add support new backup format

[khimaros]

with the update to android 12, seedvault has also bumped the metadata version.

it would be great to be able to use this tool with newer backups.

[khimaros]

@chirayudesai says:

There's a doc in the storage section which this format shares some things with
otherwise it should all be seedvault-app/seedvault#327

@grote says:

mostly this with a different key id: https://github.com/seedvault-app/seedvault/blob/android12/storage/doc/design.md
I think there's a python version of tink to make your life easier.
The k/v backup is a zipped DB now, I think there's no docs on this.

here's the tink library: https://pypi.org/project/tink/

[khimaros]

seedvault-app/seedvault#383 will be helpful for testing this change

[khimaros]

i have access to a reference backup now and am working on a python-tink based decryption tool.

traveling for the next few weeks, so not a ton of time to allocate, but making slow steady progress.

[ladar]

@khimaros please add me t o list of people waiting for an updated tool. I accidently erased several people from my contacts. I'm hoping I can extract just those contacts from backup once it is decrypted.

The only other alternative I cxan think of would involve backing up my device, restoring the seed vault I've preserved, extracting the missing contact records, and followed by a restoration of the backup I made at the beginning. But this doesn't seem like a great option given a) the time involved, and b) the likelihood that something will go wrong.

[Adri-Fa]

Did you ever managed to do this? If not, have you anything to help me?

[nettnikl]

working on a python-tink based decryption tool

Hey @khimaros, could it be an option to share your current progress? I think there are many people interested in this, maybe we could help with testing.

[jackwilsdon]

I've just finished writing a tool to extract v1 backups - it's available here: https://github.com/jackwilsdon/seedvault-extractor

Feel free to open an issue or start a discussion if you need any help!

[khimaros]

@jackwilsdon this is excellent! thank you for your efforts! i'll test this out.

what are the main challenges for supporting KV extraction?

[jackwilsdon]

I think implementing KV support should be pretty straightforward - it appears that it might just be an encrypted gzip'd SQLite database looking at KVRestore.kt. I'll see if I can find some time over the next few days to add it.

[jackwilsdon]

It ended up being simple enough to dump the SQLite database to disk, so I've gone ahead and implemented it in jackwilsdon/seedvault-extractor@e2875f7. Ideally it'd be exported in a more user-friendly format (JSON?), but this is at least a start.

[khimaros]

@jackwilsdon dumping the sqlite database seems adequate to me! it's easy enough to use other tools to export sqlite into a csv, json, or other format.

i tested that changelist against a reference backup provided by the seedvault team and it seemed to work! at least, i was able to select some rows from kv_entry and some of them were human readable.

the reference backup i'm referring to was originally uploaded to a git repo with restricted access. @chirayudesai -- is it okay if i upload a tarball and link it here? i think it would be generally useful to others.

[chirayudesai]

Thanks @jackwilsdon , glad to see this!

the reference backup i'm referring to was originally uploaded to a git repo with restricted access. @chirayudesai -- is it okay if i upload a tarball and link it here? i think it would be generally useful to others.

I'd prefer it not be, it likely doesn't have any PII but I'd rather be safe than sorry.

What we can do is just create a backup from an emulator and that should be ok to share.

The git repo idea also didn't work because I tried to put some data on it and that quickly exceeded GitHub LFS limits, but maybe we can use releases.