Adding support for SOCKS plain text authentication

This patch adds support for SOCKS plain text (username/password)
authentication as described in RFC 1929. It adds an optional third
parameter to the socks-proxy option, which is a file containing the
login credentials.

I've been using this patch for two weeks now and it does not seem to
cause any problem. The only modifications are in the SOCKS handshake
handling and the options parser.

Signed-Off-By: Pierre Bourdon <delroth@gmail.com>
Acked-by: Gert Doering <gert@greenie.muc.de>
Acked-by: David Sommerseth <dazo@users.sourceforge.net>
Signed-off-by: David Sommerseth <dazo@users.sourceforge.net>

init.c

@@ -259,6 +259,7 @@ init_proxy_dowork (struct context *c)
     {
       c->c1.socks_proxy = socks_proxy_new (c->options.ce.socks_proxy_server,
 					   c->options.ce.socks_proxy_port,
+					   c->options.ce.socks_proxy_authfile,
 					   c->options.ce.socks_proxy_retry,
 					   c->options.auto_proxy_info);
       if (c->c1.socks_proxy)

options.c

@@ -120,8 +120,11 @@ static const char usage_message[] =
   "                  AGENT user-agent\n"
 #endif
 #ifdef ENABLE_SOCKS
-  "--socks-proxy s [p]: Connect to remote host through a Socks5 proxy at address\n"
-  "                  s and port p (default port = 1080).\n"
+  "--socks-proxy s [p] [up] : Connect to remote host through a Socks5 proxy at\n"
+  "                  address s and port p (default port = 1080).\n"
+  "                  If proxy authentication is required,\n"
+  "                  up is a file containing username/password on 2 lines, or\n"
+  "                  'stdin' to prompt for console.\n"
   "--socks-proxy-retry : Retry indefinitely on Socks proxy errors.\n"
 #endif
   "--resolv-retry n: If hostname resolve fails for --remote, retry\n"
@@ -4283,6 +4286,7 @@ add_option (struct options *options,
 	  options->ce.socks_proxy_port = 1080;
 	}
       options->ce.socks_proxy_server = p[1];
+      options->ce.socks_proxy_authfile = p[3]; /* might be NULL */
     }
   else if (streq (p[0], "socks-proxy-retry"))
     {

options.h

@@ -95,6 +95,7 @@ struct connection_entry
 #ifdef ENABLE_SOCKS
   const char *socks_proxy_server;
   int socks_proxy_port;
+  const char *socks_proxy_authfile;
   bool socks_proxy_retry;
 #endif
 };

socks.c

@@ -23,10 +23,11 @@
  */
 
 /*
- * 2004-01-30: Added Socks5 proxy support
+ * 2004-01-30: Added Socks5 proxy support, see RFC 1928
  *   (Christof Meerwald, http://cmeerw.org)
  *
- * see RFC 1928, only supports "no authentication"
+ * 2010-10-10: Added Socks5 plain text authentication support (RFC 1929)
+ *   (Pierre Bourdon <delroth@gmail.com>)
  */
 
 #include "syshead.h"
@@ -38,10 +39,12 @@
 #include "win32.h"
 #include "socket.h"
 #include "fdmisc.h"
+#include "misc.h"
 #include "proxy.h"
 
 #include "memdbg.h"
 
+#define UP_TYPE_SOCKS		"SOCKS Proxy"
 
 void
 socks_adjust_frame_parameters (struct frame *frame, int proto)
@@ -53,6 +56,7 @@ socks_adjust_frame_parameters (struct frame *frame, int proto)
 struct socks_proxy_info *
 socks_proxy_new (const char *server,
 		 int port,
+		 const char *authfile,
 		 bool retry,
 		 struct auto_proxy_info *auto_proxy_info)
 {
@@ -77,6 +81,12 @@ socks_proxy_new (const char *server,
 
   strncpynt (p->server, server, sizeof (p->server));
   p->port = port;
+
+  if (authfile)
+    strncpynt (p->authfile, authfile, sizeof (p->authfile));
+  else
+    p->authfile[0] = 0;
+
   p->retry = retry;
   p->defined = true;
 
