add "chacha20-ietf", libsodium version must be higher than 1.0.4, see https://github.com/jedisct1/libsodium/releases/

shadowsocks/crypto/sodium.py

@@ -52,6 +52,12 @@ def load_libsodium():
                                                         c_char_p, c_ulonglong,
                                                         c_char_p)
 
+    libsodium.crypto_stream_chacha20_ietf_xor_ic.restype = c_int
+    libsodium.crypto_stream_chacha20_ietf_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
 
@@ -68,6 +74,8 @@ class SodiumCrypto(object):
             self.cipher = libsodium.crypto_stream_salsa20_xor_ic
         elif cipher_name == 'chacha20':
             self.cipher = libsodium.crypto_stream_chacha20_xor_ic
+        elif cipher_name == 'chacha20-ietf':
+            self.cipher = libsodium.crypto_stream_chacha20_ietf_xor_ic
         else:
             raise Exception('Unknown cipher')
         # byte counter, not block counter
@@ -97,6 +105,7 @@ class SodiumCrypto(object):
 ciphers = {
     'salsa20': (32, 8, SodiumCrypto),
     'chacha20': (32, 8, SodiumCrypto),
+    'chacha20-ietf': (32, 12, SodiumCrypto),
 }
 
 
@@ -115,6 +124,14 @@ def test_chacha20():
     util.run_cipher(cipher, decipher)
 
 
+def test_chacha20_ietf():
+
+    cipher = SodiumCrypto('chacha20-ietf', b'k' * 32, b'i' * 16, 1)
+    decipher = SodiumCrypto('chacha20-ietf', b'k' * 32, b'i' * 16, 0)
+
+    util.run_cipher(cipher, decipher)
+
 if __name__ == '__main__':
+    test_chacha20_ietf()
     test_chacha20()
     test_salsa20()