DNS Extensions R. Arends Internet-Draft Telematica Instituut Expires: August 16, 2004 M. Larson VeriSign R. Austein ISC D. Massey USC/ISI S. Rose NIST February 16, 2004 Protocol Modifications for the DNS Security Extensions draft-ietf-dnsext-dnssec-protocol-05 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 August 16, 2004. Copyright Notice Copyright (C) The Internet Society (2004). 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 August 16, 2004 [Page 1] Internet-Draft DNSSEC Protocol Modifications February 2004 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 . . . . . . . . . . . . . . . . 7 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 . . . . . . . . . . . . . . . . . . 9 3. Serving . . . . . . . . . . . . . . . . . . . . . . . . . . 10 3.1 Authoritative Name Servers . . . . . . . . . . . . . . . . . 10 3.1.1 Including RRSIG RRs in a Response . . . . . . . . . . . . . 11 3.1.2 Including DNSKEY RRs In a Response . . . . . . . . . . . . . 11 3.1.3 Including NSEC RRs In a Response . . . . . . . . . . . . . . 12 3.1.4 Including DS RRs In a Response . . . . . . . . . . . . . . . 14 3.1.5 Responding to Queries for Type AXFR or IXFR . . . . . . . . 16 3.1.6 The AD and CD Bits in an Authoritative Response . . . . . . 17 3.2 Recursive Name Servers . . . . . . . . . . . . . . . . . . . 17 3.2.1 The DO bit . . . . . . . . . . . . . . . . . . . . . . . . . 18 3.2.2 The CD bit . . . . . . . . . . . . . . . . . . . . . . . . . 18 3.2.3 The AD bit . . . . . . . . . . . . . . . . . . . . . . . . . 18 3.3 Example DNSSEC Responses . . . . . . . . . . . . . . . . . . 19 4. Resolving . . . . . . . . . . . . . . . . . . . . . . . . . 20 4.1 EDNS Support . . . . . . . . . . . . . . . . . . . . . . . . 20 4.2 Signature Verification Support . . . . . . . . . . . . . . . 20 4.3 Determining Security Status of Data . . . . . . . . . . . . 21 4.4 Preconfigured Public Keys . . . . . . . . . . . . . . . . . 22 4.5 Response Caching . . . . . . . . . . . . . . . . . . . . . . 22 4.6 Handling of the CD and AD bits . . . . . . . . . . . . . . . 22 4.7 Rate Limiting . . . . . . . . . . . . . . . . . . . . . . . 23 4.8 Stub resolvers . . . . . . . . . . . . . . . . . . . . . . . 24 4.8.1 Handling of the DO Bit . . . . . . . . . . . . . . . . . . . 24 4.8.2 Handling of the CD Bit . . . . . . . . . . . . . . . . . . . 24 Arends, et al. Expires August 16, 2004 [Page 2] Internet-Draft DNSSEC Protocol Modifications February 2004 4.8.3 Handling of the AD Bit . . . . . . . . . . . . . . . . . . . 24 5. Authenticating DNS Responses . . . . . . . . . . . . . . . . 26 5.1 Special Considerations for Islands of Security . . . . . . . 27 5.2 Authenticating Referrals . . . . . . . . . . . . . . . . . . 27 5.3 Authenticating an RRset Using an RRSIG RR . . . . . . . . . 28 5.3.1 Checking the RRSIG RR Validity . . . . . . . . . . . . . . . 29 5.3.2 Reconstructing the Signed Data . . . . . . . . . . . . . . . 30 5.3.3 Checking the Signature . . . . . . . . . . . . . . . . . . . 31 5.3.4 Authenticating A Wildcard Expanded RRset Positive Response . . . . . . . . . . . . . . . . . . . . . . . . . . 32 5.4 Authenticated Denial of Existence . . . . . . . . . . . . . 32 5.5 Authentication Example . . . . . . . . . . . . . . . . . . . 33 6. IANA Considerations . . . . . . . . . . . . . . . . . . . . 34 7. Security Considerations . . . . . . . . . . . . . . . . . . 35 8. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 36 Normative References . . . . . . . . . . . . . . . . . . . . 37 Informative References . . . . . . . . . . . . . . . . . . . 38 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . 38 A. Signed Zone Example . . . . . . . . . . . . . . . . . . . . 40 B. Example Responses . . . . . . . . . . . . . . . . . . . . . 46 B.1 Answer . . . . . . . . . . . . . . . . . . . . . . . . . . . 46 B.2 Name Error . . . . . . . . . . . . . . . . . . . . . . . . . 47 B.3 No Data Error . . . . . . . . . . . . . . . . . . . . . . . 48 B.4 Referral to Signed Zone . . . . . . . . . . . . . . . . . . 49 B.5 Referral to Unsigned Zone . . . . . . . . . . . . . . . . . 50 B.6 Wildcard Expansion . . . . . . . . . . . . . . . . . . . . . 50 B.7 Wildcard No Data Error . . . . . . . . . . . . . . . . . . . 51 B.8 DS Child Zone No Data Error . . . . . . . . . . . . . . . . 52 C. Authentication Examples . . . . . . . . . . . . . . . . . . 54 C.1 Authenticating An Answer . . . . . . . . . . . . . . . . . . 54 C.1.1 Authenticating the example DNSKEY RR . . . . . . . . . . . . 54 C.2 Name Error . . . . . . . . . . . . . . . . . . . . . . . . . 55 C.3 No Data Error . . . . . . . . . . . . . . . . . . . . . . . 55 C.4 Referral to Signed Zone . . . . . . . . . . . . . . . . . . 55 C.5 Referral to Unsigned Zone . . . . . . . . . . . . . . . . . 55 C.6 Wildcard Expansion . . . . . . . . . . . . . . . . . . . . . 56 C.7 Wildcard No Data Error . . . . . . . . . . . . . . . . . . . 56 C.8 DS Child Zone No Data Error . . . . . . . . . . . . . . . . 56 Intellectual Property and Copyright Statements . . . . . . . 57 Arends, et al. Expires August 16, 2004 [Page 3] Internet-Draft DNSSEC Protocol Modifications February 2004 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 August 16, 2004 [Page 4] Internet-Draft DNSSEC Protocol Modifications February 2004 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 August 16, 2004 [Page 5] Internet-Draft DNSSEC Protocol Modifications February 2004 2. Zone Signing DNSSEC introduces 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. A zone that does not include these records according to the rules in this section is an unsigned zone. DNSSEC requires a change to the definition of the CNAME resource record [RFC1035]. Section 2.5 changes the CNAME RR to allow RRSIG and NSEC RRs to appear at the same owner name as a CNAME RR. 