the DO bit in the initiating request received by the name server side. If the DO bit in an initiating query is not set, the name server side MUST strip any authenticating DNSSEC RRs from the response, but but MUST NOT strip any DNSSEC RRs that the initiating query explicitly Arends, et al. Expires April 26, 2004 [Page 16] Internet-Draft DNSSEC Protocol Modifications October 2003 requested. 3.2.2 The CD bit The CD bit exists in order to allow a security-aware resolver to disable signature validation in a security-aware name server's processing of a particular query. This is a useful but somewhat dangerous capability that requires careful handling by security-aware recursive name servers. A security-aware recursive name server MUST disregard the CD bit and perform normal signature validation unless: o the name server side received that query via a secure channel; or o the recursive name server's local policy dictates that the recursive name server honor the CD bit even when received via an insecure channel. Discussion of cases in which the CD bit is set to one in the rest of this section assumes that one or both of the above conditions applies to the query being processed. If neither condition applies, the recursive name server MUST process the query as if the CD bit were set to zero. Note, however, that the name server side MUST always copy the setting of the CD bit from a query to the corresponding response, regardless of whether or not the recursive name server trusts the setting of the CD bit. The name server side of a security-aware recursive name server MUST pass the sense of the CD bit to the resolver side along with the rest of an initiating query, so that the resolver side will know whether or not it is required to verify the response data it returns to the name server side. If the CD bit is set to one, it indicates that the originating resolver is willing to perform whatever authentication its local policy requires, thus the resolver side of the recursive name server need not perform authentication on the RRsets in the response. When the CD bit is set to one the recursive name server SHOULD, if possible, return the requested data to the originating resolver even if the recursive name server's local authentication policy would reject the records in question. That is, by setting the CD bit, the originating resolver has indicated that it takes responsibility for performing its own authentication, and the recursive name server should not interfere. If the resolver side implements a BAD cache (see Section 4.1) and the name server side receives a query which matches an entry in the resolver side's BAD cache, the name server side's response depends on the sense of the CD bit in the original query. If the CD bit is set, Arends, et al. Expires April 26, 2004 [Page 17] Internet-Draft DNSSEC Protocol Modifications October 2003 the name server side SHOULD return the data from the BAD cache; if the CD bit is not set, the name server side MUST return RCODE 2 (server failure). 3.2.3 The AD bit The name server side of a security-aware recursive name server MUST NOT set the AD bit in a response unless the name server considers all RRsets in the Answer or Authority sections of the response to be authentic, and SHOULD set the AD bit if and only if the resolver side considers all RRsets in the Answer section and any relevant negative response RRs in the Authority section to be authentic. The resolver side MUST follow the procedure described in Section 5 to determine whether the RRs in question are authentic. 3.3 Example DNSSEC Responses See Appendix B for example response packets. Arends, et al. Expires April 26, 2004 [Page 18] Internet-Draft DNSSEC Protocol Modifications October 2003 4. Resolving This section describes the behavior of entities which include security-aware resolver functions. In many cases such functions will be part of a security-aware recursive name server, but a stand-alone security-aware resolver has many of the same requirements. Functions specific to security-aware recursive name servers are described in Section 3.2. A security-aware resolver MUST include an EDNS [RFC2671] OPT pseudo-RR with the DO [RFC3225] bit set to one when sending queries. A security-aware resolver MUST support a message size of at least 1220 octets, SHOULD support a message size of 4000 octets, and MUST advertise the supported message size using the "sender's UDP payload size" field in the EDNS OPT pseudo-RR. A security-aware resolver MUST handle fragmented UDP packets correctly regardless of whether any such fragmented packets were received via IPv4 or IPv6. Please see [RFC3226] for discussion of these requirements. A security-aware resolver MUST support the signature verification mechanisms described in Section 5, and MUST apply them to every received response except when: o The security-aware resolver is part of a security-aware recursive name server, and the response is the result of recursion on behalf of a query received with the CD bit set; o The response is the result of a query generated directly via some form of application interface which instructed the security-aware resolver not to perform validation for this query; or o Validation for this query has been disabled by local policy. A security-aware resolver's support for signature verification MUST include support for verification of wildcard owner names. A security-aware resolver MUST attempt to retrieve missing DS, DNSKEY, or RRSIG RRs via explicit queries if the resolver needs these RRs in order to perform signature verification. A security-aware resolver MUST attempt to retrieve a missing NSEC RR which the resolver needs to authenticate a NODATA response. In general it is not possible for a resolver to retrieve missing NSEC RRs, since the resolver will have no way of knowing the owner name of the missing NSEC RR, but in the specific case of a NODATA response, the resolver does know the name of the missing NSEC RR, and must therefore attempt to retrieve it. Arends, et al. Expires April 26, 2004 [Page 19] Internet-Draft DNSSEC Protocol Modifications October 2003 When attempting to retrieve missing NSEC or DS RRs which reside on the parental side at a zone cut, a security-aware iterative-mode resolver MUST query the name servers for the parent zone, not the child zone. A security-aware resolver MUST be able to determine whether or not it should expect a particular RRset to be signed. More precisely, a security-aware resolver must be able to distinguish between three cases: 1. An RRset for which the resolver is able to build a chain of signed DNSKEY and DS RRs from a trusted starting point to the RRset. In this case, the RRset should be signed, and is subject to signature validation as described above. 2. An RRset for which the resolver knows that it has no chain of signed DNSKEY and DS RRs from any trusted starting point to the RRset. This can occur when the target RRset lies in an unsigned zone or in a descendent of an unsigned zone. In this case, the RRset may or may not be signed, but the resolver will not be able to verify the signature. 3. An RRset for which the resolver is not able to determine whether or not the RRset should be signed, because the resolver is not able to obtain the necessary DNSSEC RRs. This can occur when the security-aware resolver is not able to contact security-aware name servers for the relevant zones. A security-aware resolver MUST be capable of being preconfigured with at least one trusted public key, and MUST be capable of being preconfigured with multiple trusted public keys or DS RRs. Since a security-aware resolver will not be able to validate signatures without such a preconfigured trusted key, the resolver SHOULD have some reasonably robust mechanism for obtaining such keys when it boots. A security-aware resolver SHOULD cache each response as a single atomic entry, indexed by the triple , with the single atomic entry containing the entire answer, including the named RRset and any associated DNSSEC RRs. The resolver SHOULD discard the entire atomic entry when any of the RRs contained in it expire. A security-aware resolver MAY set the CD bit in a query to one in order to indicate that the resolver takes responsibility for performing whatever authentication its local policy requires on the RRsets in the response. See Section 3.2 for the effect this bit has on the behavior of security-aware recursive name servers. Arends, et al. Expires April 26, 2004 [Page 20] Internet-Draft DNSSEC Protocol Modifications October 2003 A security-aware resolver MUST zero the AD bit when composing query messages. 