355 lines
12 KiB
Python
355 lines
12 KiB
Python
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#!/usr/bin/python
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# -*- coding: ascii -*-
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###########################################################################
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# PBKDF2.py - PKCS#5 v2.0 Password-Based Key Derivation
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#
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# Copyright (C) 2007, 2008 Dwayne C. Litzenberger <dlitz@dlitz.net>
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# All rights reserved.
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#
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# Permission to use, copy, modify, and distribute this software and its
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# documentation for any purpose and without fee is hereby granted,
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# provided that the above copyright notice appear in all copies and that
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# both that copyright notice and this permission notice appear in
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# supporting documentation.
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#
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# THE AUTHOR PROVIDES THIS SOFTWARE ``AS IS'' AND ANY EXPRESSED OR
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# IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
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# OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
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# IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
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# INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
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# NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
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# DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
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# THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
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# (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
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# OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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#
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# Country of origin: Canada
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#
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###########################################################################
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# Sample PBKDF2 usage:
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# from Crypto.Cipher import AES
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# from PBKDF2 import PBKDF2
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# import os
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#
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# salt = os.urandom(8) # 64-bit salt
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# key = PBKDF2("This passphrase is a secret.", salt).read(32) # 256-bit key
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# iv = os.urandom(16) # 128-bit IV
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# cipher = AES.new(key, AES.MODE_CBC, iv)
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# ...
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#
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# Sample crypt() usage:
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# from PBKDF2 import crypt
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# pwhash = crypt("secret")
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# alleged_pw = raw_input("Enter password: ")
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# if pwhash == crypt(alleged_pw, pwhash):
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# print "Password good"
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# else:
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# print "Invalid password"
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#
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###########################################################################
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# History:
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#
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# 2007-07-27 Dwayne C. Litzenberger <dlitz@dlitz.net>
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# - Initial Release (v1.0)
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#
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# 2007-07-31 Dwayne C. Litzenberger <dlitz@dlitz.net>
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# - Bugfix release (v1.1)
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# - SECURITY: The PyCrypto XOR cipher (used, if available, in the _strxor
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# function in the previous release) silently truncates all keys to 64
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# bytes. The way it was used in the previous release, this would only be
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# problem if the pseudorandom function that returned values larger than
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# 64 bytes (so SHA1, SHA256 and SHA512 are fine), but I don't like
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# anything that silently reduces the security margin from what is
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# expected.
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#
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# 2008-06-17 Dwayne C. Litzenberger <dlitz@dlitz.net>
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# - Compatibility release (v1.2)
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# - Add support for older versions of Python (2.2 and 2.3).
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#
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###########################################################################
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__version__ = "1.2"
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from struct import pack
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from binascii import b2a_hex
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from random import randint
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import string
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try:
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# Use PyCrypto (if available)
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from Crypto.Hash import HMAC, SHA as SHA1
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except ImportError:
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# PyCrypto not available. Use the Python standard library.
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import hmac as HMAC
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import sha as SHA1
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def strxor(a, b):
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return "".join([chr(ord(x) ^ ord(y)) for (x, y) in zip(a, b)])
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def b64encode(data, chars="+/"):
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tt = string.maketrans("+/", chars)
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return data.encode('base64').replace("\n", "").translate(tt)
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class PBKDF2(object):
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"""PBKDF2.py : PKCS#5 v2.0 Password-Based Key Derivation
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This implementation takes a passphrase and a salt (and optionally an
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iteration count, a digest module, and a MAC module) and provides a
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file-like object from which an arbitrarily-sized key can be read.
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If the passphrase and/or salt are unicode objects, they are encoded as
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UTF-8 before they are processed.
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The idea behind PBKDF2 is to derive a cryptographic key from a
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passphrase and a salt.
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PBKDF2 may also be used as a strong salted password hash. The
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'crypt' function is provided for that purpose.
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Remember: Keys generated using PBKDF2 are only as strong as the
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passphrases they are derived from.
