 1/draftietfdnsextdnssecrsasha25605.txt 20081023 23:12:18.000000000 +0200
+++ 2/draftietfdnsextdnssecrsasha25606.txt 20081023 23:12:18.000000000 +0200
@@ 1,19 +1,19 @@
DNS Extensions working group J. Jansen
InternetDraft NLnet Labs
Intended status: Standards Track July 29, 2008
Expires: January 30, 2009
+Intended status: Standards Track October 23, 2008
+Expires: April 26, 2009
Use of SHA2 algorithms with RSA in DNSKEY and RRSIG Resource Records
for DNSSEC
 draftietfdnsextdnssecrsasha25605
+ draftietfdnsextdnssecrsasha25606
Status of this Memo
By submitting this InternetDraft, each author represents that any
applicable patent or other IPR claims of which he or she is aware
have been or will be disclosed, and any of which he or she becomes
aware will be disclosed, in accordance with Section 6 of BCP 79.
InternetDrafts are working documents of the Internet Engineering
Task Force (IETF), its areas, and its working groups. Note that
@@ 24,194 +24,202 @@
and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use InternetDrafts as reference
material or to cite them other than as "work in progress."
The list of current InternetDrafts can be accessed at
http://www.ietf.org/ietf/1idabstracts.txt.
The list of InternetDraft Shadow Directories can be accessed at
http://www.ietf.org/shadow.html.
 This InternetDraft will expire on January 30, 2009.
+ This InternetDraft will expire on April 26, 2009.
Abstract
This document describes how to produce RSA/SHA256 and RSA/SHA512
DNSKEY and RRSIG resource records for use in the Domain Name System
Security Extensions (DNSSEC, RFC 4033, RFC 4034, and RFC 4035).
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
2. DNSKEY Resource Records . . . . . . . . . . . . . . . . . . . . 3
2.1. RSA/SHA256 DNSKEY Resource Records . . . . . . . . . . . . 3
2.2. RSA/SHA512 DNSKEY Resource Records . . . . . . . . . . . . 3
3. RRSIG Resource Records . . . . . . . . . . . . . . . . . . . . 4
3.1. RSA/SHA256 RRSIG Resource Records . . . . . . . . . . . . 4
 3.2. RSA/SHA512 RRSIG Resource Records . . . . . . . . . . . . 4
+ 3.2. RSA/SHA512 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 SHA1 and SHA2 signatures . . . . . . . . . . 5
 5.2. Support for NSEC3 denial of existence . . . . . . . . . . . 5
+ 5.1. Support for SHA2 signatures . . . . . . . . . . . . . . . 5
6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 5
7. Security Considerations . . . . . . . . . . . . . . . . . . . . 6
7.1. SHA1 versus SHA2 Considerations for RRSIG Resource
Records . . . . . . . . . . . . . . . . . . . . . . . . . . 6
7.2. Signature Type Downgrade Attacks . . . . . . . . . . . . . 6
8. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . 6
 9. References . . . . . . . . . . . . . . . . . . . . . . . . . . 6
 9.1. Normative References . . . . . . . . . . . . . . . . . . . 6
+ 9. References . . . . . . . . . . . . . . . . . . . . . . . . . . 7
+ 9.1. Normative References . . . . . . . . . . . . . . . . . . . 7
9.2. Informative References . . . . . . . . . . . . . . . . . . 7
 Author's Address . . . . . . . . . . . . . . . . . . . . . . . . . 7
+ Author's Address . . . . . . . . . . . . . . . . . . . . . . . . . 8
Intellectual Property and Copyright Statements . . . . . . . . . . 9
1. Introduction
The Domain Name System (DNS) is the global hierarchical distributed
 database for Internet Addressing. The DNS has been extended to use
+ database for Internet Naming. The DNS has been extended to use
cryptographic keys and digital signatures for the verification of the
 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. RFC 4033 [RFC4033], RFC 4034
+ [RFC4034], and RFC 4035 [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
document extends that list with the algorithms RSA/SHA256 and RSA/
SHA512, and specifies how to store DNSKEY data and how to produce
RRSIG resource records with these hash algorithms.
 Familiarity with DNSSEC, RSA [SCHNEIER1996] and the SHA2
 [FIPS.1802.2002] family of algorithms is assumed in this document.
+ Familiarity with DNSSEC, RSA and the SHA2 [FIPS.1802.2002] family
+ of algorithms is assumed in this document.
To refer to both SHA256 and SHA512, this document will use the name
SHA2. This is done to improve readability. When a part of text is
specific for either SHA256 or SHA512, their specific names are
used. The same goes for RSA/SHA256 and RSA/SHA512, which will be
grouped using the name RSA/SHA2.
