""" MD5C.C - RSA Data Security, Inc., MD5 message-digest algorithm Copyright (C) 1991-2, RSA Data Security, Inc. Created 1991. All rights reserved. License to copy and use this software is granted provided that it is identified as the "RSA Data Security, Inc. MD5 Message-Digest Algorithm" in all material mentioning or referencing this software or this function. License is also granted to make and use derivative works provided that such works are identified as "derived from the RSA Data Security, Inc. MD5 Message-Digest Algorithm" in all material mentioning or referencing the derived work. RSA Data Security, Inc. makes no representations concerning either the merchantability of this software or the suitability of this software for any particular purpose. It is provided "as is" without express or implied warranty of any kind. These notices must be retained in any copies of any part of this documentation and/or software. """ # Constants for MD5Transform routine. S11 = 7 S12 = 12 S13 = 17 S14 = 22 S21 = 5 S22 = 9 S23 = 14 S24 = 20 S31 = 4 S32 = 11 S33 = 16 S34 = 23 S41 = 6 S42 = 10 S43 = 15 S44 = 21 PADDING = "\x80" + 63*"\0" # do not overlook first byte again :-) # F, G, H and I are basic MD5 functions def F(x, y, z): return (((x) & (y)) | ((~x) & (z))) def G(x, y, z): return (((x) & (z)) | ((y) & (~z))) def H(x, y, z): return ((x) ^ (y) ^ (z)) def I(x, y, z): return((y) ^ ((x) | (~z))) # ROTATE_LEFT rotates x left n bits. def ROTATE_LEFT(x, n): x = x & 0xffffffffL # make shift unsigned return (((x) << (n)) | ((x) >> (32-(n)))) & 0xffffffffL # FF, GG, HH, and II transformations for rounds 1, 2, 3, and 4. # Rotation is separate from addition to prevent recomputation. def FF(a, b, c, d, x, s, ac): a = a + F ((b), (c), (d)) + (x) + (ac) a = ROTATE_LEFT ((a), (s)) a = a + b return a # must assign this to a def GG(a, b, c, d, x, s, ac): a = a + G ((b), (c), (d)) + (x) + (ac) a = ROTATE_LEFT ((a), (s)) a = a + b return a # must assign this to a def HH(a, b, c, d, x, s, ac): a = a + H ((b), (c), (d)) + (x) + (ac) a = ROTATE_LEFT ((a), (s)) a = a + b return a # must assign this to a def II(a, b, c, d, x, s, ac): a = a + I ((b), (c), (d)) + (x) + (ac) a = ROTATE_LEFT ((a), (s)) a = a + b return a # must assign this to a class md5: def __init__(self, initial=None): self.count = 0L self.state = (0x67452301L, 0xefcdab89L, 0x98badcfeL, 0x10325476L,) self.buffer = "" if initial: self.update(initial) def update(self, input): """ MD5 block update operation. Continues an MD5 message-digest operation, processing another message block, and updating the context. """ inputLen = len(input) index = int(self.count >> 3) & 0x3F # Update number of bits self.count = self.count + (inputLen << 3) print("count = %s" % repr(self.count)) partLen = 64 - index # Transform as many times as possible. if inputLen >= partLen: self.buffer = self.buffer[:index] + input[:partLen] self.transform(self.buffer) i = partLen while i + 63 < inputLen: self.transform(input[i:i+64]) i = i + 64 index = 0 else: i = 0 # Buffer remaining input self.buffer = self.buffer[:index] + input[i:inputLen] def final(self): """ MD5 finalization. Ends an MD5 message-digest operation, writing the message digest and zeroizing the context. """ # Save number of bits bits = Encode((self.count & 0xffffffffL, self.count>>32), 8) # Pad out to 56 mod 64 index = int((self.count >> 3) & 0x3f) if index < 56: padLen = (56 - index) else: padLen = (120 - index) # Append padding self.update(PADDING[:padLen]) # Append bits self.update(bits) # Store state in digest digest = Encode(self.state, 16) # Zeroize sensitive information self.