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An Android 6.0-compatible SHA1PRNG implementation
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# An Android 6.0-compatible SHA1PRNG implementation | |
# Copyright 2017 Takahiro Yoshimura <altakey@gmail.com> | |
# | |
# Licensed under the Apache License, Version 2.0 (the "License"); | |
# you may not use this file except in compliance with the License. | |
# You may obtain a copy of the License at | |
# | |
# http://www.apache.org/licenses/LICENSE-2.0 | |
# | |
# Unless required by applicable law or agreed to in writing, software | |
# distributed under the License is distributed on an "AS IS" BASIS, | |
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. | |
# See the License for the specific language governing permissions and | |
# limitations under the License. | |
# | |
# This implementation is based on: | |
# https://github.com/android/platform_development/blob/63cb77947e22ea5a311ac267e91edab2842bb8b7/samples/BrokenKeyDerivation/src/com/example/android/brokenkeyderivation/InsecureSHA1PRNGKeyDerivator.java | |
from ctypes import c_uint32, c_uint8 | |
class SHA1PRNGKeyDerivator: | |
@staticmethod | |
def deriveKey(seed, keySizeInBytes): | |
derivator = SHA1PRNGKeyDerivator() | |
derivator.setSeed([x for x in seed]) | |
key = [b'\0'] * keySizeInBytes | |
derivator.nextBytes(key) | |
t = b''.join((b'%c' % x) for x in key) | |
return t | |
_END_FLAGS = [0x80000000, 0x800000, 0x8000, 0x80] | |
_RIGHT1 = [0,40,48,56] | |
_RIGHT2 = [0,8,16,24] | |
_LEFT = [0,24,16,8] | |
_MASK = [0xFFFFFFFF, 0x00FFFFFF, 0x0000FFFF, 0x000000FF] | |
_HASHBYTES_TO_USE = 20 | |
_FRAME_LENGTH = 16 | |
_COUNTER_BASE = 0 | |
_HASHCOPY_OFFSET = 0 | |
_EXTRAFRAME_OFFSET = 5 | |
_FRAME_OFFSET = 21 | |
_MAX_BYTES = 48 | |
_UNDEFINED = 0 | |
_SET_SEED = 1 | |
_NEXT_BYTES = 2 | |
_H0 = 0x67452301 | |
_H1 = 0xEFCDAB89 | |
_H2 = 0x98BADCFE | |
_H3 = 0x10325476 | |
_H4 = 0xC3D2E1F0 | |
_BYTES_OFFSET = 81 | |
_HASH_OFFSET = 82 | |
_DIGEST_LENGTH = 20 | |
def __init__(self): | |
self._seed = [0] * (self._HASH_OFFSET + self._EXTRAFRAME_OFFSET) | |
self._seed[self._HASH_OFFSET:self._HASH_OFFSET + 5] = [self._H0, self._H1, self._H2, self._H3, self._H4] | |
self._seedLength = 0 | |
self._copies = [0] * (2 * self._FRAME_LENGTH + self._EXTRAFRAME_OFFSET) | |
self._nextBytes = [b'\0'] * self._DIGEST_LENGTH | |
self._nextBIndex = self._HASHBYTES_TO_USE | |
self._counter = self._COUNTER_BASE | |
self._state = self._UNDEFINED | |
@staticmethod | |
def _copy(from_, from_offset, to, to_offset, len_): | |
to[to_offset:to_offset + len_] = from_[from_offset:from_offset + len_] | |
def _updateSeed(self, bytes_): | |
self._updateHash(self._seed, bytes_, 0, len(bytes_) - 1) | |
self._seedLength += len(bytes_) | |
def setSeed(self, seed): | |
assert seed is not None, "seed == null" | |
if self._state == self._NEXT_BYTES: | |
self._copy(self._copies, self._HASHCOPY_OFFSET, self._seed, self._HASHCOPY_OFFSET, self._EXTRAFRAME_OFFSET) | |
