# $Id$

#

# Copyright (C) 2005 Gregory P. Smith (greg@krypto.org)

# Licensed to PSF under a Contributor Agreement.

#

__doc__ = """hashlib module - A common interface to many hash functions.

new(name, string='') - returns a new hash object implementing the

given hash function; initializing the hash

using the given string data.

Named constructor functions are also available, these are much faster

than using new():

md5(), sha1(), sha224(), sha256(), sha384(), and sha512()

More algorithms may be available on your platform but the above are guaranteed

to exist. See the algorithms_guaranteed and algorithms_available attributes

to find out what algorithm names can be passed to new().

NOTE: If you want the adler32 or crc32 hash functions they are available in

the zlib module.

Choose your hash function wisely. Some have known collision weaknesses.

sha384 and sha512 will be slow on 32 bit platforms.

Hash objects have these methods:

- update(arg): Update the hash object with the string arg. Repeated calls

are equivalent to a single call with the concatenation of all

the arguments.

- digest(): Return the digest of the strings passed to the update() method

so far. This may contain non-ASCII characters, including

NUL bytes.

- hexdigest(): Like digest() except the digest is returned as a string of

double length, containing only hexadecimal digits.

- copy(): Return a copy (clone) of the hash object. This can be used to

efficiently compute the digests of strings that share a common

initial substring.

For example, to obtain the digest of the string 'Nobody inspects the

spammish repetition':

>>> import hashlib

>>> m = hashlib.md5()

>>> m.update("Nobody inspects")

>>> m.update(" the spammish repetition")

>>> m.digest()

'\\xbbd\\x9c\\x83\\xdd\\x1e\\xa5\\xc9\\xd9\\xde\\xc9\\xa1\\x8d\\xf0\\xff\\xe9'

More condensed:

>>> hashlib.sha224("Nobody inspects the spammish repetition").hexdigest()

'a4337bc45a8fc544c03f52dc550cd6e1e87021bc896588bd79e901e2'

"""

# This tuple and __get_builtin_constructor() must be modified if a new

# always available algorithm is added.

__always_supported = ('md5', 'sha1', 'sha224', 'sha256', 'sha384', 'sha512')

algorithms_guaranteed = set(__always_supported)

algorithms_available = set(__always_supported)

algorithms = __always_supported

__all__ = __always_supported + ('new', 'algorithms_guaranteed',

'algorithms_available', 'algorithms',

'pbkdf2_hmac')

def __get_builtin_constructor(name):

try:

if name in ('SHA1', 'sha1'):

import _sha

return _sha.new

elif name in ('MD5', 'md5'):

import _md5

return _md5.new

elif name in ('SHA256', 'sha256', 'SHA224', 'sha224'):

import _sha256

bs = name[3:]

if bs == '256':

return _sha256.sha256

elif bs == '224':

return _sha256.sha224

elif name in ('SHA512', 'sha512', 'SHA384', 'sha384'):

import _sha512

bs = name[3:]

if bs == '512':

return _sha512.sha512

elif bs == '384':

return _sha512.sha384

except ImportError:

pass # no extension module, this hash is unsupported.

raise ValueError('unsupported hash type ' + name)

def __get_openssl_constructor(name):

try:

f = getattr(_hashlib, 'openssl_' + name)

# Allow the C module to raise ValueError. The function will be

# defined but the hash not actually available thanks to OpenSSL.

f()

# Use the C function directly (very fast)

return f

except (AttributeError, ValueError):

return __get_builtin_constructor(name)

def __py_new(name, string=''):

"""new(name, string='') - Return a new hashing object using the named algorithm;

optionally initialized with a string.

"""

return __get_builtin_constructor(name)(string)

def __hash_new(name, string=''):

"""new(name, string='') - Return a new hashing object using the named algorithm;

optionally initialized with a string.

"""

try:

return _hashlib.new(name, string)

except ValueError:

# If the _hashlib module (OpenSSL) doesn't support the named

# hash, try using our builtin implementations.

# This allows for SHA224/256 and SHA384/512 support even though

# the OpenSSL library prior to 0.9.8 doesn't provide them.

return __get_builtin_constructor(name)(string)

try:

import _hashlib

new = __hash_new

__get_hash = __get_openssl_constructor

algorithms_available = algorithms_available.union(

_hashlib.openssl_md_meth_names)

except ImportError:

new = __py_new

__get_hash = __get_builtin_constructor

for __func_name in __always_supported:

# try them all, some may not work due to the OpenSSL

# version not supporting that algorithm.

try:

globals()[__func_name] = __get_hash(__func_name)

except ValueError:

import logging

logging.exception('code for hash %s was not found.', __func_name)

try:

# OpenSSL's PKCS5_PBKDF2_HMAC requires OpenSSL 1.0+ with HMAC and SHA

from _hashlib import pbkdf2_hmac

except ImportError:

import binascii

import struct

_trans_5C = b"".join(chr(x ^ 0x5C) for x in range(256))

_trans_36 = b"".join(chr(x ^ 0x36) for x in range(256))

def pbkdf2_hmac(hash_name, password, salt, iterations, dklen=None):

"""Password based key derivation function 2 (PKCS #5 v2.0)

This Python implementations based on the hmac module about as fast

as OpenSSL's PKCS5_PBKDF2_HMAC for short passwords and much faster

for long passwords.

"""

if not isinstance(hash_name, str):

raise TypeError(hash_name)

if not isinstance(password, (bytes, bytearray)):

password = bytes(buffer(password))

if not isinstance(salt, (bytes, bytearray)):

salt = bytes(buffer(salt))

# Fast inline HMAC implementation

inner = new(hash_name)

outer = new(hash_name)

blocksize = getattr(inner, 'block_size', 64)

if len(password) > blocksize:

password = new(hash_name, password).digest()

password = password + b'\x00' * (blocksize - len(password))

inner.update(password.translate(_trans_36))

outer.update(password.translate(_trans_5C))

def prf(msg, inner=inner, outer=outer):

# PBKDF2_HMAC uses the password as key. We can re-use the same

# digest objects and just update copies to skip initialization.

icpy = inner.copy()

ocpy = outer.copy()

icpy.update(msg)

ocpy.update(icpy.digest())

return ocpy.digest()

if iterations < 1:

raise ValueError(iterations)

if dklen is None:

dklen = outer.digest_size

if dklen < 1:

raise ValueError(dklen)

hex_format_string = "%%0%ix" % (new(hash_name).digest_size * 2)

dkey = b''

loop = 1

while len(dkey) < dklen:

prev = prf(salt + struct.pack(b'>I', loop))

rkey = int(binascii.hexlify(prev), 16)

for i in xrange(iterations - 1):

prev = prf(prev)

rkey ^= int(binascii.hexlify(prev), 16)

loop += 1

dkey += binascii.unhexlify(hex_format_string % rkey)

return dkey[:dklen]

# Cleanup locals()

del __always_supported, __func_name, __get_hash

del __py_new, __hash_new, __get_openssl_constructor