DeDRM_tools/Calibre_Plugins/K4MobiDeDRM_plugin/topazextract.py
Apprentice Alf 0dcd18d524 tools v5.4
2015-03-07 13:14:37 +00:00

69 lines
2.0 KiB
Python

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