[kmail2] [Bug 439904] New: Unable to decrypt PGP message sent via ProtonMail

[Richard Weinberger]

https://bugs.kde.org/show_bug.cgi?id=439904

            Bug ID: 439904
           Summary: Unable to decrypt PGP message sent via ProtonMail
           Product: kmail2
           Version: unspecified
          Platform: Other
                OS: Linux
            Status: REPORTED
          Severity: normal
          Priority: NOR
         Component: crypto
          Assignee: kdepim-bugs at kde.org
          Reporter: richard-bugs at nod.at
  Target Milestone: ---

ProtonMail seems to encode PGP messages differently than Kmail (actually
messagelib) expects.

The MIME section of such a message looks like:
--00bda24ff6a439c55df37bffe4bd232aad4d80072f16b06818700820c3d89297
Content-Transfer-Encoding: quoted-printable
Content-Type: text/plain; charset=utf-8


--00bda24ff6a439c55df37bffe4bd232aad4d80072f16b06818700820c3d89297
Content-Transfer-Encoding: base64
Content-Disposition: attachment; filename=attachment.bin
Content-Type: application/pgp-encrypted; name=attachment.bin
X-Pm-Content-Encryption: end-to-end

VmVyc2lvbjogMQ0K
--00bda24ff6a439c55df37bffe4bd232aad4d80072f16b06818700820c3d89297
Content-Transfer-Encoding: base64
Content-Disposition: attachment; filename=openpgp-encrypted-message.asc
Content-Type: application/octet-stream; name=openpgp-encrypted-message.asc
X-Pm-Content-Encryption: end-to-end

LS0tLS1CRUdJTiBQR1AgTUVTU0FHRS0tLS0tDQoNCmhRSU1BK3B1cm93N0hWSHhBUS8vUXhGdTBS
...
....MORE BASE64...
...
dDAwbA0KPTZOYmwNCi0tLS0tRU5EIFBHUCBNRVNTQUdFLS0tLS0NCg==
--00bda24ff6a439c55df37bffe4bd232aad4d80072f16b06818700820c3d89297--

messagelib (any version) does not expect the "PGP/MIME version identification"
message part being an attachment.

Interestingly messagelib emits the following warning:
org.kde.pim.mimetreeparser: Unknown PGP Version String: "-----BEGIN PGP
MESSAGE-----......"

Somehow the application/octet-stream part makes it into
ApplicationPGPEncryptedBodyPartFormatter::process().

My KDE distribution is not super fresh but from checking the code I'm sure that
no recent KDE/Kmail version is able to decrypt such an mail.

SOFTWARE/OS VERSIONS
Linux/KDE Plasma: openSUSE LEAP 15.2 
(available in About System)
KMail
Version 5.14.2 (20.04.2)

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