Reverted plugin directory location.

git-svn-id: http://svn.openvpn.net/projects/openvpn/branches/BETA21/openvpn@638 e7ae566f-a301-0410-adde-c780ea21d3b5

6 files changed, 1054 insertions, 0 deletions

diff --git a/plugin/auth-pam/.svnignore b/plugin/auth-pam/.svnignore
new file mode 100644
index 0000000..140f8cf
--- /dev/null
+++ b/plugin/auth-pam/.svnignore
@@ -0,0 +1 @@
+*.so
diff --git a/plugin/auth-pam/Makefile b/plugin/auth-pam/Makefile
new file mode 100755
index 0000000..3e7c6ce
--- /dev/null
+++ b/plugin/auth-pam/Makefile
@@ -0,0 +1,30 @@
+#
+# Build the OpenVPN auth-pam plugin module.
+#
+
+# If PAM modules are not linked against libpam.so, set DLOPEN_PAM to 1. This
+# must be done on SUSE 9.1, at least.
+DLOPEN_PAM=1
+
+ifeq ($(DLOPEN_PAM),1)
+	LIBPAM=-ldl
+else
+	LIBPAM=-lpam
+endif
+
+# This directory is where we will look for openvpn-plugin.h
+INCLUDE=-I../..
+
+CC_FLAGS=-O2 -Wall -DDLOPEN_PAM=$(DLOPEN_PAM)
+
+openvpn-auth-pam.so : auth-pam.o pamdl.o
+	gcc ${CC_FLAGS} -fPIC -shared -Wl,-soname,openvpn-auth-pam.so -o openvpn-auth-pam.so auth-pam.o pamdl.o -lc $(LIBPAM)
+
+auth-pam.o : auth-pam.c pamdl.h
+	gcc ${CC_FLAGS} -fPIC -c ${INCLUDE} auth-pam.c
+
+pamdl.o : pamdl.c pamdl.h
+	gcc ${CC_FLAGS} -fPIC -c ${INCLUDE} pamdl.c
+
+clean :
+	rm -f *.o *.so
diff --git a/plugin/auth-pam/README b/plugin/auth-pam/README
new file mode 100644
index 0000000..c957c02
--- /dev/null
+++ b/plugin/auth-pam/README
@@ -0,0 +1,74 @@
+openvpn-auth-pam
+
+SYNOPSIS
+
+The openvpn-auth-pam module implements username/password
+authentication via PAM, and essentially allows any authentication
+method supported by PAM (such as LDAP, RADIUS, or Linux Shadow
+passwords) to be used with OpenVPN.  While PAM supports
+username/password authentication, this can be combined with X509
+certificates to provide two indepedent levels of authentication.
+
+This module uses a split privilege execution model which will
+function even if you drop openvpn daemon privileges using the user,
+group, or chroot directives.
+
+BUILD
+
+To build openvpn-auth-pam, you will need to have the pam-devel
+package installed.
+
+Build with the "make" command.  The module will be named
+openvpn-auth-pam.so
+
+USAGE
+
+To use this plugin module, add to your OpenVPN config file:
+
+  plugin openvpn-auth-pam.so service-type
+
+The required service-type parameter corresponds to
+the PAM service definition file usually found
+in /etc/pam.d.
+
+This plugin also supports the usage of a list of name/value
+pairs to answer PAM module queries.
+
+For example:
+
+  plugin openvpn-auth-pam.so "login login USERNAME password PASSWORD"
+
+tells auth-pam to (a) use the "login" PAM module, (b) answer a
+"login" query with the username given by the OpenVPN client, and
+(c) answer a "password" query with the password given by the
+OpenVPN client.  This provides flexibility in dealing with the different
+types of query strings which different PAM modules might generate.