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 with the public component stored in the zone. A zone key DNSKEY RR MUST have 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 but MUST NOT be used to verify RRSIGs. 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]). DNSKEY RRs MUST NOT appear at delegation points. 2.2 Including RRSIG RRs in a Zone For each authoritative RRset in a signed zone, 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; 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 Arends, et al. Expires August 16, 2004 [Page 6] Internet-Draft DNSSEC Protocol Modifications February 2004 RRset owner name, not counting the null root label and not counting the leftmost label if it 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 that appears at the zone apex name MUST be signed, but the NS RRsets that appear at delegation points (that is, the NS RRsets in the parent zone that 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 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. 2.3 Including NSEC RRs in a Zone Each owner name in the zone which has authoritative data or a delegation point NS RRset MUST have an NSEC resource record. The process for constructing the NSEC RR for a given name is described in [I-D.ietf-dnsext-dnssec-records]. The TTL value for any NSEC RR SHOULD be the same as the minimum TTL value field in the zone SOA RR. An NSEC record (and its associated RRSIG RRset) MUST NOT be the only RRset at any particular owner name. That is, the signing process MUST NOT create NSEC or RRSIG RRs for owner names nodes which were not the owner name of any RRset before the zone was signed. 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. The difference between the set of owner names that require RRSIG Arends, et al. Expires August 16, 2004 [Page 7] Internet-Draft DNSSEC Protocol Modifications February 2004 records and the set of owner names that 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 is 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. 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 public key in the child zone used to verify the RRSIGs in that zone. All DS RRsets in a zone MUST be signed and DS RRsets MUST NOT appear 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 delegating NS RRset (i.e., the NS RRset from the same zone containing the DS 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. A KEY RRset at that name for secure dynamic update purposes is also allowed. 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. Arends, et al. Expires August 16, 2004 [Page 8] Internet-Draft DNSSEC Protocol Modifications February 2004 2.6 Example of a Secure Zone Appendix A shows a complete example of a small signed zone. Arends, et al. Expires August 16, 2004 [Page 9] Internet-Draft DNSSEC Protocol Modifications February 2004 3. Serving This section describes the behavior of entities that include security-aware name server 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 that receives a DNS query that does not include the EDNS OPT pseudo-RR or that 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 4.8 for details on the behavior of these bits. 3.1 Authoritative Name Servers Upon receiving a relevant query that 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 that 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 that 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 August 16, 2004 [Page 10] Internet-Draft DNSSEC Protocol Modifications February 2004 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 that has the DO bit set to one, a security-aware authoritative name server SHOULD attempt to send RRSIG RRs that 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 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 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 both the RRset and its associated 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 that has the DO bit set to one and that 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 August 16, 2004 [Page 11] Internet-Draft DNSSEC Protocol Modifications February 2004 3.1.3 Including NSEC RRs In a Response When responding to a query that 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 that exactly match , but does not contain any RRsets that exactly match . Name Error: The zone does not contain any RRsets that match either exactly or via wildcard name expansion. Wildcard Answer: The zone does not contain any RRsets that exactly match but does contain an RRset that matches via wildcard name expansion. Wildcard No Data: The zone does not contain any RRsets that exactly match , does contain one or more RRsets that match via wildcard name expansion, but does not contain any RRsets that 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 that the name server is returning is correct given the data that 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 August 16, 2004 [Page 12] Internet-Draft DNSSEC Protocol Modifications February 2004 o An NSEC RR proving that there is no exact match for ; and o An NSEC RR proving that the zone contains no RRsets that would match via wildcard name expansion. In some cases a single NSEC RR may prove both of these points, in that 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). The owner names of these NSEC and RRSIG RRs are not subject to wildcard name expansion when these RRs are included in the Authority section of the response. Note that this form of response includes cases in which SNAME corresponds to an empty non-terminal name within the zone (a name which is not the owner name for any RRset but which is the parent name of one or more RRsets). 