If you ever wondered how to extract ADB Backups, here is the command for it:

adb backup -f backup.ab -all
dd if=backup.ab bs=24 skip=1 | zlib-flate -uncompress | pv | tar xf - -C backup

Use pv for extra output, or -v on the tar command for verbose output of tar.

The zlib-flate command can be found in the qpdf package, since the openssl zlib does not work on every system.