+For example, suppose you were using a PAM module called
+"test" which queried for "name" rather than "login":
+
+  plugin openvpn-auth-pam.so "test name USERNAME password PASSWORD"
+
+While "USERNAME" and "PASSWORD" are special strings which substitute
+to client-supplied values, it is also possible to name literal values
+to use as PAM module query responses.  For example, suppose that the
+login module queried for a third parameter, "domain" which
+is to be answered with the constant value "mydomain.com":
+
+  plugin openvpn-auth-pam.so "login login USERNAME password PASSWORD domain mydomain.com"
+
+The following OpenVPN directives can also influence
+the operation of this plugin:
+
+  client-cert-not-required
+  username-as-common-name
+
+Run OpenVPN with --verb 7 or higher to get debugging output from
+this plugin, including the list of queries presented by the
+underlying PAM module.  This is a useful debugging tool to figure
+out which queries a given PAM module is making, so that you can
+craft the appropriate plugin directive to answer it.
+
+CAVEATS
+
+This module will only work on *nix systems which support PAM,
+not Windows.
diff --git a/plugin/auth-pam/auth-pam.c b/plugin/auth-pam/auth-pam.c
new file mode 100644
index 0000000..a2b2934
--- /dev/null
+++ b/plugin/auth-pam/auth-pam.c
@@ -0,0 +1,761 @@
+/*
+ *  OpenVPN -- An application to securely tunnel IP networks
+ *             over a single TCP/UDP port, with support for SSL/TLS-based
+ *             session authentication and key exchange,
+ *             packet encryption, packet authentication, and
+ *             packet compression.
+ *
+ *  Copyright (C) 2002-2005 OpenVPN Solutions LLC <info@openvpn.net>
+ *
+ *  This program is free software; you can redistribute it and/or modify
+ *  it under the terms of the GNU General Public License version 2
+ *  as published by the Free Software Foundation.
+ *
+ *  This program is distributed in the hope that it will be useful,
+ *  but WITHOUT ANY WARRANTY; without even the implied warranty of
+ *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ *  GNU General Public License for more details.
+ *
+ *  You should have received a copy of the GNU General Public License
+ *  along with this program (see the file COPYING included with this
+ *  distribution); if not, write to the Free Software Foundation, Inc.,
+ *  59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
+ */
+
+/*
+ * OpenVPN plugin module to do PAM authentication using a split
+ * privilege model.
+ */
+
+#if DLOPEN_PAM
+#include <dlfcn.h>
+#include "pamdl.h"
+#else
+#include <security/pam_appl.h>
+#endif
+
+#include <stdio.h>
+#include <string.h>
+#include <ctype.h>
+#include <unistd.h>
+#include <stdlib.h>
+#include <sys/types.h>
+#include <sys/socket.h>
+#include <sys/wait.h>
+#include <fcntl.h>
+#include <signal.h>
+#include <syslog.h>
+
+#include "openvpn-plugin.h"
+
+#define DEBUG(verb) ((verb) >= 4)
+
+/* Command codes for foreground -> background communication */
+#define COMMAND_VERIFY 0
+#define COMMAND_EXIT   1
+
+/* Response codes for background -> foreground communication */
+#define RESPONSE_INIT_SUCCEEDED   10
+#define RESPONSE_INIT_FAILED      11
+#define RESPONSE_VERIFY_SUCCEEDED 12
+#define RESPONSE_VERIFY_FAILED    13
+
+/*
+ * Plugin state, used by foreground
+ */
+struct auth_pam_context
+{
+  /* Foreground's socket to background process */
+  int foreground_fd;
+
+  /* Process ID of background process */
+  pid_t background_pid;
+
+  /* Verbosity level of OpenVPN */
+  int verb;
+};
+
+/*
+ * Name/Value pairs for conversation function.
+ * Special Values:
+ *
+ *  "USERNAME" -- substitute client-supplied username
+ *  "PASSWORD" -- substitute client-specified password
+ */
+
+#define N_NAME_VALUE 16
+
+struct name_value {
+  const char *name;
+  const char *value;
+};
+
+struct name_value_list {
+  int len;
+  struct name_value data[N_NAME_VALUE];
+};
+
+/*
+ * Used to pass the username/password
+ * to the PAM conversation function.
+ */
+struct user_pass {
+  int verb;
+
+  char username[128];
+  char password[128];
+
+  const struct name_value_list *name_value_list;
+};
+
+/* Background process function */
+static void pam_server (int fd, const char *service, int verb, const struct name_value_list *name_value_list);
+
+/*
+ * Given an environmental variable name, search
+ * the envp array for its value, returning it
+ * if found or NULL otherwise.