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 the 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 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 Arends, et al. Expires August 16, 2004 [Page 13] Internet-Draft DNSSEC Protocol Modifications February 2004 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. The owner names of these NSEC and RRSIG RRs are not subject to wildcard name expansion when these RRs are included in the Authority section of the response. 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). 3.1.3.5 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 [I-D.ietf-dnsext-dnssec-records]. 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. Arends, et al. Expires August 16, 2004 [Page 14] Internet-Draft DNSSEC Protocol Modifications February 2004 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) in the Authority section 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. 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 sends queries to the parent zone when looking for a needed DS RR at a delegation point (see Section 4.2). However, special rules are necessary to avoid confusing security-oblivious resolvers which might become involved in processing such a query (for example, in a network configuration that forces a security-aware resolver to channel its queries through a security-oblivious recursive name server). The rest of this section describes how a security-aware name server processes DS queries in order to avoid this problem. The need for special processing by a security-aware name server only arises when all the following conditions are met: o the name server has received a query for the DS RRset at a zone cut; and o the name server is authoritative for the child zone; and o the name server is not authoritative for the parent zone; and Arends, et al. Expires August 16, 2004 [Page 15] Internet-Draft DNSSEC Protocol Modifications February 2004 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 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 Arends, et al. Expires August 16, 2004 [Page 16] Internet-Draft DNSSEC Protocol Modifications February 2004 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. 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 and 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. The resolver side follows the usual rules for caching and negative caching which would apply to any security-aware resolver. Arends, et al. Expires August 16, 2004 [Page 17] Internet-Draft DNSSEC Protocol Modifications February 2004 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 MUST NOT strip any DNSSEC RRs that the initiating query explicitly 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. The name server side MUST copy the setting of the CD bit from a query to the corresponding response. 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 4.7) 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, 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 and Authority sections of the response to be Arends, et al. Expires August 16, 2004 [Page 18] Internet-Draft DNSSEC Protocol Modifications February 2004 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 August 16, 2004 [Page 19] Internet-Draft DNSSEC Protocol Modifications February 2004 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. 4.1 EDNS Support 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. 4.2 Signature Verification Support 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. Editors' note: The rest of this section is expected to change once the WG reaches closure on Q-23. 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. Arends, et al. Expires August 16, 2004 [Page 20] Internet-Draft DNSSEC Protocol Modifications February 2004 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 may know the name of the missing NSEC RR, and in such cases must therefore attempt to retrieve it. When attempting to retrieve missing NSEC 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. When attempting to retrieve a missing DS, a security-aware iterative-mode resolver MUST query the name servers for the parent zone, not the child zone. As explained in Section 3.1.4.1, security-aware name servers need to apply special processing rules to handle the DS RR, and in some situations the resolver may also need to apply special rules to locate the name servers for the parent zone if the resolver does not already have the parent's NS RRset. To locate the parent NS RRset, the resolver can start with the delegation name, strip off the leftmost label, and query for an NS RRset by that name; if no NS RRset is present at that name, the resolver then strips of the leftmost remaining label and retries the query for that name, repeating this process of walking up the tree until it either finds the NS RRset or runs out of labels. Editors' note: This algorithm could easily be read as an invitation to careless implementors to hammer the root zone servers. Better wording would be welcome. 4.3 Determining Security Status of Data Editors' note: This section is waiting for resolution of Q-28. 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 security anchor 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 Arends, et al. Expires August 16, 2004 [Page 21] Internet-Draft DNSSEC Protocol Modifications February 2004 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. 4.4 Preconfigured Public Keys A security-aware resolver MUST be capable of being preconfigured with at least one trusted public key or DS RR, and SHOULD 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; examples of such a mechanism would be some form of non-volatile storage (such as a disk drive) or some form of trusted local network configuration mechanism. 