self._state = self._SET_SEED | |
if seed: | |
self._updateSeed(seed) | |
def nextBytes(self, bytes_): | |
i, n = 0, 0 | |
bits = 0 | |
nextByteToReturn = 0 | |
lastWord = 0 | |
extraBytes = 7 | |
assert bytes_ is not None, 'bytes == null' | |
lastWord = 0 if not self._seed[self._BYTES_OFFSET] else ((self._seed[self._BYTES_OFFSET] + extraBytes) >> 3 - 1) | |
assert self._state != self._UNDEFINED, 'No seed supplied!' | |
if self._state == self._SET_SEED: | |
self._copy(self._seed, self._HASH_OFFSET, self._copies, self._HASHCOPY_OFFSET, self._EXTRAFRAME_OFFSET) | |
for x in range(lastWord, self._FRAME_LENGTH + 2): | |
self._seed[x] = 0 | |
bits = (self._seedLength << 3) + 64 | |
if self._seed[self._BYTES_OFFSET] < self._MAX_BYTES: | |
self._seed[14] = c_uint32(bits >> 32).value | |
self._seed[15] = c_uint32(bits).value | |
else: | |
self._copies[self._EXTRAFRAME_OFFSET + 14] = c_uint32(bits >> 32).value | |
self._copies[self._EXTRAFRAME_OFFSET + 15] = c_uint32(bits).value | |
self._nextBIndex = self._HASHBYTES_TO_USE | |
self._state = self._NEXT_BYTES | |
if not len(bytes_): | |
return | |
nextByteToReturn = 0 | |
n = min(self._HASHBYTES_TO_USE - self._nextBIndex, len(bytes_) - nextByteToReturn) | |
if n > 0: | |
self._copy(self._nextBytes, self._nextBIndex, bytes_, nextByteToReturn, n) | |
self._nextBIndex += n | |
nextByteToReturn += n | |
if nextByteToReturn >= len(bytes_): | |
return | |
n = self._seed[self._BYTES_OFFSET] & 0x03 | |
while True: | |
if not n: | |
self._seed[lastWord] = c_uint32(self._counter >> 32).value | |
self._seed[lastWord + 1] = c_uint32(self._counter).value | |
self._seed[lastWord + 2] = c_uint32(self._END_FLAGS[0]).value | |
else: | |
self._seed[lastWord] |= c_uint32((self._counter >> self._RIGHT1[n]) & self._MASK[n]).value | |
self._seed[lastWord + 1] = c_uint32((self._counter >> self._RIGHT2[n])).value | |
self._seed[lastWord + 2] = c_uint32((self._counter << self._LEFT[n]) | self._END_FLAGS[n]).value | |
if self._seed[self._BYTES_OFFSET] > self._MAX_BYTES: | |
self._copies[self._EXTRAFRAME_OFFSET] = self._seed[self._FRAME_LENGTH] | |
self._copies[self._EXTRAFRAME_OFFSET + 1] = self._seed[self._FRAME_LENGTH + 1] | |
self._computeHash(self._seed) | |
if self._seed[self._BYTES_OFFSET] > self._MAX_BYTES: | |
self._copy(self._seed, 0, self._copies, self._FRAME_OFFSET, self._FRAME_LENGTH) | |
self._copy(self._copies, self._EXTRAFRAME_OFFSET, self._seed, 0, self._FRAME_LENGTH) | |
self._computeHash(self._seed) | |
self._copy(self._copies, self._FRAME_OFFSET, self._seed, 0, self._FRAME_LENGTH) | |
self._counter += 1 | |
j = 0 | |
for i in range(self._EXTRAFRAME_OFFSET): | |
k = self._seed[self._HASH_OFFSET + i] | |
self._nextBytes[j] = c_uint8(k >> 24).value | |
self._nextBytes[j + 1] = c_uint8(k >> 16).value | |
self._nextBytes[j + 2] = c_uint8(k >> 8).value | |
self._nextBytes[j + 3] = c_uint8(k).value | |
j += 4 | |
self._nextBIndex = 0 | |
j = min(self._HASHBYTES_TO_USE, len(bytes_) - nextByteToReturn) | |
