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: 1384
Status: Verified
Type: Technical
Publication Format(s) : TEXT
Reported By: Tony Hansen
Date Reported: 2008-03-22
Verifier Name: Pasi Eronen
Date Verified: 2009-05-14

Section 4.3.4 says:

   The "relaxed" body canonicalization algorithm:

   o  Ignores all whitespace at the end of lines.  Implementations MUST
      NOT remove the CRLF at the end of the line.

   o  Reduces all sequences of WSP within a line to a single SP
      character.

   o  Ignores all empty lines at the end of the message body.  "Empty
      line" is defined in Section 3.4.3.

It should say:

   The "relaxed" body canonicalization algorithm MUST apply the
   following steps (a) and (b) in order:

   a) Reduce whitespace:
      *  Ignore all whitespace at the end of lines.  Implementations MUST
         NOT remove the CRLF at the end of the line.

      *  Reduce all sequences of WSP within a line to a single SP
         character.

   b)  Ignore all empty lines at the end of the message body.  "Empty
      line" is defined in Section 3.4.3.

Notes:

This was discussed on the dkim interop mailing list.

You can wind up with different results depending on whether steps 1 and 3 are executed in that order or swapped around. Half of the implementations were found to do it one way and another half the other way.

It was decided that the same text applied to section 4.3.2

The "relaxed" header canonicalization algorithm MUST apply the
following steps in order:

should be used in 4.3.4 as well, that is

The "relaxed" body canonicalization algorithm MUST apply the
following steps in order:

But since steps 1&2 can still be done in either order, make those sub-bullets of step 1.

Just to be totally clear, following this decision we would wind up with this sequence.

Given this input:

testing<cr><lf>
<sp><sp><cr><lf>
<cr><lf>

a) Reduce whitespace:
* Ignore all whitespace at the end of lines. Implementations MUST
NOT remove the CRLF at the end of the line.

testing<cr><lf>
<cr><lf>
<cr><lf>

* Reduce all sequences of WSP within a line to a single SP
character.

testing<cr><lf>
<cr><lf>
<cr><lf>

b) Ignore all empty lines at the end of the message body. "Empty
line" is defined in Section 3.4.3.

testing<cr><lf>

If the two steps in (a) are performed in the opposite order,

testing<cr><lf>
<sp><sp><cr><lf>
<cr><lf>

a) Reduce whitespace:
* Reduce all sequences of WSP within a line to a single SP
character.

testing<cr><lf>
<sp><cr><lf>
<cr><lf>

* Ignore all whitespace at the end of lines. Implementations MUST
NOT remove the CRLF at the end of the line.

testing<cr><lf>
<cr><lf>
<cr><lf>

b) Ignore all empty lines at the end of the message body. "Empty
line" is defined in Section 3.4.3.

testing<cr><lf>

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