4.5 Response Caching Editors' note: RIPE "last call" workshop felt that the WG needs to reexamine and discuss this section. A security-aware resolver SHOULD cache each response as a 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. In most cases the appropriate cache index for the atomic entry will be the triple , but in cases such as the response form described in Section 3.1.3.2 the appropriate cache index will be the double . 4.6 Handling of the CD and AD bits 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. A security-aware resolver MUST zero the AD bit when composing query messages to protect against buggy name servers which blindly copy header bits which they do not understand from the query message to Arends, et al. Expires August 16, 2004 [Page 22] Internet-Draft DNSSEC Protocol Modifications February 2004 the response message. A resolver MUST disregard the meaning of the CD and AD bits in a response unless the response was obtained using a secure channel or the resolver was specifically configured to regard the message header bits without using a secure channel. 4.7 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. Arends, et al. Expires August 16, 2004 [Page 23] Internet-Draft DNSSEC Protocol Modifications February 2004 4.8 Stub resolvers 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. 4.8.1 Handling of the DO Bit A non-validating security-aware stub resolver MAY include the DNSSEC RRs returned by a security-aware recursive name server as part of the data that the stub resolver hands back to the application which invoked it but is not required to do so. A non-validating stub resolver that wishes to do this will need to set the DO bit in receive DNSSEC RRs from the recursive name server. A validating security-aware stub resolver MUST set the DO bit, since otherwise it will not receive the DNSSEC RRs it needs to perform signature validation. 4.8.2 Handling of the CD Bit A non-validating security-aware stub resolver SHOULD NOT set the CD bit when sending queries unless requested by the application layer, since by definition, a non-validating stub resolver depends on the security-aware recursive name server to perform validation on its behalf. A validating security-aware stub resolver SHOULD set the CD bit, since otherwise the security-aware recursive name server will answer the query using the name server's local policy, which may prevent the stub resolver from receiving data which would be acceptable to the stub resolver's local policy. 4.8.3 Handling of the AD Bit A non-validating 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 Arends, et al. Expires August 16, 2004 [Page 24] Internet-Draft DNSSEC Protocol Modifications February 2004 recursive name server via a secure channel. A validating security-aware stub resolver SHOULD NOT examine the setting of the AD bit in response messages, since, by definition, the stub resolver performs its own signature validation regardless of the setting of the AD bit. Arends, et al. Expires August 16, 2004 [Page 25] Internet-Draft DNSSEC Protocol Modifications February 2004 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 MUST have the Zone Key Flag (DNSKEY RDATA bit 7) set to one. 2. Verify that there is some RRSIG RR that 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 (by setting the DO bit), 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 that that lacks the appropriate DNSSEC RRs, whether due to configuration issues such as a security-oblivious recursive name server that Arends, et al. Expires August 16, 2004 [Page 26] Internet-Draft DNSSEC Protocol Modifications February 2004 accidentally 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 Arends, et al. Expires August 16, 2004 [Page 27] Internet-Draft DNSSEC Protocol Modifications February 2004 and the key tag of a DNSKEY RR in the child zone's apex DNSKEY RRset that, when hashed using the digest algorithm specified in the DS RR's Digest Type field, results in a digest value that 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 that 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 that 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. If the resolver does not support any of the algorithms listed in an authenticated DS RRset, then the resolver will not be able to verify the authentication path to the child zone. In this case, the resolver SHOULD treat the child zone as if it were unsigned. 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 Arends, et al. Expires August 16, 2004 [Page 28] Internet-Draft DNSSEC Protocol Modifications February 2004 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. 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 public 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 Arends, et al. Expires August 16, 2004 [Page 29] Internet-Draft DNSSEC Protocol Modifications February 2004 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 that the resolver has been preconfigured to believe to be authentic. 