On 2/1/2024 6:38 AM, Alessandro Vesely wrote:
On Wed 31/Jan/2024 18:34:46 +0100 Hector Santos wrote:
If I add this feature to wcDKIM, it can be introduced as:
[X] Enable DKIM Replay Protection
That'd be deceptive, as DKIM replay in Dave's sense won't be
blocked, while there can be other effects on signature robustness.
First, thanks to your and Murray's input.
I need to review Dave's "DKIM Replay" concerns. Legacy systems have
many entry points to create, import/export methods, transformation,
filling missing fields, etc. Overall, I considered the potential
"Replay" concern was about taking an existing signed message (from a
purported "trusted signer" ) but MUA display fields, namely, To: and
Subject: are missing or not signed. These can potentially be replayed
with tampered To:, Subject fields and exported. The multiple
5322.From headers MUA concern was highlighted many moons ago. Easily
Addressed with incoming SMTP filters rejecting multi-From messages.
A better sentence could be:
[X] Prevent further additions of this field
"This" meaning there is a header selection to monitor? See below
Note that some packages allow choices such as
[ ] Sign and oversign only if present in the message
[ ] Oversign only if already present in the h= list
[ ] Oversign anyway
Given how our package offer the signing defaults:
UseRequiredHeadersOnly = 1 # optional, 1 - use
RequireHeaders
RequiredHeaders =
From:To:Date:Message-Id:Organization:Subject:Received*:List-ID
SkipHeaders =
X-*:Authentication-Results:DKIM-Signature:DomainKey-Signature:Return-Path
StripHeaders = # optional, headers
stripped by resigners
Basically, as the message to be signed headers are read in, each are
checked again the RequiredHeaders (when enabled). If missing, the
header is not signed. The exception is From: which is always
signed. Signed headers are added to the "h=" fields.
So how about this, if I follow this, new namespace fields:
OversignHeader.To = # default blank
OversignHeader.Subject = # default blank
.
.
OversignHeader.Field-Name= # future oversign header
This allows an oversign header to be signed if missing. If correct,
easily to update the code.
Of course, the MUA is another issue. What read order should be
expected for Oversign headers? Each MUA can be different although I
would think streamed in data are naturally read sequentially and the
first display headers found are used in the UI. Only To: is allowed
to be a list.
--
Hector Santos,
https://santronics.com
https://winserver.com
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