OpenVPN-2.2.2-obfs.patch

--- openvpn-2.2.2.orig/options.c 2011-12-14 00:58:56.000000000 +0800
+++ openvpn-2.2.2/options.c 2012-12-21 10:44:57.683130505 +0800
@@ -54,6 +54,10 @@
 
 #include "memdbg.h"
 
+extern char* _socket_obfs_salt;
+extern int _socket_obfs_salt_len;
+extern int _socket_obfs_padlen;
+
 const char title_string[] =
   PACKAGE_STRING
   " " TARGET_ALIAS
@@ -6008,6 +6012,19 @@
       options->persist_mode = 1;
     }
 #endif
+  else if (streq (p[0], "obfs-salt") && p[1])
+    {
+      VERIFY_PERMISSION (OPT_P_GENERAL);
+      _socket_obfs_salt = p[1];
+      _socket_obfs_salt_len = strlen(_socket_obfs_salt);
+    }
+  else if (streq (p[0], "obfs-padlen") && p[1])
+    {
+      VERIFY_PERMISSION (OPT_P_GENERAL);
+      _socket_obfs_padlen = atoi(p[1]);
+      if (_socket_obfs_padlen < 0) 
+	msg(M_ERR, "--obfs-padlen must be positive");
+    }
   else
     {
       if (file)
--- openvpn-2.2.2.orig/socket.c	2011-12-14 00:58:56.000000000 +0800
+++ openvpn-2.2.2/socket.c	2012-12-21 10:44:57.707131191 +0800
@@ -35,6 +35,56 @@
 
 #include "memdbg.h"
 
