-DNS Extensions working group J. Jansen
-Internet-Draft NLnet Labs
-Intended status: Standards Track June 04, 2009
-Expires: December 6, 2009
- Use of SHA-2 algorithms with RSA in DNSKEY and RRSIG Resource Records
- for DNSSEC
- draft-ietf-dnsext-dnssec-rsasha256-14
-Status of this Memo
+Network Working Group J. Jansen
+Request for Comments: 5702 NLnet Labs
+Category: Standards Track October 2009
- This Internet-Draft is submitted to IETF in full conformance with the
- provisions of BCP 78 and BCP 79.
- 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.
+ Use of SHA-2 Algorithms with RSA in
+ DNSKEY and RRSIG Resource Records for DNSSEC
- 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."
+Abstract
- The list of current Internet-Drafts can be accessed at
- http://www.ietf.org/ietf/1id-abstracts.txt.
+ This document describes how to produce RSA/SHA-256 and RSA/SHA-512
+ DNSKEY and RRSIG resource records for use in the Domain Name System
+ Security Extensions (RFC 4033, RFC 4034, and RFC 4035).
- The list of Internet-Draft Shadow Directories can be accessed at
- http://www.ietf.org/shadow.html.
+Status of This Memo
- This Internet-Draft will expire on December 6, 2009.
+ This document specifies an Internet standards track protocol for the
+ Internet community, and requests discussion and suggestions for
+ improvements. Please refer to the current edition of the "Internet
+ Official Protocol Standards" (STD 1) for the standardization state
+ and status of this protocol. Distribution of this memo is unlimited.
Copyright Notice
document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal
- Provisions Relating to IETF Documents in effect on the date of
- publication of this document (http://trustee.ietf.org/license-info).
- Please review these documents carefully, as they describe your rights
- and restrictions with respect to this document.
-
-Abstract
-
- This document describes how to produce RSA/SHA-256 and RSA/SHA-512
- DNSKEY and RRSIG resource records for use in the Domain Name System
-
-
-
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-
-
- Security Extensions (DNSSEC, RFC 4033, RFC 4034, and RFC 4035).
-
-
-Table of Contents
-
- 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
- 2. DNSKEY Resource Records . . . . . . . . . . . . . . . . . . . 3
- 2.1. RSA/SHA-256 DNSKEY Resource Records . . . . . . . . . . . 3
- 2.2. RSA/SHA-512 DNSKEY Resource Records . . . . . . . . . . . 4
- 3. RRSIG Resource Records . . . . . . . . . . . . . . . . . . . . 4
- 3.1. RSA/SHA-256 RRSIG Resource Records . . . . . . . . . . . . 4
- 3.2. RSA/SHA-512 RRSIG Resource Records . . . . . . . . . . . . 5
- 4. Deployment Considerations . . . . . . . . . . . . . . . . . . 5
- 4.1. Key Sizes . . . . . . . . . . . . . . . . . . . . . . . . 5
- 4.2. Signature Sizes . . . . . . . . . . . . . . . . . . . . . 5
- 5. Implementation Considerations . . . . . . . . . . . . . . . . 5
- 5.1. Support for SHA-2 signatures . . . . . . . . . . . . . . . 5
- 5.2. Support for NSEC3 Denial of Existence . . . . . . . . . . 5
- 6. Examples . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
- 6.1. RSA/SHA-256 Key and Signature . . . . . . . . . . . . . . 6
- 6.2. RSA/SHA-512 Key and Signature . . . . . . . . . . . . . . 7
- 7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 8
- 8. Security Considerations . . . . . . . . . . . . . . . . . . . 8
- 8.1. SHA-1 versus SHA-2 Considerations for RRSIG Resource
- Records . . . . . . . . . . . . . . . . . . . . . . . . . 8
- 8.2. Signature Type Downgrade Attacks . . . . . . . . . . . . . 8
- 9. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 9
- 10. References . . . . . . . . . . . . . . . . . . . . . . . . . . 9
- 10.1. Normative References . . . . . . . . . . . . . . . . . . . 9
- 10.2. Informative References . . . . . . . . . . . . . . . . . . 9
- Author's Address . . . . . . . . . . . . . . . . . . . . . . . . . 10
-
-
-
+ Provisions Relating to IETF Documents
+ (http://trustee.ietf.org/license-info) in effect on the date of
+ publication of this document. Please review these documents
+ carefully, as they describe your rights and restrictions with respect
+ to this document. Code Components extracted from this document must
+ include Simplified BSD License text as described in Section 4.e of
+ the Trust Legal Provisions and are provided without warranty as
+ described in the BSD License.
