RFC 4871, "DomainKeys Identified Mail (DKIM) Signatures", May 2007

Note: This RFC has been obsoleted by RFC 6376

Note: This RFC has been updated by RFC 5672

Errata ID: 1487
Status: Verified
Type: Technical
Publication Format(s) : TEXT
Reported By: Murray S. Kucherawy
Date Reported: 2008-08-14
Verifier Name: Pasi Eronen
Date Verified: 2009-05-14

Section 3.6.1 says:

   v=  Version of the DKIM key record (plain-text; RECOMMENDED, default
       is "DKIM1").  If specified, this tag MUST be set to "DKIM1"
       (without the quotes).  This tag MUST be the first tag in the
       record.  Records beginning with a "v=" tag with any other value
       MUST be discarded.  Note that verifiers must do a string
       comparison on this value; for example, "DKIM1" is not the same as
       "DKIM1.0".

       ABNF:

       key-v-tag    = %x76 [FWS] "=" [FWS] "DKIM1"

It should say:

   v=  Version of the DKIM key record (plain-text; RECOMMENDED, default
       is "DKIM1").  If specified, this tag MUST be set to "DKIM1"
       (without the quotes).  This tag MUST be the first tag in the
       record.  Records beginning with a "v=" tag with any other value
       MUST be discarded.  Note that verifiers must do a string
       comparison on this value; for example, "DKIM1" is not the same as
       "DKIM1.0".

       ABNF:

       key-v-tag    = %x76 [FWS] "=" [FWS] %x44 %x4B %x49 %x4D %x31

Notes:

RFC5234 section 2.3 says string literals in ABNF are case-insensitive. However, RFC4871 section 3.2 says tag values are case-sensitive unless stated otherwise. This renders the defintion of "v=" in section 3.6.1 of this RFC ambiguous.

Therefore, one interpretation of "DKIM1" here allows "dkim1" and one does not.

Either the "case-sensitive" nature of tag values should be changed, or the ABNF needs to be revised to be more precise.

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