[sql-51] session: handle removed linked account

[ViktorTigerstrom]

This PR fixes a edge case in the sessions migration, which was found during the creation of the actions migration.

If a user creates a session linked to an account, but later deletes that account using the litcli accounts remove command, the KVDB session will still contain the account ID of the removed account.

During the KVDB to SQL migration, the accounts migration runs before the sessions migration. Since the deleted account no longer exists, it cannot be migrated. As a result, the migrated SQL session cannot link to the now non-existent account in the SQL store.

In such cases, we will migrate the session and not link to any account in the SQL session.

[gemini-code-assist]

Summary of Changes

Hello @ViktorTigerstrom, I'm Gemini Code Assist¹! I'm currently reviewing this pull request and will post my feedback shortly. In the meantime, here's a summary to help you and other reviewers quickly get up to speed!

This pull request addresses an edge case in the KVDB to SQL session migration process. It ensures that sessions which were originally linked to an account, but where that account was subsequently deleted (e.g., via litcli accounts remove), are still successfully migrated. The changes allow such sessions to be migrated to the SQL store without an associated account, preventing migration failures and maintaining data integrity for these specific scenarios. This improves the robustness of the session migration, particularly when the accounts migration runs before the sessions migration.

Highlights

• Improved Session Migration Robustness: The migration process now gracefully handles sessions linked to accounts that have been subsequently deleted, ensuring these sessions are still migrated to SQL without an associated account.
• Error Handling for Missing Accounts: Modified the migrateSingleSessionToSQL function to treat sql.ErrNoRows for account lookups as a non-fatal error, allowing sessions to migrate without an account link if the linked account is not found.
• New overrideRemovedAccount Function: Introduced a helper function to reconcile differences between KVDB and SQL sessions during validation, specifically for cases where an account was removed.
• Enhanced Test Coverage: Added a new test case to TestSessionsStoreMigration to explicitly cover the scenario of migrating a session with a previously deleted linked account, and updated randomizedSessions to simulate account removal during testing.

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Code Review

This pull request correctly handles an edge case during the session migration where a session is linked to an account that has been removed. The changes ensure that the migration proceeds without error by creating the session without the account link, and includes appropriate logging. The test suite has been expanded to cover this scenario. I have a couple of minor suggestions to improve logging and test robustness.

[bitromortac]

In such cases, we will migrate the session and not link to any account in the SQL session.

Are there any safety concerns with removing the account id from the session? I think that any macaroon that carries an unknown account id will not be valid to make requests, rendering the session useless? If that's the case should we just not migrate the session?

[ViktorTigerstrom]

In such cases, we will migrate the session and not link to any account in the SQL session.

Are there any safety concerns with removing the account id from the session? I think that any macaroon that carries an unknown account id will not be valid to make requests, rendering the session useless? If that's the case should we just not migrate the session?

I don't think there should be any. I tested this locally with one kvdb session which has a removed account linked, and when sending requests over that session it errors with:
rpc error: code = Unknown desc = error getting account cd88c53a03a3e66d: account not found

Similarly, I tested running with an SQL session, which has null set for the account_id, but everything else for the account correctly set (i.e. type=account + the correct macaroon_recipe set). Once the account has been removed, requests sent over this session also errors with:
rpc error: code = Unknown desc = error getting account c595104329a7cfe3: account not found

I do see your point though, and can see the motivation for just not migrating the session as it's useless once the account has been removed. Potentially instead of dropping the session, we could also just revoke it during the migration. Would be great to get Elle's perspective on this whenever possible.