hkdf-extractor

#!/usr/bin/env python

'''
Requirements
------------
* Install hkdf globally.
    sudo pip install hkdf
* Copy file `hkdf-extractor` to /usr/local/bin
* Make `hkdf-extractor` executable
    sudo chmod +x /usr/local/bin/hkdf-extractor

Help
----
    hkdf-extractor --help

Testme
------
    echo -n hFtWoAyknKOorIBXUjgOptpVwCfmOFUN | ./hkdf-extractor --hex
'''

import sys
import argparse
import hkdf
import hashlib

parser = argparse.ArgumentParser(description='HKDF extractor')
parser.add_argument("--salt", default=None, type=str,
                    help="The salt (optional)")
parser.add_argument("--hash", default='sha512',
                    help="Hash algorithm (sha1/sha256/sha512; default: sha512)")
parser.add_argument("--hex", action='store_true',
                    help="output hexadecimal (default: raw)")
parser.add_argument("-n", action='store_true',
                    help="do not output the trailing newline in hexmode")
args = parser.parse_args()

hash_algos = { 'sha1':   hashlib.sha1,
               'sha256': hashlib.sha256,
               'sha512': hashlib.sha512 }

infile = sys.stdin
ikm = bytearray("")
for line in infile:
    ikm += bytearray(line)

prk = hkdf.hkdf_extract(args.salt, ikm, hash_algos[args.hash])

if args.hex:
    sys.stdout.write(prk.encode('hex'))
    if not args.n:
        sys.stdout.write("\n")
else:
    sys.stdout.write(prk)