def shadow(password):
"""Generate a random salt and return a new hash for the password."""
if isinstance(password, str): password = password.encode('utf-8')
salt = b64encode(urandom(SALT_LENGTH))
p = b64encode(ensureBytes(pbkdf2_bin(password, salt, COST_FACTOR, KEY_LENGTH, getattr(hashlib, HASH_FUNCTION))))
return 'PBKDF2${}${}${}${}'.format(
HASH_FUNCTION,
COST_FACTOR,
ensureString(salt, "ascii"),
ensureString(p, "ascii"),
)
def verify(password, shadow):
"""Check a password against an existing hash."""
password = ensureString(password)
algorithm, hash_function, cost_factor, salt, hash_a = shadow.split('$')
assert algorithm == 'PBKDF2'
salt = ensureBytes(salt)
hash_a = b64decode(hash_a)
hash_b = pbkdf2_bin(password, salt, int(cost_factor), len(hash_a), getattr(hashlib, hash_function))
assert len(hash_a) == len(hash_b) # we requested this from pbkdf2_bin()
# Same as "return hash_a == hash_b" but takes a constant time.
# See http://carlos.bueno.org/2011/10/timing.html
diff = 0
for char_a, char_b in zip(hash_a, hash_b):
if IS_PYTHON3:
diff |= char_a ^ ord(char_b)
else:
diff |= ord(char_a) ^ ord(char_b)
return diff == 0
def pbkdf2_bin(data, salt, iterations=1000, keylen=24, hashfunc=None):
"""Returns a binary digest for the PBKDF2 hash algorithm of `data`
with the given `salt`. It iterates `iterations` time and produces a
key of `keylen` bytes. By default SHA-1 is used as hash function,
a different hashlib `hashfunc` can be provided.
"""
hashfunc = hashfunc or hashlib.sha1
if type(data) is unicode: data = data.encode()
mac = hmac.new(data, None, hashfunc)
def _pseudorandom(x, mac=mac):
h = mac.copy()
h.update(ensureBytes(x))
if not IS_PYTHON3:
return list(map(ord, h.digest()))
else:
return list(h.digest())
buf = []
for block in range(1, -(-keylen // mac.digest_size) + 1):
rv = u = _pseudorandom(salt + _pack_int(block))
for i in range(iterations - 1):
u = _pseudorandom(''.join(map(chr, u)))
rv = starmap(xor, zip(rv, u))
buf.extend(rv)
return ensureString(''.join(map(chr, buf))[:keylen])
