mir/bind
2
0
Fork 0
mirror of https://gitlab.isc.org/isc-projects/bind9 synced 2025-08-30 05:57:52 +00:00
Code Issues Releases Wiki Activity

new draft

Browse Source
This commit is contained in:
Mark Andrews 2005-04-27 00:49:30 +00:00
parent 1cb73c69f7
commit b37b169ded
1 changed files with 200 additions and 83 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

283
doc/draft/draft-ietf-dnsext-tsig-sha-01.txt → doc/draft/draft-ietf-dnsext-tsig-sha-03.txt
View File

@ -1,12 +1,13 @@
INTERNET-DRAFT Donald E. Eastlake 3rd
UPDATES RFC 2845 Motorola Laboratories
Expires: August 2005 February 2005
Expires: October 2005 April 2005
HMAC SHA TSIG Algorithm Identifiers
---- --- ---- --------- -----------
<draft-ietf-dnsext-tsig-sha-01.txt>
<draft-ietf-dnsext-tsig-sha-03.txt>
Status of This Document
@ -44,7 +45,7 @@ Abstract
have been specified only for the HMAC-MD5 and GSS TSIG algorithms.
This document standardizes identifiers and implementation
requirements for additional HMAC SHA TSIG algorithms and standardizes
how to specify the truncation of HMAC values.
how to specify and handle the truncation of HMAC values.
Copyright Notice
@ -73,19 +74,19 @@ Table of Contents
2. Algorithms and Identifiers..............................4
3. Specifying Truncation...................................5
3.1 Truncation Specification...............................5
4. IANA Considerations.....................................6
5. Security Considerations.................................6
6. Copyright and Disclaimer................................6
7. Normative References....................................7
8. Informative References..................................7
Author's Address...........................................8
Expiration and File Name...................................8
4. TSIG Policy Provisions and Truncation Error.............7
5. IANA Considerations.....................................8
6. Security Considerations.................................8
6. Copyright and Disclaimer................................8
7. Normative References....................................9
8. Informative References..................................9
Author's Address..........................................10
Expiration and File Name..................................10
@ -129,22 +130,22 @@ INTERNET-DRAFT HMAC-SHA TSIG Identifiers
identifier for TSIG authentication where the cryptographic operations
are delegated to GSS [RFC 3645].
In section 2, this document specifies additional names for TSIG
In Section 2, this document specifies additional names for TSIG
authentication algorithms based on US NIST SHA algorithms and HMAC
and specifies the implementation requirements for those algorithms.
In section 3, this document specifies the meaning of inequality
In Section 3, this document specifies the meaning of inequality
between the normal output size of the specified hash function and the
length of MAC (message authentication code) data given in the TSIG
RR. In particular, it specifies that a shorter length field value
specifies truncation and a longer length field is an error.
In Section 4, policy restrictions and implications related to
truncation and a new error code to indicate truncation shorter than
permitted by policy are described and specified.
The use herein of MUST, SHOULD, MAY, MUST NOT, and SHOULD NOT is as
defined in [RFC 2119].
@ -190,12 +191,13 @@ INTERNET-DRAFT HMAC-SHA TSIG Identifiers
The use of SHA-1 [FIPS 180-1, RFC 3174], which is a 160 bit hash, as
compared with the 128 bits for MD5, and additional hash algorithms in
the SHA family [FIPS 180-2, RFC 3874] with 224, 256, 384, and 512
bits, may be preferred in some case particularly since increasingly
bits, may be preferred in some cases particularly since increasingly
successful cryptanalytic attacks are being made on the shorter
hashes. Use of TSIG between a DNS resolver and server is by mutual
agreement. That agreement can include the support of additional
algorithms and may specify policies as to which algorithms are
acceptable.
algorithms and may specify policies as to which algorithms and
truncations are acceptable subject to the restrication and guidelines
in Section 3 and 4 below.