4.1 Rate Limiting A security-aware resolver SHOULD NOT cache data with invalid signatures under normal circumstances. However, a security-aware resolver SHOULD take steps to rate limit the number of identical queries that it generates if signature validation of the responses fails repeatedly. Conceptually, this is similar in some respects to negative caching [RFC2308], but since the resolver has no way of obtaining an appropriate caching TTL from received data in this case, the TTL will have to be set by the implementation. This document refers to the data retained as part of such a rate limiting mechanism as the "BAD cache". A security-aware resolver MAY chose to retain RRsets for which signature validation has failed in its BAD cache, but MUST NOT return such RRsets from its BAD cache unless both of the following conditions are met: o The resolver has recently generated enough queries identical to this one that the resolver is suppressing queries for this ; and o The resolver is not required to validate the signatures of the RRsets in question under the rules given in Section 4 of this document. The intent of the above rule is to provide the raw data to clients which are capable of performing their own signature verification checks while protecting clients which depend on this resolver to perform such checks. Several of the possible reasons why signature validation might fail involve conditions which may not apply equally to this resolver and the client which invoked it: for example, this resolver's clock may be set incorrectly, or the client may have knowledge of a relevant island of security which this resolver does not share. In such cases, "protecting" a client which is capable of performing its own signature validation from ever seeing the "bad" data does not help the client. 4.2 Stub resolvers A security-aware stub resolver MUST include an EDNS [RFC2671] OPT pseudo-RR with the DO [RFC3225] bit set to one when sending queries. Arends, et al. Expires April 26, 2004 [Page 21] Internet-Draft DNSSEC Protocol Modifications October 2003 A security-aware stub resolver MUST support a message size of at least 1220 octets, SHOULD support a message size of 4000 octets, and MUST advertise the supported message size using the "sender's UDP payload size" field in the EDNS OPT pseudo-RR. A security-aware stub resolver MUST handle fragmented UDP packets correctly regardless of whether any such fragmented packets were received via IPv4 or IPv6. Please see [RFC3226] for discussion of these requirements. A security-aware stub resolver MUST support the DNSSEC RR types, at least to the extent of not mishandling responses just because they contain DNSSEC RRs. A security-aware stub resolver MAY include the DNSSEC RRs returned by a security-aware recursive name server as part of the data that it the stub resolver hands back to the application which invoked it but is not required to do so. A security-aware stub resolver SHOULD NOT set the CD bit when sending queries, since, by definition, a security-aware stub resolver does not validate signatures and thus depends on the security-aware recursive name server to perform validation on its behalf. A security-aware stub resolver MAY chose to examine the setting of the AD bit in response messages that it receives in order to determine whether the security-aware recursive name server which sent the response claims to have cryptographically verified the data in the Answer and Authority sections of the response message. Note, however, that the responses received by a security-aware stub resolver are heavily dependent on the local policy of the security-aware recursive name server, so as a practical matter there may be little practical value to checking the status of the AD bit except perhaps as a debugging aid. In any case, a security-aware stub resolver MUST NOT place any reliance on signature validation allegedly performed on its behalf except when the security-aware stub resolver obtained the data in question from a trusted security-aware recursive name server via a secure channel. Arends, et al. Expires April 26, 2004 [Page 22] Internet-Draft DNSSEC Protocol Modifications October 2003 5. Authenticating DNS Responses In order to use DNSSEC RRs for authentication, a security-aware resolver requires preconfigured knowledge of at least one authenticated DNSKEY or DS RR. The process for obtaining and authenticating this initial DNSKEY or DS RR is achieved via some external mechanism. For example, a resolver could use some off-line authenticated exchange to obtain a zone's DNSKEY RR or obtain a DS RR that identifies and authenticates a zone's DNSKEY RR. The remainder of this section assumes that the resolver has somehow obtained an initial set of authenticated DNSKEY RRs. An initial DNSKEY RR can be used to authenticate a zone's apex DNSKEY RRset. To authenticate an apex DNSKEY RRset using an initial key, the resolver MUST: 1. Verify that the initial DNSKEY RR appears in the apex DNSKEY RRset, and verify that the DNSKEY RR has the Zone Key Flag (DNSKEY RDATA bit 7) set to one. 2. Verify that there is some RRSIG RR which covers the apex DNSKEY RRset, and that the combination of the RRSIG RR and the initial DNSKEY RR authenticates the DNSKEY RRset. The process for using an RRSIG RR to authenticate an RRset is described in Section 5.3. Once the resolver has authenticated the apex DNSKEY RRset using an initial DNSKEY RR, delegations from that zone can be authenticated using DS RRs. This allows a resolver to start from an initial key, and use DS RRsets to proceed recursively down the DNS tree obtaining other apex DNSKEY RRsets. If the resolver were preconfigured with a root DNSKEY RR, and if every delegation had a DS RR associated with it, then the resolver could obtain and validate any apex DNSKEY RRset. The process of using DS RRs to authenticate referrals is described in Section 5.2. Once the resolver has authenticated a zone's apex DNSKEY RRset, Section 5.3 shows how the resolver can use DNSKEY RRs in the apex DNSKEY RRset and RRSIG RRs from the zone to authenticate any other RRsets in the zone. Section 5.4 shows how the resolver can use authenticated NSEC RRsets from the zone to prove that an RRset is not present in the zone. When a resolver indicates support for DNSSEC, a security-aware name server should attempt to provide the necessary DNSKEY, RRSIG, NSEC, and DS RRsets in a response (see Section 3). However, a security-aware resolver may still receive a response which that lacks the appropriate DNSSEC RRs, whether due to configuration issues such as a security-oblivious recursive name server which accidentally Arends, et al. Expires April 26, 2004 [Page 23] Internet-Draft DNSSEC Protocol Modifications October 2003 interfere with DNSSEC RRs or due to a deliberate attack in which an adversary forges a response, strips DNSSEC RRs from a response, or modifies a query so that DNSSEC RRs appear not to be requested. The absence of DNSSEC data in a response MUST NOT by itself be taken as an indication that no authentication information exists. A resolver SHOULD expect authentication information from signed zones. A resolver SHOULD believe that a zone is signed if the resolver has been configured with public key information for the zone, or if the zone's parent is signed and the delegation from the parent contains a DS RRset. 