+Jansen Standards Track [Page 1]
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+Table of Contents
+ 1. Introduction ....................................................2
+ 2. DNSKEY Resource Records .........................................3
+ 2.1. RSA/SHA-256 DNSKEY Resource Records ........................3
+ 2.2. RSA/SHA-512 DNSKEY Resource Records ........................3
+ 3. RRSIG Resource Records ..........................................3
+ 3.1. RSA/SHA-256 RRSIG Resource Records .........................4
+ 3.2. RSA/SHA-512 RRSIG Resource Records .........................4
+ 4. Deployment Considerations .......................................5
+ 4.1. Key Sizes ..................................................5
+ 4.2. Signature Sizes ............................................5
+ 5. Implementation Considerations ...................................5
+ 5.1. Support for SHA-2 Signatures ...............................5
+ 5.2. Support for NSEC3 Denial of Existence ......................5
+ 6. Examples ........................................................6
+ 6.1. RSA/SHA-256 Key and Signature ..............................6
+ 6.2. RSA/SHA-512 Key and Signature ..............................7
+ 7. IANA Considerations .............................................8
+ 8. Security Considerations .........................................8
+ 8.1. SHA-1 versus SHA-2 Considerations for RRSIG
+ Resource Records ...........................................8
+ 8.2. Signature Type Downgrade Attacks ...........................8
+ 9. Acknowledgments .................................................9
+ 10. References .....................................................9
+ 10.1. Normative References ......................................9
+ 10.2. Informative References ....................................9
1. Introduction
- The Domain Name System (DNS) is the global hierarchical distributed
+ The Domain Name System (DNS) is the global, hierarchical distributed
database for Internet Naming. The DNS has been extended to use
cryptographic keys and digital signatures for the verification of the
- authenticity and integrity of its data. RFC 4033 [RFC4033], RFC 4034
- [RFC4034], and RFC 4035 [RFC4035] describe these DNS Security
- Extensions, called DNSSEC.
+ authenticity and integrity of its data. [RFC4033], [RFC4034], and
+ [RFC4035] describe these DNS Security Extensions, called DNSSEC.
RFC 4034 describes how to store DNSKEY and RRSIG resource records,
and specifies a list of cryptographic algorithms to use. This
SHA-512, and specifies how to store DNSKEY data and how to produce
RRSIG resource records with these hash algorithms.
- Familiarity with DNSSEC, RSA and the SHA-2 [FIPS.180-3.2008] family
+ Familiarity with DNSSEC, RSA, and the SHA-2 [FIPS.180-3.2008] family
of algorithms is assumed in this document.
+
+
+
+
+
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+
To refer to both SHA-256 and SHA-512, this document will use the name
SHA-2. This is done to improve readability. When a part of text is
specific for either SHA-256 or SHA-512, their specific names are
used. The same goes for RSA/SHA-256 and RSA/SHA-512, which will be
grouped using the name RSA/SHA-2.
- The term "SHA-2" is not officially defined, but is usually used to
- refer to the collection of the algorithms SHA-224, SHA-256, SHA-384
+ The term "SHA-2" is not officially defined but is usually used to
+ refer to the collection of the algorithms SHA-224, SHA-256, SHA-384,
and SHA-512. Since SHA-224 and SHA-384 are not used in DNSSEC, SHA-2
will only refer to SHA-256 and SHA-512 in this document.
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in [RFC2119].
-
2. DNSKEY Resource Records
- The format of the DNSKEY RR can be found in RFC 4034 [RFC4034]. RFC
- 3110 [RFC3110] describes the use of RSA/SHA-1 for DNSSEC signatures.
+ The format of the DNSKEY RR can be found in [RFC4034]. [RFC3110]
+ describes the use of RSA/SHA-1 for DNSSEC signatures.
2.1. RSA/SHA-256 DNSKEY Resource Records
RSA public keys for use with RSA/SHA-256 are stored in DNSKEY
- resource records (RRs) with the algorithm number {TBA1}.
