Recovering

[doctormo]

I have a backup which suffers from the Bad MAC issue. This tool can decrypt it and stores all the various bits of information.

I did have to fix one thing. __handle_statement was trying to create a table called sqlite_sequence so I special excepted it out. Apparently in my version of sqlite (Ubuntu 18.04) it's a special value.

What I need now is the ability to repack the information I have to reconstruct a clean backup. This looks like it should be possible to do, but I'd like to hear your expertise on if you think this is even possible.

[pshem]

I'm running into the same bug as @doctormo :

Traceback (most recent call last):
  File "/home/pshem/z/source/debruitage/debruitage/bin/signal-bkp-decrypt", line 11, in <module>
    load_entry_point('signal-backup-manager', 'console_scripts', 'signal-bkp-decrypt')()
  File "/home/pshem/z/source/debruitage/signal_backup_manager/cli.py", line 23, in run
    bkp = SignalBackup(args.backup_file, args.passphrase)
  File "/home/pshem/z/source/debruitage/signal_backup_manager/signal_backup.py", line 56, in __init__
    self.__handle_statement(frame.statement)
  File "/home/pshem/z/source/debruitage/signal_backup_manager/signal_backup.py", line 193, in __handle_statement
    self.db_cursor.execute(statement.statement, params)
sqlite3.OperationalError: object name reserved for internal use: sqlite_sequence

Would you mind saying how you fixed it, @doctormo? Trying to catch the exception with

        try:
            self.db_cursor.execute(statement.statement, params)
        except sqlite3.OperationalError:
            pass

Gave me an sqlite3.IntegrityError instead, so I'm assuming you've found a better way.

Traceback (most recent call last):
  File "/home/pshem/z/source/debruitage/debruitage/bin/signal-bkp-decrypt", line 11, in <module>
    load_entry_point('signal-backup-manager', 'console_scripts', 'signal-bkp-decrypt')()
  File "/home/pshem/z/source/debruitage/signal_backup_manager/cli.py", line 23, in run
    bkp = SignalBackup(args.backup_file, args.passphrase)
  File "/home/pshem/z/source/debruitage/signal_backup_manager/signal_backup.py", line 56, in __init__
    self.__handle_statement(frame.statement)
  File "/home/pshem/z/source/debruitage/signal_backup_manager/signal_backup.py", line 193, in __handle_statement
    self.db_cursor.execute(statement.statement, params)
sqlite3.IntegrityError: UNIQUE constraint failed: recipient.group_id

[doctormo]

diff --git a/signal_backup_manager/signal_backup.py b/signal_backup_manager/signal_backup.py
index 6c2aacd..b8b9c3f 100644
--- a/signal_backup_manager/signal_backup.py
+++ b/signal_backup_manager/signal_backup.py
@@ -190,6 +190,10 @@ class SignalBackup():
             if param.HasField('nullparameter'):
                 params += (param.nullparameter,)
 
+        if 'sqlite_sequence(name,seq)' in statement.statement:
+            print(f"REFUSING: {statement.statement}")
+            return
+        print(f"BEEP: {statement.statement} {params}")
         self.db_cursor.execute(statement.statement, params)
 
     def __handle_preference(self, preference):

[pshem]

Thanks, I applied your patch but the effects are the same as my try except, so the sqlite3.IntegrityError has got to be a separate issue.

[elkhadiy]

@doctormo

I have a backup which suffers from the Bad MAC issue. This tool can decrypt it and stores all the various bits of information.

I did have to fix one thing. __handle_statement was trying to create a table called sqlite_sequence so I special excepted it out. Apparently in my version of sqlite (Ubuntu 18.04) it's a special value.

Yup nice catch, seems like they forgot to drop some tables in the 'new' (been a while since I looked into signal) backup code signalapp/Signal-Android@128da6d

If you send a PR this way with your patch I can merge it if you want.

What I need now is the ability to repack the information I have to reconstruct a clean backup. This looks like it should be possible to do, but I'd like to hear your expertise on if you think this is even possible.

I am by no means an expert on the subject but yeah that was the idea I had when I wrote this tool. Wanted to make a bridging tool to export conversation history from messenger to signal. Last time I worked on it (a while back), I think I was able to create new threads and new messages (should be in the notebooks). And I'm pretty sure it's feasible to re-encrypt the backup with the same passphrase.
Unfortunately I really don't have spare time to work on this right now.

@pshem

Thanks, I applied your patch but the effects are the same as my try except, so the sqlite3.IntegrityError has got to be a separate issue.

Maybe try with if 'sqlite_' in statement.statement:?

[pshem]

@elkhadiy I tried that and it catches the same single statement as if 'sqlite_sequence(name,seq)' in statement.statement: does. Interestingly, even when erroring out, a valid database is produced, it just lacks the vast majority of data. I'm assuming that's because your tool works frame by frame.

I got the full database out with https://github.com/tbvdm/sigbak/tree/portable

[elkhadiy]

@pshem Good to hear! Unfortunately I can't have a crack at it right now but thanks for the input.

Some other good tools out there (from my history):

• https://github.com/pajowu/signal-backup-decode
• https://github.com/xeals/signal-back