The current HMAC-MD5.SIG-ALG.REG.INT identifier is included in the
table below for convenience. Implementations which support TSIG MUST
@ -227,7 +229,6 @@ INTERNET-DRAFT HMAC-SHA TSIG Identifiers
D. Eastlake 3rd [Page 4]
@ -236,53 +237,53 @@ INTERNET-DRAFT HMAC-SHA TSIG Identifiers
3. Specifying Truncation
In some cases, it is reasonable to truncate the output of HMAC and
When space is at a premium and the strength of the full length of an
HMAC is not needed, it is reasonable to truncate the HMAC output and
use the truncated value for authentication. HMAC SHA-1 truncated to
96 bits is an optional available in several IETF protocols including
96 bits is an option available in several IETF protocols including
IPSEC and TLS.
The TSIG RR [RFC 2845] includes a "MAC size" field, which gives the
size of the MAC field in octets. But [RFC 2845] does not specify what
to do if this MAC size differs from the length of the output of HMAC
for a particular hash function.
for a particular hash function. Truncation is indicated by a MAC size
less than the HMAC size as specified below.
3.1 Truncation Specification
The specification for TSIG handling is changed as follows:
1. If The "MAC size" field is larger than the HMAC output length or
is zero: This case MUST NOT be generated and if received MUST
cause the packet to be dropped and RCODE 1 (FORMERR) to be
returned.
2. If the "MAC size" field equals the HMAC output length: Operation
is as described in [RFC 2845].
3. If the "MAC size" field is less than the HMAC output length but is
not zero: This is sent when the signer has truncated the HMAC
output as described in RFC 2104, taking initial octets and
discarding trailing octets. TSIG truncation can only be to an
integral number of octets. On receipt of a packet with truncation
thus indicated, the locally calculated MAC is similarly truncated
and only the truncated values compared for authentication.
TSIG implementations SHOULD implement SHA-1 truncated to 96 bits (12
octets) and MAY implement any or all other truncations valid under
case 3 above.
1. If "MAC size" field is greater than HMAC output length:
This case MUST NOT be generated and if received MUST cause the
packet to be dropped and RCODE 1 (FORMERR) to be returned.
2. If "MAC size" field equals HMAC output length:
Operation is as described in [RFC 2845] with the entire output
HMAC output present.
3. "MAC size" field is less than HMAC output length but greater than
that specified in case 4 below:
This is sent when the signer has truncated the HMAC output to
an allowable length, as described in RFC 2104, taking initial
octets and discarding trailing octets. TSIG truncation can only be
to an integral number of octets. On receipt of a packet with
truncation thus indicated, the locally calculated MAC is similarly
truncated and only the truncated values compared for
authentication. The request MAC used when calculating the TSIG MAC
for a reply is the trucated request MAC.
4. "MAC size" field is less than the larger of 10 (octets) and half
the length of the hash function in use:
With the exception of certain TSIG error messages described in
RFC 2845 section 3.2 where it is permitted that the MAC size be
zero, this case MUST NOT be generated and if received MUST cause
the packet to be dropped and RCODE 1 (FORMERR) to be returned. The
size limit for this case can also, for the hash functions
mentioned in this document, be stated as less than half the hash
function length for hash functions other than MD5 and less than 10
octets for MD5.
@ -292,31 +293,150 @@ D. Eastlake 3rd [Page 5]
INTERNET-DRAFT HMAC-SHA TSIG Identifiers
4. IANA Considerations
SHA-1 truncated to 96 bits (12 octets) SHOULD be implemented.
D. Eastlake 3rd [Page 6]
INTERNET-DRAFT HMAC-SHA TSIG Identifiers
4. TSIG Policy Provisions and Truncation Error
Use of TSIG is by mutual agreement between a resolver and server.
Implicit in such "agreement" are policies as to acceptable keys and
algorithms and, with the extensions in this doucment, truncations. In
particular note the following:
Such policies MAY require the rejection of TSIGs even though they
use an algorithm for which implementation is mandatory.
When a policy calls for the acceptance of a TSIG with a particular
algorithm and a particular non-zero amount of trunction it SHOULD
also permit the use of that algorithm with lesser truncation (a
longer MAC) up to the full HMAC output.