+ */
+static const char *
+get_env (const char *name, const char *envp[])
+{
+  if (envp)
+    {
+      int i;
+      const int namelen = strlen (name);
+      for (i = 0; envp[i]; ++i)
+	{
+	  if (!strncmp (envp[i], name, namelen))
+	    {
+	      const char *cp = envp[i] + namelen;
+	      if (*cp == '=')
+		return cp + 1;
+	    }
+	}
+    }
+  return NULL;
+}
+
+/*
+ * Return the length of a string array
+ */
+static int
+string_array_len (const char *array[])
+{
+  int i = 0;
+  if (array)
+    {
+      while (array[i])
+	++i;
+    }
+  return i;
+}
+
+/*
+ * Socket read/write functions.
+ */
+
+static int
+recv_control (int fd)
+{
+  unsigned char c;
+  const ssize_t size = read (fd, &c, sizeof (c));
+  if (size == sizeof (c))
+    return c;
+  else
+    {
+      /*fprintf (stderr, "AUTH-PAM: DEBUG recv_control.read=%d\n", (int)size);*/
+      return -1;
+    }
+}
+
+static int
+send_control (int fd, int code)
+{
+  unsigned char c = (unsigned char) code;
+  const ssize_t size = write (fd, &c, sizeof (c));
+  if (size == sizeof (c))
+    return (int) size;
+  else
+    return -1;
+}
+
+static int
+recv_string (int fd, char *buffer, int len)
+{
+  if (len > 0)
+    {
+      ssize_t size;
+      memset (buffer, 0, len);
+      size = read (fd, buffer, len);
+      buffer[len-1] = 0;
+      if (size >= 1)
+	return (int)size;
+    }
+  return -1;
+}
+
+static int
+send_string (int fd, const char *string)
+{
+  const int len = strlen (string) + 1;
+  const ssize_t size = write (fd, string, len);
+  if (size == len)
+    return (int) size;
+  else
+    return -1;
+}
+
+#ifdef DO_DAEMONIZE
+
+/*
+ * Daemonize if "daemon" env var is true.
+ * Preserve stderr across daemonization if
+ * "daemon_log_redirect" env var is true.
+ */
+static void
+daemonize (const char *envp[])
+{
+  const char *daemon_string = get_env ("daemon", envp);
+  if (daemon_string && daemon_string[0] == '1')
+    {
+      const char *log_redirect = get_env ("daemon_log_redirect", envp);
+      int fd = -1;
+      if (log_redirect && log_redirect[0] == '1')
+	fd = dup (2);
+      if (daemon (0, 0) < 0)
+	{
+	  fprintf (stderr, "AUTH-PAM: daemonization failed\n");
+	}
+      else if (fd >= 3)
+	{
+	  dup2 (fd, 2);
+	  close (fd);
+	}
+    }
+}
+
+#endif
+
+/*
+ * Close most of parent's fds.
+ * Keep stdin/stdout/stderr, plus one
+ * other fd which is presumed to be
+ * our pipe back to parent.
+ * Admittedly, a bit of a kludge,
+ * but posix doesn't give us a kind
+ * of FD_CLOEXEC which will stop
+ * fds from crossing a fork().
+ */
+static void
+close_fds_except (int keep)
+{
+  int i;
+  closelog ();
+  for (i = 3; i <= 100; ++i)
+    {
+      if (i != keep)
+	close (i);
+    }
+}
+
+/*
+ * Usually we ignore signals, because our parent will
+ * deal with them.
+ */
+static void
+set_signals (void)
+{
+  signal (SIGTERM, SIG_DFL);
+
+  signal (SIGINT, SIG_IGN);
+  signal (SIGHUP, SIG_IGN);
+  signal (SIGUSR1, SIG_IGN);
+  signal (SIGUSR2, SIG_IGN);
+  signal (SIGPIPE, SIG_IGN);
+}
+
+/*
+ * Return 1 if query matches match.