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"""
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def __init__(self, passphrase, salt, iterations=1000,
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digestmodule=SHA1, macmodule=HMAC):
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self.__macmodule = macmodule
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self.__digestmodule = digestmodule
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self._setup(passphrase, salt, iterations, self._pseudorandom)
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def _pseudorandom(self, key, msg):
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"""Pseudorandom function. e.g. HMAC-SHA1"""
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return self.__macmodule.new(key=key, msg=msg,
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digestmod=self.__digestmodule).digest()
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def read(self, bytes):
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"""Read the specified number of key bytes."""
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if self.closed:
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raise ValueError("file-like object is closed")
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size = len(self.__buf)
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blocks = [self.__buf]
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i = self.__blockNum
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while size < bytes:
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i += 1
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if i > 0xffffffffL or i < 1:
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# We could return "" here, but
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raise OverflowError("derived key too long")
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block = self.__f(i)
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blocks.append(block)
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size += len(block)
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buf = "".join(blocks)
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retval = buf[:bytes]
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self.__buf = buf[bytes:]
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self.__blockNum = i
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return retval
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def __f(self, i):
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# i must fit within 32 bits
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assert 1 <= i <= 0xffffffffL
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U = self.__prf(self.__passphrase, self.__salt + pack("!L", i))
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result = U
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for j in xrange(2, 1+self.__iterations):
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U = self.__prf(self.__passphrase, U)
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result = strxor(result, U)
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return result
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def hexread(self, octets):
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"""Read the specified number of octets. Return them as hexadecimal.
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Note that len(obj.hexread(n)) == 2*n.
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"""
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return b2a_hex(self.read(octets))
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def _setup(self, passphrase, salt, iterations, prf):
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# Sanity checks:
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# passphrase and salt must be str or unicode (in the latter
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# case, we convert to UTF-8)
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if isinstance(passphrase, unicode):
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passphrase = passphrase.encode("UTF-8")
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if not isinstance(passphrase, str):
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raise TypeError("passphrase must be str or unicode")
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if isinstance(salt, unicode):
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salt = salt.encode("UTF-8")
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if not isinstance(salt, str):
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raise TypeError("salt must be str or unicode")
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# iterations must be an integer >= 1
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if not isinstance(iterations, (int, long)):
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raise TypeError("iterations must be an integer")
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if iterations < 1:
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raise ValueError("iterations must be at least 1")
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# prf must be callable
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if not callable(prf):
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raise TypeError("prf must be callable")
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self.__passphrase = passphrase
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self.__salt = salt
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self.__iterations = iterations
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self.__prf = prf
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self.__blockNum = 0
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self.__buf = ""
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self.closed = False
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def close(self):
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"""Close the stream."""
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if not self.closed:
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del self.__passphrase
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del self.__salt
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del self.__iterations
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del self.__prf
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del self.__blockNum
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del self.__buf
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self.closed = True
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def crypt(word, salt=None, iterations=None):
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"""PBKDF2-based unix crypt(3) replacement.
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The number of iterations specified in the salt overrides the 'iterations'
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parameter.
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The effective hash length is 192 bits.
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"""
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# Generate a (pseudo-)random salt if the user hasn't provided one.
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if salt is None:
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salt = _makesalt()
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# salt must be a string or the us-ascii subset of unicode
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if isinstance(salt, unicode):
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salt = salt.encode("us-ascii")
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if not isinstance(salt, str):
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raise TypeError("salt must be a string")
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# word must be a string or unicode (in the latter case, we convert to UTF-8)
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if isinstance(word, unicode):
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word = word.encode("UTF-8")
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if not isinstance(word, str):
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raise TypeError("word must be a string or unicode")
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# Try to extract the real salt and iteration count from the salt
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if salt.startswith("$p5k2$"):
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(iterations, salt, dummy) = salt.split("$")[2:5]
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if iterations == "":
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iterations = 400
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else:
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converted = int(iterations, 16)
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if iterations != "%x" % converted: # lowercase hex, minimum digits
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raise ValueError("Invalid salt")
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iterations = converted
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if not (iterations >= 1):
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raise ValueError("Invalid salt")
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# Make sure the salt matches the allowed character set
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allowed = "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789./"
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for ch in salt:
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if ch not in allowed:
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raise ValueError("Illegal character %r in salt" % (ch,))
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if iterations is None or iterations == 400:
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iterations = 400
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salt = "$p5k2$$" + salt
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else:
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salt = "$p5k2$%x$%s" % (iterations, salt)
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rawhash = PBKDF2(word, salt, iterations).read(24)
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return salt + "$" + b64encode(rawhash, "./")
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# Add crypt as a static method of the PBKDF2 class
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# This makes it easier to do "from PBKDF2 import PBKDF2" and still use
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# crypt.
