Re: [exim] dkim signature is including empty headers, seems…

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Auteur: Jeremy Harris
Datum:  
Aan: exim-users
Onderwerp: Re: [exim] dkim signature is including empty headers, seems like it shouldn't be
On 24/10/17 23:05, Ian Kelling wrote:
> How can I make exim only sign headers that are
> in the message I send?


Actually being sure to not oversign is pretty tricky, currently.
You have to examine the message headers and build a header-names
list for signing which does not include any not present.

A truly nasty oneliner:

${filter \
   {From:Sender:Reply-To:Subject:Date} \
   {inlist {$item} \
           {<\n ${map \
                   {<\n ${sg {$message_headers} {\N\n\t\N} {}}} \
                   {${listextract {1}{$item}}}}} \
   } \
 }


[ take the current message headers. Collapse any in-header
continuation lines, then extract the header name.
Check each proposed header name against that list, only
accepting those present.
]

... nasty because it evaluates the "map" again for each new
proposed header-name. For efficiency do it in two lines.
It also does not handle the possible cases of multiple headers.


Opened bug 2180 for better ways of specifying (over)signing.
--
Cheers,
Jeremy