+ */
+static int
+name_value_match (const char *query, const char *match)
+{
+  while (!isalnum (*query))
+    {
+      if (*query == '\0')
+	return 0;
+      ++query;
+    }
+  return strncasecmp (match, query, strlen (match)) == 0;
+}
+
+OPENVPN_EXPORT openvpn_plugin_handle_t
+openvpn_plugin_open_v1 (unsigned int *type_mask, const char *argv[], const char *envp[])
+{
+  pid_t pid;
+  int fd[2];
+
+  struct auth_pam_context *context;
+  struct name_value_list name_value_list;
+
+  const int base_parms = 2;
+
+  /*
+   * Allocate our context
+   */
+  context = (struct auth_pam_context *) calloc (1, sizeof (struct auth_pam_context));
+  context->foreground_fd = -1;
+
+  /*
+   * Intercept the --auth-user-pass-verify callback.
+   */
+  *type_mask = OPENVPN_PLUGIN_MASK (OPENVPN_PLUGIN_AUTH_USER_PASS_VERIFY);
+
+  /*
+   * Make sure we have two string arguments: the first is the .so name,
+   * the second is the PAM service type.
+   */
+  if (string_array_len (argv) < base_parms)
+    {
+      fprintf (stderr, "AUTH-PAM: need PAM service parameter\n");
+      goto error;
+    }
+
+  /*
+   * See if we have optional name/value pairs to match against
+   * PAM module queried fields in the conversation function.
+   */
+  name_value_list.len = 0;
+  if (string_array_len (argv) > base_parms)
+    {
+      const int nv_len = string_array_len (argv) - base_parms;
+      int i;
+
+      if ((nv_len & 1) == 1 || (nv_len / 2) > N_NAME_VALUE)
+	{
+	  fprintf (stderr, "AUTH-PAM: bad name/value list length\n");
+	  goto error;
+	}
+
+      name_value_list.len = nv_len / 2;
+      for (i = 0; i < name_value_list.len; ++i)
+	{
+	  const int base = base_parms + i * 2;
+	  name_value_list.data[i].name = argv[base];
+	  name_value_list.data[i].value = argv[base+1];
+	}
+    }
+
+  /*
+   * Get verbosity level from environment
+   */
+  {
+    const char *verb_string = get_env ("verb", envp);
+    if (verb_string)
+      context->verb = atoi (verb_string);
+  }
+
+  /*
+   * Make a socket for foreground and background processes
+   * to communicate.
+   */
+  if (socketpair (PF_UNIX, SOCK_DGRAM, 0, fd) == -1)
+    {
+      fprintf (stderr, "AUTH-PAM: socketpair call failed\n");
+      goto error;
+    }
+
+  /*
+   * Fork off the privileged process.  It will remain privileged
+   * even after the foreground process drops its privileges.
+   */
+  pid = fork ();
+
+  if (pid)
+    {
+      int status;
+
+      /*
+       * Foreground Process
+       */
+
+      context->background_pid = pid;
+
+      /* close our copy of child's socket */
+      close (fd[1]);
+
+      /* don't let future subprocesses inherit child socket */
+      if (fcntl (fd[0], F_SETFD, FD_CLOEXEC) < 0)
+	fprintf (stderr, "AUTH-PAM: Set FD_CLOEXEC flag on socket file descriptor failed\n");
+
+      /* wait for background child process to initialize */
+      status = recv_control (fd[0]);
+      if (status == RESPONSE_INIT_SUCCEEDED)
+	{
+	  context->foreground_fd = fd[0];
+	  return (openvpn_plugin_handle_t) context;
+	}
+    }
+  else
+    {
+      /*
+       * Background Process
+       */
+
+      /* close all parent fds except our socket back to parent */
+      close_fds_except (fd[1]);
+
+      /* Ignore most signals (the parent will receive them) */
