From 933e75b9a7b1d36c0bdca7f6f822cc944685c3c4 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?=E7=A0=B4=E5=A8=83=E9=85=B1?= <mmgac001@gmail.com>
Date: Tue, 20 Sep 2016 17:21:32 +0800
Subject: [PATCH] add auth_sha1_v4

---
 shadowsocks/obfsplugin/auth.py | 229 +++++++++++++++++++++++++++++++++
 1 file changed, 229 insertions(+)

diff --git a/shadowsocks/obfsplugin/auth.py b/shadowsocks/obfsplugin/auth.py
index 23b7cca..10aff0b 100644
--- a/shadowsocks/obfsplugin/auth.py
+++ b/shadowsocks/obfsplugin/auth.py
@@ -45,6 +45,9 @@ def create_auth_sha1_v2(method):
 def create_auth_sha1_v3(method):
     return auth_sha1_v3(method)
 
+def create_auth_sha1_v4(method):
+    return auth_sha1_v4(method)
+
 obfs_map = {
         'auth_sha1': (create_auth_sha1,),
         'auth_sha1_compatible': (create_auth_sha1,),
@@ -52,6 +55,8 @@ obfs_map = {
         'auth_sha1_v2_compatible': (create_auth_sha1_v2,),
         'auth_sha1_v3': (create_auth_sha1_v3,),
         'auth_sha1_v3_compatible': (create_auth_sha1_v3,),
+        'auth_sha1_v4': (create_auth_sha1_v4,),
+        'auth_sha1_v4_compatible': (create_auth_sha1_v4,),
 }
 
 def match_begin(str1, str2):
@@ -819,3 +824,227 @@ class auth_sha1_v3(verify_base):
             self.decrypt_packet_num += 1
         return (out_buf, sendback)
 
