ietf-dkim
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Re: [ietf-dkim] Base-02 signature process clarification requested

2006-06-07 07:33:23
On Wed, 2006-06-07 at 09:01 -0400, Tony Hansen wrote:
You have to differentiate between a DKIM-Signature header that's being
created and/or verified, and a DKIM-Signature that was there previously
and has now been included in the list of headers that are part of the
message being signed and/or verified.

The b= nullification applies only to the DKIM-Signature being created
and/or verified. It does not apply to any other DKIM-Signature headers
that may be included as part of the message header.

When I read -base, this seemed clear enough to me.

It would seem this is also not very clear either:

,---
| 3.7  Computing the Message Hashes
|
| 2.  The "DKIM-Signature" header field that exists (verifying) or will
|    be inserted (signing) in the message, with the value of the "b="
|    tag deleted (i.e., treated as the empty string), canonicalized
|    using the header canonicalization algorithm specified in the "c="
|    tag, and without a trailing CRLF.
|
| All tags and their values in the DKIM-Signature header field are
| included in the cryptographic hash with the sole exception of the
| value portion of the "b=" (signature) tag, which MUST be treated as
| the null string.  All tags MUST be included even if they might not be
| understood by the verifier.  The header field MUST be presented to
| the hash algorithm after the body of the message rather than with the
| rest of the header fields and MUST be canonicalized as specified in
| the "c=" (canonicalization) tag.  The DKIM-Signature header field
| MUST NOT be included in its own h= tag.
'---

Where is the text that describes the different treatment of a previously
existing DKIM-Signature header?

-Doug



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