解码伯克利数据库字符串

Question

Having trouble decoding data from berkeley db. I've dumped data with db4.8_dump or db4.8_dump -p and decoding using python.decode()

So, here's what the data looks like after db4.8_dump in hex coding

036b65794104053ca761cf8062cfff09a2ec355a2694da4eed0677b510cf0c43a0d8486694e9966f2133302c5aa51664e9003b04cfa3847ce20de92040844b9b05aa15b5ab58

and same data with -p switch db4.8_dump -p :

\03keyA\04\05<\a7a\cf\80b\cf\ff\09\a2\ec5Z&\94\daN\ed\06w\b5\10\cf\0cC\a0\d8Hf\94\e9\96o!30,Z\a5\16d\e9\00;\04\cf\a3\84|\e2\0d\e9 @\84K\9b\05\aa\15\b5\abX

I can decode it like his, but still unreadable :

mbstr = b'036b65794104053ca761cf8062cfff09a2ec355a2694da4eed0677b510cf0c43a0d8486694e9966f2133302c5aa51664e9003b04cfa3847ce20de92040844b9b05aa15b5ab58'

mbstr.decode('hex')
'\x03keyA\x04\x05<\xa7a\xcf\x80b\xcf\xff\t\xa2\xec5Z&\x94\xdaN\xed\x06w\xb5\x10\xcf\x0cC\xa0\xd8Hf\x94\xe9\x96o!30,Z\xa5\x16d\xe9\x00;\x04\xcf\xa3\x84|\xe2\r\xe9 @\x84K\x9b\x05\xaa\x15\xb5\xabX'

Per documentation https://docs.oracle.com/cd/E17275_01/html/programmer_reference/dumpload_format.html

If the backslash character precedes any other character, the next two characters must be interpreted as hexadecimal specification of a single character; for example, \\0a is a newline character in the ASCII character set. but this doesn't work for me. ie

>>> mbstr.decode('hex')
'\x03keyA\x04\x05<\xa7a\xcf\x80b\xcf\xff\t\xa2\xec5Z&\x94\xdaN\xed\x06w\xb5\x10\xcf\x0cC\xa0\xd8Hf\x94\xe9\x96o!30,Z\xa5\x16d\xe9\x00;\x04\xcf\xa3\x84|\xe2\r\xe9 @\x84K\x9b\x05\xaa\x15\xb5\xabX'
>>> mbstr.decode('hex').decode('ascii')
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
UnicodeDecodeError: 'ascii' codec can't decode byte 0xa7 in position 8: ordinal not in range(128)

How can I convert data into readable string format? Thank you

Answer 1

Berkeley DB keys and data are frequently not strings. Actually, I can't recall a time when I've ever used strings for the keys. Data, sure. Sometimes. But the key comparison function is so performance critical, it nearly always makes sense to represent keys in binary, like it would sit in a packed C struct.

To make sense of the data stored in Berkeley DB, you need the source code for the application that populated it.