A naive restic brute force tool implemented in C

Of course, it would have been much easier to implement this in go using restic code.

I just wanted to refresh my C knowledge and learn something about the internals of restic and the API of OpenSSL.

Usage

Get crypto parameters from restic-repo:

$ jq <keys/bb4d5f30181bf3d2350a8145aba10ac7b2ad595b3ce9c7e32c263a0194ba95e3

{
  "created": "2020-12-18T16:21:46.888133781Z",
  "username": "alarm",
  "hostname": "alarm",
  "kdf": "scrypt",
  "N": 8192,
  "r": 8,
  "p": 1,
  "salt": "7SmtZZSHl6J18Vsdo2/dKwJHp3ctaez98hFB2Df7B4C2+0jPfMw+QUahBd7g30hRJW4gRnHZfHGMfmtKeoz7dQ==",
  "data": "h5rMFX2qATIY/Mz2tgviDx5SuqiTaYpYnwJhZfUbux2gOwpdtCiF2Lz/s0AwsLsmcW6ffJUMzLZ0SU1j0QTuiAjnE6fUg6ag7zaxSqrGUuqjqSsS+dekz+rXLtCiFsyusN35xulKqEyCWQrppv/BtItPuhY2Nf+04GM95miCflZ+jINFOa4Y11C+b4+G8SEBsEq5JvpXADjrb3jvYCHBsQ=="
}

Start cracking using above parameters:

time ./build/restic-brute -v -n 8192 -r 8 -p 1 7SmtZZSHl6J18Vsdo2/dKwJHp3ctaez98hFB2Df7B4C2+0jPfMw+QUahBd7g30hRJW4gRnHZfHGMfmtKeoz7dQ== h5rMFX2qATIY/Mz2tgviDx5SuqiTaYpYnwJhZfUbux2gOwpdtCiF2Lz/s0AwsLsmcW6ffJUMzLZ0SU1j0QTuiAjnE6fUg6ag7zaxSqrGUuqjqSsS+dekz+rXLtCiFsyusN35xulKqEyCWQrppv/BtItPuhY2Nf+04GM95miCflZ+jINFOa4Y11C+b4+G8SEBsEq5JvpXADjrb3jvYCHBsQ== </usr/share/dict/cracklib-small 

Using parameters (N=8192, r=8, p=1) on 8 Threads
Checked 558 passwords
Checked 1111 passwords
Checked 1661 passwords
Checked 2209 passwords
Checked 2746 passwords
Checked 3291 passwords
Checked 3838 passwords
Checked 4384 passwords
Checked 4921 passwords
Checked 5465 passwords
Checked 5994 passwords
Checked 6529 passwords
Checked 7061 passwords
...
Checked 35028 passwords
Checked 35560 passwords
Found: penance

real	3m5,189s
user	23m45,713s
sys	0m0,987s