+      set_signals ();
+
+#ifdef DO_DAEMONIZE
+      /* Daemonize if --daemon option is set. */
+      daemonize (envp);
+#endif
+
+      /* execute the event loop */
+      pam_server (fd[1], argv[1], context->verb, &name_value_list);
+
+      close (fd[1]);
+
+      exit (0);
+      return 0; /* NOTREACHED */
+    }
+
+ error:
+  if (context)
+    free (context);
+  return NULL;
+}
+
+OPENVPN_EXPORT int
+openvpn_plugin_func_v1 (openvpn_plugin_handle_t handle, const int type, const char *argv[], const char *envp[])
+{
+  struct auth_pam_context *context = (struct auth_pam_context *) handle;
+
+  if (type == OPENVPN_PLUGIN_AUTH_USER_PASS_VERIFY && context->foreground_fd >= 0)
+    {
+      /* get username/password from envp string array */
+      const char *username = get_env ("username", envp);
+      const char *password = get_env ("password", envp);
+
+      if (username && strlen (username) > 0 && password)
+	{
+	  if (send_control (context->foreground_fd, COMMAND_VERIFY) == -1
+	      || send_string (context->foreground_fd, username) == -1
+	      || send_string (context->foreground_fd, password) == -1)
+	    {
+	      fprintf (stderr, "AUTH-PAM: Error sending auth info to background process\n");
+	    }
+	  else
+	    {
+	      const int status = recv_control (context->foreground_fd);
+	      if (status == RESPONSE_VERIFY_SUCCEEDED)
+		return OPENVPN_PLUGIN_FUNC_SUCCESS;
+	      if (status == -1)
+		fprintf (stderr, "AUTH-PAM: Error receiving auth confirmation from background process\n");
+	    }
+	}
+    }
+  return OPENVPN_PLUGIN_FUNC_ERROR;
+}
+
+OPENVPN_EXPORT void
+openvpn_plugin_close_v1 (openvpn_plugin_handle_t handle)
+{
+  struct auth_pam_context *context = (struct auth_pam_context *) handle;
+
+  if (DEBUG (context->verb))
+    fprintf (stderr, "AUTH-PAM: close\n");
+
+  if (context->foreground_fd >= 0)
+    {
+      /* tell background process to exit */
+      if (send_control (context->foreground_fd, COMMAND_EXIT) == -1)
+	fprintf (stderr, "AUTH-PAM: Error signaling background process to exit\n");
+
+      /* wait for background process to exit */
+      if (context->background_pid > 0)
+	waitpid (context->background_pid, NULL, 0);
+
+      close (context->foreground_fd);
+      context->foreground_fd = -1;
+    }
+
+  free (context);
+}
+
+OPENVPN_EXPORT void
+openvpn_plugin_abort_v1 (openvpn_plugin_handle_t handle)
+{
+  struct auth_pam_context *context = (struct auth_pam_context *) handle;
+
+  /* tell background process to exit */
+  if (context->foreground_fd >= 0)
+    {
+      send_control (context->foreground_fd, COMMAND_EXIT);
+      close (context->foreground_fd);
+      context->foreground_fd = -1;
+    }
+}
+
+/*
+ * PAM conversation function
+ */
+static int
+my_conv (int n, const struct pam_message **msg_array,
+	 struct pam_response **response_array, void *appdata_ptr)
+{
+  const struct user_pass *up = ( const struct user_pass *) appdata_ptr;
+  struct pam_response *aresp;
+  int i;
+  int ret = PAM_SUCCESS;
+
+  *response_array = NULL;
+
+  if (n <= 0 || n > PAM_MAX_NUM_MSG)
+    return (PAM_CONV_ERR);
+  if ((aresp = calloc (n, sizeof *aresp)) == NULL)
+    return (PAM_BUF_ERR);
+
+  /* loop through each PAM-module query */
