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#!/usr/bin/env python
# Copyright (c) 2011 The Chromium Authors. All rights reserved.
# Use of this source code is governed by a BSD-style license that can be
# found in the LICENSE file.
""" Read a CRX file and write out the App ID and the Full Hash of the ID.
See: http://code.google.com/chrome/extensions/crx.html
and 'http://stackoverflow.com/questions/'
+ '1882981/google-chrome-alphanumeric-hashes-to-identify-extensions'
for docs on the format.
"""
import sys
import hashlib
EXPECTED_CRX_MAGIC_NUM = 'Cr24'
EXPECTED_CRX_VERSION = 2
def usage(argv):
print "%s: crx_file" % argv[0]
def HexToInt(hex_chars):
""" Convert bytes like \xab -> 171 """
val = 0
for i in xrange(len(hex_chars)):
val += pow(256, i) * ord(hex_chars[i])
return val
def HexToMPDecimal(hex_chars):
""" Convert bytes to an MPDecimal string. Example \x00 -> "aa"
This gives us the AppID for a chrome extension.
"""
result = ''
base = ord('a')
for i in xrange(len(hex_chars)):
value = ord(hex_chars[i])
dig1 = value / 16
dig2 = value % 16
result += chr(dig1 + base)
result += chr(dig2 + base)
return result
def HexTo256(hex_chars):
""" Convert bytes to pairs of hex digits. E.g., \x00\x11 -> "{0x00, 0x11}"
The format is taylored for copy and paste into C code:
const uint8 sha256_hash[] = { ... }; """
result = []
for i in xrange(len(hex_chars)):
value = ord(hex_chars[i])
dig1 = value / 16
dig2 = value % 16
result.append('0x' + hex(dig1)[2:] + hex(dig2)[2:])
return '{%s}' % ', '.join(result)
def GetPublicKey(f):
magic_num = f.read(4)
if magic_num != EXPECTED_CRX_MAGIC_NUM:
raise 'Invalid magic number: %s (expecting %s)' % (magic_num,
EXPECTED_CRX_MAGIC_NUM)
version = f.read(4)
if not version[0] != EXPECTED_CRX_VERSION:
raise 'Invalid version number: %s (expecting %s)' % (version,
EXPECTED_CRX_VERSION)
pub_key_len_bytes = HexToInt(f.read(4))
sig_len_bytes = HexToInt(f.read(4))
pub_key = f.read(pub_key_len_bytes)
return pub_key
def GetCRXHash(filename):
f = open(filename, 'rb')
pub_key = GetPublicKey(f)
f.close()
pub_key_hash = hashlib.sha256(pub_key).digest()
return HexTo256(pub_key_hash)
def GetCRXAppID(filename):
f = open(filename, 'rb')
pub_key = GetPublicKey(f)
f.close()
pub_key_hash = hashlib.sha256(pub_key).digest()
# AppID is the MPDecimal of only the first 128 bits of the hash.
return HexToMPDecimal(pub_key_hash[:128/8])
def main(argv):
if len(argv) != 2:
usage(argv)
return 1
print 'Raw Bytes: %s' % GetCRXHash(sys.argv[1])
print 'AppID: %s' % GetCRXAppID(sys.argv[1])
if __name__ == '__main__':
sys.exit(main(sys.argv))
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