__dict__.clear() return digest digest = final # alias def transform(self, block): """ MD5 basic transformation. Transforms state based on block """ a, b, c, d = state = self.state x = Decode(block, 64) # Round 1 a = FF (a, b, c, d, x[ 0], S11, 0xd76aa478)#; /* 1 */ d = FF (d, a, b, c, x[ 1], S12, 0xe8c7b756)#; /* 2 */ c = FF (c, d, a, b, x[ 2], S13, 0x242070db)#; /* 3 */ b = FF (b, c, d, a, x[ 3], S14, 0xc1bdceee)#; /* 4 */ a = FF (a, b, c, d, x[ 4], S11, 0xf57c0faf)#; /* 5 */ d = FF (d, a, b, c, x[ 5], S12, 0x4787c62a)#; /* 6 */ c = FF (c, d, a, b, x[ 6], S13, 0xa8304613)#; /* 7 */ b = FF (b, c, d, a, x[ 7], S14, 0xfd469501)#; /* 8 */ a = FF (a, b, c, d, x[ 8], S11, 0x698098d8)#; /* 9 */ d = FF (d, a, b, c, x[ 9], S12, 0x8b44f7af)#; /* 10 */ c = FF (c, d, a, b, x[10], S13, 0xffff5bb1)#; /* 11 */ b = FF (b, c, d, a, x[11], S14, 0x895cd7be)#; /* 12 */ a = FF (a, b, c, d, x[12], S11, 0x6b901122)#; /* 13 */ d = FF (d, a, b, c, x[13], S12, 0xfd987193)#; /* 14 */ c = FF (c, d, a, b, x[14], S13, 0xa679438e)#; /* 15 */ b = FF (b, c, d, a, x[15], S14, 0x49b40821)#; /* 16 */ # Round 2 a = GG (a, b, c, d, x[ 1], S21, 0xf61e2562)#; /* 17 */ d = GG (d, a, b, c, x[ 6], S22, 0xc040b340)#; /* 18 */ c = GG (c, d, a, b, x[11], S23, 0x265e5a51)#; /* 19 */ b = GG (b, c, d, a, x[ 0], S24, 0xe9b6c7aa)#; /* 20 */ a = GG (a, b, c, d, x[ 5], S21, 0xd62f105d)#; /* 21 */ d = GG (d, a, b, c, x[10], S22, 0x2441453)#; /* 22 */ c = GG (c, d, a, b, x[15], S23, 0xd8a1e681)#; /* 23 */ b = GG (b, c, d, a, x[ 4], S24, 0xe7d3fbc8)#; /* 24 */ a = GG (a, b, c, d, x[ 9], S21, 0x21e1cde6)#; /* 25 */ d = GG (d, a, b, c, x[14], S22, 0xc33707d6)#; /* 26 */ c = GG (c, d, a, b, x[ 3], S23, 0xf4d50d87)#; /* 27 */ b = GG (b, c, d, a, x[ 8], S24, 0x455a14ed)#; /* 28 */ a = GG (a, b, c, d, x[13], S21, 0xa9e3e905)#; /* 29 */ d = GG (d, a, b, c, x[ 2], S22, 0xfcefa3f8)#; /* 30 */ c = GG (c, d, a, b, x[ 7], S23, 0x676f02d9)#; /* 31 */ b = GG (b, c, d, a, x[12], S24, 0x8d2a4c8a)#; /* 32 */ # Round 3 a = HH (a, b, c, d, x[ 5], S31, 0xfffa3942)#; /* 33 */ d = HH (d, a, b, c, x[ 8], S32, 0x8771f681)#; /* 34 */ c = HH (c, d, a, b, x[11], S33, 0x6d9d6122)#; /* 35 */ b = HH (b, c, d, a, x[14], S34, 0xfde5380c)#; /* 36 */ a = HH (a, b, c, d, x[ 1], S31, 0xa4beea44)#; /* 37 */ d = HH (d, a, b, c, x[ 4], S32, 0x4bdecfa9)#; /* 38 */ c = HH (c, d, a, b, x[ 7], S33, 0xf6bb4b60)#; /* 39 */ b = HH (b, c, d, a, x[10], S34, 0xbebfbc70)#; /* 40 */ a = HH (a, b, c, d, x[13], S31, 0x289b7ec6)#; /* 41 */ d = HH (d, a, b, c, x[ 0], S32, 0xeaa127fa)#; /* 42 */ c = HH (c, d, a, b, x[ 3], S33, 0xd4ef3085)#; /* 43 */ b = HH (b, c, d, a, x[ 6], S34, 0x4881d05)#; /* 44 */ a = HH (a, b, c, d, x[ 9], S31, 0xd9d4d039)#; /* 45 */ d = HH (d, a, b, c, x[12], S32, 0xe6db99e5)#; /* 46 */ c = HH (c, d, a, b, x[15], S33, 0x1fa27cf8)#; /* 47 */ b = HH (b, c, d, a, x[ 2], S34, 0xc4ac5665)#; /* 48 */ # Round 4 a = II (a, b, c, d, x[ 0], S41, 0xf4292244)#; /* 49 */ d = II (d, a, b, c, x[ 7], S42, 0x432aff97)#; /* 50 */ c = II (c, d, a, b, x[14], S43, 0xab9423a7)#; /* 51 */ b = II (b, c, d, a, x[ 5], S44, 0xfc93a039)#; /* 52 */ a = II (a, b, c, d, x[12], S41, 