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69 lines
2.0 KiB
Python
69 lines
2.0 KiB
Python
# A simple implementation of pbkdf2 using stock python modules. See RFC2898
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# for details. Basically, it derives a key from a password and salt.
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# Copyright 2004 Matt Johnston <matt @ ucc asn au>
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# Copyright 2009 Daniel Holth <dholth@fastmail.fm>
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# This code may be freely used and modified for any purpose.
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# Revision history
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# v0.1 October 2004 - Initial release
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# v0.2 8 March 2007 - Make usable with hashlib in Python 2.5 and use
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# v0.3 "" the correct digest_size rather than always 20
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# v0.4 Oct 2009 - Rescue from chandler svn, test and optimize.
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import sys
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import hmac
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from struct import pack
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try:
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# only in python 2.5
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import hashlib
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sha = hashlib.sha1
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md5 = hashlib.md5
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sha256 = hashlib.sha256
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except ImportError: # pragma: NO COVERAGE
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# fallback
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import sha
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import md5
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# this is what you want to call.
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def pbkdf2( password, salt, itercount, keylen, hashfn = sha ):
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try:
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# depending whether the hashfn is from hashlib or sha/md5
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digest_size = hashfn().digest_size
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except TypeError: # pragma: NO COVERAGE
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digest_size = hashfn.digest_size
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# l - number of output blocks to produce
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l = keylen / digest_size
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if keylen % digest_size != 0:
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l += 1
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h = hmac.new( password, None, hashfn )
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T = ""
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for i in range(1, l+1):
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T += pbkdf2_F( h, salt, itercount, i )
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return T[0: keylen]
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def xorstr( a, b ):
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if len(a) != len(b):
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raise ValueError("xorstr(): lengths differ")
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return ''.join((chr(ord(x)^ord(y)) for x, y in zip(a, b)))
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def prf( h, data ):
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hm = h.copy()
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hm.update( data )
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return hm.digest()
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# Helper as per the spec. h is a hmac which has been created seeded with the
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# password, it will be copy()ed and not modified.
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def pbkdf2_F( h, salt, itercount, blocknum ):
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U = prf( h, salt + pack('>i',blocknum ) )
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T = U
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for i in range(2, itercount+1):
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U = prf( h, U )
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T = xorstr( T, U )
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return T
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