2. DNSKEY Resource Records
 The format of the DNSKEY RR can be found in RFC 4034 [RFC4034] and
 RFC 3110 [RFC3110].
+ The format of the DNSKEY RR can be found in RFC 4034 [RFC4034], RFC
+ 3110 [RFC3110] describes the use of RSA/SHA1 for DNSSEC signatures.
2.1. RSA/SHA256 DNSKEY Resource Records
RSA public keys for use with RSA/SHA256 are stored in DNSKEY
resource records (RRs) with the algorithm number {TBA1}.
 The key size for RSA/SHA256 keys MUST NOT be less than 512 bits, and
 MUST NOT be more than 4096 bits.
+ For use with NSEC3 [RFC5155], the algorithm number for RSA/SHA256
+ will be {TBA2}. The use of a different algorithm number to
+ differentiate between the use of NSEC and NSEC3 is in keeping with
+ the approach adopted in RFC5155.
+
+ For interoperability, as in RFC 3110 [RFC3110], the key size of RSA/
+ SHA256 keys MUST NOT be less than 512 bits, and MUST NOT be more
+ than 4096 bits.
2.2. RSA/SHA512 DNSKEY Resource Records
RSA public keys for use with RSA/SHA512 are stored in DNSKEY
 resource records (RRs) with the algorithm number {TBA2}.
+ resource records (RRs) with the algorithm number {TBA3}.
 The key size for RSA/SHA512 keys MUST NOT be less than 1024 bits,
 and MUST NOT be more than 4096 bits.
+ For use with NSEC3, the algorithm number for RSA/SHA512 will be
+ {TBA4}. The use of a different algorithm number to differentiate
+ between the use of NSEC and NSEC3 is in keeping with the approach
+ adopted in RFC5155.
+
+ The key size of RSA/SHA512 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 follow the RSASSA
+ The value of the signature field in the RRSIG RR follows the RSASSA
PKCS1v1_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].
hash = SHAXXX(data)
 Where XXX is either 256 or 512, depending on the algorithm used.
+ Here XXX is either 256 or 512, depending on the algorithm used, as
+ specified in FIPS PUB 1802 [FIPS.1802.2002], and "data" is the wire
+ format data of the resource record set that is signed, as specified
+ in RFC 4034 [RFC4034].
signature = ( 00  01  FF*  00  prefix  hash ) ** e (mod n)
 Where SHAXXX is the message digest algorithm as specified in FIPS
 PUB 1802 [FIPS.1802.2002], "" 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
 maximum number of times so that the total length of the signature
 equals the length of the modulus of the signer's public key ("n").
 "data" is the data of the resource record set that is signed, as
 specified in RFC 4034 [RFC4034].
+ 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
 specification of EMSAPKCS1v1_5 encoding in PKCS #1 v2.1 section 9.2
+ specifications of RSASSAPKCS1v1_5 in PKCS #1 v2.1 section 8.2
+ [RFC3447], and EMSAPKCS1v1_5 encoding in PKCS #1 v2.1 section 9.2
[RFC3447]. The prefixes for the different algorithms are specified
below.
3.1. RSA/SHA256 RRSIG Resource Records
RSA/SHA256 signatures are stored in the DNS using RRSIG resource
 records (RRs) with algorithm number {TBA1}.
+ records (RRs) with algorithm number {TBA1} for use with NSEC, or
+ {TBA2} for use with NSEC3.
The prefix is the ASN.1 BER SHA256 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
3.2. RSA/SHA512 RRSIG Resource Records
RSA/SHA512 signatures are stored in the DNS using RRSIG resource
 records (RRs) with algorithm number {TBA2}.
+ records (RRs) with algorithm number {TBA3} for use with NSEC, or
+ {TBA4} for use with NSEC3.
The prefix is the ASN.1 BER SHA512 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
4. Deployment Considerations
4.1. Key Sizes
 Apart from prohibiting RSA/SHA512 signatures smaller than 1024
 bytes, 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. Some good starting points for more information might
 be DNSSEC Operational Practises [RFC4641], section 3.5, and NIST SP
 80057 [NIST80057].
+ Apart from the restrictions specified 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 80057
+ [NIST80057].
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/SHA256 or RSA/SHA512 shall have the same size as those produced
+ RSA/SHA256 or RSA/SHA512 will have the same size as those produced
with RSA/SHA1, if the keys have the same length.
5. Implementation Considerations
5.1. Support for SHA1 and SHA2 signatures
+5.1. Support for SHA2 signatures
DNSSEC aware implementations SHOULD be able to support RRSIG resource
records with the RSA/SHA2 algorithms.
5.2. Support for NSEC3 denial of existence