5.1 Special Considerations for Islands of Security Islands of security (see [I-D.ietf-dnsext-dnssec-intro]) are signed zones for which it is not possible to construct an authentication chain to the zone from its parent. Validating signatures within an island of security requires the validator to have some other means of obtaining an initial authenticated zone key for the island. If a validator cannot obtain such a key, it will have to choose whether to accept the unvalidated responses or not based on local policy. All the normal processes for validating responses apply to islands of security. The only difference between normal validation and validation within an island of security is in how the validator obtains a starting point for the authentication chain. 5.2 Authenticating Referrals Once the apex DNSKEY RRset for a signed parent zone has been authenticated, DS RRsets can be used to authenticate the delegation to a signed child zone. A DS RR identifies a DNSKEY RR in the child zone's apex DNSKEY RRset, and contains a cryptographic digest of the child zone's DNSKEY RR. A strong cryptographic digest algorithm ensures that an adversary can not easily generate a DNSKEY RR that matches the digest. Thus, authenticating the digest allows a resolver to authenticate the matching DNSKEY RR. The resolver can then use this child DNSKEY RR to authenticate the entire child apex DNSKEY RRset. Given a DS RR for a delegation, the child zone's apex DNSKEY RRset can be authenticated if all of the following hold: o The DS RR has been authenticated using some DNSKEY RR in the parent's apex DNSKEY RRset (see Section 5.3); o The Algorithm and Key Tag in the DS RR match the Algorithm field and the key tag of a DNSKEY RR in the child zone's apex DNSKEY Arends, et al. Expires April 26, 2004 [Page 24] Internet-Draft DNSSEC Protocol Modifications October 2003 RRset which, when hashed using the digest algorithm specified in the DS RR's Digest Type field, results in a digest value which matches the Digest field of the DS RR; and o The matching DNSKEY RR in the child zone has the Zone Flag bit set to one, the corresponding private key has signed the child zone's apex DNSKEY RRset, and the resulting RRSIG RR authenticates the child zone's apex DNSKEY RRset. If the referral from the parent zone did not contain a DS RRset, the response should have included a signed NSEC RRset proving that no DS RRset exists for the delegated name (see Section 3.1.4). A security-aware resolver MUST query the name servers for the parent zone for the DS RRset if the referral includes neither a DS RRset nor a NSEC RRset proving that the DS RRset does not exist (see Section 4). If the resolver authenticates an NSEC RRset which proves that no DS RRset is present for this zone, then there is no authentication path leading from the parent to the child. If the resolver has an initial DNSKEY or DS RR which belongs to the child zone or to any delegation below the child zone, this initial DNSKEY or DS RR MAY be used to re-establish an authentication path. If no such initial DNSKEY or DS RR exists, the resolver can not authenticate RRsets in or below the child zone. Note that, for a signed delegation, there are two NSEC RRs associated with the delegated name. One NSEC RR resides in the parent zone, and can be used to prove whether a DS RRset exists for the delegated name. The second NSEC RR resides in the child zone, and identifies which RRsets are present at the apex of the child zone. The parent NSEC RR and child NSEC RR can always be distinguished, since the SOA bit will be set in the child NSEC RR and clear in the parent NSEC RR. A security-aware resolver MUST use the parent NSEC RR when attempting to prove that a DS RRset does not exist. 5.3 Authenticating an RRset Using an RRSIG RR A resolver can use an RRSIG RR and its corresponding DNSKEY RR to attempt to authenticate RRsets. The resolver first checks the RRSIG RR to verify that it covers the RRset, has a valid time interval, and identifies a valid DNSKEY RR. The resolver then constructs the canonical form of the signed data by appending the RRSIG RDATA (excluding the Signature Field) with the canonical form of the covered RRset. Finally, resolver uses the public key and signature to authenticate the signed data. Section 5.3.1, Section 5.3.2, and Section 5.3.3 describe each step in detail. Arends, et al. Expires April 26, 2004 [Page 25] Internet-Draft DNSSEC Protocol Modifications October 2003 5.3.1 Checking the RRSIG RR Validity A security-aware resolver can use an RRSIG RR to authenticate an RRset if all of the following conditions hold: o The RRSIG RR and the RRset MUST have the same owner name and the same class; o The RRSIG RR's Signer's Name field MUST be the name of the zone that contains the RRset; o The RRSIG RR's Type Covered field MUST equal the RRset's type; o The number of labels in the RRset owner name MUST be greater than or equal to the value in the RRSIG RR's Labels field; o The resolver's notion of the current time MUST be less than or equal to the time listed in the RRSIG RR's Expiration field; o The resolver's notion of the current time MUST be greater than or equal to the time listed in the RRSIG RR's Inception field; o The RRSIG RR's Signer's Name, Algorithm, and Key Tag fields MUST match the owner name, algorithm, and key tag for some DNSKEY RR in the zone's apex DNSKEY RRset; o The matching DNSKEY RR MUST be present in the zone's apex DNSKEY RRset, and MUST have the Zone Flag bit (DNSKEY RDATA Flag bit 7) set to one. It is possible for more than one DNSKEY RR to match the conditions above. In this case, the resolver can not predetermine which DNSKEY RR to use to authenticate the signature, MUST try each matching DNSKEY RR until the resolver has either validated the signature or has run out of matching keys to try. Note that this authentication process is only meaningful if the resolver authenticates the DNSKEY RR before using it to validate signatures. The matching DNSKEY RR is considered to be authentic if: o The apex DNSKEY RRset containing the DNSKEY RR is considered authentic; or o The RRset covered by the RRSIG RR is the apex DNSKEY RRset itself, and the DNSKEY RR either matches an authenticated DS RR from the parent zone or matches a DS RR or DNSKEY RR which the resolver has been preconfigured to believe to be authentic. Arends, et al. Expires April 26, 2004 [Page 26] Internet-Draft DNSSEC Protocol Modifications October 2003 5.3.2 Reconstructing the Signed Data Once the RRSIG RR has met the validity requirements described in Section 5.3.1, the resolver needs to reconstruct the original signed data. The original signed data includes RRSIG RDATA (excluding the Signature field) and the canonical form of the RRset. Aside from being ordered, the canonical form of the RRset might also differ from the received RRset due to DNS name compression, decremented TTLs, or wildcard expansion. The resolver should use the following to reconstruct the original signed data: signed_data = RRSIG_RDATA | RR(1) | RR(2)... where "|" denotes concatenation RRSIG_RDATA is the wire format of the RRSIG RDATA fields with the Signature field excluded and the Signer's Name in canonical form. RR(i) = name | class | type | OrigTTL | RDATA length | RDATA name is calculated according to the function below class is the RRset's class type is the RRset type and all RRs in the class OrigTTL is the value from the RRSIG Original TTL field All names in the RDATA field are in canonical form The set of all RR(i) is sorted into canonical order. To calculate the name: let rrsig_labels = the value of the RRSIG Labels field let fqdn = RRset's fully qualified domain name in canonical form let fqdn_labels = RRset's fully qualified domain name in canonical form if rrsig_labels = fqdn_labels, name = fqdn if rrsig_labels < fqdn_labels, name = "*." | the leftmost rrsig_label labels of the fqdn Arends, et al. Expires April 26, 2004 [Page 27] Internet-Draft DNSSEC Protocol Modifications October 2003 if rrsig_labels > fqdn the RRSIG RR did not pass the necessary validation checks and MUST NOT be used to authenticate this RRset. The canonical forms for names and RRsets are defined in [I-D.ietf-dnsext-dnssec-records]. NSEC RRsets at a delegation boundary require special processing. There are two distinct NSEC RRsets associated with a signed delegated name. One NSEC RRset resides in the parent zone, and specifies which RRset are present at the parent zone. The second NSEC RRset resides at the child zone, and identifies which RRsets are present at the apex in the child zone. The parent NSEC RRset and child NSEC RRset can always be distinguished since only the child NSEC RRs will specify an SOA RRset exists at the name. When reconstructing the original NSEC RRset for the delegation from the parent zone, the NSEC RRs MUST NOT be combined with NSEC RRs from the child zone, and when reconstructing the original NSEC RRset for the apex of the child zone, the NSEC RRs MUST NOT be combined with NSEC RRs from the parent zone. Note also that each of the two NSEC RRsets at a delegation point has a corresponding RRSIG RR with an owner name matching the delegated name, and each of these RRSIG RRs is authoritative data associated with the same zone which contains the corresponding NSEC RRset. If necessary, a resolver can tell these RRSIG RRs apart by checking the Signer's Name field. 