+ resource records (RRs) with the algorithm number 8.
- For interoperability, as in RFC 3110 [RFC3110], the key size of RSA/
- SHA-256 keys MUST NOT be less than 512 bits, and MUST NOT be more
- than 4096 bits.
+ For interoperability, as in [RFC3110], the key size of RSA/SHA-256
+ keys MUST NOT be less than 512 bits and MUST NOT be more than 4096
+ bits.
+2.2. RSA/SHA-512 DNSKEY Resource Records
+ RSA public keys for use with RSA/SHA-512 are stored in DNSKEY
+ resource records (RRs) with the algorithm number 10.
+ The key size of RSA/SHA-512 keys MUST NOT be less than 1024 bits and
+ MUST NOT be more than 4096 bits.
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+3. RRSIG Resource Records
+ The value of the signature field in the RRSIG RR follows the RSASSA-
+ PKCS1-v1_5 signature scheme and is calculated as follows. The values
+ for the RDATA fields that precede the signature data are specified in
+ [RFC4034].
-2.2. RSA/SHA-512 DNSKEY Resource Records
- RSA public keys for use with RSA/SHA-512 are stored in DNSKEY
- resource records (RRs) with the algorithm number {TBA2}.
- The key size of RSA/SHA-512 keys MUST NOT be less than 1024 bits, and
- MUST NOT be more than 4096 bits.
-3. RRSIG Resource Records
- The value of the signature field in the RRSIG RR follows the RSASSA-
- PKCS1-v1_5 signature scheme, and is calculated as follows. The
- values for the RDATA fields that precede the signature data are
- specified in RFC 4034 [RFC4034].
+
+
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+
hash = SHA-XXX(data)
Here XXX is either 256 or 512, depending on the algorithm used, as
- specified in FIPS PUB 180-3 [FIPS.180-3.2008], and "data" is the wire
- format data of the resource record set that is signed, as specified
- in RFC 4034 [RFC4034].
+ specified in FIPS PUB 180-3; "data" is the wire format data of the
+ resource record set that is signed, as specified in [RFC4034].
signature = ( 00 | 01 | FF* | 00 | prefix | hash ) ** e (mod n)
- Here "|" is concatenation, "00", "01", "FF" and "00" are fixed octets
- of corresponding hexadecimal value, "e" is the private exponent of
- the signing RSA key, and "n" is the public modulus of the signing
- key. The FF octet MUST be repeated the exact number of times so that
- the total length of the concatenated term in parentheses equals the
- length of the modulus of the signer's public key ("n").
+ Here "|" is concatenation; "00", "01", "FF", and "00" are fixed
+ octets of corresponding hexadecimal value; "e" is the private
+ exponent of the signing RSA key; and "n" is the public modulus of the
+ signing key. The FF octet MUST be repeated the exact number of times
+ so that the total length of the concatenated term in parentheses
+ equals the length of the modulus of the signer's public key ("n").
The "prefix" is intended to make the use of standard cryptographic
libraries easier. These specifications are taken directly from the
- specifications of RSASSA-PKCS1-v1_5 in PKCS #1 v2.1 section 8.2
- [RFC3447], and EMSA-PKCS1-v1_5 encoding in PKCS #1 v2.1 section 9.2
- [RFC3447]. The prefixes for the different algorithms are specified
- below.
+ specifications of RSASSA-PKCS1-v1_5 in PKCS #1 v2.1 (Section 8.2 of
+ [RFC3447]), and EMSA-PKCS1-v1_5 encoding in PKCS #1 v2.1 (Section 9.2
+ of [RFC3447]). The prefixes for the different algorithms are
+ specified below.
3.1. RSA/SHA-256 RRSIG Resource Records
RSA/SHA-256 signatures are stored in the DNS using RRSIG resource
- records (RRs) with algorithm number {TBA1}.
+ records (RRs) with algorithm number 8.
- The prefix is the ASN.1 DER SHA-256 algorithm designator prefix as
+ The prefix is the ASN.1 DER SHA-256 algorithm designator prefix, as
specified in PKCS #1 v2.1 [RFC3447]:
hex 30 31 30 0d 06 09 60 86 48 01 65 03 04 02 01 05 00 04 20
-
-
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-
-
3.2. RSA/SHA-512 RRSIG Resource Records
RSA/SHA-512 signatures are stored in the DNS using RRSIG resource
- records (RRs) with algorithm number {TBA2}.