+  for (i = 0; i < n; ++i)
+    {
+      const struct pam_message *msg = msg_array[i];
+      aresp[i].resp_retcode = 0;
+      aresp[i].resp = NULL;
+
+      if (DEBUG (up->verb))
+	{
+	  fprintf (stderr, "AUTH-PAM: BACKGROUND: my_conv[%d] query='%s' style=%d\n",
+		   i,
+		   msg->msg ? msg->msg : "NULL",
+		   msg->msg_style);
+	}
+
+      if (up->name_value_list && up->name_value_list->len > 0)
+	{
+	  /* use name/value list match method */
+	  const struct name_value_list *list = up->name_value_list;
+	  int j;
+
+	  /* loop through name/value pairs */
+	  for (j = 0; j < list->len; ++j)
+	    {
+	      const char *match_name = list->data[j].name;
+	      const char *match_value = list->data[j].value;
+
+	      if (name_value_match (msg->msg, match_name))
+		{
+		  /* found name/value match */
+		  const char *return_value = NULL;
+
+		  if (DEBUG (up->verb))
+		    fprintf (stderr, "AUTH-PAM: BACKGROUND: name match found, query/match-string ['%s', '%s'] = '%s'\n",
+			     msg->msg,
+			     match_name,
+			     match_value);
+
+		  if (!strcmp (match_value, "USERNAME"))
+		    return_value = up->username;
+		  else if (!strcmp (match_value, "PASSWORD"))
+		    return_value = up->password;
+		  else
+		    return_value = match_value;
+
+		  aresp[i].resp = strdup (return_value);
+		  if (aresp[i].resp == NULL)
+		    ret = PAM_CONV_ERR;
+		  break;
+		}
+	    }
+
+	  if (j == list->len)
+	    ret = PAM_CONV_ERR;
+	}
+      else
+	{
+	  /* use PAM_PROMPT_ECHO_x hints */
+	  switch (msg->msg_style)
+	    {
+	    case PAM_PROMPT_ECHO_OFF:
+	      aresp[i].resp = strdup (up->password);
+	      if (aresp[i].resp == NULL)
+		ret = PAM_CONV_ERR;
+	      break;
+
+	    case PAM_PROMPT_ECHO_ON:
+	      aresp[i].resp = strdup (up->username);
+	      if (aresp[i].resp == NULL)
+		ret = PAM_CONV_ERR;
+	      break;
+
+	    case PAM_ERROR_MSG:
+	    case PAM_TEXT_INFO:
+	      break;
+
+	    default:
+	      ret = PAM_CONV_ERR;
+	      break;
+	    }
+	}
+    }
+
+  if (ret == PAM_SUCCESS)
+    *response_array = aresp;
+  return ret;
+}
+
+/*
+ * Return 1 if authenticated and 0 if failed.
+ * Called once for every username/password
+ * to be authenticated.
+ */
+static int
+pam_auth (const char *service, const struct user_pass *up)
+{
+  struct pam_conv conv;
+  pam_handle_t *pamh = NULL;
+  int status = PAM_SUCCESS;
+  int ret = 0;
+  const int name_value_list_provided = (up->name_value_list && up->name_value_list->len > 0);
+
+  /* Initialize PAM */
+  conv.conv = my_conv;
+  conv.appdata_ptr = (void *)up;
+  status = pam_start (service, name_value_list_provided ? NULL : up->username, &conv, &pamh);
+  if (status == PAM_SUCCESS)
+    {
+      /* Call PAM to verify username/password */
+      status = pam_authenticate(pamh, 0);
+      if (status == PAM_SUCCESS)
+	status = pam_acct_mgmt (pamh, 0);
+      if (status == PAM_SUCCESS)
+	ret = 1;
+
+      /* Output error message if failed */
+      if (!ret)
+	{
+	  fprintf (stderr, "AUTH-PAM: BACKGROUND: user '%s' failed to authenticate: %s\n",
+		   up->username,
+		   pam_strerror (pamh, status));
+	}
+
+      /* Close PAM */
+      pam_end (pamh, status);      
+    }
+
+  return ret;
+}
+
+/*
+ * Background process -- runs with privilege.