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PBKDF2.crypt = staticmethod(crypt)
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def _makesalt():
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"""Return a 48-bit pseudorandom salt for crypt().
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This function is not suitable for generating cryptographic secrets.
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"""
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binarysalt = "".join([pack("@H", randint(0, 0xffff)) for i in range(3)])
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return b64encode(binarysalt, "./")
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def test_pbkdf2():
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"""Module self-test"""
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from binascii import a2b_hex
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#
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# Test vectors from RFC 3962
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#
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# Test 1
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result = PBKDF2("password", "ATHENA.MIT.EDUraeburn", 1).read(16)
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expected = a2b_hex("cdedb5281bb2f801565a1122b2563515")
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if result != expected:
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raise RuntimeError("self-test failed")
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# Test 2
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result = PBKDF2("password", "ATHENA.MIT.EDUraeburn", 1200).hexread(32)
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expected = ("5c08eb61fdf71e4e4ec3cf6ba1f5512b"
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"a7e52ddbc5e5142f708a31e2e62b1e13")
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if result != expected:
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raise RuntimeError("self-test failed")
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# Test 3
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result = PBKDF2("X"*64, "pass phrase equals block size", 1200).hexread(32)
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expected = ("139c30c0966bc32ba55fdbf212530ac9"
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"c5ec59f1a452f5cc9ad940fea0598ed1")
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if result != expected:
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raise RuntimeError("self-test failed")
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# Test 4
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result = PBKDF2("X"*65, "pass phrase exceeds block size", 1200).hexread(32)
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expected = ("9ccad6d468770cd51b10e6a68721be61"
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"1a8b4d282601db3b36be9246915ec82a")
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if result != expected:
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raise RuntimeError("self-test failed")
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#
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# Other test vectors
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#
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# Chunked read
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f = PBKDF2("kickstart", "workbench", 256)
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result = f.read(17)
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result += f.read(17)
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result += f.read(1)
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result += f.read(2)
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result += f.read(3)
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expected = PBKDF2("kickstart", "workbench", 256).read(40)
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if result != expected:
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raise RuntimeError("self-test failed")
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#
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# crypt() test vectors
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#
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# crypt 1
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result = crypt("cloadm", "exec")
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expected = '$p5k2$$exec$r1EWMCMk7Rlv3L/RNcFXviDefYa0hlql'
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if result != expected:
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raise RuntimeError("self-test failed")
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# crypt 2
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result = crypt("gnu", '$p5k2$c$u9HvcT4d$.....')
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expected = '$p5k2$c$u9HvcT4d$Sd1gwSVCLZYAuqZ25piRnbBEoAesaa/g'
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if result != expected:
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raise RuntimeError("self-test failed")
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# crypt 3
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result = crypt("dcl", "tUsch7fU", iterations=13)
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expected = "$p5k2$d$tUsch7fU$nqDkaxMDOFBeJsTSfABsyn.PYUXilHwL"
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if result != expected:
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raise RuntimeError("self-test failed")
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# crypt 4 (unicode)
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result = crypt(u'\u0399\u03c9\u03b1\u03bd\u03bd\u03b7\u03c2',
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'$p5k2$$KosHgqNo$9mjN8gqjt02hDoP0c2J0ABtLIwtot8cQ')
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expected = '$p5k2$$KosHgqNo$9mjN8gqjt02hDoP0c2J0ABtLIwtot8cQ'
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if result != expected:
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raise RuntimeError("self-test failed")
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if __name__ == '__main__':
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test_pbkdf2()
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# vim:set ts=4 sw=4 sts=4 expandtab:
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