"Unable to decrypt message" eror when trying to read older E2EE messages (including my own) in new web sessions

[strypey]

Steps to reproduce

I'm opening a new issue as requested here; #28090 (comment)

Using chat.iridescent.nz, the community-hosted Element-web app for matrix.iridescent.nz, I created a new session, and verified it from my Android session. I'm able to access all my rooms, but in all the encrypted rooms (including DMs), all previous messages say "unable to decrypt" (including my own).

It's not out of the question that there's some user error involved. But I've been using Matrix for about 5 years and I've tried everything I can think of, done some web searching, and followed various advice on joinmatrix.org etc. Nothing has worked so far.

When the problem last happened I was using LibreWolf 130.0-3, on Fedora 40 Mate-Compiz. Today I upgraded to LibreWolf 130.0.1-1, from the Fedora repos. Not sure which version of Element-web I was using when I first noticed the problem, but it persists now in If there's any more info I can supply to help you track down the bug, please let me know.

Outcome

What did you expect?

To be able to view E2EE messages in rooms and Direct Chats even when they were sent before I created the new session.

What happened instead?

Every message, including my own, displays an "unable to decrypt" error message instead of the message contents.

Operating system

Fedora 40 Mate-Compiz

Browser information

LibreWolf 130.0-3

URL for webapp

https://chat.iridescent.nz

Application version

Element version: 1.11.74 Crypto version: Rust SDK 0.7.1 (c8c9d15), Vodozemac 0.6.0

Homeserver

https://matrix.iridescent.nz

Will you send logs?

Yes

[richvdh]

@strypey I don't see debug logs from your android device. Did you send them?

[strypey]

@richvdh

I don't see debug logs from your android device. Did you send them?

Yes. Would you like me to send them again? FYI I'm using the SchildiChat fork, not vanilla Element, in case that makes any difference.

[richvdh]

Oh, maybe. @SpiritCroc: do you use a separate rageshake repo for SchildiChat?

[richvdh]

Looking at your logs, there are lots of lines like this:

2024-09-28T11:13:46.449Z W Error decrypting event (id=$<redacted> type=m.room.encrypted sender=@strypey:matrix.iridescent.nz room=!<redacted> ts=2023-09-25T05:45:35.486Z): DecryptionError[msg: This message was sent before this device logged in. Key backup is working, but we still do not (yet) have the key., session: <redacted>]

and

2024-09-28T11:13:47.049Z I [PerSessionKeyBackupDownloader] No luck requesting key backup for session 1HtKuFD7gX2p78upX09Hb3h3bOWIpXFcR3UIH64NVps: M_NOT_FOUND: MatrixError: [404] No room_keys found (https://matrix.iridescent.nz/_matrix/client/v3/room_keys/keys/!<redacted>/<redacted>?version=2)

That tells us that the keys you are hoping to be in key backup, aren't. It sounds like you're expecting your SchildiChat instance to have backed up the keys; if it isn't, then that's a matter to take up with the maintainer of that client.

If you can get hold of logs for your SchildiChat instance, I can take a look at what might be going wrong but you'd need to approach the SchildiChat maintainers in the first instance.