+class auth_sha1_v4(verify_base):
+    def __init__(self, method):
+        super(auth_sha1_v4, self).__init__(method)
+        self.recv_buf = b''
+        self.unit_len = 8100
+        self.decrypt_packet_num = 0
+        self.raw_trans = False
+        self.has_sent_header = False
+        self.has_recv_header = False
+        self.client_id = 0
+        self.connection_id = 0
+        self.max_time_dif = 60 * 60 * 24 # time dif (second) setting
+        self.salt = b"auth_sha1_v4"
+        self.no_compatible_method = 'auth_sha1_v4'
+
+    def init_data(self):
+        return obfs_auth_v2_data()
+
+    def set_server_info(self, server_info):
+        self.server_info = server_info
+        try:
+            max_client = int(server_info.protocol_param)
+        except:
+            max_client = 64
+        self.server_info.data.set_max_client(max_client)
+
+    def rnd_data(self, buf_size):
+        if buf_size > 1200:
+            return b'\x01'
+
+        if buf_size > 400:
+            rnd_data = os.urandom(common.ord(os.urandom(1)[0]) % 256)
+        else:
+            rnd_data = os.urandom(struct.unpack('>H', os.urandom(2))[0] % 512)
+
+        if len(rnd_data) < 128:
+            return common.chr(len(rnd_data) + 1) + rnd_data
+        else:
+            return common.chr(255) + struct.pack('>H', len(rnd_data) + 3) + rnd_data
+
+    def pack_data(self, buf):
+        data = self.rnd_data(len(buf)) + buf
+        data_len = len(data) + 8
+        crc = binascii.crc32(struct.pack('>H', data_len)) & 0xFFFF
+        data = struct.pack('<H', crc) + data
+        data = struct.pack('>H', data_len) + data
+        adler32 = zlib.adler32(data) & 0xFFFFFFFF
+        data += struct.pack('<I', adler32)
+        return data
+
+    def pack_auth_data(self, buf):
+        if len(buf) == 0:
+            return b''
+        data = self.rnd_data(len(buf)) + buf
+        data_len = len(data) + 16
+        crc = binascii.crc32(struct.pack('>H', data_len) + self.salt + self.server_info.key) & 0xFFFFFFFF
+        data = struct.pack('<I', crc) + data
+        data = struct.pack('>H', data_len) + data
+        data += hmac.new(self.server_info.iv + self.server_info.key, data, hashlib.sha1).digest()[:10]
+        return data
+
+    def auth_data(self):
+        utc_time = int(time.time()) & 0xFFFFFFFF
+        if self.server_info.data.connection_id > 0xFF000000:
+            self.server_info.data.local_client_id = b''
+        if not self.server_info.data.local_client_id:
+            self.server_info.data.local_client_id = os.urandom(4)
+            logging.debug("local_client_id %s" % (binascii.hexlify(self.server_info.data.local_client_id),))
+            self.server_info.data.connection_id = struct.unpack('<I', os.urandom(4))[0] & 0xFFFFFF
+        self.server_info.data.connection_id += 1
+        return b''.join([struct.pack('<I', utc_time),
+                self.server_info.data.local_client_id,
+                struct.pack('<I', self.server_info.data.connection_id)])
+
+    def client_pre_encrypt(self, buf):
+        ret = b''
+        if not self.has_sent_header:
+            head_size = self.get_head_size(buf, 30)
+            datalen = min(len(buf), random.randint(0, 31) + head_size)
+            ret += self.pack_auth_data(self.auth_data() + buf[:datalen])
+            buf = buf[datalen:]
+            self.has_sent_header = True
+        while len(buf) > self.unit_len:
+            ret += self.pack_data(buf[:self.unit_len])
+            buf = buf[self.unit_len:]
+        ret += self.pack_data(buf)
+        return ret
+
+    def client_post_decrypt(self, buf):
+        if self.raw_trans:
+            return buf
+        self.recv_buf += buf
+        out_buf = b''
+        while len(self.recv_buf) > 4:
+            crc = struct.pack('<H', binascii.crc32(self.recv_buf[:2]) & 0xFFFF)
+            if crc != self.recv_buf[2:4]:
+                raise Exception('client_post_decrypt data uncorrect crc')
+            length = struct.unpack('>H', self.recv_buf[:2])[0]
+            if length >= 8192 or length < 7:
+                self.raw_trans = True
+                self.recv_buf = b''
+                raise Exception('client_post_decrypt data error')
+            if length > len(self.recv_buf):
+                break
+
+            if struct.pack('<I', zlib.adler32(self.recv_buf[:length - 4]) & 0xFFFFFFFF) != self.recv_buf[length - 4:length]:
+                self.raw_trans = True
+                self.recv_buf = b''
+                raise Exception('client_post_decrypt data uncorrect checksum')
+
+            pos = common.ord(self.recv_buf[4])
+            if pos < 255:
+                pos += 4
+            else:
+                pos = struct.unpack('>H', self.recv_buf[5:7])[0] + 4
+            out_buf += self.recv_buf[pos:length - 4]
+            self.recv_buf = self.recv_buf[length:]
+
+        if out_buf:
+            self.decrypt_packet_num += 1
