[ietf-dkim] Use of "sender" in -base

[Paul Hoffman]

At 8:43 AM -0700 6/8/06, Dave Crocker wrote:
>  > 3.4.5 Body Length Limits
>>
>...
>>
>>  INFORMATIVE IMPLEMENTATION NOTE: Body length limits could be useful in
>>  increasing signature robustness when sending to a mailing list that both
>>  appends to content sent to it and does not sign its messages. However, using
>>  such limits enables an attack in which a sender with malicious intent
>>  modifies a message to include content that solely benefits the attacker. It
>>  is possible for the appended content to completely replace the original
>>  content in the end recipient's eyes and to defeat duplicate 
>>message detection
>>  algorithms. To avoid this attack, signers should be wary of using this tag,
>>  and verifiers might wish to ignore the tag or remove text that appears after
>>  the specified content length, perhaps based on other criteria.
>
>
>(dhc) I think the use of "sender" here refers to the signer, but it 
>might refer
>to the originator.  I'm not sure.  Who is really the source of the threat?

It seems to be clearly that "sender" means "attacker" here. sender -> attacker

>  > 5.1 Determine if the Email Should be Signed and by Whom
>>
>...
>>
>  > A SUBMISSION server MAY sign if the sender is authenticated by some secure
>>  means, e.g., SMTP AUTH. Within a trusted enclave the signing address MAY be
>>  derived from the header field according to local signer policy. Within a
>>  trusted enclave an MTA MAY do the signing.
>>
>
>(dhc)  signer -> submitter

This one confuses me. Did you mean "if the sender is authenticated" 
-> "if the submitter is authenticated"?

+1 to the rest.