[IPsec] [Editorial Errata Reported] RFC7427 (4296)

[Tero Kivinen <[e-mail]>]

RFC Errata System writes:
> The following errata report has been submitted for RFC7427,
> "Signature Authentication in the Internet Key Exchange Version 2 (IKEv2)".
> 
> --------------------------------------
> You may review the report below and at:
> http://www.rfc-editor.org/errata_search.php?rfc=7427&eid=4296
> 
> --------------------------------------
> Type: Editorial
> Reported by: Annie Yousar <[e-mail]>
> 
> Section: A.4.3
> 
> Original Text
> -------------
>    Here the parameters are present and contain hashAlgorithm of SHA-256,
> |  maskGenAlgorithm of SHA-256, saltLength of 32, and trailerField of 1.
> 
>    0000 : SEQUENCE
>    0002 :   OBJECT IDENTIFIER  RSASSA-PSS (1.2.840.113549.1.1.10)
>    000d :   SEQUENCE
>    000f :     CONTEXT 0
>    0011 :       SEQUENCE
>    0013 :         OBJECT IDENTIFIER  id-sha256 (2.16.840.1.101.3.4.2.1)
>    001e :         NULL
>    0020 :     CONTEXT 1
>    0022 :       SEQUENCE
> |  0024 :         OBJECT IDENTIFIER  1.2.840.113549.1.1.8
>    002f :         SEQUENCE
>    0031 :           OBJECT IDENTIFIER id-sha256 (2.16.840.1.101.3.4.2.1)
>    003c :           NULL
>    003e :     CONTEXT 2
>    0040 :       INTEGER   0x20 (6 bits)
> |  0043 :     CONTEXT 3
> |  0045 :       INTEGER   0x1 (1 bits)
> 
>    Name = RSASSA-PSS with sha-256, oid = 1.2.840.113549.1.1.10
> |  Length = 72
>    0000: 3046 0609 2a86 4886 f70d 0101 0a30 39a0
>    0010: 0f30 0d06 0960 8648 0165 0304 0201 0500
>    0020: a11c 301a 0609 2a86 4886 f70d 0101 0830
>    0030: 0d06 0960 8648 0165 0304 0201 0500 a203
> |  0040: 0201 20a3 0302 0101
> 
> 
> Corrected Text
> --------------
>    Here the parameters are present and contain hashAlgorithm of SHA-256,
> |  maskGenAlgorithm of MGF1 with SHA-256, saltLength of 32, and 
> |  trailerField of 1.
> |  Note that since the trailerField has the default value it MUST NOT be
> |  encoded according to the Distiguished Encoding Rules (DER) of ASN.1.
> 
>    0000 : SEQUENCE
>    0002 :   OBJECT IDENTIFIER  RSASSA-PSS (1.2.840.113549.1.1.10)
>    000d :   SEQUENCE
>    000f :     CONTEXT 0
>    0011 :       SEQUENCE
>    0013 :         OBJECT IDENTIFIER  id-sha256 (2.16.840.1.101.3.4.2.1)
>    001e :         NULL
>    0020 :     CONTEXT 1
>    0022 :       SEQUENCE
> |  0024 :         OBJECT IDENTIFIER  id-mgf1 (1.2.840.113549.1.1.8)
>    002f :         SEQUENCE
>    0031 :           OBJECT IDENTIFIER id-sha256 (2.16.840.1.101.3.4.2.1)
>    003c :           NULL
>    003e :     CONTEXT 2
>    0040 :       INTEGER   0x20 (6 bits)
> 
>    Name = RSASSA-PSS with sha-256, oid = 1.2.840.113549.1.1.10
> |  Length = 67
>    0000: 3046 0609 2a86 4886 f70d 0101 0a30 39a0
>    0010: 0f30 0d06 0960 8648 0165 0304 0201 0500
>    0020: a11c 301a 0609 2a86 4886 f70d 0101 0830
>    0030: 0d06 0960 8648 0165 0304 0201 0500 a203
> |  0040: 0201 20
> 
> 
> Notes
> -----
> 1. The maskGenAlgorithm is in fact not SHA-256
> (2.16.840.1.101.3.4.2.1), but MGF1 (1.2.840.113549.1.1.8) based on
> SHA-256 (2.16.840.1.101.3.4.2.1). 

The id-mgf1 oid is there in the example, the tool I used didn't know
the name for it thus it just printed out the oid. As this does not
affect the binary object at all there is no problem in here.

> 2. Section 3 requires the use of DER:
> The ASN.1 used here is the same ASN.1 used in the
> AlgorithmIdentifier of PKIX (see Section 4.1.1.2 of [RFC5280]),
> encoded using distinguished encoding rules (DER) [CCITT.X690.2002]. 

Yes, but RFC4055 says that:

      trailerField

         The trailerField field is an integer.  It provides
	 compatibility with IEEE Std 1363a-2004 [P1363A].  The value
	 MUST be 1, which represents the trailer field with hexadecimal
	 value 0xBC.  Other trailer fields, including the trailer field
	 composed of HashID concatenated with 0xCC that is specified in
	 IEEE Std 1363a, are not supported.  Implementations that
	 perform signature generation MUST omit the trailerField field,
	 indicating that the default trailer field value was used.
	 Implementations that perform signature validation MUST
	 recognize both a present trailerField field with value 1 and an
	 absent trailerField field.

I.e. you should recognize both formats. Yes, we could have another
example also showing the object value to used when generating these
and when omitting the default values (like we do have for SHA-1).

> Instructions:
> -------------
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> 
> --------------------------------------
> RFC7427 (draft-kivinen-ipsecme-signature-auth-07)
> --------------------------------------
> Title               : Signature Authentication in the Internet Key Exchange Version 2 (IKEv2)
> Publication Date    : January 2015
> Author(s)           : T. Kivinen, J. Snyder
> Category            : PROPOSED STANDARD
> Source              : IP Security Maintenance and Extensions
> Area                : Security
> Stream              : IETF
> Verifying Party     : IESG
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