+        return out_buf
+
+    def server_pre_encrypt(self, buf):
+        if self.raw_trans:
+            return buf
+        ret = b''
+        while len(buf) > self.unit_len:
+            ret += self.pack_data(buf[:self.unit_len])
+            buf = buf[self.unit_len:]
+        ret += self.pack_data(buf)
+        return ret
+
+    def server_post_decrypt(self, buf):
+        if self.raw_trans:
+            return (buf, False)
+        self.recv_buf += buf
+        out_buf = b''
+        if not self.has_recv_header:
+            if len(self.recv_buf) <= 6:
+                return (b'', False)
+            crc = struct.pack('<I', binascii.crc32(self.recv_buf[:2] + self.salt + self.server_info.key) & 0xFFFFFFFF)
+            if crc != self.recv_buf[2:6]:
+                return self.not_match_return(self.recv_buf)
+            length = struct.unpack('>H', self.recv_buf[:2])[0]
+            if length > len(self.recv_buf):
+                return (b'', False)
+            sha1data = hmac.new(self.server_info.recv_iv + self.server_info.key, self.recv_buf[:length - 10], hashlib.sha1).digest()[:10]
+            if sha1data != self.recv_buf[length - 10:length]:
+                logging.error('auth_sha1_v4 data uncorrect auth HMAC-SHA1')
+                return self.not_match_return(self.recv_buf)
+            pos = common.ord(self.recv_buf[6])
+            if pos < 255:
+                pos += 6
+            else:
+                pos = struct.unpack('>H', self.recv_buf[7:9])[0] + 6
+            out_buf = self.recv_buf[pos:length - 10]
+            if len(out_buf) < 12:
+                logging.info('auth_sha1_v4: too short, data %s' % (binascii.hexlify(self.recv_buf),))
+                return self.not_match_return(self.recv_buf)
+            utc_time = struct.unpack('<I', out_buf[:4])[0]
+            client_id = struct.unpack('<I', out_buf[4:8])[0]
+            connection_id = struct.unpack('<I', out_buf[8:12])[0]
+            time_dif = common.int32(utc_time - (int(time.time()) & 0xffffffff))
+            if time_dif < -self.max_time_dif or time_dif > self.max_time_dif:
+                logging.info('auth_sha1_v4: wrong timestamp, time_dif %d, data %s' % (time_dif, binascii.hexlify(out_buf),))
+                return self.not_match_return(self.recv_buf)
+            elif self.server_info.data.insert(client_id, connection_id):
+                self.has_recv_header = True
+                out_buf = out_buf[12:]
+                self.client_id = client_id
+                self.connection_id = connection_id
+            else:
+                logging.info('auth_sha1_v4: auth fail, data %s' % (binascii.hexlify(out_buf),))
+                return self.not_match_return(self.recv_buf)
+            self.recv_buf = self.recv_buf[length:]
+            self.has_recv_header = True
+
+        sendback = False
+        while len(self.recv_buf) > 4:
+            crc = struct.pack('<H', binascii.crc32(self.recv_buf[:2]) & 0xFFFF)
+            if crc != self.recv_buf[2:4]:
+                self.raw_trans = True
+                logging.info('auth_sha1_v4: wrong crc')
+                if self.decrypt_packet_num == 0:
+                    logging.info('auth_sha1_v4: wrong crc')
+                    return (b'E', False)
+                else:
+                    raise Exception('server_post_decrype data error')
+            length = struct.unpack('>H', self.recv_buf[:2])[0]
+            if length >= 8192 or length < 7:
+                self.raw_trans = True
+                self.recv_buf = b''
+                if self.decrypt_packet_num == 0:
+                    logging.info('auth_sha1_v4: over size')
+                    return (b'E', False)
+                else:
+                    raise Exception('server_post_decrype data error')
+            if length > len(self.recv_buf):
+                break
+
+            if struct.pack('<I', zlib.adler32(self.recv_buf[:length - 4]) & 0xFFFFFFFF) != self.recv_buf[length - 4:length]:
+                logging.info('auth_sha1_v4: checksum error, data %s' % (binascii.hexlify(self.recv_buf[:length]),))
+                self.raw_trans = True
+                self.recv_buf = b''
+                if self.decrypt_packet_num == 0:
+                    return (b'E', False)
+                else:
+                    raise Exception('server_post_decrype data uncorrect checksum')
+
+            pos = common.ord(self.recv_buf[4])
+            if pos < 255:
+                pos += 4
+            else:
+                pos = struct.unpack('>H', self.recv_buf[5:7])[0] + 4
+            out_buf += self.recv_buf[pos:length - 4]
+            self.recv_buf = self.recv_buf[length:]
+            if pos == length - 4:
+                sendback = True
+
+        if out_buf:
+            self.server_info.data.update(self.client_id, self.connection_id)
+            self.decrypt_packet_num += 1
+        return (out_buf, sendback)
+