Just for learn

crypto/sodium.py

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+#!/usr/bin/env python
+#
+# Copyright 2015 clowwindy
+#
+# 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.
+
+from __future__ import absolute_import, division, print_function, \
+    with_statement
+
+from ctypes import c_char_p, c_int, c_ulonglong, byref, \
+    create_string_buffer, c_void_p
+
+from shadowsocks.crypto import util
+
+__all__ = ['ciphers']
+
+libsodium = None
+loaded = False
+
+buf_size = 2048
+
+# for salsa20 and chacha20
+BLOCK_SIZE = 64
+
+
+def load_libsodium():
+    global loaded, libsodium, buf
+
+    libsodium = util.find_library('sodium', 'crypto_stream_salsa20_xor_ic',
+                                  'libsodium')
+    if libsodium is None:
+        raise Exception('libsodium not found')
+
+    libsodium.crypto_stream_salsa20_xor_ic.restype = c_int
+    libsodium.crypto_stream_salsa20_xor_ic.argtypes = (c_void_p, c_char_p,
+                                                       c_ulonglong,
+                                                       c_char_p, c_ulonglong,
+                                                       c_char_p)
+    libsodium.crypto_stream_chacha20_xor_ic.restype = c_int
+    libsodium.crypto_stream_chacha20_xor_ic.argtypes = (c_void_p, c_char_p,
+                                                        c_ulonglong,
+                                                        c_char_p, c_ulonglong,
+                                                        c_char_p)
+
+    buf = create_string_buffer(buf_size)
+    loaded = True
+
+
+class SodiumCrypto(object):
+    def __init__(self, cipher_name, key, iv, op):
+        if not loaded:
+            load_libsodium()
+        self.key = key
+        self.iv = iv
+        self.key_ptr = c_char_p(key)
+        self.iv_ptr = c_char_p(iv)
+        if cipher_name == 'salsa20':
+            self.cipher = libsodium.crypto_stream_salsa20_xor_ic
+        elif cipher_name == 'chacha20':
+            self.cipher = libsodium.crypto_stream_chacha20_xor_ic
+        else:
+            raise Exception('Unknown cipher')
+        # byte counter, not block counter
+        self.counter = 0
+
+    def update(self, data):
+        global buf_size, buf
+        l = len(data)
+
+        # we can only prepend some padding to make the encryption align to
+        # blocks
+        padding = self.counter % BLOCK_SIZE
+        if buf_size < padding + l:
+            buf_size = (padding + l) * 2
+            buf = create_string_buffer(buf_size)
+
+        if padding:
+            data = (b'\0' * padding) + data
+        self.cipher(byref(buf), c_char_p(data), padding + l,
+                    self.iv_ptr, int(self.counter / BLOCK_SIZE), self.key_ptr)
+        self.counter += l
+        # buf is copied to a str object when we access buf.raw
+        # strip off the padding
+        return buf.raw[padding:padding + l]
+
+
+ciphers = {
+    'salsa20': (32, 8, SodiumCrypto),
+    'chacha20': (32, 8, SodiumCrypto),
+}
+
+
+def test_salsa20():
+    cipher = SodiumCrypto('salsa20', b'k' * 32, b'i' * 16, 1)
+    decipher = SodiumCrypto('salsa20', b'k' * 32, b'i' * 16, 0)
+
+    util.run_cipher(cipher, decipher)
+
+
+def test_chacha20():
+
+    cipher = SodiumCrypto('chacha20', b'k' * 32, b'i' * 16, 1)
+    decipher = SodiumCrypto('chacha20', b'k' * 32, b'i' * 16, 0)
+
+    util.run_cipher(cipher, decipher)
+
+
+if __name__ == '__main__':
+    test_chacha20()
+    test_salsa20()