@@ -90,15 +100,99 @@ socks_proxy_close (struct socks_proxy_info *sp)
 }
 
 static bool
-socks_handshake (socket_descriptor_t sd, volatile int *signal_received)
+socks_username_password_auth (struct socks_proxy_info *p,
+                              socket_descriptor_t sd,
+                              volatile int *signal_received)
+{
+  char to_send[516];
+  char buf[2];
+  int len = 0;
+  const int timeout_sec = 5;
+  struct user_pass creds;
+  ssize_t size;
+
+  creds.defined = 0;
+
+  get_user_pass (&creds, p->authfile, UP_TYPE_SOCKS, GET_USER_PASS_MANAGEMENT);
+  snprintf (to_send, sizeof (to_send), "\x01%c%s%c%s", strlen(creds.username),
+            creds.username, strlen(creds.password), creds.password);
+  size = send (sd, to_send, strlen(to_send), MSG_NOSIGNAL);
+
+  if (size != strlen (to_send))
+    {
+      msg (D_LINK_ERRORS | M_ERRNO_SOCK, "socks_username_password_auth: TCP port write failed on send()");
+      return false;
+    }
+
+  while (len < 2)
+    {
+      int status;
+      ssize_t size;
+      fd_set reads;
+      struct timeval tv;
+      char c;
+
+      FD_ZERO (&reads);
+      FD_SET (sd, &reads);
+      tv.tv_sec = timeout_sec;
+      tv.tv_usec = 0;
+
+      status = select (sd + 1, &reads, NULL, NULL, &tv);
+
+      get_signal (signal_received);
+      if (*signal_received)
+	return false;
+
+      /* timeout? */
+      if (status == 0)
+	{
+	  msg (D_LINK_ERRORS | M_ERRNO_SOCK, "socks_username_password_auth: TCP port read timeout expired");
+	  return false;
+	}
+
+      /* error */
+      if (status < 0)
+	{
+	  msg (D_LINK_ERRORS | M_ERRNO_SOCK, "socks_username_password_auth: TCP port read failed on select()");
+	  return false;
+	}
+
+      /* read single char */
+      size = recv(sd, &c, 1, MSG_NOSIGNAL);
+
+      /* error? */
+      if (size != 1)
+	{
+	  msg (D_LINK_ERRORS | M_ERRNO_SOCK, "socks_username_password_auth: TCP port read failed on recv()");
+	  return false;
+	}
+
+      /* store char in buffer */
+      buf[len++] = c;
+    }
+
+  /* VER = 5, SUCCESS = 0 --> auth success */
+  if (buf[0] != 5 && buf[1] != 0)
+  {
+    msg (D_LINK_ERRORS, "socks_username_password_auth: server refused the authentication");
+    return false;
+  }
+
+  return true;
+}
+
+static bool
+socks_handshake (struct socks_proxy_info *p,
+                 socket_descriptor_t sd,
+                 volatile int *signal_received)
 {
   char buf[2];
   int len = 0;
   const int timeout_sec = 5;
 
-  /* VER = 5, NMETHODS = 1, METHODS = [0] */
-  const ssize_t size = send (sd, "\x05\x01\x00", 3, MSG_NOSIGNAL);
-  if (size != 3)
+  /* VER = 5, NMETHODS = 2, METHODS = [0 (no auth), 2 (plain login)] */
+  const ssize_t size = send (sd, "\x05\x02\x00\x02", 4, MSG_NOSIGNAL);
+  if (size != 4)
     {
       msg (D_LINK_ERRORS | M_ERRNO_SOCK, "socks_handshake: TCP port write failed on send()");
       return false;
@@ -151,13 +245,37 @@ socks_handshake (socket_descriptor_t sd, volatile int *signal_received)
       buf[len++] = c;
     }
 
-  /* VER == 5 && METHOD == 0 */
-  if (buf[0] != '\x05' || buf[1] != '\x00')
+  /* VER == 5 */
+  if (buf[0] != '\x05')
     {
       msg (D_LINK_ERRORS, "socks_handshake: Socks proxy returned bad status");
       return false;
     }
 
+  /* select the appropriate authentication method */
+  switch (buf[1])
+    {
+    case 0: /* no authentication */
+      break;
+
+    case 2: /* login/password */
+      if (!p->authfile[0])
+      {
+	msg(D_LINK_ERRORS, "socks_handshake: server asked for username/login auth but we were "
+	                   "not provided any credentials");
+	return false;
+      }
+
+      if (!socks_username_password_auth(p, sd, signal_received))
+	return false;
+
+      break;
+
+    default: /* unknown auth method */
+      msg(D_LINK_ERRORS, "socks_handshake: unknown SOCKS auth method");
+      return false;
+    }
+
   return true;
 }
 
@@ -281,7 +399,7 @@ establish_socks_proxy_passthru (struct socks_proxy_info *p,
   char buf[128];
   size_t len;
 
-  if (!socks_handshake (sd, signal_received))
+  if (!socks_handshake (p, sd, signal_received))
     goto error;
 
   /* format Socks CONNECT message */
@@ -328,7 +446,7 @@ establish_socks_proxy_udpassoc (struct socks_proxy_info *p,
 				struct openvpn_sockaddr *relay_addr,
 			        volatile int *signal_received)
 {
-  if (!socks_handshake (ctrl_sd, signal_received))
+  if (!socks_handshake (p, ctrl_sd, signal_received))
     goto error;
 
   {

socks.h

@@ -43,12 +43,14 @@ struct socks_proxy_info {
 
   char server[128];
   int port;
+  char authfile[256];
 };
 
 void socks_adjust_frame_parameters (struct frame *frame, int proto);
 
 struct socks_proxy_info *socks_proxy_new (const char *server,
 					  int port,
+					  const char *authfile,
 					  bool retry,
 					  struct auto_proxy_info *auto_proxy_info);