+const char* _socket_obfs_salt = NULL;
+int _socket_obfs_salt_len = 0;
+int _socket_obfs_padlen = 0;
+const unsigned int crc_table[] =
+{
+    0x00000000, 0x77073096, 0xee0e612c, 0x990951ba, 0x076dc419, 0x706af48f,
+    0xe963a535, 0x9e6495a3, 0x0edb8832, 0x79dcb8a4, 0xe0d5e91e, 0x97d2d988,
+    0x09b64c2b, 0x7eb17cbd, 0xe7b82d07, 0x90bf1d91, 0x1db71064, 0x6ab020f2,
+    0xf3b97148, 0x84be41de, 0x1adad47d, 0x6ddde4eb, 0xf4d4b551, 0x83d385c7,
+    0x136c9856, 0x646ba8c0, 0xfd62f97a, 0x8a65c9ec, 0x14015c4f, 0x63066cd9,
+    0xfa0f3d63, 0x8d080df5, 0x3b6e20c8, 0x4c69105e, 0xd56041e4, 0xa2677172,
+    0x3c03e4d1, 0x4b04d447, 0xd20d85fd, 0xa50ab56b, 0x35b5a8fa, 0x42b2986c,
+    0xdbbbc9d6, 0xacbcf940, 0x32d86ce3, 0x45df5c75, 0xdcd60dcf, 0xabd13d59,
+    0x26d930ac, 0x51de003a, 0xc8d75180, 0xbfd06116, 0x21b4f4b5, 0x56b3c423,
+    0xcfba9599, 0xb8bda50f, 0x2802b89e, 0x5f058808, 0xc60cd9b2, 0xb10be924,
+    0x2f6f7c87, 0x58684c11, 0xc1611dab, 0xb6662d3d, 0x76dc4190, 0x01db7106,
+    0x98d220bc, 0xefd5102a, 0x71b18589, 0x06b6b51f, 0x9fbfe4a5, 0xe8b8d433,
+    0x7807c9a2, 0x0f00f934, 0x9609a88e, 0xe10e9818, 0x7f6a0dbb, 0x086d3d2d,
+    0x91646c97, 0xe6635c01, 0x6b6b51f4, 0x1c6c6162, 0x856530d8, 0xf262004e,
+    0x6c0695ed, 0x1b01a57b, 0x8208f4c1, 0xf50fc457, 0x65b0d9c6, 0x12b7e950,
+    0x8bbeb8ea, 0xfcb9887c, 0x62dd1ddf, 0x15da2d49, 0x8cd37cf3, 0xfbd44c65,
+    0x4db26158, 0x3ab551ce, 0xa3bc0074, 0xd4bb30e2, 0x4adfa541, 0x3dd895d7,
+    0xa4d1c46d, 0xd3d6f4fb, 0x4369e96a, 0x346ed9fc, 0xad678846, 0xda60b8d0,
+    0x44042d73, 0x33031de5, 0xaa0a4c5f, 0xdd0d7cc9, 0x5005713c, 0x270241aa,
+    0xbe0b1010, 0xc90c2086, 0x5768b525, 0x206f85b3, 0xb966d409, 0xce61e49f,
+    0x5edef90e, 0x29d9c998, 0xb0d09822, 0xc7d7a8b4, 0x59b33d17, 0x2eb40d81,
+    0xb7bd5c3b, 0xc0ba6cad, 0xedb88320, 0x9abfb3b6, 0x03b6e20c, 0x74b1d29a,
+    0xead54739, 0x9dd277af, 0x04db2615, 0x73dc1683, 0xe3630b12, 0x94643b84,
+    0x0d6d6a3e, 0x7a6a5aa8, 0xe40ecf0b, 0x9309ff9d, 0x0a00ae27, 0x7d079eb1,
+    0xf00f9344, 0x8708a3d2, 0x1e01f268, 0x6906c2fe, 0xf762575d, 0x806567cb,
+    0x196c3671, 0x6e6b06e7, 0xfed41b76, 0x89d32be0, 0x10da7a5a, 0x67dd4acc,
+    0xf9b9df6f, 0x8ebeeff9, 0x17b7be43, 0x60b08ed5, 0xd6d6a3e8, 0xa1d1937e,
+    0x38d8c2c4, 0x4fdff252, 0xd1bb67f1, 0xa6bc5767, 0x3fb506dd, 0x48b2364b,
+    0xd80d2bda, 0xaf0a1b4c, 0x36034af6, 0x41047a60, 0xdf60efc3, 0xa867df55,
+    0x316e8eef, 0x4669be79, 0xcb61b38c, 0xbc66831a, 0x256fd2a0, 0x5268e236,
+    0xcc0c7795, 0xbb0b4703, 0x220216b9, 0x5505262f, 0xc5ba3bbe, 0xb2bd0b28,
+    0x2bb45a92, 0x5cb36a04, 0xc2d7ffa7, 0xb5d0cf31, 0x2cd99e8b, 0x5bdeae1d,
+    0x9b64c2b0, 0xec63f226, 0x756aa39c, 0x026d930a, 0x9c0906a9, 0xeb0e363f,
+    0x72076785, 0x05005713, 0x95bf4a82, 0xe2b87a14, 0x7bb12bae, 0x0cb61b38,
+    0x92d28e9b, 0xe5d5be0d, 0x7cdcefb7, 0x0bdbdf21, 0x86d3d2d4, 0xf1d4e242,
+    0x68ddb3f8, 0x1fda836e, 0x81be16cd, 0xf6b9265b, 0x6fb077e1, 0x18b74777,
+    0x88085ae6, 0xff0f6a70, 0x66063bca, 0x11010b5c, 0x8f659eff, 0xf862ae69,
+    0x616bffd3, 0x166ccf45, 0xa00ae278, 0xd70dd2ee, 0x4e048354, 0x3903b3c2,
+    0xa7672661, 0xd06016f7, 0x4969474d, 0x3e6e77db, 0xaed16a4a, 0xd9d65adc,
+    0x40df0b66, 0x37d83bf0, 0xa9bcae53, 0xdebb9ec5, 0x47b2cf7f, 0x30b5ffe9,
+    0xbdbdf21c, 0xcabac28a, 0x53b39330, 0x24b4a3a6, 0xbad03605, 0xcdd70693,
+    0x54de5729, 0x23d967bf, 0xb3667a2e, 0xc4614ab8, 0x5d681b02, 0x2a6f2b94,
+    0xb40bbe37, 0xc30c8ea1, 0x5a05df1b, 0x2d02ef8d
+};
+
 const int proto_overhead[] = { /* indexed by PROTO_x */
   IPv4_UDP_HEADER_SIZE,
   IPv4_TCP_HEADER_SIZE,
@@ -42,6 +46,57 @@
   IPv4_TCP_HEADER_SIZE
 };
 