Regardless of a lower acceptable truncated MAC length specified by
policy, a reply SHOULD be sent with a MAC at least as long as that in
the corresponding request unless the request specified a MAC length
longer than the HMAC output.
Implementations permitting policies with multiple acceptable
algorithms and/or truncations SHOULD permit this list to be ordered
by presumed strength and SHOULD allow different truncations for the
same algorithm to be treatred as spearate entities in this list. When
so implemented, policies SHOULD accept a presumed stronger algorithm
and truncation than the minimum strength required by the policy.
If a TSIG is received with truncation which is permitted under
Section 3 above but the MAC is too short for the policy in force, an
RCODE of TBA [22 suggested](BADTRUNC) MUST be returned.
D. Eastlake 3rd [Page 7]
INTERNET-DRAFT HMAC-SHA TSIG Identifiers
5. IANA Considerations
This document, on approval for publication as a standards track RFC,
registers the new TSIG algorithm identifiers listed in Section 2 with
IANA.
(1) registers the new TSIG algorithm identifiers listed in Section 2
with IANA and (2) Section 4 allocates the BADTRUNC RCODE TBA [22
suggested].
5. Security Considerations
6. Security Considerations
For all of the message authentication code algorithms listed herein,
those producing longer values are believed to be stronger; however,
while there are some arguments that mild truncation can strengthen a
MAC by reducing the information available to an attacker, excessive
truncation clearly weakens authentication by reducing the number of
bits an attacker has to try to force. See [RFC 2104] which recommends
that an HMAC never be truncated to less than half its length nor to
less than 80 bits (10 octets).
while there have been some arguments that mild truncation can
strengthen a MAC by reducing the information available to an
attacker, excessive truncation clearly weakens authentication by
reducing the number of bits an attacker has to try to brute force
[RFC 2104].
Significant progress has been made recently in cryptanalysis of hash
function of the type used herein. While the results so far should not
effect HMAC, the stronger SHA-1 and SHA-256 algorithms are being made
mandatory due to caution.
function of the type used herein, all of which ultimately derive from
the design of MD4. While the results so far should not effect HMAC,
the stronger SHA-1 and SHA-256 algorithms are being made mandatory
due to caution.
See also the Security Considerations section of [RFC 2845].
See also the Security Considerations section of [RFC 2845] from which
the limits on truncation in this RFC were taken.
@ -341,10 +461,7 @@ INTERNET-DRAFT HMAC-SHA TSIG Identifiers
D. Eastlake 3rd [Page 6]
D. Eastlake 3rd [Page 8]
INTERNET-DRAFT HMAC-SHA TSIG Identifiers
@ -362,8 +479,8 @@ INTERNET-DRAFT HMAC-SHA TSIG Identifiers
[RFC 2104] - Krawczyk, H., Bellare, M., and R. Canetti, "HMAC: Keyed-
Hashing for Message Authentication", RFC 2104, February 1997.
[RFC 2434] - Narten, T. and H. Alvestrand, "Guidelines for Writing an
IANA Considerations Section in RFCs", BCP 26, RFC 2434, October 1998.
[RFC 2119] - Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC 2845] - Vixie, P., Gudmundsson, O., Eastlake 3rd, D., and B.
Wellington, "Secret Key Transaction Authentication for DNS (TSIG)",
@ -402,7 +519,7 @@ INTERNET-DRAFT HMAC-SHA TSIG Identifiers
D. Eastlake 3rd [Page 7]
D. Eastlake 3rd [Page 9]
INTERNET-DRAFT HMAC-SHA TSIG Identifiers
@ -416,16 +533,16 @@ Author's Address
Milford, MA 01757 USA
Telephone: +1-508-786-7554 (w)
+1-508-634-2066 (h)
EMail: Donald.Eastlake@motorola.com
Expiration and File Name
This draft expires in August 2005.
This draft expires in October 2005.
Its file name is draft-ietf-dnsext-tsig-sha-01.txt
Its file name is draft-ietf-dnsext-tsig-sha-03.txt
@ -460,6 +577,6 @@ Expiration and File Name
D. Eastlake 3rd [Page 8]
D. Eastlake 3rd [Page 10]