+ records (RRs) with algorithm number 10.
- The prefix is the ASN.1 DER SHA-512 algorithm designator prefix as
+ The prefix is the ASN.1 DER SHA-512 algorithm designator prefix, as
specified in PKCS #1 v2.1 [RFC3447]:
hex 30 51 30 0d 06 09 60 86 48 01 65 03 04 02 03 05 00 04 40
+
+
+
+
+
+
+
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+
4. Deployment Considerations
4.1. Key Sizes
- Apart from the restrictions in section 2, this document will not
+ Apart from the restrictions in Section 2, this document will not
specify what size of keys to use. That is an operational issue and
depends largely on the environment and intended use. A good starting
point for more information would be NIST SP 800-57 [NIST800-57].
4.2. Signature Sizes
In this family of signing algorithms, the size of signatures is
- related to the size of the key, and not the hashing algorithm used in
- the signing process. Therefore, RRSIG resource records produced with
- RSA/SHA-256 or RSA/SHA-512 will have the same size as those produced
- with RSA/SHA-1, if the keys have the same length.
-
+ related to the size of the key and not to the hashing algorithm used
+ in the signing process. Therefore, RRSIG resource records produced
+ with RSA/SHA-256 or RSA/SHA-512 will have the same size as those
+ produced with RSA/SHA-1, if the keys have the same length.
5. Implementation Considerations
-5.1. Support for SHA-2 signatures
+5.1. Support for SHA-2 Signatures
- DNSSEC aware implementations SHOULD be able to support RRSIG and
+ DNSSEC-aware implementations SHOULD be able to support RRSIG and
DNSKEY resource records created with the RSA/SHA-2 algorithms as
defined in this document.
5.2. Support for NSEC3 Denial of Existence
- RFC 5155 [RFC5155] defines new algorithm identifiers for existing
- signing algorithms, to indicate that zones signed with these
- algorithm identifiers can use NSEC3 as well as NSEC records to
- provide denial of existence. That mechanism was chosen to protect
- implementations predating RFC5155 from encountering resource records
- they could not know about. This document does not define such
- algorithm aliases.
+ [RFC5155] defines new algorithm identifiers for existing signing
+ algorithms, to indicate that zones signed with these algorithm
+ identifiers can use NSEC3 as well as NSEC records to provide denial
+ of existence. That mechanism was chosen to protect implementations
+ predating RFC 5155 from encountering resource records about which
+ they could not know. This document does not define such algorithm
+ aliases.
A DNSSEC validator that implements RSA/SHA-2 MUST be able to validate
+ negative answers in the form of both NSEC and NSEC3 with hash
+ algorithm 1, as defined in [RFC5155]. An authoritative server that
+ does not implement NSEC3 MAY still serve zones that use RSA/SHA-2
+ with NSEC denial of existence.
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- negative answers in the form of both NSEC and NSEC3 with hash
- algorithm 1, as defined in [RFC5155]. An authoritative server that
- does not implement NSEC3 MAY still serve zones that use RSA/SHA-2
- with NSEC denial of existence.
+
+
+
+
+
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6. Examples
the expiration date at 00:00 hours on January 1st, 2030, the
following signature should be created:
- www.example.net. 3600 IN RRSIG (A 8 3 3600 20300101000000
- 20000101000000 9033 example.net. kRCOH6u7l0QGy9qpC9
- l1sLncJcOKFLJ7GhiUOibu4teYp5VE9RncriShZNz85mwlMgNEa
- cFYK/lPtPiVYP4bwg== ;{id = 9033}
+ www.example.net. 3600 IN RRSIG (A 8 3 3600 20300101000000
+ 20000101000000 9033 example.net. kRCOH6u7l0QGy9qpC9
+ l1sLncJcOKFLJ7GhiUOibu4teYp5VE9RncriShZNz85mwlMgNEa
+ cFYK/lPtPiVYP4bwg==);{id = 9033}
+
+
+
+
+
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6.2. RSA/SHA-512 Key and Signature
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7. IANA Considerations
This document updates the IANA registry "DNS SECURITY ALGORITHM
- NUMBERS -- per [RFC4035] "
- (http://www.iana.org/assignments/dns-sec-alg-numbers). The following
- entries are added to the registry:
-
- Zone Trans.