 Implementations that have support for RSA/SHA2 MUST also have
 support for NSEC3 denial of existence, as specified in RFC 5155
 [RFC5155].

6. IANA Considerations
 IANA has not yet assigned an algorithm number for RSA/SHA256 and
 RSA/SHA512.
+ IANA has assigned DNS Security Algorithm Numbers {TBA1} for RSA/
+ SHA256 with NSEC, {TBA2} for RSA/SHA256 with NSEC3, {TBA3} for RSA/
+ SHA512 with NSEC, and {TBA4} for RSA/SHA512 with NSEC3.
The algorithm list from RFC 4034 Appendix A.1 [RFC4034] is extended
with the following entries:
Zone
 Value Algorithm [Mnemonic] Signing References Status
      
 {TBA1} RSA/SHA256 RSASHA256 y {this memo} OPTIONAL
 {TBA2} RSA/SHA512 RSASHA512 y {this memo} OPTIONAL
+ Value Algorithm [Mnemonic] Signing References
+ {TBA1} RSA/SHA256 RSASHA256 y {this memo}
+ {TBA2} RSA/SHA256NSEC3 RSASHA256NSEC3 y {this memo}
+ {TBA3} RSA/SHA512 RSASHA512 y {this memo}
+ {TBA4} RSA/SHA512NSEC3 RSASHA512NSEC3 y {this memo}
7. Security Considerations
7.1. SHA1 versus SHA2 Considerations for RRSIG Resource Records
Users of DNSSEC are encouraged to deploy SHA2 as soon as software
implementations allow for it. SHA2 is widely believed to be more
resilient to attack than SHA1, and confidence in SHA1's strength is
being eroded by recentlyannounced attacks. Regardless of whether or
not the attacks on SHA1 will affect DNSSEC, it is believed (at the
@@ 221,87 +229,80 @@
SHA2 is considered sufficiently strong for the immediate future, but
predictions about future development in cryptography and
cryptanalysis are beyond the scope of this document.
The signature scheme RSASSAPKCS1v1_5 is chosen to match the one
used for RSA/SHA1 signatures. This should ease implementation of
the new hashing algorithms in DNSSEC software.
7.2. 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
+ 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/SHA2 RRSIG, and force the
validator to use the RSA/SHA1 signature if both are present in the
zone. This should provide resilience against algorithm downgrade
attacks, if the validator supports RSA/SHA2.
8. 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.
The following people provided additional feedback and text: Jaap
 Akkerhuis, Roy Arends, Rob Austein, Miek Gieben, Alfred Hoenes,
 Michael St. Johns, Scott Rose and Wouter Wijngaards.
+ Akkerhuis, Roy Arends, Rob Austein, Francis Dupont, Miek Gieben,
+ Alfred Hoenes, Paul Hoffman, Peter Koch, Michael St. Johns, Scott
+ Rose and Wouter Wijngaards.
9. References
9.1. Normative References
+ [FIPS.1802.2002]
+ National Institute of Standards and Technology, "Secure
+ Hash Standard", FIPS PUB 1802, August 2002.
+
+ [RFC3110] Eastlake, D., "RSA/SHA1 SIGs and RSA KEYs in the Domain
+ Name System (DNS)", RFC 3110, May 2001.
+
[RFC4033] Arends, R., Austein, R., Larson, M., Massey, D., and S.
Rose, "DNS Security Introduction and Requirements",
RFC 4033, March 2005.
[RFC4034] Arends, R., Austein, R., Larson, M., Massey, D., and S.
Rose, "Resource Records for the DNS Security Extensions",
RFC 4034, March 2005.
[RFC4035] Arends, R., Austein, R., Larson, M., Massey, D., and S.
Rose, "Protocol Modifications for the DNS Security
Extensions", RFC 4035, March 2005.
+9.2. Informative References
+
+ [NIST80057]
+ Barker, E., Barker, W., Burr, W., Polk, W., and M. Smid,
+ "Recommendations for Key Management", NIST SP 80057,
+ March 2007.
+
[RFC3447] Jonsson, J. and B. Kaliski, "PublicKey Cryptography
Standards (PKCS) #1: RSA Cryptography Specifications
Version 2.1", RFC 3447, February 2003.
 [FIPS.1802.2002]
 National Institute of Standards and Technology, "Secure
 Hash Standard", FIPS PUB 1802, August 2002.

 [RFC3110] Eastlake, D., "RSA/SHA1 SIGs and RSA KEYs in the Domain
 Name System (DNS)", RFC 3110, May 2001.
+ [RFC4509] Hardaker, W., "Use of SHA256 in DNSSEC Delegation Signer
+ (DS) Resource Records (RRs)", RFC 4509, May 2006.
[RFC5155] Laurie, B., Sisson, G., Arends, R., and D. Blacka, "DNS
Security (DNSSEC) Hashed Authenticated Denial of
Existence", RFC 5155, March 2008.
9.2. Informative References

 [SCHNEIER1996]
 Schneier, B., "Applied Cryptography Second Edition:
 protocols, algorithms, and source code in C", Wiley and
 Sons , ISBN 0471117099, 1996.

 [RFC4509] Hardaker, W., "Use of SHA256 in DNSSEC Delegation Signer
 (DS) Resource Records (RRs)", RFC 4509, May 2006.

 [RFC4641] Kolkman, O. and R. Gieben, "DNSSEC Operational Practices",
 RFC 4641, September 2006.

 [NIST80057]
 Barker, E., Barker, W., Burr, W., Polk, W., and M. Smid,
 "Recommendations for Key Management", NIST SP 80057,
 March 2007.

Author's Address
Jelte Jansen
NLnet Labs
Kruislaan 419
Amsterdam 1098VA
NL
Email: jelte@NLnetLabs.nl
URI: http://www.nlnetlabs.nl/