openvpn/plugin/examples/simple.c

   1 /*
   2  *  OpenVPN -- An application to securely tunnel IP networks
   3  *             over a single TCP/UDP port, with support for SSL/TLS-based
   4  *             session authentication and key exchange,
   5  *             packet encryption, packet authentication, and
   6  *             packet compression.
   7  *
   8  *  Copyright (C) 2002-2005 OpenVPN Solutions LLC <info@openvpn.net>
   9  *
  10  *  This program is free software; you can redistribute it and/or modify
  11  *  it under the terms of the GNU General Public License version 2
  12  *  as published by the Free Software Foundation.
  13  *
  14  *  This program is distributed in the hope that it will be useful,
  15  *  but WITHOUT ANY WARRANTY; without even the implied warranty of
  16  *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  17  *  GNU General Public License for more details.
  18  *
  19  *  You should have received a copy of the GNU General Public License
  20  *  along with this program (see the file COPYING included with this
  21  *  distribution); if not, write to the Free Software Foundation, Inc.,
  22  *  59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
  23  */
  24
  25 /*
  26  * This file implements a simple OpenVPN plugin module which
  27  * will examine the username/password provided by a client,
  28  * and make an accept/deny determination.  Will run
  29  * on Windows or *nix.
  30  *
  31  * See the README file for build instructions.
  32  */
  33
  34 #include <stdio.h>
  35 #include <string.h>
  36 #include <stdlib.h>
  37
  38 #include "openvpn-plugin.h"
  39
  40 /*
  41  * Our context, where we keep our state.
  42  */
  43 struct plugin_context {
  44   const char *username;
  45   const char *password;
  46 };
  47
  48 /*
  49  * Given an environmental variable name, search
  50  * the envp array for its value, returning it
  51  * if found or NULL otherwise.
  52  */
  53 static const char *
  54 get_env (const char *name, const char *envp[])
  55 {
  56   if (envp)
  57     {
  58       int i;
  59       const int namelen = strlen (name);
  60       for (i = 0; envp[i]; ++i)
  61         {
  62           if (!strncmp (envp[i], name, namelen))
  63             {
  64               const char *cp = envp[i] + namelen;
  65               if (*cp == '=')
  66                 return cp + 1;
  67             }
  68         }
  69     }
  70   return NULL;
  71 }
  72
  73 OPENVPN_EXPORT openvpn_plugin_handle_t
  74 openvpn_plugin_open_v1 (unsigned int *type_mask, const char *argv[], const char *envp[])
  75 {
  76   struct plugin_context *context;
  77
  78   /*
  79    * Allocate our context
  80    */
  81   context = (struct plugin_context *) calloc (1, sizeof (struct plugin_context));
  82
  83   /*
  84    * Set the username/password we will require.
  85    */
  86   context->username = "foo";
  87   context->password = "bar";
  88
  89   /*
  90    * We are only interested in intercepting the
  91    * --auth-user-pass-verify callback.
  92    */
  93   *type_mask = OPENVPN_PLUGIN_MASK (OPENVPN_PLUGIN_AUTH_USER_PASS_VERIFY);
  94
  95   return (openvpn_plugin_handle_t) context;
  96 }
  97
  98 OPENVPN_EXPORT int
  99 openvpn_plugin_func_v1 (openvpn_plugin_handle_t handle, const int type, const char *argv[], const char *envp[])
 100 {
 101   struct plugin_context *context = (struct plugin_context *) handle;
 102
 103   /* get username/password from envp string array */
 104   const char *username = get_env ("username", envp);
 105   const char *password = get_env ("password", envp);
 106
 107   /* check entered username/password against what we require */
 108   if (username && !strcmp (username, context->username)
 109       && password && !strcmp (password, context->password))
 110     return OPENVPN_PLUGIN_FUNC_SUCCESS;
 111   else
 112     return OPENVPN_PLUGIN_FUNC_ERROR;
 113 }
 114
 115 OPENVPN_EXPORT void
 116 openvpn_plugin_close_v1 (openvpn_plugin_handle_t handle)
 117 {
 118   struct plugin_context *context = (struct plugin_context *) handle;
 119   free (context);
 120 }