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 = Label count of the fqdn above. if rrsig_labels = fqdn_labels, Arends, et al. Expires August 16, 2004 [Page 30] Internet-Draft DNSSEC Protocol Modifications February 2004 name = fqdn if rrsig_labels < fqdn_labels, name = "*." | the rightmost rrsig_label labels of the fqdn if rrsig_labels > fqdn_labels 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 that 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 used to generate the signature. The signature itself is contained in the Signature field of the RRSIG RDATA, and the public key used to verify the signature is contained in the Public Key field of the matching DNSKEY RR(s) (found in Section 5.3.1). Arends, et al. Expires August 16, 2004 [Page 31] Internet-Draft DNSSEC Protocol Modifications February 2004 [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 determine which DNSKEY RR by trying each matching public 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 RRset, 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 owner name is greater than the Labels field of the covering RRSIG RR, 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 Arends, et al. Expires August 16, 2004 [Page 32] Internet-Draft DNSSEC Protocol Modifications February 2004 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 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. If the number of labels in an authenticated NSEC RR's owner name equals the Labels field of the covering RRSIG RR, then the existence of the NSEC RR proves that wildcard expansion could not have been used to match the request. o If the requested RR name would appear after an authenticated NSEC RR's 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 RRsets with the requested name exist 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 RRset exists that 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 message 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. 5.5 Authentication Example Appendix C shows an example the authentication process. Arends, et al. Expires August 16, 2004 [Page 33] Internet-Draft DNSSEC Protocol Modifications February 2004 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 [RFC3655] 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 August 16, 2004 [Page 34] Internet-Draft DNSSEC Protocol Modifications February 2004 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; see [I-D.ietf-dnsext-dnssec-intro] for considerations specific to the DNSSEC resource record types. 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 4.8 for further discussion. The protocol described in this document attempts to extend the benefits of DNSSEC to security-oblivious stub resolvers. However, since recovery from validation failures is likely to be specific to particular applications, the facilities that DNSSEC provides for stub resolvers may prove inadequate. Operators of security-aware recursive name servers will need to pay close attention to the behavior of the applications which use their services when choosing a local validation policy; failure to do so could easily result in the recursive name server accidently denying service to the clients it is intended to support. Arends, et al. Expires August 16, 2004 [Page 35] Internet-Draft DNSSEC Protocol Modifications February 2004 8. Acknowledgements This document was created from the input and ideas of the 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. While explicitly listing everyone who has contributed during the decade during which DNSSEC has been under development would be an impossible task, [I-D.ietf-dnsext-dnssec-intro] includes a list of some of the participants who were kind enough to comment on these documents. Arends, et al. Expires August 16, 2004 [Page 36] Internet-Draft DNSSEC Protocol Modifications February 2004 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-09 (work in progress), February 2004. [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-07 (work in progress), February 2004. Arends, et al. Expires August 16, 2004 [Page 37] Internet-Draft DNSSEC Protocol Modifications February 2004 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. [RFC3655] Wellington, B. and O. Gudmundsson, "Redefinition of DNS Authenticated Data (AD) bit", RFC 3655, November 2003. [RFC3658] Gudmundsson, O., "Delegation Signer (DS) Resource Record (RR)", RFC 3658, December 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. Authors' Addresses Roy Arends Telematica Instituut Drienerlolaan 5 7522 NB Enschede NL EMail: roy.arends@telin.nl Matt Larson VeriSign, Inc. 21345 Ridgetop Circle Dulles, VA 20166-6503 USA EMail: mlarson@verisign.com Arends, et al. Expires August 16, 2004 [Page 38] Internet-Draft DNSSEC Protocol Modifications February 2004 Rob Austein Internet Systems Consortium 950 Charter Street Redwood City, CA 94063 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 August 16, 2004 [Page 39] Internet-Draft DNSSEC Protocol Modifications February 2004 Appendix A. Signed Zone Example The following example shows a (small) complete signed zone. example. 3600 IN SOA ns1.example. bugs.x.w.example. ( 1071609350 3600 300 3600000 3600 ) 3600 RRSIG SOA 5 1 3600 20040115201552 ( 20031216201552 41681 example. F1KxMLu2zwDUFgUtdAqCq6F9zkaIPb3B7dzA hRLp8riOMQQgCCQ4x9KvSu2xLJa539jQIRW0 VBU6+FZWzC2IJcc5liv2SXzyfiPu8diB9+Bj CSITjVX0IGrQgd+PKkaTxWQzG9TDZ2TtgnyM owLe/OV+Qqqic7ShV/S9l2YJF9I= ) 3600 NS ns1.example. 3600 NS ns2.example. 3600 RRSIG NS 5 1 3600 20040115201552 ( 20031216201552 41681 example. YgTFj4yXRzbOddwfOTQhLHGPWm7x55ZRoPVz +bxuPHTozw3I2gpno81Em1RuVekWJHivAvQj s1h72oh+ipBadjCGSRu46u1T9JYUSLxLecgY eEw9qDeQIoZHRny5bYrX1x87ItEo5+n1lwOH FTVyQbVkcaxQ6U2FbZtMbfo//go= ) 3600 MX 1 xx.example. 