if j > 0: | |
self._copy(self._nextBytes, 0, bytes_, nextByteToReturn, j) | |
nextByteToReturn += j | |
self._nextBIndex += j | |
if nextByteToReturn >= len(bytes_): | |
break | |
def _computeHash(self, arrW): | |
def _rol(t, b): | |
return c_uint32((t << b) | (t >> (32-b))).value | |
a = arrW[self._HASH_OFFSET ] | |
b = arrW[self._HASH_OFFSET +1] | |
c = arrW[self._HASH_OFFSET +2] | |
d = arrW[self._HASH_OFFSET +3] | |
e = arrW[self._HASH_OFFSET +4] | |
temp = 0 | |
for t in range(16, 80): | |
temp = arrW[t-3] ^ arrW[t-8] ^ arrW[t-14] ^ arrW[t-16] | |
arrW[t] = _rol(temp, 1) | |
for t in range(0, 20): | |
temp = c_uint32(_rol(a, 5) + ((b & c) | ((~b) & d)) + (e + arrW[t] + 0x5A827999)).value | |
e = d | |
d = c | |
c = _rol(b, 30) | |
b = a | |
a = temp | |
for t in range(20, 40): | |
temp = c_uint32(_rol(a, 5) + (b ^ c ^ d) + (e + arrW[t] + 0x6ED9EBA1)).value | |
e = d | |
d = c | |
c = _rol(b, 30) | |
b = a | |
a = temp | |
for t in range(40, 60): | |
temp = c_uint32(_rol(a, 5) + ((b & c) | (b & d) | (c & d)) + (e + arrW[t] + 0x8F1BBCDC)).value | |
e = d | |
d = c | |
c = _rol(b, 30) | |
b = a | |
a = temp | |
for t in range(60, 80): | |
temp = c_uint32(_rol(a, 5) + (b ^ c ^ d) + (e + arrW[t] + 0xCA62C1D6)).value | |
e = d | |
d = c | |
c = _rol(b, 30) | |
b = a | |
a = temp | |
arrW[self._HASH_OFFSET+0] = c_uint32(arrW[self._HASH_OFFSET+0] + a).value | |
arrW[self._HASH_OFFSET+1] = c_uint32(arrW[self._HASH_OFFSET+1] + b).value | |
arrW[self._HASH_OFFSET+2] = c_uint32(arrW[self._HASH_OFFSET+2] + c).value | |
arrW[self._HASH_OFFSET+3] = c_uint32(arrW[self._HASH_OFFSET+3] + d).value | |
arrW[self._HASH_OFFSET+4] = c_uint32(arrW[self._HASH_OFFSET+4] + e).value | |
def _updateHash(self, intArray, byteInput, fromByte, toByte): | |
index = intArray[self._BYTES_OFFSET] | |
i = fromByte | |
maxWord = 0 | |
nBytes = 0 | |
wordIndex = index >>2 | |
byteIndex = index & 0x03 | |
intArray[self._BYTES_OFFSET] = (index + toByte - fromByte + 1) & 0o077 | |
if byteIndex: | |
while i <= toByte and byteIndex < 4: | |
intArray[wordIndex] |= c_uint8(byteInput[i]).value << ((3 - byteIndex)<<3) | |
byteIndex += 1 | |
i += 1 | |
if byteIndex == 4: | |
wordIndex += 1 | |
if wordIndex == 16: | |
self._computeHash(intArray) | |
wordIndex = 0 | |
if i > toByte: | |
return | |
maxWord = (toByte - i + 1) >> 2 | |
for k in range(0, maxWord): | |
intArray[wordIndex] = (c_uint8(byteInput[i]).value <<24) | (c_uint8(byteInput[i+1]).value <<16) | (c_uint8(byteInput[i+2]).value <<8) | c_uint8(byteInput[i+3]).value | |
i += 4 | |
wordIndex += 1 | |
if wordIndex < 16: | |
continue | |
self._computeHash(intArray) | |
wordIndex = 0 | |
nBytes = toByte - i +1 | |
if nBytes: | |
w = c_uint8(byteInput[i]).value <<24 | |
if nBytes != 1: | |
w |= c_uint8(byteInput[i+1]).value <<16 | |
if nBytes != 2: | |
w |= c_uint8(byteInput[i+2]).value <<8 | |
intArray[wordIndex] = w | |
return |
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