- Value Description Mnemonic Signing Sec. References
- {TBA1} RSA/SHA-256 RSASHA256 y * {this memo}
- {TBA2} RSA/SHA-512 RSASHA512 y * {this memo}
+ NUMBERS -- per [RFC4035]" (http://www.iana.org/protocols). The
+ following entries are added to the registry:
- * There has been no determination of standardization of the use of this
- algorithm with Transaction Security.
+ Zone Trans.
+ Value Description Mnemonic Signing Sec. References
+ 8 RSA/SHA-256 RSASHA256 Y * RFC 5702
+ 10 RSA/SHA-512 RSASHA512 Y * RFC 5702
+ * There has been no determination of standardization of the use of
+ this algorithm with Transaction Security.
8. Security Considerations
Users of DNSSEC are encouraged to deploy SHA-2 as soon as software
implementations allow for it. SHA-2 is widely believed to be more
resilient to attack than SHA-1, and confidence in SHA-1's strength is
- being eroded by recently-announced attacks. Regardless of whether or
+ being eroded by recently announced attacks. Regardless of whether or
not the attacks on SHA-1 will affect DNSSEC, it is believed (at the
time of this writing) that SHA-2 is the better choice for use in
DNSSEC records.
8.2. Signature Type Downgrade Attacks
Since each RRSet MUST be signed with each algorithm present in the
- DNSKEY RRSet at the zone apex (see [RFC4035] Section 2.2), a
- malicious party cannot filter out the RSA/SHA-2 RRSIG, and force the
+ DNSKEY RRSet at the zone apex (see Section 2.2 of [RFC4035]), a
+ malicious party cannot filter out the RSA/SHA-2 RRSIG and force the
validator to use the RSA/SHA-1 signature if both are present in the
zone. This should provide resilience against algorithm downgrade
attacks, if the validator supports RSA/SHA-2.
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9. Acknowledgments
- This document is a minor extension to RFC 4034 [RFC4034]. Also, we
- try to follow the documents RFC 3110 [RFC3110] and RFC 4509 [RFC4509]
- for consistency. The authors of and contributors to these documents
- are gratefully acknowledged for their hard work.
+ This document is a minor extension to [RFC4034]. Also, we try to
+ follow the documents [RFC3110] and [RFC4509] for consistency. The
+ authors of and contributors to these documents are gratefully
+ acknowledged for their hard work.
The following people provided additional feedback and text: Jaap
Akkerhuis, Mark Andrews, Roy Arends, Rob Austein, Francis Dupont,
- Miek Gieben, Alfred Hoenes, Paul Hoffman, Peter Koch, Michael St.
- Johns, Scott Rose and Wouter Wijngaards.
-
+ Miek Gieben, Alfred Hoenes, Paul Hoffman, Peter Koch, Scott Rose,
+ Michael St. Johns, and Wouter Wijngaards.
10. References
Hash Standard", FIPS PUB 180-3, October 2008.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
- Requirement Levels", RFC 2119, March 1997.
+ Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC3110] Eastlake, D., "RSA/SHA-1 SIGs and RSA KEYs in the Domain
Name System (DNS)", RFC 3110, May 2001.
[RFC3447] Jonsson, J. and B. Kaliski, "Public-Key Cryptography
Standards (PKCS) #1: RSA Cryptography Specifications
+ Version 2.1", RFC 3447, February 2003.
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- Version 2.1", RFC 3447, February 2003.
-
[RFC4509] Hardaker, W., "Use of SHA-256 in DNSSEC Delegation Signer
(DS) Resource Records (RRs)", RFC 4509, May 2006.
Security (DNSSEC) Hashed Authenticated Denial of
Existence", RFC 5155, March 2008.
-
Author's Address
Jelte Jansen
NLnet Labs
- Kruislaan 419
- Amsterdam 1098VA
+ Science Park 140
+ 1098 XG Amsterdam
NL
- Email: jelte@NLnetLabs.nl
+ EMail: jelte@NLnetLabs.nl
URI: http://www.nlnetlabs.nl/
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+
+
+
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projects / thirdparty / bind9.git / commitdiff
