[Akonadi] [Bug 505459] New: Possible email modification after download from IMAP may break DKIM

Benjamin Girault bugzilla_noreply at kde.org
Wed Jun 11 08:52:06 BST 2025


https://bugs.kde.org/show_bug.cgi?id=505459

            Bug ID: 505459
           Summary: Possible email modification after download from IMAP
                    may break DKIM
    Classification: Frameworks and Libraries
           Product: Akonadi
      Version First 6.4.1
       Reported In:
          Platform: Arch Linux
                OS: Linux
            Status: REPORTED
          Severity: normal
          Priority: NOR
         Component: IMAP resource
          Assignee: kdepim-bugs at kde.org
          Reporter: benjamin.girault at nebux.org
                CC: carl at carlschwan.eu
  Target Milestone: ---

SUMMARY

When syncing an IMAP account, it appears that emails are modified before being
stored. This observed issue is (at least) with CRLF being modified. With text
only emails, this alteration does not seem to prevent DKIM signature check from
passing. However, with a multi-part MIME body an extra space is introduced that
trigger a failed body hash check. More precisely, the emails I have have a
header that ends with two CRLF sequences (checked with okteta), and then the
string "This is a multi-part message in MIME format.". After syncing with
kmail, the stored email has two LF characters, a space, and then the string
above. Removing the space allows for a successful DKIM check.

All other CRLF sequences converted to LF do not seem to prevent DKIM checks
from passing, only the space is an issue.

I checked that this is likely not an issue with the IMAP server using
Thunderbird. The synced email were not altered there (CRLF kept, and no extra
space), and the synced emails pass DKIM checks.

STEPS TO REPRODUCE
1. Sync IMAP account
2. Check DKIM signature with a multipart MIME body

OBSERVED RESULT

Failed DKIM verification: body hash mismatch

EXPECTED RESULT

Passed DKIM verification

SOFTWARE/OS VERSIONS
Linux/KDE Plasma: ArchLinux
KDE Plasma Version: 6.3.5
KDE Frameworks Version: 25.04.1
Qt Version: 6.9.1

ADDITIONAL INFORMATION

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