[kmail2] [Bug 323168] New: GPG signature validation fails due to KMail modifying headers within received mails

[Xavier Guerrin]

https://bugs.kde.org/show_bug.cgi?id=323168

            Bug ID: 323168
           Summary: GPG signature validation fails due to KMail modifying
                    headers within received mails
    Classification: Unclassified
           Product: kmail2
           Version: 4.10.5
          Platform: Debian unstable
                OS: Linux
            Status: UNCONFIRMED
          Severity: normal
          Priority: NOR
         Component: crypto
          Assignee: kdepim-bugs at kde.org
          Reporter: xavier at kindwolf.org

Hello,

It appears KMail rewrites some headers within received mails before storing and
displaying them.
Indeed, a two-parts multipart mail (the first part being the effective message,
the second part being the related GPG signature) sent using another MUA (e.g.
Mutt) and having the following header in the first part:
Content-Type: text/plain; charset=us-ascii
... gets rewritten at some point to:
Content-Type: text/plain; charset="us-ascii"
... i.e. KMail would add double-quotes to the charset value, probably in an
attempt to "normalize" headers.
Alas, this has the immediate side-effect of breaking the GPG signature; KMail
then displays the mail content within a red frame titled "Invalid signature"
while the original message and signature were perfectly matching.

Reproducible: Always

Steps to Reproduce:
1. Get sent a signed mail with a quote-less Content-Type header in the signed
part
2. Receive that mail with KMail (tested with the POPS protocol)
Actual Results:  
* Double quotes were added to the Content-Type header in the signed part
* The signature is considered invalid

Expected Results:  
* The mail should be left as untouched as possible
* The signature should be considered valid

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