3600 RRSIG MX 5 1 3600 20040115201552 ( 20031216201552 41681 example. JE9Kcx4NaXpaO2Jjyo5yi+DT6wgxwregHg18 7xOOF0KjIYQpaoFY3Kp8MAKT7aupZpr5DmHe IpBNI6jC59A2uNVP+6UfqAyJMoNnq9d/paM+ M+adwb+xrT+dZYpFZzyeXPmBqA/PVAtw1d5Q 7wxkDWyzgasGiMNIKgYrm9vXz04= ) 3600 NSEC a.example. NS SOA MX RRSIG NSEC DNSKEY 3600 RRSIG NSEC 5 1 3600 20040115201552 ( 20031216201552 41681 example. kE9ARiewdQSCsLXY9ldasZEW54kKhfEN2lsT vDD4biJsTPeaOXJ6bJ7s0CvybknENin3uqIX TAy6bsL919sEI3/SoHiRCwHalVmUPIWCsz4g Ee7gkQ+1uFzi7L8LGX9NjQI74s3M//OW2+T4 7T/nOEOVZujD8IN/Utv+KUg+P6U= ) 3600 DNSKEY 256 3 5 ( AQPmfvH5TF0S/vnd08C9EbVlG/+wbmFecyjH UtEh3d8h045BE36XSbr0XZU6kPLgA/Shf7TV fKduDMH7ASlP8MpUX4ci9ZiXffBjUKvsHORv BgtAcUYRofvzRZ/jl078bI/JJg9ee4ndY6FO Arends, et al. Expires August 16, 2004 [Page 40] Internet-Draft DNSSEC Protocol Modifications February 2004 5LtAM3ElSpRIIhAm4b2c69IMdwrU2Q== ) 3600 DNSKEY 257 3 5 ( AQOwHAYrbYVzzKHF0PDHSt4zY+Vz1+yLz1/U Pv2j2nukkWKLipnqg8X2vI754SRpqwpPCKpv klUr36CE0byYLOpRE5WlKZjXm3uzDFIVdHUE 2lFwkMP9tSHUrXbjypiZWZP71qNuBeYCDAyT nLu7mxrT1Y7GdSV7I6vwt0mDSWQDXQ== ) 3600 RRSIG DNSKEY 5 1 3600 20040115201552 ( 20031216201552 41681 example. Pkxt/YJHVcnm3+56YGYziM69NDFJDEernUEU pU1yBY8H7TlvIWhJz/qHsWcPt79ri0lP0Ho5 YDVp6GOFxBcR/7ejtV/izHO5tb88WM8xJLNc tJZeSSVG62kt1q5fiKKsxhhpqZFQgc+h6htG PjJstq6fvRq8kX7TPJcljUmDFKM= ) 3600 RRSIG DNSKEY 5 1 3600 20040115201552 ( 20031216201552 60717 example. EVJnkWJSUTdaxIRX374Ki84OhYRYB+7TM/Z/ C8ufeGjcZkAPpkA3XjPao+4kG/lR/qW8oyNK L0g5BI9fkcptXjf+0y3n5y/con6f+FOwHgdY J7/fjSW27L3Je0MSrR3T/RNaokZafWDCT/34 Uu/YHFJKdBxs7sMeSBJ4UPm2uwc= ) a.example. 3600 IN NS ns1.a.example. 3600 IN NS ns2.a.example. 3600 DS 48327 5 1 ( DFEB5E00E71A4DED5CABBBD7F15F24871983 CAB7 ) 3600 RRSIG DS 5 2 3600 20040115201552 ( 20031216201552 41681 example. wj4ME4MuuZN77PGiE8xgBmCXpRpUocRJLbW/ hBbMGk2qtA9ose1Jr2F9rOU6zvU9Z0HQgxnb rSBfaeCZFmk3yOlo9Uqref4ukk9hwIjzxo7c ZbJstCYWiLF57i1k5Cj6npMbUZSIgRGcB+dC 0yfe2uolEkeegjesDZuF+fC61Eg= ) 3600 NSEC ai.example. NS DS RRSIG NSEC 3600 RRSIG NSEC 5 2 3600 20040115201552 ( 20031216201552 41681 example. iq8exEVhvdx4s3w3VmK3Mzfngwpmpv3NwOpb RMtgba/u5kyD4Mf03jyLtJLUevry2rZcRjF1 3kDuKmewJ0jWA4sMuljJpx10rhvwlcKaJE3O ViEb66GFqDxCXExikKWsPm8qckYZLQ7ABNjf YgfAHJEJJj7K88QbKEK4/Je1hyk= ) 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 5 2 3600 20040115201552 ( 20031216201552 41681 example. Arends, et al. Expires August 16, 2004 [Page 41] Internet-Draft DNSSEC Protocol Modifications February 2004 hxNyPE9Wn675NDH/IpB2LZzhrUtV9eEndid8 jiteGyki6CAEJKm1Dr2bjlrzdgfFBrpIac9c Up4zMlAkitX/7D9vFus8nLSvEHngpdc12Hlk OrvT0EsYA2XeQ0h3PPQk5FcK2ekxZvw5Zm7A sWifTxvcG5hv+A6TOd0O2xJYRik= ) 3600 HINFO "KLH-10" "ITS" 3600 RRSIG HINFO 5 2 3600 20040115201552 ( 20031216201552 41681 example. 4aSnKLykRT7htnnS8HtlM0YLMwU1Z92pvf/C hxETE5B6W8x+uJs9KV9nlZ/B6TNk4nFRgKg2 KpKvEq7xUybNKwbbeGZE9n2fDH0FeDgHjqW2 Ke0lQuszRxjx+McTEqVJMyHrBKnqNdUh1G92 xo9NLoltg0GuwggZM240pRoTwO8= ) 3600 AAAA 2001:db8::f00:baa9 3600 RRSIG AAAA 5 2 3600 20040115201552 ( 20031216201552 41681 example. oq16/pU4MuvkgQyFqGrHqggz47i6iZL714u5 9UsmGM1Y/qyQZsR4wi6hC2zIWXNJxIPIhitJ G6M5pjExUH/vOe0DIW73t/NHzcj0zOjxAPEI A+jBlOwn2EY5q87PMzBIeHWSx7DxtEIMC8XI zkK+1+Z5aqj1pmZ4yXUvd2znGnQ= ) 3600 NSEC b.example. A HINFO AAAA RRSIG NSEC 3600 RRSIG NSEC 5 2 3600 20040115201552 ( 20031216201552 41681 example. Xr3qBss/U0yN12SL2stWs0AACeQjvRms9+xE ishTjb4B/XQ8yAfAmby5yF5DKR8900M0hT3Y ikp/wIF4TmtH5W7UFN13To/GWGJygaa7wyzU 4AtgtRwmmevSAgzxhC7yRXUWyhpfQoW7zwpR ovChG5Ih3TOa8Qnch4IJQVfSFNU= ) b.example. 3600 IN NS ns1.b.example. 3600 IN NS ns2.b.example. 3600 NSEC ns1.example. NS RRSIG NSEC 3600 RRSIG NSEC 5 2 3600 20040115201552 ( 20031216201552 41681 example. nFufQRM2UtSYTAwQaKEnIpua5ZHLqJrcLGAs VUpLoPOEsAXex1N3uIJQWmoXnr9Up00G7jbW VOVaLUvXR7b/4sQkyQLbOl9GpWiA1NYjPneN k3i+OWi3NmvRN71CuNky87DrVg0p2Mf2MjLX GRIZP9W1bgeDHZRcCNz2hQ67SgY= ) 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 5 2 3600 20040115201552 ( 20031216201552 41681 example. 5FrF88yOT6iiBdkiQLqaXkma0gCQza5/kLK7 CgoMNlCR2QYhsur2X7Fex2/OYEmOkzOqO7Gs RoIc4e3nt+kfpd/4Htp9T5v+NXmMVPmW3Jmf +ZGpEf86AI7Rw3x2bSmVOzsxa4xUxE+DuINa Arends, et al. Expires August 16, 2004 [Page 42] Internet-Draft DNSSEC Protocol Modifications February 2004 WNJ/ulvIFa20d0xtlB7jazNCZ3Y= ) 3600 NSEC ns2.example. A RRSIG NSEC 3600 RRSIG NSEC 5 2 3600 20040115201552 ( 20031216201552 41681 example. WaeyPcQtFjXj4cxDcqVseuhZPA4K/qSb7ylZ sj55rJ8OqEKDYt71e1MT3F5p76wKtLaPmoc0 eLGnDD+Xouu/tWXtsjj5QpMhl13DUD0GLBiA s/wwxreW0SWkh4JJirodDE7vSIiI6gPJYhIj I2A5W86mMEbSgEF/pZHX/wi5FJI= ) ns2.example. 3600 IN A 192.0.2.2 3600 RRSIG A 5 2 3600 20040115201552 ( 20031216201552 41681 example. sfFOjxKZz1LMhyDfmB43RhIUVOHlVbLtP0lL xBsxcHt48NKLth81pzSWRFQfUtMCjaGWMtuK HFEVaAQXcwllWXXLbVpc9a32govT+hsapcht sPyxkcEpYEFTtB93edKRVQ0IgZBPOI02R6vG wCbeY0Rl8MIRcAaiIkFos/8hd1g= ) 3600 NSEC *.w.example. A RRSIG NSEC 3600 RRSIG NSEC 5 2 3600 20040115201552 ( 20031216201552 41681 example. Vxovi9gQjxqYBI5QF2ZcbZ/5my7C+22uXKVb IN5dmV82uu2TqJ4g2a2KKywlVi+4Kcnm4O3b f7pV4g7pcQopa9AFiY8byFrPftuNvraDyp6J aPllr/HnIPGP4Vw78LKW4n812K2VxV8p/IJl yCup5bk/Dr47eU2/6+lqrBTOV8Q= ) *.w.example. 3600 IN MX 1 ai.example. 3600 RRSIG MX 5 2 3600 20040115201552 ( 20031216201552 41681 example. mzcZPkLFaFycrnJuHY8LHdmvmyD8prPbQXHg OXuGLRpO+qRU04v97KYNy8si1Ijmo85nI4Ns Hl2+WpbMguW9gyPpdHqIYkKJbOrX2b4bz6WA n7NlR05Rf2tE3e54a1LP0po55yqGtxdPKWOK 91Ena87PA2MvoOE+A3ZpEk8MjEE= ) 3600 NSEC x.w.example. MX RRSIG NSEC 3600 RRSIG NSEC 5 2 3600 20040115201552 ( 20031216201552 41681 example. OeBMvLlBam90xU/KxvyAYBNGWpvMf1TbaJFr f0Ip+tTkiqeEE8fx2ZAg1JcY9uhldms/9y45 9HxO9Q3ZO6jfQzsx62YQaBte85d/Udhzf4AK /RHsZGSOabsu6DhacWC2Ew7vEgcMfiPHFzWW ANi1i3zhPOd3+Vjt4IQzaJXqVZE= ) x.w.example. 3600 IN MX 1 xx.example. 3600 RRSIG MX 5 3 3600 20040115201552 ( 20031216201552 41681 example. g2H7+tChKsYRqxDkrLZgraaKBF2pah6YNCEW ORmXLzrB6RWtXbjVHXjagBhZYsMPzkPqwn4m 8IYSaPD0X3z001aXsgsh9WF+AOgbqa0eoIIY MHIEJ9MHB5cS33XXv2fY6iFmjLuZUz+pNSfv Arends, et al. Expires August 16, 2004 [Page 43] Internet-Draft DNSSEC Protocol Modifications February 2004 btznHMFDIbtuw/tAX7xXH2pDDHY= ) 3600 NSEC x.y.w.example. MX RRSIG NSEC 3600 RRSIG NSEC 5 3 3600 20040115201552 ( 20031216201552 41681 example. zwAU3bQHLeDawvqbvlmNosGMGDz9wdEe/iia CU8DbanqOzUiPfqEgBN3evFMpGBM9H3zMjGA EjnP4fMerk7dzD8jfyLzNdCGsJjPtnEgctGA aNd+NGtSmedzeNGvlj7mNxnAdqHFY1c902pT 3lMXiX4KNWUhB87q/pT/5z+xrqY= ) x.y.w.example. 3600 IN MX 1 xx.example. 