restic repository pack file decryptor in Python

restic is a fast, efficient and secure backup program written in Go.

This script is neither fast, efficient nor secure.

This is a minimal implementation of decryption of individual restic repository pack files.

This script does not restore your backups.

The following features are implemented:

• Password hashing with scrypt
• Decryption of master key
• Decryption of the IV || ciphertext || MAC format using AES-256 CTR
• Parsing and decryption of the restic pack format
• Pack file content lengths based on type

The following features are NOT implemented:

• Everything else.

Usage

>>> password = b"test"
>>> masterkey = get_masterkey("repo/keys/da2d948...", password)
>>> decrypt_packfile(masterkey, "repo/data/96/96f1f07...")
[
    {
        'type': 'data',
        'length': 175,
        'decrypted_content':
            b'SUPERIMPORTANTDATA 0101010101010101010101010101010101010...',
        'offset': 0,
        'id': b'3e2e046f6196f2046c47bf018475166de199bcc614c0154cd8b86fbc8dddffc9'
    },
    {
        'type': 'tree',
        'length': 358,
        'decrypted_content':
            b'{"nodes":[{"name":"header","type":"file","mode":420,"mtime":"2017-01-30T2..."}]}',
        'offset': 175,
        'id': b'9b86a829a4eb4fecd9801f667511967a53a09ad4a4a7bac6efcc4c9dd2a0b9bb'
    }
]
>>> get_all_pack_content_lengths(masterkey, "repo/data")
header_length:        8688549
tree_length:         53898054
data_length:     146443506727
treeblobs:               8466
datablobs:             200975
packfiles:              29351

Details on the restic repository format can be found in the restic design document.

# restic version
restic 0.4.0 (v0.4.0-0-ga7c2f28-dirty)
compiled with go1.7.5 on linux/386