Outlook + Kleopatra can't parse email sent by Gmail + FlowCrypt

[chrissv]

I am using the FlowCrypt Chrome extension version 8.5.10 with Gmail.

I can successfully send encrypted messages from FlowCrypt+Gmail to users using ProtonMail (web app) and Thunderbird (client app).
I can successfully receive and decrypt email sent from the ProtonMail and Thunderbird, in addition to Outlook APP + Kleopatra to my FlowCrypt+Gmail.

But when I send an encrypted email from FlowCrypt+Gmail to an Outlook APP + Kleopatra user, it doesn't decode properly in Outlook+Kleopatra.
Encrypted emails sent from Thunderbird to Outlook APP + Kleopatra are decoded properly.

Examining some of the raw emails it seems one key difference is that both ProtonMail and Thunderbird send emails with an encrypted attachment "encrypted.asc" which is the encrypted message body.
But FlowCrypt+Gmail sends the encrypted message body in the email message body itself.

With the failing Outlook APP + Kleopatra situation, the message body has in it:

-----BEGIN PGP MESSAGE-----
Version: FlowCrypt Email Encryption 8.5.10
Comment: Seamlessly send and receive encrypted email

wcDMA31VWNlb2bOuAQwAtHTo2+Bc+CmQLxY4oDsBiVuk1VBzDnp115l3zE0c
JVeNh5EKoOk5XDKFKzOHDOjQxb8fx5AqYZa0AG5amrZ4lNHDeMTO4zRmZ5Fb
mAahmZvto6uTJ6Vi9WmvxlLV3lUJfOEGH8nETnyIswsLC7MchTG1vWZtutF0

... blah

Is there a way to have FlowCrypt+Gmail send the encrypted message body as an attachment?

[martgil]

Hi @chrissv,

Thank you for raising this issue.

FlowCrypt does not offer any functionality that sends encrypted message as an attachment such as "encrypted.asc" but indeed does decrypt such emails it receives based on how other PGP-compatible email client does.

So for you to send similar message using (somehow) FlowCrypt is through following the workaround below:

1. Compose a draft secure email with FlowCrypt.
2. Once your done creating a draft secure message with FlowCrypt and is ready to send it off, close the FlowCrypt Secure Compose so that it will generate the encrypted message as a draft.
3. On Gmail, access your drafts and you'll see the FlowCrypt encrypted message, do not open the email but instead, right click on it and choose "Open in new window" and you should see something like this:

4. Copy the encrypted message and save in a file with name "encrypted.asc". You should double check that it should not be named as "encrypted.asc.txt" otherwise it may not be recognized as PGP encrypted message by the expected email client to open that email.
5. Using Gmail's regular email composer, attach the "encrypted.asc" file and the recipient address as well as the title while leaving the email body blank and send it to the intended reciever and they should be able to open it as long as you're encrypting it earlier with their correct public keys.

[chrissv]

Hi, that is a good suggestion / idea.
Unfortunately Gmail gets in the way of that.

Looking at the raw message from a Thunderbird encrypted email, the encrypted.asc attachment looks like this:

--------------sOPI90uM7oW1D0wvfOUBTtJR
Content-Type: application/octet-stream; name="encrypted.asc"
Content-Description: OpenPGP encrypted message
Content-Disposition: inline; filename="encrypted.asc"

-----BEGIN PGP MESSAGE-----

wcDMA893w9R/ScsgAQwAyEmZ0OEwR32IdghY807luiTdmgQggoiNp3yUyx4H/bJPNuG7myFRKM6G
Gv88haybXqAbFPP7qX5zL4qimNp0a5RPBszogzjZcJpvwiFw4DrhmcVFKPXtiGGszCjg2K9R/Xt6
DkECSjsf9xnqqlIz1cmWDz70Cif+EWgUsGabgNaDrg3BB2/vqwcQxSNibOHPtDKFn7PiziyycAtt
UCrYfCPuVOL5+ih4JzxcpW24jO9FQSbqiX2t94QolT9WDT/aj1SckzLoklyICqwaJr15nX+yvaIX
9CQ8IMUniCB5f+lYR4KUao7jzjJvufY0AYBSps0+/JwTTka636O3m0xX22sdxlkqLokAtYkGOElT

But when I follow your suggestion, this is what it looks like:

--000000000000f6fd610631d7ba43--
--000000000000f6fd620631d7ba45
Content-Type: application/octet-stream; name="encrypted.asc"
Content-Disposition: attachment; filename="encrypted.asc"
Content-Transfer-Encoding: base64
Content-ID: <f_m90tnm010>
X-Attachment-Id: f_m90tnm010

LS0tLS1CRUdJTiBQR1AgTUVTU0FHRS0tLS0tDQpWZXJzaW9uOiBGbG93Q3J5cHQgRW1haWwgRW5j
cnlwdGlvbiA4LjUuMTANCkNvbW1lbnQ6IFNlYW1sZXNzbHkgc2VuZCBhbmQgcmVjZWl2ZSBlbmNy
eXB0ZWQgZW1haWwNCg0Kd2NETUExdTZwVXptei9DSUFRdjhEUzJtMFNKS3ZsSHBtM1VMblZlSEJR
eGJjK3ZlMTRzU0xHUmNpc21NDQo0eUY3WEpqUU9rc1pvcmlkdm5uVFZFaTBkR2YzSHorRDBlRk81
U041Y241S252em5Kbm5iUENQWE0wQysNClFnejJMU1hRMmhmYXgxbzdzRDJ5alB3V3NaOGZhZVNh
R1pQSlBOeFZTYVlwNmtvRDU4VWlqeU1nM2QvOA0KRkh2em1yYzI5Z0RjNWN4Z05OOEU0eS8rUUdy

Apparently Gmail thinks it needs to base64 encode the attachment, which confuses the receiving software and it doesn't recognize that it is an encrypted message.

So it was a good idea, but didn't work.

[martgil]

Thanks, @chrissv, for the additional info. I apologize for not realizing the MIME message structure earlier. It indeed needs to be in the PGP MIME message format.

@sosnovsky Good day! Do you think it’s time to work on this addition, or is it a feature that we’ll need to wait for?

[sosnovsky]

It looks like an issue with PGP/Inline messages decryption in Kleopatra, I found another report describing the same case - https://www.reddit.com/r/GnuPG/comments/1juvibw/kleopatra_outlook_app_fails_to_decode_inline_gpg/

encrypted.asc attachment is used in PGP/MIME messages, while PGP/Inline messages store encrypted message directly in email body (https://proton.me/support/pgp-mime-pgp-inline). We currently support PGP/MIME messages only in Firefox version, as there are still some issues with sending such messages through Gmail (#5971)

[chrissv]

It looks like an issue with PGP/Inline messages decryption in Kleopatra, I found another report describing the same case - https://www.reddit.com/r/GnuPG/comments/1juvibw/kleopatra_outlook_app_fails_to_decode_inline_gpg/

FYI that other report is from me as well - I was hitting all avenues to try to get the problem noticed and addressed.