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# Licensed to PSF under a Contributor Agreement.

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

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

given hash function; initializing the hash

using the given binary data.

Named constructor functions are also available, these are faster

than using new(name):

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 bytes in arg. Repeated calls

are equivalent to a single call with the concatenation of all

the arguments.

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

so far.

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

object 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(b"Nobody inspects")

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

>>> m.digest()

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

More condensed:

>>> hashlib.sha224(b"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)

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

'algorithms_available')

def __get_builtin_constructor(name):

try:

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

import _sha1

return _sha1.sha1

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

import _md5

return _md5.md5

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, data=b''):

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

optionally initialized with data (which must be bytes).

"""

return __get_builtin_constructor(name)(data)

def __hash_new(name, data=b''):

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

optionally initialized with data (which must be bytes).

"""

try:

return _hashlib.new(name, data)

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)(data)

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)

# Cleanup locals()

del __always_supported, __func_name, __get_hash

del __py_new, __hash_new, __get_openssl_constructor

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