Missing encryption keys in secret storage

[yostyle]

Steps to reproduce

1. Install Element 1.5.32 or older (any other version without crypto rust)
2. Send some events in rooms to have a significant history.
3. Upgrade to Element 1.6.8 (higher version could crash, it's another problem to report...)
4. Don't open the rooms
5. Reset secure backup
6. Create a new session on any Matrix client like Element X (or Element Web)
7. On the new session restore from backup
8. Open a room

Outcome

What did you expect?

All events should be decryptable.

What happened instead?

All events are undecryptable because message keys (Megolm sessions) are not backed up.

Only message keys migrated to the Rust crypto store are backed up to the server-side key backup. Message keys that are not present in the Rust crypto store are missing in the key backup.

Your phone model

Pixel 8 Pro

Operating system version

Android 14

Application version and app store

No response

Homeserver

matrix.org

Will you send logs?

No

Are you willing to provide a PR?

No

[giomfo]

This is possible to reproduce this issue on any Element-Android client which has been updated from Element (without crypto rust) to ElementR (with crypto rust).
After a reset of the Secure Backup on ER-Android, the keys stored locally in the Realm DB are uploaded in the key backup only when they are used to decrypt an event. These keys are missing in the backup by default

[yostyle]

On Element Web and Element iOS it seems the realm db is migrated totally. A similar behavior is needed on Android.

Element iOS :
https://github.com/matrix-org/matrix-ios-sdk/blob/develop/MatrixSDK/Crypto/Migration/MXCryptoMigrationV2.swift
https://github.com/matrix-org/matrix-ios-sdk/blob/develop/MatrixSDK/Crypto/MXCryptoV2.swift

Element Web :
https://github.com/matrix-org/matrix-js-sdk/blob/develop/src/rust-crypto/libolm_migration.ts

[yostyle]

@giomfo do you have a plan about this issue ?

It could impact some users on Element X, Element 1.6.8 and higher.

[giomfo]

@yostyle internal discussions are still in progress about this key migration issue

[toshanmugaraj]

Here is another issue in open related to the crash happening on migration in Android:

#8799

[toshanmugaraj]

@yostyle internal discussions are still in progress about this key migration issue

@giomfo we reached any conclusion on the issue.