def safe_string(s):
out = b('')
for c in s:
i = byte_ord(c)
if 32 <= i <= 127:
out += byte_chr(i)
else:
out += b('%%%02X' % i)
return out
def generate_key_bytes(hash_alg, salt, key, nbytes):
"""
Given a password, passphrase, or other human-source key, scramble it
through a secure hash into some keyworthy bytes. This specific algorithm
is used for encrypting/decrypting private key files.
:param function hash_alg: A function which creates a new hash object, such
as ``hashlib.sha256``.
:param salt: data to salt the hash with.
:type salt: byte string
:param str key: human-entered password or passphrase.
:param int nbytes: number of bytes to generate.
:return: Key data `str`
"""
keydata = bytes()
digest = bytes()
if len(salt) > 8:
salt = salt[:8]
while nbytes > 0:
hash_obj = hash_alg()
if len(digest) > 0:
hash_obj.update(digest)
hash_obj.update(b(key))
hash_obj.update(salt)
digest = hash_obj.digest()
size = min(nbytes, len(digest))
keydata += digest[:size]
nbytes -= size
return keydata
def asbytes(s):
if not isinstance(s, bytes_types):
if isinstance(s, string_types):
s = b(s)
else:
try:
s = s.asbytes()
except Exception:
raise Exception('Unknown type')
return s
