Issue #19254: Provide an optimized Python implementation of PBKDF2_HMAC
diff --git a/Lib/hashlib.py b/Lib/hashlib.py
index 73882d1..56a9360 100644
--- a/Lib/hashlib.py
+++ b/Lib/hashlib.py
@@ -1,4 +1,4 @@
-# Copyright (C) 2005-2010 Gregory P. Smith (greg@krypto.org)
+#. Copyright (C) 2005-2010 Gregory P. Smith (greg@krypto.org)
# Licensed to PSF under a Contributor Agreement.
#
@@ -61,7 +61,7 @@
algorithms_available = set(__always_supported)
__all__ = __always_supported + ('new', 'algorithms_guaranteed',
- 'algorithms_available')
+ 'algorithms_available', 'pbkdf2_hmac')
def __get_builtin_constructor(name):
@@ -147,13 +147,70 @@
new = __py_new
__get_hash = __get_builtin_constructor
-# PBKDF2 requires OpenSSL 1.0+ with HMAC and SHA
try:
+ # OpenSSL's PKCS5_PBKDF2_HMAC requires OpenSSL 1.0+ with HMAC and SHA
from _hashlib import pbkdf2_hmac
except ImportError:
- pass
-else:
- __all__ += ('pbkdf2_hmac',)
+ _trans_5C = bytes((x ^ 0x5C) for x in range(256))
+ _trans_36 = bytes((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(memoryview(password))
+ if not isinstance(salt, (bytes, bytearray)):
+ salt = bytes(memoryview(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 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)
+
+ dkey = b''
+ loop = 1
+ from_bytes = int.from_bytes
+ while len(dkey) < dklen:
+ prev = prf(salt + loop.to_bytes(4, 'big'))
+ # endianess doesn't matter here as long to / from use the same
+ rkey = int.from_bytes(prev, 'big')
+ for i in range(iterations - 1):
+ prev = prf(prev)
+ # rkey = rkey ^ prev
+ rkey ^= from_bytes(prev, 'big')
+ loop += 1
+ dkey += rkey.to_bytes(inner.digest_size, 'big')
+
+ return dkey[:dklen]
+
for __func_name in __always_supported:
# try them all, some may not work due to the OpenSSL