Simple tool to extract a tar from an unencrypted adb backup

Author: tcrs

README.md

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+# Extract a `tar` from an `adb backup` file
+
+Backup file goes into stdin, tar file comes out on stdout.
+
+## Limitations
+
+ - Does not support encrypted backups (pull requests welcome!)
+ - Does not support uncompressed backups (not sure how to create these?)
+
+## Examples
+
+To view the contents of a backup
+
+```
+./extract.py < backup | tar -tv
+```
+
+To extract all files from a backup
+
+```
+./extract.py < backup | tar -x
+```
+
+# Further info
+
+(Details of backup file structure)[https://android.stackexchange.com/questions/23357/is-there-a-way-to-look-inside-and-modify-an-adb-backup-created-file]
+(Further Details)[https://nelenkov.blogspot.co.uk/2012/06/unpacking-android-backups.html] - could be used as a reference to implement backup decryption

extract.py

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+#!/usr/bin/python3
+
+import collections
+import struct
+import zlib
+import sys
+
+def read_header(inp):
+    buf = inp.read(24)
+
+    lines = buf.decode('ascii').split('\n')
+    if lines[0] != 'ANDROID BACKUP':
+        raise ValueError('Header invalid')
+    if lines[1] != '4':
+        raise ValueError('Unsupported version')
+    if lines[2] != '1':
+        raise ValueError('Uncompressed not supported')
+    if lines[3] != 'none':
+        raise ValueError('Encryption not supported!')
+
+def flate_stream(inp):
+    d = zlib.decompressobj()
+    buf = inp.read(4096)
+    while buf:
+        yield d.decompress(buf)
+        buf = inp.read(4096)
+    yield d.flush()
+
+if __name__ == '__main__':
+    hdr = read_header(sys.stdin.buffer)
+    for buf in flate_stream(sys.stdin.buffer):
+        sys.stdout.buffer.write(buf)
+