3600 RRSIG MX 5 4 3600 20040115201552 ( 20031216201552 41681 example. slLY7KbPseET3XMJz/yGJBJpDczy1N2W4SAD v5Jx/osOWviEJBpUEwRndX+VmsmQJqKsQxtE unmxl4Sh9cuVyALJy1ByF9hZ0+E3i35qoxOK Oe+JZyiEiebZfZ8doH5J+keCkIQ8EHzw8Hnk Iykd5UmaTO5j4LlRnAvF8Z1m9/k= ) 3600 NSEC xx.example. MX RRSIG NSEC 3600 RRSIG NSEC 5 4 3600 20040115201552 ( 20031216201552 41681 example. sjHnEm4kiIK64bRskNc3vxEHe12l9Lg8Y7G8 VsXMUEEDeBCB3qlrGQeqhdl+gsQGRBiOA8Jj Jr5F9RNZepVLGv+t5fALeoe0gLHsWoTlfTdq AJ8a2E5BZYYvy9hjh9Y4Kqd23HOv21o2OC0J viOQHZ6I4xoZQP5G7r98/PhlrLM= ) xx.example. 3600 IN A 192.0.2.10 3600 RRSIG A 5 2 3600 20040115201552 ( 20031216201552 41681 example. fQfj8RhKKhC2vI0OJxgnZLeXFhpMmpjwV/ap tCkUP1YagLF9gB4NLRUrV1QO/e1f2zyxSngq iDW9yUJjKQcv9EWzbDd0kzXxPu11y/iS7oMS KOsVB4Mp7BM5q2kcBXBrM+Rr0eibvBXmHs8G 0ToQVY81bPc3WXKZjRxQl3jiKtU= ) 3600 HINFO "KLH-10" "TOPS-20" 3600 RRSIG HINFO 5 2 3600 20040115201552 ( 20031216201552 41681 example. fZIotOyJqpRTZ0KH5lsZIksuyslAMckBclZw p3LJiaYAibf+rwNFpS3CPUFsyCrA8UL+iVfA gTxa6O8+yKYsDXZ2x6wPPDqmBEeHT1XiKEA/ pC+O35tVS6oLMYWJyGAGBJitXZQGr+MiBvSp EDXT07qFXtGntvBSpF9uQbEub6Y= ) 3600 AAAA 2001:db8::f00:baaa 3600 RRSIG AAAA 5 2 3600 20040115201552 ( 20031216201552 41681 example. kLh5dTA0XBIIjEV/guGo9pEOKNZ0Elvbuhm2 dFbnHuZ1tLirjzCYr8CsmF9bSIKLbiMRc/SD mDhMUKFMhsVqCMwqfYjxXvTOG21BKyCki0Gg CgvRD47lC4NnCSaB6B6Ysj0Aupv75Nnqwi9Z Arends, et al. Expires August 16, 2004 [Page 44] Internet-Draft DNSSEC Protocol Modifications February 2004 D4ZubIon0XGe9fIjLnmb3pX/FUk= ) 3600 NSEC example. A HINFO AAAA RRSIG NSEC 3600 RRSIG NSEC 5 2 3600 20040115201552 ( 20031216201552 41681 example. sbF8bfC6zqyuio2iov0C9byDCejWvxMJYgjn uy3nXbvVXXzcA+d2zG6uPQ8VLRSolCE+OQqE NsABxmoBhBwdxCrCpnU8SvzAkrRLwuOqAu1a 1yBIfd352PHkQg1sxVDHGoFo3cFKzvkuD187 sSNF3PAC0HPadh7SdHmXlFQtQ44= ) 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 August 16, 2004 [Page 45] Internet-Draft DNSSEC Protocol Modifications February 2004 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 5 3 3600 20040115201552 ( 20031216201552 41681 example. g2H7+tChKsYRqxDkrLZgraaKBF2pah6YNCEW ORmXLzrB6RWtXbjVHXjagBhZYsMPzkPqwn4m 8IYSaPD0X3z001aXsgsh9WF+AOgbqa0eoIIY MHIEJ9MHB5cS33XXv2fY6iFmjLuZUz+pNSfv btznHMFDIbtuw/tAX7xXH2pDDHY= ) ;; Authority example. 3600 NS ns1.example. example. 3600 NS ns2.example. example. 3600 RRSIG NS 5 1 3600 20040115201552 ( 20031216201552 41681 example. YgTFj4yXRzbOddwfOTQhLHGPWm7x55ZRoPVz +bxuPHTozw3I2gpno81Em1RuVekWJHivAvQj s1h72oh+ipBadjCGSRu46u1T9JYUSLxLecgY eEw9qDeQIoZHRny5bYrX1x87ItEo5+n1lwOH FTVyQbVkcaxQ6U2FbZtMbfo//go= ) ;; Additional xx.example. 3600 IN A 192.0.2.10 xx.example. 3600 RRSIG A 5 2 3600 20040115201552 ( 20031216201552 41681 example. fQfj8RhKKhC2vI0OJxgnZLeXFhpMmpjwV/ap tCkUP1YagLF9gB4NLRUrV1QO/e1f2zyxSngq iDW9yUJjKQcv9EWzbDd0kzXxPu11y/iS7oMS KOsVB4Mp7BM5q2kcBXBrM+Rr0eibvBXmHs8G 0ToQVY81bPc3WXKZjRxQl3jiKtU= ) xx.example. 3600 AAAA 2001:db8::f00:baaa xx.example. 3600 RRSIG AAAA 5 2 3600 20040115201552 ( 20031216201552 41681 example. kLh5dTA0XBIIjEV/guGo9pEOKNZ0Elvbuhm2 Arends, et al. Expires August 16, 2004 [Page 46] Internet-Draft DNSSEC Protocol Modifications February 2004 dFbnHuZ1tLirjzCYr8CsmF9bSIKLbiMRc/SD mDhMUKFMhsVqCMwqfYjxXvTOG21BKyCki0Gg CgvRD47lC4NnCSaB6B6Ysj0Aupv75Nnqwi9Z D4ZubIon0XGe9fIjLnmb3pX/FUk= ) ns1.example. 3600 IN A 192.0.2.1 ns1.example. 3600 RRSIG A 5 2 3600 20040115201552 ( 20031216201552 41681 example. 5FrF88yOT6iiBdkiQLqaXkma0gCQza5/kLK7 CgoMNlCR2QYhsur2X7Fex2/OYEmOkzOqO7Gs RoIc4e3nt+kfpd/4Htp9T5v+NXmMVPmW3Jmf +ZGpEf86AI7Rw3x2bSmVOzsxa4xUxE+DuINa WNJ/ulvIFa20d0xtlB7jazNCZ3Y= ) ns2.example. 3600 IN A 192.0.2.2 ns2.example. 3600 RRSIG A 5 2 3600 20040115201552 ( 20031216201552 41681 example. sfFOjxKZz1LMhyDfmB43RhIUVOHlVbLtP0lL xBsxcHt48NKLth81pzSWRFQfUtMCjaGWMtuK HFEVaAQXcwllWXXLbVpc9a32govT+hsapcht sPyxkcEpYEFTtB93edKRVQ0IgZBPOI02R6vG wCbeY0Rl8MIRcAaiIkFos/8hd1g= ) 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.x.w.example. ( 1071609350 3600 300 3600000 3600 ) example. 3600 RRSIG SOA 5 1 3600 20040115201552 ( 20031216201552 41681 example. F1KxMLu2zwDUFgUtdAqCq6F9zkaIPb3B7dzA hRLp8riOMQQgCCQ4x9KvSu2xLJa539jQIRW0 VBU6+FZWzC2IJcc5liv2SXzyfiPu8diB9+Bj Arends, et al. Expires August 16, 2004 [Page 47] Internet-Draft DNSSEC Protocol Modifications February 2004 CSITjVX0IGrQgd+PKkaTxWQzG9TDZ2TtgnyM owLe/OV+Qqqic7ShV/S9l2YJF9I= ) b.example. 3600 NSEC ns1.example. NS RRSIG NSEC b.example. 3600 RRSIG NSEC 5 2 3600 20040115201552 ( 20031216201552 41681 example. nFufQRM2UtSYTAwQaKEnIpua5ZHLqJrcLGAs VUpLoPOEsAXex1N3uIJQWmoXnr9Up00G7jbW VOVaLUvXR7b/4sQkyQLbOl9GpWiA1NYjPneN k3i+OWi3NmvRN71CuNky87DrVg0p2Mf2MjLX GRIZP9W1bgeDHZRcCNz2hQ67SgY= ) example. 3600 NSEC a.example. NS SOA MX RRSIG NSEC DNSKEY example. 3600 RRSIG NSEC 5 1 3600 20040115201552 ( 20031216201552 41681 example. kE9ARiewdQSCsLXY9ldasZEW54kKhfEN2lsT vDD4biJsTPeaOXJ6bJ7s0CvybknENin3uqIX TAy6bsL919sEI3/SoHiRCwHalVmUPIWCsz4g Ee7gkQ+1uFzi7L8LGX9NjQI74s3M//OW2+T4 7T/nOEOVZujD8IN/Utv+KUg+P6U= ) ;; 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.x.w.example. ( 1071609350 3600 300 3600000 3600 ) example. 3600 RRSIG SOA 5 1 3600 20040115201552 ( 20031216201552 41681 example. F1KxMLu2zwDUFgUtdAqCq6F9zkaIPb3B7dzA hRLp8riOMQQgCCQ4x9KvSu2xLJa539jQIRW0 Arends, et al. Expires August 16, 2004 [Page 48] Internet-Draft DNSSEC Protocol Modifications February 2004 VBU6+FZWzC2IJcc5liv2SXzyfiPu8diB9+Bj CSITjVX0IGrQgd+PKkaTxWQzG9TDZ2TtgnyM owLe/OV+Qqqic7ShV/S9l2YJF9I= ) ns1.example. 3600 NSEC ns2.example. A RRSIG NSEC ns1.example. 3600 RRSIG NSEC 5 2 3600 20040115201552 ( 20031216201552 41681 example. WaeyPcQtFjXj4cxDcqVseuhZPA4K/qSb7ylZ sj55rJ8OqEKDYt71e1MT3F5p76wKtLaPmoc0 eLGnDD+Xouu/tWXtsjj5QpMhl13DUD0GLBiA s/wwxreW0SWkh4JJirodDE7vSIiI6gPJYhIj I2A5W86mMEbSgEF/pZHX/wi5FJI= ) ;; 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 48327 5 1 ( DFEB5E00E71A4DED5CABBBD7F15F24871983 CAB7 ) a.example. 