5.3.3 Checking the Signature Once the resolver has validated the RRSIG RR as described in Section 5.3.1 and reconstructed the original signed data as described in Section 5.3.2, the resolver can attempt to use the cryptographic signature to authenticate the signed data, and thus (finally!) authenticate the RRset. The Algorithm field in the RRSIG RR identifies the cryptographic algorithm to generate the signature. The signature itself is contained in the Signature field of the RRSIG RDATA, and the public key to used generate the signature is contained in the Public Key field of the matching DNSKEY RR(s) (found in Section 5.3.1). [I-D.ietf-dnsext-dnssec-records] provides a list of algorithm types, and provides pointers to the documents that define each algorithm's use. Note that it is possible for more than one DNSKEY RR to match the conditions in Section 5.3.1. In this case, the resolver can only Arends, et al. Expires April 26, 2004 [Page 28] Internet-Draft DNSSEC Protocol Modifications October 2003 determine which DNSKEY RR by trying each matching key until the resolver either succeeds in validating the signature or runs out of keys to try. If the Labels field of the RRSIG RR is not equal to the number of labels in the RRset's fully qualified owner name, then the RRset is either invalid or the result of wildcard expansion. The resolver MUST verify that wildcard expansion was applied properly before considering the RRset to be authentic. Section 5.3.4 describes how to determine whether a wildcard was applied properly. If other RRSIG RRs also cover this RRSIG RR, the local resolver security policy determines whether the resolver also needs to test these RRSIG RRs, and determines how to resolve conflicts if these RRSIG RRs lead to differing results. If the resolver accepts the RRset as authentic, the resolver MUST set the TTL of the RRSIG RR and each RR in the authenticated RRset to a value no greater than the minimum of: o The RRset's TTL as received in the response; o The RRSIG RR's TTL as received in the response; and o The value in the RRSIG RR's Original TTL field. 5.3.4 Authenticating A Wildcard Expanded RRset Positive Response If the number of labels in an RRset's fully qualified domain name is greater than the Labels field in the covering RRSIG RDATA, then the RRset and its covering RRSIG RR were created as a result of wildcard expansion. Once the resolver has verified the signature as described in Section 5.3, the resolver must take additional steps to verify the non-existence of an exact match or closer wildcard match for the query. Section 5.4 discusses these steps. Note that the response received by the resolver should include all NSEC RRs needed to authenticate the response (see Section 3.1.3). 5.4 Authenticated Denial of Existence A resolver can use authenticated NSEC RRs to prove that an RRset is not present in a signed zone. Security-aware name servers should automatically include any necessary NSEC RRs for signed zones in their responses to security-aware resolvers. Security-aware resolvers MUST first authenticate NSEC RRsets Arends, et al. Expires April 26, 2004 [Page 29] Internet-Draft DNSSEC Protocol Modifications October 2003 according to the standard RRset authentication rules described in Section 5.3, then apply the NSEC RRsets as follows: o If the requested RR name matches the owner name of an authenticated NSEC RR, then the NSEC RR's type bit map field lists all RR types present at that owner name, and a resolver can prove that the requested RR type does not exist by checking for the RR type in the bit map. Since the existence of the authenticated NSEC RR proves that the owner name exists in the zone, wildcard expansion could not have been used to match the requested RR owner name and type. o If the requested RR name would appear after an authenticated NSEC RR owner name and before the name listed in that NSEC RR's Next Domain Name field according to the canonical DNS name order defined in [I-D.ietf-dnsext-dnssec-records], then no exact match for the requested RR name exists in the zone. However, it is possible that a wildcard could be used to match the requested RR owner name and type, so proving that the requested RRset does not exist also requires proving that no possible wildcard exists which could have been used to generate a positive response. To prove non-existence of an RRset, the resolver must be able to verify both that the queried RRset does not exist and that no relevant wildcard RRset exists. Proving this may require more than one NSEC RRset from the zone. If the complete set of necessary NSEC RRsets is not present in a response (perhaps due to truncation), then a security-aware resolver MUST resend the query in order to attempt to obtain the full collection of NSEC RRs necessary to verify non-existence of the requested RRset. As with all DNS operations, however, the resolver MUST bound the work it puts into answering any particular query. Since a verified NSEC RR proves the existence of both itself and its corresponding RRSIG RR, a verifier MUST ignore the settings of the NSEC and RRSIG bits in an NSEC RR. Authentication examples are given in Section Appendix C. Arends, et al. Expires April 26, 2004 [Page 30] Internet-Draft DNSSEC Protocol Modifications October 2003 6. IANA Considerations [I-D.ietf-dnsext-dnssec-records] contains a review of the IANA considerations introduced by DNSSEC. The additional IANA considerations discussed in this document: [RFC2535] reserved the CD and AD bits in the message header. The meaning of the AD bit was redefined in [I-D.ietf-dnsext-ad-is-secure] and the meaning of both the CD and AD bit are restated in this document. No new bits in the DNS message header are defined in this document. [RFC2671] introduced EDNS and [RFC3225] reserved the DNSSEC OK bit and defined its use. The use is restated but not altered in this document. Arends, et al. Expires April 26, 2004 [Page 31] Internet-Draft DNSSEC Protocol Modifications October 2003 7. Security Considerations This document describes how the DNS security extensions use public key cryptography to sign and authenticate DNS resource record sets. Please see [I-D.ietf-dnsext-dnssec-intro] for terminology and general security considerations related to DNSSEC. An active attacker who can set the CD bit in a DNS query message or the AD bit in a DNS response message can use these bits to defeat the protection which DNSSEC attempts to provide to security-oblivious recursive-mode resolvers. For this reason, use of these control bits by a security-aware recursive-mode resolver requires a secure channel. See Section 3.2.2 and Section 4.2 for further discussion. DNSSEC introduces a number of denial of service issues. These issues will also be addressed in a future version of these security considerations. Arends, et al. Expires April 26, 2004 [Page 32] Internet-Draft DNSSEC Protocol Modifications October 2003 8. Acknowledgements This document was created