0x655b59c3)#; /* 53 */ d = II (d, a, b, c, x[ 3], S42, 0x8f0ccc92)#; /* 54 */ c = II (c, d, a, b, x[10], S43, 0xffeff47d)#; /* 55 */ b = II (b, c, d, a, x[ 1], S44, 0x85845dd1)#; /* 56 */ a = II (a, b, c, d, x[ 8], S41, 0x6fa87e4f)#; /* 57 */ d = II (d, a, b, c, x[15], S42, 0xfe2ce6e0)#; /* 58 */ c = II (c, d, a, b, x[ 6], S43, 0xa3014314)#; /* 59 */ b = II (b, c, d, a, x[13], S44, 0x4e0811a1)#; /* 60 */ a = II (a, b, c, d, x[ 4], S41, 0xf7537e82)#; /* 61 */ d = II (d, a, b, c, x[11], S42, 0xbd3af235)#; /* 62 */ c = II (c, d, a, b, x[ 2], S43, 0x2ad7d2bb)#; /* 63 */ b = II (b, c, d, a, x[ 9], S44, 0xeb86d391)#; /* 64 */ self.state = (0xffffffffL & (state[0] + a), 0xffffffffL & (state[1] + b), 0xffffffffL & (state[2] + c), 0xffffffffL & (state[3] + d),) # Zeroize sensitive information. del x # Some helper functions to decode and encode binary data import struct, string def Encode(input, len): k = len >> 2 res = apply(struct.pack, ("%iI" % k,) + tuple(input[:k])) return string.join(res, "") def Decode(input, len): k = len >> 2 res = struct.unpack("%iI" % k, input[:len]) return list(res) # ================= # = Spoofing Code = # ================= def spoof_digest(originalDigest, originalLen, spoofMessage=""): # first decode digest back into state tuples state = Decode(originalDigest, 16) # generate a seed md5 object spoof = md5() # seed the count variable for calculation of index, padLen, and bits spoof.count += originalLen << 3 # calculate some variables to generate the original padding index = int((spoof.count >> 3) & 0x3f) padLen = (56 - index) if index < 56 else (120 - index) bits = Encode((spoof.count & 0xffffffffL, spoof.count>>32), 8) # construct the original padding padding = PADDING[:padLen] # augment the count with the new padding and trailing bits spoof.count += len(padding) << 3 spoof.count += len(bits) << 3 spoof.state = state # run an update spoof.update(spoofMessage) # We now have a digest of the original secret + message + some_padding return (spoof.digest(), padding + bits) def test_md5_matches_stdlib(): from hashlib import md5 as md5stdlib std_signature = md5stdlib('hello').digest() this_md5_signature = md5('hello').digest() assert this_md5_signature == std_signature def test_spoofing(): originalMsg = "secret" + "my message" appendedMsg = "my message extension" # This is the signature that a legitimate user sends # over the wire in clear text. originalSignature = md5(originalMsg).digest() # This is how an attacker would spoof the signature where, # the message == originalMsg + padbits + appendedMsg . # Notice that this method implies that the attacker # knows the original length of the "secret" ... # Most apis such as Flickr assign secrets that are of # uniform length for all of their api users. spoofSignature, padbits = spoof_digest(originalSignature, len(originalMsg), appendedMsg) # This is how a legitimate user would construct the # a signature when message == originalMsg + padbits + appendedMsg testSignature = md5(originalMsg + padbits + appendedMsg).digest() # make sure the spoof signature and the test signature match. # if, this passes, we've successfully constructed a spoofed message # of the form: secret + orginal_message + padding + appended_message # without actually knowing the secret. assert testSignature == spoofSignature if __name__=="__main__": test_spoofing()