+/**
+ * @return int	The length of the random string that should be padding to the packet
+ */
+int obfs_buffer(const struct buffer* buf, const void* rand, int randlen, int maxpadlen) {
+  unsigned char md[SHA_DIGEST_LENGTH];
+  unsigned char iv[randlen + _socket_obfs_salt_len + SHA_DIGEST_LENGTH];
+  unsigned char *c;
+  int i, len, pad_len = 0;
+
+  if (maxpadlen > 255)
+    maxpadlen = 255;
+  
+  /* key_1 = SHA1(rand + obfs_salt) */
+  /* pad_len = Low _rand_pad_level_ bits of (unsigned char)MD5(rand + obfs_salt)[0] */
+  memcpy(iv, rand, randlen);
+  memcpy(iv + randlen, _socket_obfs_salt, _socket_obfs_salt_len);
+  
+  /* Caculate length of padding string */
+  ASSERT(SHA_DIGEST_LENGTH >= MD5_DIGEST_LENGTH);
+  MD5(iv, randlen + _socket_obfs_salt_len, md);	/* SHA_DIGEST_LENGTH is bigger than MD5_DIGEST_LENGTH, it's safe here */
+  if (maxpadlen <= 0)
+    pad_len = 0;
+  else
+    pad_len = md[0] % (maxpadlen + 1);
+  
+  /* Obsfucation data */
+  len = BLEN(buf);
+  SHA1(iv, randlen + _socket_obfs_salt_len, md);  
+  for (i = 0, c = BPTR(buf); i < len; i++, c++)
+  {
+    *c ^= md[i % SHA_DIGEST_LENGTH];
+    
+    /* Regenerate obsfuction key: key_n+1 = SHA1(key_n) */
+    if (i % SHA_DIGEST_LENGTH == SHA_DIGEST_LENGTH - 1)
+    {
+      memcpy(iv, md, SHA_DIGEST_LENGTH);
+      SHA1(iv, SHA_DIGEST_LENGTH, md);
+    }
+  }
+  
+  return pad_len;
+}
+
+inline unsigned int crc32(unsigned int crc,unsigned char *buffer, unsigned int size)  
+{  
+    unsigned int i;  
+    for (i = 0; i < size; i++) {  
+        crc = crc_table[(crc ^ buffer[i]) & 0xff] ^ (crc >> 8);  
+    }  
+    return crc ;  
+} 
 /*
  * Convert sockflags/getaddr_flags into getaddr_flags
  */
--- openvpn-2.2.2.orig/socket.h	2011-12-14 00:58:56.000000000 +0800
+++ openvpn-2.2.2/socket.h	2013-01-24 10:48:37.559033278 +0800
@@ -36,6 +36,12 @@
 #include "socks.h"
 #include "misc.h"
 