from the input and ideas of several members of the DNS Extensions Working Group and working group mailing list. The editors would like to express their thanks for the comments and suggestions received during the revision of these security extension specifications. Arends, et al. Expires April 26, 2004 [Page 33] Internet-Draft DNSSEC Protocol Modifications October 2003 Normative References [RFC1034] Mockapetris, P., "Domain names - concepts and facilities", STD 13, RFC 1034, November 1987. [RFC1035] Mockapetris, P., "Domain names - implementation and specification", STD 13, RFC 1035, November 1987. [RFC1982] Elz, R. and R. Bush, "Serial Number Arithmetic", RFC 1982, August 1996. [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997. [RFC2181] Elz, R. and R. Bush, "Clarifications to the DNS Specification", RFC 2181, July 1997. [RFC2671] Vixie, P., "Extension Mechanisms for DNS (EDNS0)", RFC 2671, August 1999. [RFC3225] Conrad, D., "Indicating Resolver Support of DNSSEC", RFC 3225, December 2001. [RFC3226] Gudmundsson, O., "DNSSEC and IPv6 A6 aware server/resolver message size requirements", RFC 3226, December 2001. [I-D.ietf-dnsext-dnssec-intro] Arends, R., Austein, R., Larson, M., Massey, D. and S. Rose, "DNS Security Introduction and Requirements", draft-ietf-dnsext-dnssec-intro-07 (work in progress), October 2003. [I-D.ietf-dnsext-dnssec-records] Arends, R., Austein, R., Larson, M., Massey, D. and S. Rose, "Resource Records for DNS Security Extensions", draft-ietf-dnsext-dnssec-records-05 (work in progress), October 2003. Arends, et al. Expires April 26, 2004 [Page 34] Internet-Draft DNSSEC Protocol Modifications October 2003 Informative References [RFC2308] Andrews, M., "Negative Caching of DNS Queries (DNS NCACHE)", RFC 2308, March 1998. [RFC2535] Eastlake, D., "Domain Name System Security Extensions", RFC 2535, March 1999. [RFC2930] Eastlake, D., "Secret Key Establishment for DNS (TKEY RR)", RFC 2930, September 2000. [RFC2931] Eastlake, D., "DNS Request and Transaction Signatures ( SIG(0)s)", RFC 2931, September 2000. [I-D.ietf-dnsext-delegation-signer] Gudmundsson, O., "Delegation Signer Resource Record", draft-ietf-dnsext-delegation-signer-15 (work in progress), June 2003. [I-D.ietf-dnsext-wcard-clarify] Halley, B. and E. Lewis, "Clarifying the Role of Wild Card Domains in the Domain Name System", draft-ietf-dnsext-wcard-clarify-02 (work in progress), September 2003. [I-D.ietf-dnsext-ad-is-secure] Wellington, B. and O. Gudmundsson, "Redefinition of DNS AD bit", draft-ietf-dnsext-ad-is-secure-06 (work in progress), June 2002. Authors' Addresses Roy Arends Telematica Instituut Drienerlolaan 5 7522 NB Enschede NL EMail: roy.arends@telin.nl Arends, et al. Expires April 26, 2004 [Page 35] Internet-Draft DNSSEC Protocol Modifications October 2003 Matt Larson VeriSign, Inc. 21345 Ridgetop Circle Dulles, VA 20166-6503 USA EMail: mlarson@verisign.com Rob Austein Internet Software Consortium 40 Gavin Circle Reading, MA 01867 USA EMail: sra@isc.org Dan Massey USC Information Sciences Institute 3811 N. Fairfax Drive Arlington, VA 22203 USA EMail: masseyd@isi.edu Scott Rose National Institute for Standards and Technology 100 Bureau Drive Gaithersburg, MD 20899-8920 USA EMail: scott.rose@nist.gov Arends, et al. Expires April 26, 2004 [Page 36] Internet-Draft DNSSEC Protocol Modifications October 2003 Appendix A. Signed Zone Example The following example shows a (small) complete signed zone. example. 3600 IN SOA ns1.example. bugs.ns1.example. ( 1065745538 3600 300 3600000 3600 ) 3600 RRSIG SOA 1 1 3600 20031108232541 ( 20031009232541 5742 example. 0EhIo5SFK2xwM2CMh3P6FJUmpV5VFotM5pzb 8f3cL3SyKfOswI2osc3VvbtiEDQHEcE4/b+v BNx99Wc4jm3llWlsDOxlIbtR/S44xeOVRpff pLuMW4IZmdwGY/xh/WHOCV+bqVl+s9un0OcX LQTbyhlNTWdVYxPLo2T2dNP8a+0= ) 3600 NS ns1.example. 3600 NS ns2.example. 3600 RRSIG NS 1 1 3600 20031108232541 ( 20031009232541 5742 example. KBhJYJ0vFNyMJrt07gvHN9WAOijhXbcikUNw ZEJxkL+UCv/GFJi1ABGMDowschPkpHIgDEOQ exaLWGGUrOA5xMHYONWZpkL4rQ3URAKF46VJ dMg0UTdw3pTD7Lvs8t6Dim46dj9h/QQEgNLF BYpCn/jKFJ7lYnYYGLAUofh/+mo= ) 3600 MX 1 xx.example. 3600 RRSIG MX 1 1 3600 20031108232541 ( 20031009232541 5742 example. CSB4g+vSxyrfsfycsZwAx2hKhwK/x7GAIY0p MLBgAA/USiiMben0II4aYf5lybs0NINnFDju 2Kc78M8t9zBGeJcZCZEs9mKiXhW8WJanvIjg BwJgWXwAnVnq20TXlsHiuwuhmtrb76/Avl4i lnX6XA3eeDlQlOTuPe0B91MCuow= ) 3600 NSEC a.example. NS SOA MX RRSIG NSEC DNSKEY 3600 RRSIG NSEC 1 1 3600 20031108232541 ( 20031009232541 5742 example. 10XG3f8uExTPfof30CoonvXSMeqrhrkcN9YG krhJD4xeVKarTkQMt0dFe66Bbuy961Bv9go1 IEp0R+sV3B5ldqSKBrcIRsh4QFqQp6IPZ+By yxyYV25L68I1dkM1JoV7IMFsfcTDPjyl3wv2 2LAQ2lyqLBpow5BRR4sAgjZ7Yaw= ) 3600 DNSKEY 256 3 1 ( AQPdhnap0Oj2jUq74g+vel5cukdH+wpzjiH8 ZOQSOHrw+s3TmbhyqXbZ/j5Uu9p65ARoevvG yv459dxxZCKZ4wftXe5BUkJvZVf8HnhYW5R+ kQduVeqGVlkBarL5haKX28Pxvs8tV7CyY/Rd Arends, et al. Expires April 26, 2004 [Page 37] Internet-Draft DNSSEC Protocol Modifications October 2003 cfnJlZyJcfwY0ETo4P2gntVMERZuJQ== ) 3600 DNSKEY 257 3 1 ( AQOwRqeRkdYUD6UCyJXTaErj0UYLHxOHlhDb qik1k/j2PJFOZ7GZhc95HnYco611O5VRQ6WQ pK0dL9eiwcc+gSS2L6V9pWxCfDnEPWFC6eVm jRZAdAU6gsyNSZCT7rF1lAXdmWcwkaIdNaDL oNqpieIQd2t+rd/oF8/++DRtzF0toQ== ) 3600 RRSIG DNSKEY 1 1 3600 20031108232541 ( 20031009232541 5742 example. EtFrBqs8i80Ath+xOtjPHcepV/cjATf2E1fo +fhSggjw2vAXDY4Sygk2tKZ9Tvhahmw1rRC3 CnApLvsjQ9qmnYAvkZdMILw9gPx1rBaq9d7H nt7mPc/LFrO4G9JS6JNwBCnjwcxro8kNYLo6 97FCO3y4T7y9Hb80OvCZ36cNdps= ) 3600 RRSIG DNSKEY 1 1 3600 20031108232541 ( 20031009232541 23853 example. VseD0IGDKqJXiZMJnRNuq89ibF5g8VGPmMJS h/hS8+nu5vLiyEObJcVxfanslAlBQSGHmJsM AvXpeJUrT/zOyZ8vfy/igMhd25rnSxAD6uhl 4ohJiiPtFvHgLEvT0QZHizrP4wMvpXvfwn03 1/VEFzXZ0rULlTdWjoNzSMIYBwg= ) a.example. 3600 IN NS ns1.a.example. 3600 IN NS ns2.a.example. 3600 DS 42939 1 1 ( 4BA08982E5739A60E02B69409B0927F9524E 3494 ) 3600 RRSIG DS 1 2 3600 20031108232541 ( 20031009232541 5742 example. Dp6ySNq7SgIfndS4N5wFynmqXXf+WQ7RTAW/ gC4RPDljbV8WnjZp5P7ip9zsHO9A7hEW8LPp zEMMzUPfucrSnZ/Jmc60BYIkzkt493QPfz1H YFRaJ6VyZoF38oN0s/H+a97c+HxAt4TElW+c iHQEOrm7yXIHwnrre1iuzMZn1jY= ) 3600 NSEC ai.example. NS DS RRSIG NSEC 3600 RRSIG NSEC 1 2 3600 20031108232541 ( 20031009232541 5742 example. mhov2WXDa2Swk/7/VQoI36e5OKvd/0CmMWdi +3k/+i7mo9omz854ZBFMLaQzFvaS7Cn//I/H 7tYSY/fScUrs/UfB7le0DzdocsoaMYtexSS1 KA7ofbPdYpBHngIGbO5EHaGrqbKGY61fIQ/g /WvT0KXnoX+v31Oq3VstBoWmizo= ) ns1.a.example. 3600 IN A 192.0.2.5 ns2.a.example. 3600 IN A 192.0.2.6 ai.example. 3600 IN A 192.0.2.9 3600 RRSIG A 1 2 3600 20031108232541 ( 20031009232541 5742 example. Arends, et al. Expires April 26, 2004 [Page 38] Internet-Draft DNSSEC Protocol Modifications October 2003 MtQkYPqpRfM5ntlRR/Wg7pdFt5fuf+ESoV+a 0RTtEUW9Q5ac7uV3luTnOSmWFFjes1x9Anqn KVeWcZJU/wRYqbUK2Q9s/kLb3cPMFavHal9n 3gR5v5zNaTQxBrdFlxGNgX/aa9Bs3LfxK14F UU/kYIPkm9qpSE3wtELJEq2cNsU= ) 3600 HINFO "KLH-10" "ITS" 3600 RRSIG HINFO 1 2 3600 20031108232541 ( 20031009232541 5742 example. jDn/zgIqY5ucajWNW333u+KfxORI55wvnZDs pCHZQ9ISjWNT7467wUcfJKBaG+alNlCOJExg z8yUS5NwySlrFtGL/CBCxmrSVioKMMetg7gP Qb6x5A53OhsQAGT6azS9bdBM2RFbqBkeZkXA 8mJ/QOldXdH5iPpmZb2Pn47x7V4= ) 3600 AAAA 2001:db8::f00:baa9 3600 RRSIG AAAA 1 2 3600 20031108232541 ( 20031009232541 5742 example. LcSkeCXOOcYClsS9GYJoG/yGeuyaUJrNICK1 ONN4PEzGWJ7kcF+C4N972x05bPX+wsWszBbC uP/RqMyNenc8Is25te6hZ8MU7Z0zBDtKeTTG qz4ir4NZfqvB6moHjcVu6Pwb5KkSb8nAobCv 8gB4wQFPYoozOQYTprwGtIHR2k8= ) 3600 NSEC b.example. A HINFO AAAA RRSIG NSEC 3600 RRSIG NSEC 1 2 3600 20031108232541 ( 20031009232541 5742 example. W3fFJqdRtmpz9QikpK+v5rL+Y5iNpx5H7X7c 1yPMlcaS0nhowHGjCPnNbCP28Ktv9I5eqhO1 N/A75FLTOe9L5Qzetb/C3/ME8D46apKLBEv5 0GWsJqTsijj4dAjup60yeLPXTWxIdO6RNdfe Qd56t0fY79/kd25RzRCFGs2qHXs= ) b.example. 3600 IN NS ns1.b.example. 3600 IN NS ns2.b.example. 3600 NSEC ns1.example. NS RRSIG NSEC 3600 RRSIG NSEC 1 2 3600 20031108232541 ( 20031009232541 5742 example. csgLA1XphdEtY9WiwZOHjcOvGiBShTobK+th 0xDnKv7ZUxcMRi/g88Z99It+FV/Qufcf5zmM RxEVOjD1e7an1X/dxD389/6Qzo6NAtSu85ps TDKZscoaPBr/wYv6PG73F5yfm1hh31nhnD8f BFydo6dXwQ4WK8OUC6sMCM+OHEg= ) ns1.b.example. 3600 IN A 192.0.2.7 ns2.b.example. 3600 IN A 192.0.2.8 ns1.example. 