Double-encrypted PGP emails with attachments gets garbled in Thunderbird

[ta4563321]

Prerequisites

• [X] I have searched open and closed issues to make sure that the bug has not yet been reported.

Bug report

Describe the bug Attachments are not properly handed in Thunderbird (shows as 0 bytes files) when the default mailbox in SimpleLogin is set up with a public PGP key to encrypt all incoming emails and an incoming email is already encrypted.

The problem seems to stem from multiple Content-Type-multipart-headers. Manually massaging the email source and removing the outer headers applied by SimpleLogin the attachments are correctly handled.

One simple solution might be to (optionally?) disable SimpleLogin general encryption on already encrypted emails.

Expected behavior The email attachments of the double-encrypted email shall be possible to open.

Screenshots Full headers of the decrypted email (with the multiple content-type headers)

Subject: Encrypted Email
From: XXX <xxx@simplelogin.co>
To: XXX <xxx@XXX>
Content-Type: multipart/signed; micalg=pgp-sha256;
 protocol="application/pgp-signature";
 boundary="------------9ZRghjLJOeEESFN0m5X0Zh6N"

Content-Type: multipart/mixed; boundary="------------uhaghxftayPop5EXFqS5gXc0";
 protected-headers="v1"
Subject: Encrypted Email
From: XXX <xxx@XXX>
To: XXX <xxx@XXX>
Message-ID: <xxx@XXX>
References: <xxx@XXX>
In-Reply-To: <xxx@XXX>

--------------uhaghxftayPop5EXFqS5gXc0
Content-Type: multipart/mixed; boundary="------------adCnlLlS0tVTSLGHizwMZbMS"

--------------adCnlLlS0tVTSLGHizwMZbMS
Content-Type: text/plain; charset=UTF-8; format=flowed
Content-Transfer-Encoding: base64 

Environment (If applicable):

• OS: Linux
• Mail reader: Mozilla Thunderbird
• Version 91.6.1

[c0nfigurati0n]

when saying:

One simple solution might be to (optionally?) disable SimpleLogin general encryption on already encrypted emails.

Are you asking them to add an option to disable pgp encryption or TLS encryption? Because if it's pgp encryption, then you could just turn it off under "more" selection of the alias you want to disable it for in the web app/dashboard.

[ta4563321]

@MrMuffinIsTaken

Are you asking them to add an option to disable pgp encryption or TLS encryption?

PGP

Because if it's pgp encryption, then you could just turn it off under "more" selection of the alias you want to disable it for in the web app/dashboard.

Yes, this would work if all received emails to the alias are already encrypted but any unencrypted emails would be left untouched as well. My suggestion was to leave any already encrypted emails intact (aside from changing the headers) while encrypting any unencrypted emails with the general PGP key, hence supporting the mix of both encrypted/unencrypted.

[c0nfigurati0n]

@ta4563321

Are you asking them to add an option to disable pgp encryption or TLS encryption?

PGP

Because if it's pgp encryption, then you could just turn it off under "more" selection of the alias you want to disable it for in the web app/dashboard.

Yes, this would work if all received emails to the alias are already encrypted but any unencrypted emails would be left untouched as well. My suggestion was to leave any already encrypted emails intact (aside from changing the headers) while encrypting any unencrypted emails with the general PGP key, hence supporting the mix of both encrypted/unencrypted.

So if i understand correctly, you want to me sure that any already pgp encrypted emails sent to an alias isn't touched and encrypted again with the same pgp key? While having non pgp encrypted emails sent to the alias be encrypted with the pgp key.

[ta4563321]

@MrMuffinIsTaken

So if i understand correctly, you want to me sure that any already pgp encrypted emails sent to an alias isn't touched and encrypted again with the same pgp key? While having non pgp encrypted emails sent to the alias be encrypted with the pgp key.

Correct. But preferably regardless if the original email is encrypted with the configured key or another (to simple login unknown) key, just leave already encrypted email bodies as they are.