+extern int _socket_obfs_salt_len;
+extern int _socket_obfs_padlen;
+
+int obfs_buffer(const struct buffer* buf, const void* rand, int randlen, int rand_pad_level);
+inline unsigned int crc32(unsigned int crc,unsigned char *buffer, unsigned int size) ;
+
 /*
  * OpenVPN's default port number as assigned by IANA.
  */
@@ -740,28 +745,61 @@
 		  int maxsize,
 		  struct link_socket_actual *from)
 {
+  int res;
+  
+  struct buffer tbuf;
+  
+  
   if (sock->info.proto == PROTO_UDPv4)
     {
-      int res;
-
 #ifdef WIN32
       res = link_socket_read_udp_win32 (sock, buf, from);
 #else
       res = link_socket_read_udp_posix (sock, buf, maxsize, from);
 #endif
-      return res;
     }
   else if (sock->info.proto == PROTO_TCPv4_SERVER || sock->info.proto == PROTO_TCPv4_CLIENT)
     {
       /* from address was returned by accept */
       from->dest.sa = sock->info.lsa->actual.dest.sa;
-      return link_socket_read_tcp (sock, buf);
+      res = link_socket_read_tcp (sock, buf);
     }
   else
     {
       ASSERT (0);
       return -1; /* NOTREACHED */
     }
+    
+    /* Decode obsfucated traffic */
+    if (_socket_obfs_salt_len > 0 && BLEN(buf) > 4)
+    {
+      int r;
+      int pad_len = 0;
+      unsigned int crc = 0xffffffff;
+      unsigned int crc_r;
+      memcpy((void*)&crc_r, BPTR(buf), 4);
+      memcpy((void*)&r, BPTR(buf)+4, 4);
+      msg(M_DEBUG, "1, read buflen=%d crc=%x", BLEN(buf),crc_r);
+      r^=crc_r;
+      tbuf = alloc_buf(BLEN(buf) - 4);
+      buf_copy_range(&tbuf, 0, buf, 8, BLEN(buf) - 8);
+      pad_len = obfs_buffer(&tbuf, &r, 4, _socket_obfs_padlen);
+     
+      /* Remove padding random string */
+      buf_clear(buf);
+      buf_prepend(buf, BLEN(&tbuf) - pad_len);
+      buf_copy_range(buf, 0, &tbuf, 0, BLEN(&tbuf) - pad_len);
+      crc = crc32(crc,BPTR(buf),BLEN(buf));
+      msg(M_DEBUG, "1, read buflen=%d, padlen=%d", BLEN(buf), pad_len);
+      if(crc != crc_r) msg(M_DEBUG, "3, CRC error %x", crc);
+      free_buf(&tbuf);
+      
+      res -= 8;
+      res -= pad_len;
+      
+    }
+    
+    return res;
 }
 
 /*
@@ -846,6 +883,38 @@
 		   struct buffer *buf,
 		   struct link_socket_actual *to)
 {
+  struct buffer tbuf;
+  
+  /* Obsfucate traffic */
+  if (_socket_obfs_salt_len > 0)
+  {
+    int pad_len, i;
+    int r = rand();
+    unsigned int crc = 0xffffffff;
+    crc = crc32(crc,BPTR(buf),BLEN(buf));
+    msg(M_DEBUG, "1, write buflen=%d", BLEN(buf));
+    pad_len = obfs_buffer(buf, &r, sizeof(r), _socket_obfs_padlen);
+    r^=crc;
+    tbuf = alloc_buf(BLEN(buf) + 8 + pad_len);
+    buf_write(&tbuf, (void*)&crc, 4);
+    buf_write(&tbuf, (void*)&r, 4);
+    buf_copy_range(&tbuf, 8, buf, 0, BLEN(buf));
+    for (i = 0; i < pad_len; i++) 
+    {
+      if (unlikely(i % 4 == 0)) 
+	r = rand();
+      
+      buf_write(&tbuf, (void*)&r + i % 4, 1);
+    }
+    
+    buf_copy_range(buf, 0, &tbuf, 0, BLEN(&tbuf));
+    
+    msg(M_DEBUG, "2, write buflen=%d", BLEN(buf));
+          
+    free_buf(&tbuf);
+  }
+  
+  
   if (sock->info.proto == PROTO_UDPv4)
     {
       return link_socket_write_udp (sock, buf, to);