3600 IN A 192.0.2.1 3600 RRSIG A 1 2 3600 20031108232541 ( 20031009232541 5742 example. dJTb+VNXApV4lPaEwlyZxOS17eofL95DJe58 +ija8iaROK9a9D7bAI7lIKJ/4hSfBN8lIjhF cpVeuGXCxldaSTOhAU5bg2GZJfxS4onfvBTE HBf19SZAT9rHBeNJISau8EwDaNBHBweiaC/s Arends, et al. Expires April 26, 2004 [Page 39] Internet-Draft DNSSEC Protocol Modifications October 2003 Oett68JnQVQq2l/DhWsJSjuIFBQ= ) 3600 NSEC ns2.example. A RRSIG NSEC 3600 RRSIG NSEC 1 2 3600 20031108232541 ( 20031009232541 5742 example. M8q/t6bDqPktgMyfa2LjkEDZiGloFp+I8LaO KBQt96RzZ9xiXOA/7wE5ZrBrgzfl1eotLn0L zbOwCwpZf7XoVm/IYCOlIEPj6kJHYvIIzp3a ZBn7uDx1kInt7qc2AmTpPiWCPtSD5KTBwdLk o3hJ8fow/NDw5Lsb6RQOSQ5Qxuo= ) ns2.example. 3600 IN A 192.0.2.2 3600 RRSIG A 1 2 3600 20031108232541 ( 20031009232541 5742 example. VGTTFv2DZ+KN+tm7dzAP1vWGZTLdYn9v/yuQ tu9rQYAwVWoGq7iiADgLlY0cjR58GCKCGfn4 mXMyM9mDljOj3VmHxUjRNMgUo+AoIi8Jysr9 +huB5dgYRKFukcCpxKb1SmXNmSLfdS75gCas 8Ic8f9zHwZmCUc0wnxX6x+422PM= ) 3600 NSEC *.w.example. A RRSIG NSEC 3600 RRSIG NSEC 1 2 3600 20031108232541 ( 20031009232541 5742 example. kkYPMaBn4zJM/iQAOO9i81X57MMCQnzk+pch 6tWUFF/D1ZFZf8QY2MzwDA5Bv/1DluWVbo3x WjzyUV7fn77k9QKLQseUSXGnpyL2HR1hGfBV 6ZHAqJc99t5+5vjyiflLtOpA0+Ri46SlQGZf IZ4X2Ksgn+hpIu77NRQMdmh59M8= ) *.w.example. 3600 IN MX 1 ai.example. 3600 RRSIG MX 1 2 3600 20031108232541 ( 20031009232541 5742 example. Uht2mND0Kzc4hnM4Pq4zM+fjiGTEcCzx+wSD b2flOHxLQPv75mXfnH1tZv7iwrzQmcyucWsd agwalJcGa3A2+UL45fjYR6zDEsag4cdg1D0/ +T7gIqOGWhYfiXbXuTOgUfyZRXqyGsHsAu20 FxfIqrcIL24dO4Ytdz2ifqvJmuM= ) 3600 NSEC x.w.example. MX RRSIG NSEC 3600 RRSIG NSEC 1 2 3600 20031108232541 ( 20031009232541 5742 example. fsk9iik9+gpte3I4tffoXyca5jfuYnLLy7/9 7LAVd4KKj9zqSB8f3QD1mjditUK9PGTTtlPL 4mq8F3T8PIt0pfgV8mPl6GP+bR+iVQEEE1YH yzR21az4Od5KBYYdsPjZzJnOhzCtgyleAoOx vOHmndDhRTDwVCg179qlrEIsOgE= ) x.w.example. 3600 IN MX 1 xx.example. 3600 RRSIG MX 1 3 3600 20031108232541 ( 20031009232541 5742 example. i65kcyRnXBHd3ynSNTVKpd71DS85EjGDTi7d NQR+E4/qtXVaU78hmG4BhyFMVbvyPNpj83z5 UqpB0baVoSVTSqGMSLxi1T38H8gqPgaYd+4r uEEXZj5I+s8Cq/1RHXi0yqISqeUGAqMHqryp Arends, et al. Expires April 26, 2004 [Page 40] Internet-Draft DNSSEC Protocol Modifications October 2003 IKZXg2219TD4UqJuRATLhxZj2fU= ) 3600 NSEC x.y.w.example. MX RRSIG NSEC 3600 RRSIG NSEC 1 3 3600 20031108232541 ( 20031009232541 5742 example. VTRE+Bu91QK7dBiMshr04tE/I5HCvSrjqDv+ b4tlUqUqkv4MoxfoceUwavMkdLm9Pi/aYUrS m6XVGBDAjpDmjivlMKNkME8c0f7oQ3E1CtHS pPLjTcB9WfxEOzjJJGK5BDDT6A56P4eibLiw +bNx4OGknGvVqhg9pu5qEWi814s= ) x.y.w.example. 3600 IN MX 1 xx.example. 3600 RRSIG MX 1 4 3600 20031108232541 ( 20031009232541 5742 example. yDPXa5Osa4r1AF0AjKWOo87kGNDlnVPmCbIi MPvBpzJ91d5TFtEZWYJpYv+eGWZCJhK7SsnL Zbbjthkn7YmX1tReDQhn8aCQ6DyrIU6wZpj5 ywBx0z3HGcqoYmv+AiFtcYVPxG0elsrakIwG /e+CPi2yE2c9M+NnwMxhpEFVGRs= ) 3600 NSEC xx.example. MX RRSIG NSEC 3600 RRSIG NSEC 1 4 3600 20031108232541 ( 20031009232541 5742 example. cn4aj3I/EQDa+vysa08xMQSnTz8YGtLLzqAj R8gy8Yqa4uSm7J17NydsWqgJkhlVxD3oBtnb w/6tDzx45IHcbnVm6UDrc3DVby21AivrsZ8P sm5Escp1X+qBLGSNAg2K6dlX/i2vut6g3vDa 66FPTb3/hhrHYkMneBO2Yvfvpj8= ) xx.example. 3600 IN A 192.0.2.10 3600 RRSIG A 1 2 3600 20031108232541 ( 20031009232541 5742 example. ZW+++XV6FyceT4UtcfbVwcsx3u5tRfFLfAHp Ji11YMdORJKIJS0uVfu+UuAbe/FImnBmQq4v ShjQXbLeN9BKLvde4dlMphHSKhp24913/KFd +N0DMDWGZ/wPoACnqrpn1gDKWdT0l+gkF3y4 aI16ggg9/UEWRbvn+7tp2UfMYSw= ) 3600 HINFO "KLH-10" "TOPS-20" 3600 RRSIG HINFO 1 2 3600 20031108232541 ( 20031009232541 5742 example. vteMgDuG1ekaSmWlXlwVRoqTXjvZ8kGWCAku 6Rd3t/wPeVmn3YSbC8+szYRgP8n0HvYzmVYj qPyC1HCFoqIJIaNLkDEyCSHuhBwpVhyKGJdM EbJ1P8Yk3w5Szjap6wn7QxcLnr8Df3xUMXnB AAwDzum3fUKzVM274T9O8ggeXgE= ) 3600 AAAA 2001:db8::f00:baaa 3600 RRSIG AAAA 1 2 3600 20031108232541 ( 20031009232541 5742 example. LY9gLxiep4FO8uuiegMzc1zdE/O7ApxjiO43 YDBVfuf3z+IghfPRY9IhkAJss6zBxMxciC27 ZmlPBrysWcKDfWF7fX+q0CDZ3ZbqdU32MuK+ AcWaIFu9JcYUIwFRCKt/0LA0OrycwELStUB0 Arends, et al. Expires April 26, 2004 [Page 41] Internet-Draft DNSSEC Protocol Modifications October 2003 GxlD/3EneV4+IIIv0hekxzpR8Qs= ) 3600 NSEC example. A HINFO AAAA RRSIG NSEC 3600 RRSIG NSEC 1 2 3600 20031108232541 ( 20031009232541 5742 example. cKkFJS6Em56M0XCjMma4zFzy5ylHh2ma62oe yHrqkMYS+QVUuJ8yfAoXoFbok/kDLN3rsCKK ICJl1dFA3fvJnMejg0JVabQHShO2W1LmWegr dh251WZQVtJHDRY8/ltYB+GHUuFpZ1CF4m+c 6EPqS1uLrFpRg3k4BV5y6146nZ8= ) The apex DNSKEY set includes two DNSKEY RRs, and the DNSKEY RDATA Flags indicate that each of these DNSKEY RRs is a zone key. One of these DNSKEY RRs also has the SEP flag set and has been used to sign the apex DNSKEY RRset; this is the key which should be hashed to generate a DS record to be inserted into the parent zone. The other DNSKEY is used to sign all the other RRsets in the zone. The zone includes a wildcard entry "*.w.example". Note that the name "*.w.example" is used in constructing NSEC chains, and that the RRSIG covering the "*.w.example" MX RRset has a label count of 2. The zone also includes two delegations. The delegation to "b.example" includes an NS RRset, glue address records, and an NSEC RR; note that only the NSEC RRset is signed. The delegation to "a.example" provides a DS RR; note that only the NSEC and DS RRsets are signed. Arends, et al. Expires April 26, 2004 [Page 42] Internet-Draft DNSSEC Protocol Modifications October 2003 Appendix B. Example Responses The examples in this section show response messages using the signed zone example in Appendix A. B.1 Answer A successful query to an authoritative server. ;; Header: QR AA DO RCODE=0 ;; ;; Question x.w.example. IN MX ;; Answer x.w.example. 3600 IN MX 1 xx.example. x.w.example. 3600 RRSIG MX 1 3 3600 20031108232541 ( 20031009232541 5742 example. i65kcyRnXBHd3ynSNTVKpd71DS85EjGDTi7d NQR+E4/qtXVaU78hmG4BhyFMVbvyPNpj83z5 UqpB0baVoSVTSqGMSLxi1T38H8gqPgaYd+4r uEEXZj5I+s8Cq/1RHXi0yqISqeUGAqMHqryp IKZXg2219TD4UqJuRATLhxZj2fU= ) ;; Authority example. 3600 NS ns1.example. example. 3600 NS ns2.example. example. 3600 RRSIG NS 1 1 3600 20031108232541 ( 20031009232541 5742 example. KBhJYJ0vFNyMJrt07gvHN9WAOijhXbcikUNw ZEJxkL+UCv/GFJi1ABGMDowschPkpHIgDEOQ exaLWGGUrOA5xMHYONWZpkL4rQ3URAKF46VJ dMg0UTdw3pTD7Lvs8t6Dim46dj9h/QQEgNLF BYpCn/jKFJ7lYnYYGLAUofh/+mo= ) ;; Additional xx.example. 3600 IN A 192.0.2.10 xx.example. 3600 RRSIG A 1 2 3600 20031108232541 ( 20031009232541 5742 example. ZW+++XV6FyceT4UtcfbVwcsx3u5tRfFLfAHp Ji11YMdORJKIJS0uVfu+UuAbe/FImnBmQq4v ShjQXbLeN9BKLvde4dlMphHSKhp24913/KFd +N0DMDWGZ/wPoACnqrpn1gDKWdT0l+gkF3y4 aI16ggg9/UEWRbvn+7tp2UfMYSw= ) xx.example. 3600 AAAA 2001:db8::f00:baaa xx.example. 3600 RRSIG AAAA 1 2 3600 20031108232541 ( 20031009232541 5742 example. LY9gLxiep4FO8uuiegMzc1zdE/O7ApxjiO43 Arends, et al. Expires April 26, 2004 [Page 43] Internet-Draft DNSSEC Protocol Modifications October 2003 YDBVfuf3z+IghfPRY9IhkAJss6zBxMxciC27 ZmlPBrysWcKDfWF7fX+q0CDZ3ZbqdU32MuK+ AcWaIFu9JcYUIwFRCKt/0LA0OrycwELStUB0 GxlD/3EneV4+IIIv0hekxzpR8Qs= ) ns1.example. 3600 IN A 192.0.2.1 ns1.example. 3600 RRSIG A 1 2 3600 20031108232541 ( 20031009232541 5742 example. dJTb+VNXApV4lPaEwlyZxOS17eofL95DJe58 +ija8iaROK9a9D7bAI7lIKJ/4hSfBN8lIjhF cpVeuGXCxldaSTOhAU5bg2GZJfxS4onfvBTE HBf19SZAT9rHBeNJISau8EwDaNBHBweiaC/s Oett68JnQVQq2l/DhWsJSjuIFBQ= ) ns2.example. 3600 IN A 192.0.2.2 ns2.example. 3600 RRSIG A 1 2 3600 20031108232541 ( 20031009232541 5742 example. VGTTFv2DZ+KN+tm7dzAP1vWGZTLdYn9v/yuQ tu9rQYAwVWoGq7iiADgLlY0cjR58GCKCGfn4 mXMyM9mDljOj3VmHxUjRNMgUo+AoIi8Jysr9 +huB5dgYRKFukcCpxKb1SmXNmSLfdS75gCas 8Ic8f9zHwZmCUc0wnxX6x+422PM= ) B.2 Name Error An authoritative name error. The NSEC RRs prove that the name does not exist and that no covering wildcard exists. ;; Header: QR AA DO RCODE=3 ;; ;; Question ml.example. IN A ;; Answer ;; (empty) ;; Authority example. 3600 IN SOA ns1.example. bugs.ns1.example. ( 1065745538 3600 300 3600000 3600 ) example. 3600 RRSIG SOA 1 1 3600 20031108232541 ( 20031009232541 5742 example. 0EhIo5SFK2xwM2CMh3P6FJUmpV5VFotM5pzb 8f3cL3SyKfOswI2osc3VvbtiEDQHEcE4/b+v BNx99Wc4jm3llWlsDOxlIbtR/S44xeOVRpff Arends, et al. Expires April 26, 2004 [Page 44] Internet-Draft DNSSEC Protocol Modifications October 2003 pLuMW4IZmdwGY/xh/WHOCV+bqVl+s9un0OcX LQTbyhlNTWdVYxPLo2T2dNP8a+0= ) b.example. 