[omemo] Remove fallback GCM implementation
This commit is contained in:
Philipp Hörist
@@ -20,15 +20,11 @@
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import sys
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import logging
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from .aes_gcm_native import aes_decrypt
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from .aes_gcm_native import aes_encrypt
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log = logging.getLogger('gajim.plugin_system.omemo')
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try:
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from .aes_gcm_native import aes_decrypt
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from .aes_gcm_native import aes_encrypt
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log.debug('Using fast cryptography')
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except ImportError:
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from .aes_gcm_fallback import aes_decrypt
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from .aes_gcm_fallback import aes_encrypt
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log.debug('Using slow cryptography')
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def encrypt(key, iv, plaintext):
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@@ -1,162 +0,0 @@
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# -*- coding: utf-8 -*-
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#
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# Copyright 2014 Jonathan Zdziarski <jonathan@zdziarski.com>
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#
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# All rights reserved.
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#
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# Redistribution and use in source and binary forms, with or without
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# modification, are permitted provided that the following conditions are met:
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#
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# 1. Redistributions of source code must retain the above copyright notice, this
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# list of conditions and the following disclaimer.
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#
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# 2. Redistributions in binary form must reproduce the above copyright notice,
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# this list of conditions and the following disclaimer in the documentation
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# and/or other materials provided with the distribution.
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#
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# 3. Neither the name of the copyright holder nor the names of its contributors
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# may be used to endorse or promote products derived from this software without
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# specific prior written permission.
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#
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# THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
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# AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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# IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
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# DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
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# FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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# DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
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# SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
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# CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
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# OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
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# OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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import logging
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from struct import pack, unpack
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from Crypto.Cipher import AES
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from Crypto.Util import strxor
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log = logging.getLogger('gajim.plugin_system.omemo')
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def gcm_rightshift(vec):
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for x in range(15, 0, -1):
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c = vec[x] >> 1
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c |= (vec[x - 1] << 7) & 0x80
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vec[x] = c
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vec[0] >>= 1
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return vec
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def gcm_gf_mult(a, b):
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mask = [0x80, 0x40, 0x20, 0x10, 0x08, 0x04, 0x02, 0x01]
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poly = [0x00, 0xe1]
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Z = [0] * 16
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V = [c for c in a]
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for x in range(128):
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if b[x >> 3] & mask[x & 7]:
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Z = [V[y] ^ Z[y] for y in range(16)]
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bit = V[15] & 1
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V = gcm_rightshift(V)
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V[0] ^= poly[bit]
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return Z
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def ghash(h, auth_data, data):
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u = (16 - len(data)) % 16
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v = (16 - len(auth_data)) % 16
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x = auth_data + chr(0) * v + data + chr(0) * u
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x += pack('>QQ', len(auth_data) * 8, len(data) * 8)
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y = [0] * 16
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vec_h = [ord(c) for c in h]
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for i in range(0, len(x), 16):
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block = [ord(c) for c in x[i:i + 16]]
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y = [y[j] ^ block[j] for j in range(16)]
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y = gcm_gf_mult(y, vec_h)
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return ''.join(chr(c) for c in y)
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def inc32(block):
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counter, = unpack('>L', block[12:])
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counter += 1
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return block[:12] + pack('>L', counter)
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def gctr(k, icb, plaintext):
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y = ''
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if len(plaintext) == 0:
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return y
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aes = AES.new(k)
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cb = icb
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for i in range(0, len(plaintext), aes.block_size):
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cb = inc32(cb)
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encrypted = aes.encrypt(cb)
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plaintext_block = plaintext[i:i + aes.block_size]
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y += strxor.strxor(plaintext_block, encrypted[:len(plaintext_block)])
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return y
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def gcm_decrypt(k, iv, encrypted, auth_data, tag):
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aes = AES.new(k)
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h = aes.encrypt(chr(0) * aes.block_size)
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if len(iv) == 12:
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y0 = iv + "\x00\x00\x00\x01"
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else:
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y0 = ghash(h, '', iv)
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decrypted = gctr(k, y0, encrypted)
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s = ghash(h, auth_data, encrypted)
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t = aes.encrypt(y0)
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T = strxor.strxor(s, t)
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if T != tag:
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raise ValueError('Decrypted data is invalid')
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else:
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return decrypted
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def gcm_encrypt(k, iv, plaintext, auth_data):
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aes = AES.new(k)
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h = aes.encrypt(chr(0) * aes.block_size)
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if len(iv) == 12:
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y0 = iv + "\x00\x00\x00\x01"
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else:
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y0 = ghash(h, '', iv)
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encrypted = gctr(k, y0, plaintext)
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s = ghash(h, auth_data, encrypted)
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t = aes.encrypt(y0)
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T = strxor.strxor(s, t)
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return (encrypted, T)
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def aes_encrypt(key, nonce, plaintext):
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""" Use AES128 GCM with the given key and iv to encrypt the payload. """
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return gcm_encrypt(key, nonce, plaintext, '')
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def aes_decrypt(_key, nonce, payload):
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""" Use AES128 GCM with the given key and iv to decrypt the payload. """
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if len(_key) >= 32:
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# XEP-0384
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log.debug('XEP Compliant Key/Tag')
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ciphertext = payload
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key = _key[:16]
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mac = _key[16:]
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else:
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# Legacy
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log.debug('Legacy Key/Tag')
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ciphertext = payload[:-16]
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key = _key
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mac = payload[-16:]
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return gcm_decrypt(key, nonce, ciphertext, '', mac)
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