SOLIDUI: Add backup functionality to the Avatar menu

[tonypioneer]

Description

Add a Backup option to the Avatar menu. Clicking this option should open a dialog similar to the existing TodoPod Backup feature, allowing users to back up and export all contents of the current app's data folder in the POD, as well as import data previously backed up from either the same POD or a different POD.

Requirements

1. Single backup file

   • Export all data as a single backup file.
   • A custom file format may be used.

2. Application identifier

   • Store the current application's full URL in the file header.
   • This will be used during import to verify that the backup was created from the same application, regardless of whether it originated from the same POD or another POD.

3. Security key verification

   • Store a verification fingerprint of the security key used during export in the file header.
   • The fingerprint must not allow reconstruction of the original security key, but must uniquely verify whether a user-provided security key matches the one used for encryption.

4. Compressed and encrypted backup

   • The backup data must remain encrypted.
   • The exported backup file must also be compressed.

5. Import validation

   • Before importing, verify whether the backup was created by the same application.

   • If the backup originates from a different application, reject the import.

   • If it originates from the same application, prompt the user to provide:

     • the original security key used when creating the backup, and
     • the current security key for the destination POD.

   • This is necessary because different applications may use different security keys, and users may have changed the original security key after the backup was created.

6. Import process

   • The import workflow should perform the following steps:

     1. Decompress the backup file.
     2. Decrypt the backup data using the original security key.
     3. Re-encrypt the data using the current (destination) security key.
     4. Upload the re-encrypted data to the destination POD, overwriting the existing contents of the app's data folder.

Closing Criteria

Checklist for closing the issue:

• No errors from make prep
• All tests pass make qtest
• Users can backup all the data on the POD.
• Users can import backup data to the POD.

[tonypioneer]

Implemented backup and restore for all files in the app data folder:

• Custom backup format: All files are exported into a single .solidbak file using gzip-compressed JSON with an embedded encrypted payload.

• Application identifier: The header stores the source application's full data folder URL, along with a POD-independent application ID (a normalized application name) for reliable cross-POD application matching.

• Security Key fingerprint: A one-way, domain-separated PBKDF2-HMAC-SHA256 derivation is used. The original Security Key cannot be reconstructed, but the fingerprint can uniquely verify that the provided key is correct.

• Compression + encryption: The payload is encrypted using AES-256-CBC, and the entire backup file is compressed with gzip.

• Import validation: Backups created by a different application are rejected. Otherwise, the user is prompted to enter both the original Security Key (used during export) and the current Security Key (for the target location).

• Import workflow: Decompress → decrypt using the original Security Key → re-encrypt via writePod using the destination's current Security Key → upload and replace/overwrite the contents of the data folder.

[tonypioneer]

The following is the files in my demopod app's data folder.

We can click on the avatar, and tap 'Backup' on the avatar menu.

A dialog will pop up and allow users to export backup file and import backup file.

Tap the "Export Backup" button, and then input the security key. The app will verify the security key and save the backup file into a specific folder.

Then, we can remove the files on the app's data folder, and import the backup file for testing.

Then, we change the security key.

Tap "Import Backup", and then input the security key when we created this backup, and the security key of current app.

If the key doesn't match, there'll be an error message.

Only when the old key and the new key are correct at the same time, the backup can be restored to the POD.

Refresh the file browser.

The files are restored.

We can also restore it to another POD (but the same app). I changed the POD, and restored it.

The files can also be restored to the POD. (Please note the webID on the bottom left. It's a different POD)

If it's a different app, there will be an error.

I changed the app name to demopod2, and did another round of test.