3600 NSEC ns1.example. NS RRSIG NSEC b.example. 3600 RRSIG NSEC 1 2 3600 20031108232541 ( 20031009232541 5742 example. csgLA1XphdEtY9WiwZOHjcOvGiBShTobK+th 0xDnKv7ZUxcMRi/g88Z99It+FV/Qufcf5zmM RxEVOjD1e7an1X/dxD389/6Qzo6NAtSu85ps TDKZscoaPBr/wYv6PG73F5yfm1hh31nhnD8f BFydo6dXwQ4WK8OUC6sMCM+OHEg= ) example. 3600 NSEC a.example. NS SOA MX RRSIG NSEC DNSKEY example. 3600 RRSIG NSEC 1 1 3600 20031108232541 ( 20031009232541 5742 example. 10XG3f8uExTPfof30CoonvXSMeqrhrkcN9YG krhJD4xeVKarTkQMt0dFe66Bbuy961Bv9go1 IEp0R+sV3B5ldqSKBrcIRsh4QFqQp6IPZ+By yxyYV25L68I1dkM1JoV7IMFsfcTDPjyl3wv2 2LAQ2lyqLBpow5BRR4sAgjZ7Yaw= ) ;; Additional ;; (empty) B.3 No Data Error A "NODATA" response. The NSEC RR proves that the name exists and that the requested RR type does not. ;; Header: QR AA DO RCODE=0 ;; ;; Question ns1.example. IN MX ;; Answer ;; (empty) ;; Authority example. 3600 IN SOA ns1.example. bugs.ns1.example. ( 1065745538 3600 300 3600000 3600 ) example. 3600 RRSIG SOA 1 1 3600 20031108232541 ( 20031009232541 5742 example. 0EhIo5SFK2xwM2CMh3P6FJUmpV5VFotM5pzb 8f3cL3SyKfOswI2osc3VvbtiEDQHEcE4/b+v Arends, et al. Expires April 26, 2004 [Page 45] Internet-Draft DNSSEC Protocol Modifications October 2003 BNx99Wc4jm3llWlsDOxlIbtR/S44xeOVRpff pLuMW4IZmdwGY/xh/WHOCV+bqVl+s9un0OcX LQTbyhlNTWdVYxPLo2T2dNP8a+0= ) ns1.example. 3600 NSEC ns2.example. A RRSIG NSEC ns1.example. 3600 RRSIG NSEC 1 2 3600 20031108232541 ( 20031009232541 5742 example. M8q/t6bDqPktgMyfa2LjkEDZiGloFp+I8LaO KBQt96RzZ9xiXOA/7wE5ZrBrgzfl1eotLn0L zbOwCwpZf7XoVm/IYCOlIEPj6kJHYvIIzp3a ZBn7uDx1kInt7qc2AmTpPiWCPtSD5KTBwdLk o3hJ8fow/NDw5Lsb6RQOSQ5Qxuo= ) ;; Additional ;; (empty) B.4 Referral to Signed Zone Referral to a signed zone. The DS RR contains the data which the resolver will need to validate the corresponding DNSKEY RR in the child zone's apex. ;; Header: QR DO RCODE=0 ;; ;; Question mc.a.example. IN MX ;; Answer ;; (empty) ;; Authority a.example. 3600 IN NS ns1.a.example. a.example. 3600 IN NS ns2.a.example. a.example. 3600 DS 42939 1 1 ( 4BA08982E5739A60E02B69409B0927F9524E 3494 ) a.example. 3600 RRSIG DS 1 2 3600 20031108232541 ( 20031009232541 5742 example. Dp6ySNq7SgIfndS4N5wFynmqXXf+WQ7RTAW/ gC4RPDljbV8WnjZp5P7ip9zsHO9A7hEW8LPp zEMMzUPfucrSnZ/Jmc60BYIkzkt493QPfz1H YFRaJ6VyZoF38oN0s/H+a97c+HxAt4TElW+c iHQEOrm7yXIHwnrre1iuzMZn1jY= ) ;; Additional ns1.a.example. 3600 IN A 192.0.2.5 ns2.a.example. 3600 IN A 192.0.2.6 Arends, et al. Expires April 26, 2004 [Page 46] Internet-Draft DNSSEC Protocol Modifications October 2003 B.5 Referral to Unsigned Zone Referral to an unsigned zone. The NSEC RR proves that no DS RR for this delegation exists in the parent zone. ;; Header: QR DO RCODE=0 ;; ;; Question mc.b.example. IN MX ;; Answer ;; (empty) ;; Authority b.example. 3600 IN NS ns1.b.example. b.example. 3600 IN NS ns2.b.example. b.example. 3600 NSEC ns1.example. NS RRSIG NSEC b.example. 3600 RRSIG NSEC 1 2 3600 20031108232541 ( 20031009232541 5742 example. csgLA1XphdEtY9WiwZOHjcOvGiBShTobK+th 0xDnKv7ZUxcMRi/g88Z99It+FV/Qufcf5zmM RxEVOjD1e7an1X/dxD389/6Qzo6NAtSu85ps TDKZscoaPBr/wYv6PG73F5yfm1hh31nhnD8f BFydo6dXwQ4WK8OUC6sMCM+OHEg= ) ;; Additional ns1.b.example. 3600 IN A 192.0.2.7 ns2.b.example. 3600 IN A 192.0.2.8 B.6 Wildcard Expansion A successful query which was answered via wildcard expansion. The label count in the answer's RRSIG RR indicates that a wildcard RRset was expanded to produce this response, and the NSEC RR proves that no closer match exists in the zone. ;; Header: QR AA DO RCODE=0 ;; ;; Question a.z.w.example. IN MX ;; Answer a.z.w.example. 3600 IN MX 1 ai.example. a.z.w.example. 3600 RRSIG MX 1 2 3600 20031108232541 ( 20031009232541 5742 example. Uht2mND0Kzc4hnM4Pq4zM+fjiGTEcCzx+wSD b2flOHxLQPv75mXfnH1tZv7iwrzQmcyucWsd Arends, et al. Expires April 26, 2004 [Page 47] Internet-Draft DNSSEC Protocol Modifications October 2003 agwalJcGa3A2+UL45fjYR6zDEsag4cdg1D0/ +T7gIqOGWhYfiXbXuTOgUfyZRXqyGsHsAu20 FxfIqrcIL24dO4Ytdz2ifqvJmuM= ) ;; Authority example. 3600 NS ns1.example. example. 3600 NS ns2.example. example. 3600 RRSIG NS 1 1 3600 20031108232541 ( 20031009232541 5742 example. KBhJYJ0vFNyMJrt07gvHN9WAOijhXbcikUNw ZEJxkL+UCv/GFJi1ABGMDowschPkpHIgDEOQ exaLWGGUrOA5xMHYONWZpkL4rQ3URAKF46VJ dMg0UTdw3pTD7Lvs8t6Dim46dj9h/QQEgNLF BYpCn/jKFJ7lYnYYGLAUofh/+mo= ) x.y.w.example. 3600 NSEC xx.example. MX RRSIG NSEC x.y.w.example. 3600 RRSIG NSEC 1 4 3600 20031108232541 ( 20031009232541 5742 example. cn4aj3I/EQDa+vysa08xMQSnTz8YGtLLzqAj R8gy8Yqa4uSm7J17NydsWqgJkhlVxD3oBtnb w/6tDzx45IHcbnVm6UDrc3DVby21AivrsZ8P sm5Escp1X+qBLGSNAg2K6dlX/i2vut6g3vDa 66FPTb3/hhrHYkMneBO2Yvfvpj8= ) ;; Additional ai.example. 3600 IN A 192.0.2.9 ai.example. 3600 RRSIG A 1 2 3600 20031108232541 ( 20031009232541 5742 example. MtQkYPqpRfM5ntlRR/Wg7pdFt5fuf+ESoV+a 0RTtEUW9Q5ac7uV3luTnOSmWFFjes1x9Anqn KVeWcZJU/wRYqbUK2Q9s/kLb3cPMFavHal9n 3gR5v5zNaTQxBrdFlxGNgX/aa9Bs3LfxK14F UU/kYIPkm9qpSE3wtELJEq2cNsU= ) ai.example. 3600 AAAA 2001:db8::f00:baa9 ai.example. 3600 RRSIG AAAA 1 2 3600 20031108232541 ( 20031009232541 5742 example. LcSkeCXOOcYClsS9GYJoG/yGeuyaUJrNICK1 ONN4PEzGWJ7kcF+C4N972x05bPX+wsWszBbC uP/RqMyNenc8Is25te6hZ8MU7Z0zBDtKeTTG qz4ir4NZfqvB6moHjcVu6Pwb5KkSb8nAobCv 8gB4wQFPYoozOQYTprwGtIHR2k8= ) B.7 Wildcard No Data Error A "NODATA" response for a name covered by a wildcard. The NSEC RRs prove that the matching wildcard name does not have any RRs of the requested type and that no closer match exists in the zone. Arends, et al. Expires April 26, 2004 [Page 48] Internet-Draft DNSSEC Protocol Modifications October 2003 ;; Header: QR AA DO RCODE=0 ;; ;; Question a.z.w.example. IN AAAA ;; Answer ;; (empty) ;; Authority example. 3600 IN SOA ns1.example. bugs.ns1.example. ( 1065745538 3600 300 3600000 3600 ) example. 3600 RRSIG SOA 1 1 3600 20031108232541 ( 20031009232541 5742 example. 0EhIo5SFK2xwM2CMh3P6FJUmpV5VFotM5pzb 8f3cL3SyKfOswI2osc3VvbtiEDQHEcE4/b+v BNx99Wc4jm3llWlsDOxlIbtR/S44xeOVRpff pLuMW4IZmdwGY/xh/WHOCV+bqVl+s9un0OcX LQTbyhlNTWdVYxPLo2T2dNP8a+0= ) x.y.w.example. 3600 NSEC xx.example. MX RRSIG NSEC x.y.w.example. 3600 RRSIG NSEC 1 4 3600 20031108232541 ( 20031009232541 5742 example. cn4aj3I/EQDa+vysa08xMQSnTz8YGtLLzqAj R8gy8Yqa4uSm7J17NydsWqgJkhlVxD3oBtnb w/6tDzx45IHcbnVm6UDrc3DVby21AivrsZ8P sm5Escp1X+qBLGSNAg2K6dlX/i2vut6g3vDa 66FPTb3/hhrHYkMneBO2Yvfvpj8= ) *.w.example. 3600 NSEC x.w.example. MX RRSIG NSEC *.w.example. 3600 RRSIG NSEC 1 2 3600 20031108232541 ( 20031009232541 5742 example. fsk9iik9+gpte3I4tffoXyca5jfuYnLLy7/9 7LAVd4KKj9zqSB8f3QD1mjditUK9PGTTtlPL 4mq8F3T8PIt0pfgV8mPl6GP+bR+iVQEEE1YH yzR21az4Od5KBYYdsPjZzJnOhzCtgyleAoOx vOHmndDhRTDwVCg179qlrEIsOgE= ) ;; Additional ;; (empty) B.8 DS Child Zone No Data Error A "NODATA" response for a QTYPE=DS query which was mistakenly sent to a name server for the child zone. Arends, et al. Expires April 26, 2004 [Page 49] Internet-Draft DNSSEC Protocol Modifications October 2003 ;; Header: QR AA DO RCODE=0 ;; ;; Question example. IN DS ;; Answer ;; (empty) ;; Authority example. 3600 IN SOA ns1.example. bugs.ns1.example. ( 1065745538 3600 300 3600000 3600 ) example. 3600 RRSIG SOA 1 1 3600 20031108232541 ( 20031009232541 5742 example. 0EhIo5SFK2xwM2CMh3P6FJUmpV5VFotM5pzb 8f3cL3SyKfOswI2osc3VvbtiEDQHEcE4/b+v BNx99Wc4jm3llWlsDOxlIbtR/S44xeOVRpff pLuMW4IZmdwGY/xh/WHOCV+bqVl+s9un0OcX LQTbyhlNTWdVYxPLo2T2dNP8a+0= ) example. 3600 NSEC a.example. NS SOA MX RRSIG NSEC DNSKEY example. 3600 RRSIG NSEC 1 1 3600 20031108232541 ( 20031009232541 5742 example. 