Re: [ietf-dkim] Mailing lists and s/mime & dkim signatures - mua conside

On 25-08-10, Hector Santos <hsantos(_at_)isdg(_dot_)net> wrote:

Rolf E. Sonneveld wrote:

> Although DKIM does not specify (as far as I know) what to do with DKIM
> signatures in inner bodyparts, I think DKIM signatures should never be
> removed without a good reason.

If you believe this, then you have to advocate the removal of the RFC
4871 mandate regarding invalid signatures changing to no-signature
status as if it never existed and the message was never signed.

No, absolutely not! It seems you state here that a broken signature is worse than no signature. It isn't. They're to be treated equally.

 

What this means is that if a MLM keeps broken tracings of signatures,
the only existing trace signature is the valid one. 

No, this is not what it means. It's quite simple: ANY verifier can encounter ZERO, ONE or MORE DKIM signatures, some of them can be broken (by MLM's or by other mail agents), some of them can proof to verify correctly. The only conclusion a verifier can make for EACH VALID signature is, that the domain that's in the d= value of THAT signature takes (some) responsibility for that message (in the incarnation of the message of the moment, when that domain signed the message). All other (non-valid) signatures are to be ignored.

 

All others must
be ignored.

And ANY non-valid signature must be treated as if it were not present in the message at all. The fact that an MLM breaks a signature is not unique for MLMs. Any agent in the path between signer(s) and verifier(s) can break a signature. Let's keep it clear: a broken signature is to be ignored (base DKIM spec). But removing signatures without a good reason is wrong.

/rolf

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