3600 RRSIG DS 5 2 3600 20040115201552 ( 20031216201552 41681 example. wj4ME4MuuZN77PGiE8xgBmCXpRpUocRJLbW/ hBbMGk2qtA9ose1Jr2F9rOU6zvU9Z0HQgxnb rSBfaeCZFmk3yOlo9Uqref4ukk9hwIjzxo7c ZbJstCYWiLF57i1k5Cj6npMbUZSIgRGcB+dC 0yfe2uolEkeegjesDZuF+fC61Eg= ) ;; 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 August 16, 2004 [Page 49] Internet-Draft DNSSEC Protocol Modifications February 2004 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 5 2 3600 20040115201552 ( 20031216201552 41681 example. nFufQRM2UtSYTAwQaKEnIpua5ZHLqJrcLGAs VUpLoPOEsAXex1N3uIJQWmoXnr9Up00G7jbW VOVaLUvXR7b/4sQkyQLbOl9GpWiA1NYjPneN k3i+OWi3NmvRN71CuNky87DrVg0p2Mf2MjLX GRIZP9W1bgeDHZRcCNz2hQ67SgY= ) ;; 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 5 2 3600 20040115201552 ( 20031216201552 41681 example. mzcZPkLFaFycrnJuHY8LHdmvmyD8prPbQXHg OXuGLRpO+qRU04v97KYNy8si1Ijmo85nI4Ns Arends, et al. Expires August 16, 2004 [Page 50] Internet-Draft DNSSEC Protocol Modifications February 2004 Hl2+WpbMguW9gyPpdHqIYkKJbOrX2b4bz6WA n7NlR05Rf2tE3e54a1LP0po55yqGtxdPKWOK 91Ena87PA2MvoOE+A3ZpEk8MjEE= ) ;; Authority example. 3600 NS ns1.example. example. 3600 NS ns2.example. example. 3600 RRSIG NS 5 1 3600 20040115201552 ( 20031216201552 41681 example. YgTFj4yXRzbOddwfOTQhLHGPWm7x55ZRoPVz +bxuPHTozw3I2gpno81Em1RuVekWJHivAvQj s1h72oh+ipBadjCGSRu46u1T9JYUSLxLecgY eEw9qDeQIoZHRny5bYrX1x87ItEo5+n1lwOH FTVyQbVkcaxQ6U2FbZtMbfo//go= ) x.y.w.example. 3600 NSEC xx.example. MX RRSIG NSEC x.y.w.example. 3600 RRSIG NSEC 5 4 3600 20040115201552 ( 20031216201552 41681 example. sjHnEm4kiIK64bRskNc3vxEHe12l9Lg8Y7G8 VsXMUEEDeBCB3qlrGQeqhdl+gsQGRBiOA8Jj Jr5F9RNZepVLGv+t5fALeoe0gLHsWoTlfTdq AJ8a2E5BZYYvy9hjh9Y4Kqd23HOv21o2OC0J viOQHZ6I4xoZQP5G7r98/PhlrLM= ) ;; Additional ai.example. 3600 IN A 192.0.2.9 ai.example. 3600 RRSIG A 5 2 3600 20040115201552 ( 20031216201552 41681 example. hxNyPE9Wn675NDH/IpB2LZzhrUtV9eEndid8 jiteGyki6CAEJKm1Dr2bjlrzdgfFBrpIac9c Up4zMlAkitX/7D9vFus8nLSvEHngpdc12Hlk OrvT0EsYA2XeQ0h3PPQk5FcK2ekxZvw5Zm7A sWifTxvcG5hv+A6TOd0O2xJYRik= ) ai.example. 3600 AAAA 2001:db8::f00:baa9 ai.example. 3600 RRSIG AAAA 5 2 3600 20040115201552 ( 20031216201552 41681 example. oq16/pU4MuvkgQyFqGrHqggz47i6iZL714u5 9UsmGM1Y/qyQZsR4wi6hC2zIWXNJxIPIhitJ G6M5pjExUH/vOe0DIW73t/NHzcj0zOjxAPEI A+jBlOwn2EY5q87PMzBIeHWSx7DxtEIMC8XI zkK+1+Z5aqj1pmZ4yXUvd2znGnQ= ) 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 August 16, 2004 [Page 51] Internet-Draft DNSSEC Protocol Modifications February 2004 ;; Header: QR AA DO RCODE=0 ;; ;; Question a.z.w.example. IN AAAA ;; Answer ;; (empty) ;; Authority example. 3600 IN SOA ns1.example. bugs.x.w.example. ( 1071609350 3600 300 3600000 3600 ) example. 3600 RRSIG SOA 5 1 3600 20040115201552 ( 20031216201552 41681 example. F1KxMLu2zwDUFgUtdAqCq6F9zkaIPb3B7dzA hRLp8riOMQQgCCQ4x9KvSu2xLJa539jQIRW0 VBU6+FZWzC2IJcc5liv2SXzyfiPu8diB9+Bj CSITjVX0IGrQgd+PKkaTxWQzG9TDZ2TtgnyM owLe/OV+Qqqic7ShV/S9l2YJF9I= ) x.y.w.example. 3600 NSEC xx.example. MX RRSIG NSEC x.y.w.example. 3600 RRSIG NSEC 5 4 3600 20040115201552 ( 20031216201552 41681 example. sjHnEm4kiIK64bRskNc3vxEHe12l9Lg8Y7G8 VsXMUEEDeBCB3qlrGQeqhdl+gsQGRBiOA8Jj Jr5F9RNZepVLGv+t5fALeoe0gLHsWoTlfTdq AJ8a2E5BZYYvy9hjh9Y4Kqd23HOv21o2OC0J viOQHZ6I4xoZQP5G7r98/PhlrLM= ) *.w.example. 3600 NSEC x.w.example. MX RRSIG NSEC *.w.example. 3600 RRSIG NSEC 5 2 3600 20040115201552 ( 20031216201552 41681 example. OeBMvLlBam90xU/KxvyAYBNGWpvMf1TbaJFr f0Ip+tTkiqeEE8fx2ZAg1JcY9uhldms/9y45 9HxO9Q3ZO6jfQzsx62YQaBte85d/Udhzf4AK /RHsZGSOabsu6DhacWC2Ew7vEgcMfiPHFzWW ANi1i3zhPOd3+Vjt4IQzaJXqVZE= ) ;; 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 August 16, 2004 [Page 52] Internet-Draft DNSSEC Protocol Modifications February 2004 ;; Header: QR AA DO RCODE=0 ;; ;; Question example. IN DS ;; Answer ;; (empty) ;; Authority example. 3600 IN SOA ns1.example. bugs.x.w.example. ( 1071609350 3600 300 3600000 3600 ) example. 3600 RRSIG SOA 5 1 3600 20040115201552 ( 20031216201552 41681 example. F1KxMLu2zwDUFgUtdAqCq6F9zkaIPb3B7dzA hRLp8riOMQQgCCQ4x9KvSu2xLJa539jQIRW0 VBU6+FZWzC2IJcc5liv2SXzyfiPu8diB9+Bj CSITjVX0IGrQgd+PKkaTxWQzG9TDZ2TtgnyM owLe/OV+Qqqic7ShV/S9l2YJF9I= ) example. 3600 NSEC a.example. NS SOA MX RRSIG NSEC DNSKEY example. 3600 RRSIG NSEC 5 1 3600 20040115201552 ( 20031216201552 41681 example. kE9ARiewdQSCsLXY9ldasZEW54kKhfEN2lsT vDD4biJsTPeaOXJ6bJ7s0CvybknENin3uqIX TAy6bsL919sEI3/SoHiRCwHalVmUPIWCsz4g Ee7gkQ+1uFzi7L8LGX9NjQI74s3M//OW2+T4 7T/nOEOVZujD8IN/Utv+KUg+P6U= ) ;; Additional ;; (empty) Arends, et al. Expires August 16, 2004 [Page 53] Internet-Draft DNSSEC Protocol Modifications February 2004 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 5 and key tag 41681. 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 August 16, 2004 [Page 54] Internet-Draft DNSSEC Protocol Modifications February 2004 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 5 and has a key tag of 41681. This DNSKEY is used to authenticated the RRSIG included in the response. If multiple "example" DNSKEY RRs have algorithm 5 and key tag of 41681, 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 August 16, 2004 [Page 55] Internet-Draft DNSSEC Protocol Modifications February 2004 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 5 and key tag 41681. 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 August 16, 2004 [Page 56] Internet-Draft DNSSEC Protocol Modifications February 2004 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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Expires August 16, 2004 [Page 57] Internet-Draft DNSSEC Protocol Modifications February 2004 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 August 16, 2004 [Page 58]