10XG3f8uExTPfof30CoonvXSMeqrhrkcN9YG krhJD4xeVKarTkQMt0dFe66Bbuy961Bv9go1 IEp0R+sV3B5ldqSKBrcIRsh4QFqQp6IPZ+By yxyYV25L68I1dkM1JoV7IMFsfcTDPjyl3wv2 2LAQ2lyqLBpow5BRR4sAgjZ7Yaw= ) ;; Additional ;; (empty) Arends, et al. Expires April 26, 2004 [Page 50] Internet-Draft DNSSEC Protocol Modifications October 2003 Appendix C. Authentication Examples The examples in this section show how the response messages in Appendix B are authenticated. C.1 Authenticating An Answer The query in section Appendix B.1 returned an MX RRset for "x.w.example.com". The corresponding RRSIG indicates the MX RRset was signed by an "example" DNSKEY with algorithm 1 and key tag 5742. The resolver needs the corresponding DNSKEY RR in order to authenticate this answer. The discussion below describes how a resolver might obtain this DNSKEY RR. The RRSIG indicates the original TTL of the MX RRset was 3600 and, for the purpose of authentication, the current TTL is replaced by 3600. The RRSIG labels field value of 3 indicates the answer was not the result of wildcard expansion. The "x.w.example.com" MX RRset is placed in canonical form and, assuming the current time falls between the signature inception and expiration dates, the signature is authenticated. C.1.1 Authenticating the example DNSKEY RR This example shows the logical authentication process that starts from the a preconfigured root DNSKEY (or DS RR) and moves down the tree to authenticate the desired "example" DNSKEY RR. Note the logical order is presented for clarity and an implementation may choose to construct the authentication as referrals are received or may choose to construct the authentication chain only after all RRsets have been obtained, or in any other combination it sees fit. The example here demonstrates only the logical process and does not dictate any implementation rules. We assume the resolver starts with an preconfigured DNSKEY RR for the root zone (or a preconfigured DS RR for the root zone). The resolver checks this preconfigured DNSKEY RR is present in the root DNSKEY RRset (or the DS RR matches some DNSKEY in the root DNSKEY RRset), this DNSKEY RR has signed the root DNSKEY RRset and the signature lifetime is valid. If all these conditions are met, all keys in the DNSKEY RRset are considered authenticated. The resolver then uses one (or more) of the root DNSKEY RRs to authenticate the "example" DS RRset. Note the resolver may need to query the root zone to obtain the root DNSKEY RRset and/or "example" DS RRset. Once the DS RRset has been authenticated using the root DNSKEY, the resolver checks the "example" DNSKEY RRset for some "example" DNSKEY RR that matches one of the authenticated "example" DS RRs. If such a Arends, et al. Expires April 26, 2004 [Page 51] Internet-Draft DNSSEC Protocol Modifications October 2003 matching "example" DNSKEY is found, the resolver checks this DNSKEY RR has signed the "example" DNSKEY RRset and the signature lifetime is valid. If all these conditions are met, all keys in the "example" DNSKEY RRset are considered authenticated. Finally the resolver checks that some DNSKEY RR in the "example" DNSKEY RRset uses algorithm 1 and has a key tag of 5742. This DNSKEY is used to authenticated the RRSIG included in the response. If multiple "example" DNSKEY RRs have algorithm 1 and key tag of 5742, then each DNSKEY RR is tried and the answer is authenticated if either DNSKEY RR validates the signature as described above. C.2 Name Error The query in section Appendix B.2 returned NSEC RRs that prove the requested data does not exist and no wildcard applies. The negative reply is authenticated by verifying both NSEC RRs. The NSEC RRs are authenticated in a manner identical to that of the MX RRset discussed above. C.3 No Data Error The query in section Appendix B.3 returned an NSEC RR that proves the requested name exists, but the requested RR type does not exist. The negative reply is authenticated by verifying the NSEC RR. The NSEC RR is authenticated in a manner identical to that of the MX RRset discussed above. C.4 Referral to Signed Zone The query in section Appendix B.4 returned a referral to the signed "a.example." zone. The DS RR is authenticated in a manner identical to that of the MX RRset discussed above. This DS RR is used to authenticate the "a.example" DNSKEY RRset. Once the "a.example" DS RRset has been authenticated using the "example" DNSKEY, the resolver checks the "a.example" DNSKEY RRset for some "a.example" DNSKEY RR that matches the DS RR. If such a matching "a.example" DNSKEY is found, the resolver checks this DNSKEY RR has signed the "a.example" DNSKEY RRset and the signature lifetime is valid. If all these conditions are met, all keys in the "a.example" DNSKEY RRset are considered authenticated. C.5 Referral to Unsigned Zone The query in section Appendix B.5 returned a referral to an unsigned "b.example." zone. The NSEC proves that no authentication leads from "example" to "b.example" and the NSEC RR is authenticated in a manner Arends, et al. Expires April 26, 2004 [Page 52] Internet-Draft DNSSEC Protocol Modifications October 2003 identical to that of the MX RRset discussed above. C.6 Wildcard Expansion The query in section Appendix B.6 returned an answer that was produced as a result of wildcard expansion. The RRset expanded as the similar to The corresponding RRSIG indicates the MX RRset was signed by an "example" DNSKEY with algorithm 1 and key tag 5742. The RRSIG indicates the original TTL of the MX RRset was 3600 and, for the purpose of authentication, the current TTL is replaced by 3600. The RRSIG labels field value of 2 indicates the answer the result of wildcard expansion since the "a.z.w.example" name contains 4 labels. The name "a.z.w.w.example" is replaced by "*.w.example", the MX RRset is placed in canonical form and, assuming the current time falls between the signature inception and expiration dates, the signature is authenticated. The NSEC proves that no closer match (exact or closer wildcard) could have been used to answer this query and the NSEC RR must also be authenticated before the answer is considered valid. C.7 Wildcard No Data Error The query in section Appendix B.7 returned NSEC RRs that prove the requested data does not exist and no wildcard applies. The negative reply is authenticated by verifying both NSEC RRs. C.8 DS Child Zone No Data Error The query in section Appendix B.8 returned NSEC RRs that shows the requested was answered by a child server ("example" server). The NSEC RR indicates the presence of an SOA RR, showing the answer is from the child . Queries for the "example" DS RRset should be sent to the parent servers ("root" servers). Arends, et al. Expires April 26, 2004 [Page 53] Internet-Draft DNSSEC Protocol Modifications October 2003 Intellectual Property Statement The IETF takes no position regarding the validity or scope of any intellectual property or other rights that might be claimed to pertain to the implementation or use of the technology described in this document or the extent to which any license under such rights might or might not be available; neither does it represent that it has made any effort to identify any such rights. Information on the IETF's procedures with respect to rights in standards-track and standards-related documentation can be found in BCP-11. Copies of claims of rights made available for publication and any assurances of licenses to be made available, or the result of an attempt made to obtain a general license or permission for the use of such proprietary rights by implementors or users of this specification can be obtained from the IETF Secretariat. 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However, this document itself may not be modified in any way, such as by removing the copyright notice or references to the Internet Society or other Internet organizations, except as needed for the purpose of developing Internet standards in which case the procedures for copyrights defined in the Internet Standards process must be followed, or as required to translate it into languages other than English. The limited permissions granted above are perpetual and will not be revoked by the Internet Society or its successors or assignees. This document and the information contained herein is provided on an "AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING TASK FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION Arends, et al. Expires April 26, 2004 [Page 54] Internet-Draft DNSSEC Protocol Modifications October 2003 HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE. Acknowledgement Funding for the RFC Editor function is currently provided by the Internet Society. Arends, et al. Expires April 26, 2004 [Page 55]