+ */
+static void
+pam_server (int fd, const char *service, int verb, const struct name_value_list *name_value_list)
+{
+  struct user_pass up;
+  int command;
+#if DLOPEN_PAM
+  static const char pam_so[] = "libpam.so";
+#endif
+
+  /*
+   * Do initialization
+   */
+  if (DEBUG (verb))
+    fprintf (stderr, "AUTH-PAM: BACKGROUND: INIT service='%s'\n", service);
+
+#if DLOPEN_PAM
+  /*
+   * Load PAM shared object
+   */
+  if (!dlopen_pam (pam_so))
+    {
+      fprintf (stderr, "AUTH-PAM: BACKGROUND: could not load PAM lib %s: %s\n", pam_so, dlerror());
+      send_control (fd, RESPONSE_INIT_FAILED);
+      goto done;
+    }
+#endif
+
+  /*
+   * Tell foreground that we initialized successfully
+   */
+  if (send_control (fd, RESPONSE_INIT_SUCCEEDED) == -1)
+    {
+      fprintf (stderr, "AUTH-PAM: BACKGROUND: write error on response socket [1]\n");
+      goto done;
+    }
+
+  /*
+   * Event loop
+   */
+  while (1)
+    {
+      memset (&up, 0, sizeof (up));
+      up.verb = verb;
+      up.name_value_list = name_value_list;
+
+      /* get a command from foreground process */
+      command = recv_control (fd);
+
+      if (DEBUG (verb))
+	fprintf (stderr, "AUTH-PAM: BACKGROUND: received command code: %d\n", command);
+
+      switch (command)
+	{
+	case COMMAND_VERIFY:
+	  if (recv_string (fd, up.username, sizeof (up.username)) == -1
+	      || recv_string (fd, up.password, sizeof (up.password)) == -1)
+	    {
+	      fprintf (stderr, "AUTH-PAM: BACKGROUND: read error on command channel: code=%d, exiting\n",
+		       command);
+	      goto done;
+	    }
+
+	  if (DEBUG (verb))
+	    fprintf (stderr, "AUTH-PAM: BACKGROUND: USER/PASS: %s/%s\n",
+		     up.username, up.password);
+
+	  if (pam_auth (service, &up)) /* Succeeded */
+	    {
+	      if (send_control (fd, RESPONSE_VERIFY_SUCCEEDED) == -1)
+		{
+		  fprintf (stderr, "AUTH-PAM: BACKGROUND: write error on response socket [2]\n");
+		  goto done;
+		}
+	    }
+	  else /* Failed */
+	    {
+	      if (send_control (fd, RESPONSE_VERIFY_FAILED) == -1)
+		{
+		  fprintf (stderr, "AUTH-PAM: BACKGROUND: write error on response socket [3]\n");
+		  goto done;
+		}
+	    }
+	  break;
+
+	case COMMAND_EXIT:
+	  goto done;
+
+	case -1:
+	  fprintf (stderr, "AUTH-PAM: BACKGROUND: read error on command channel\n");
+	  goto done;
+
+	default:
+	  fprintf (stderr, "AUTH-PAM: BACKGROUND: unknown command code: code=%d, exiting\n",
+		   command);
+	  goto done;
+	}
+    }
+ done:
+
+#if DLOPEN_PAM
+  dlclose_pam ();
+#endif
+  if (DEBUG (verb))
+    fprintf (stderr, "AUTH-PAM: BACKGROUND: EXIT\n");
+
+  return;
+}
diff --git a/plugin/auth-pam/pamdl.c b/plugin/auth-pam/pamdl.c
new file mode 100644
index 0000000..aaac240
--- /dev/null
+++ b/plugin/auth-pam/pamdl.c
@@ -0,0 +1,181 @@
+#if DLOPEN_PAM
+/*
+ * If you want to dynamically load libpam using dlopen() or something,
+ * then dlopen( ' this shared object ' ); It takes care of exporting
+ * the right symbols to any modules loaded by libpam.
+ *
+ * Modified by JY for use with openvpn-pam-auth
+ */
+
+#include <stdio.h>
+#include <dlfcn.h>
+#include <security/pam_appl.h>
+#include <security/_pam_macros.h>
+
+#include "pamdl.h"
+
+static void *libpam_h = NULL;
+
+#define RESOLVE_PAM_FUNCTION(x, y, z, err) \
+    { \
+        union { const void *tpointer; y (*fn) z ; } fptr; \
+	fptr.tpointer = dlsym(libpam_h, #x); real_##x = fptr.fn; \
+	if (real_##x == NULL) { \
+	    fprintf (stderr, "PAMDL: unable to resolve '%s': %s\n", #x, dlerror()); \
+	    return err; \
+	} \
+    }
+
+int
+dlopen_pam (const char *so)
+{
+  if (libpam_h == NULL)
+    {
+      libpam_h = dlopen(so, RTLD_GLOBAL|RTLD_NOW);
+    }
+  return libpam_h != NULL;
+}
+
+void
+dlclose_pam (void)
+{
+  if (libpam_h != NULL)
+    {
+      dlclose(libpam_h);
+      libpam_h = NULL;
+    }
+}
+
+int pam_start(const char *service_name, const char *user,
+	      const struct pam_conv *pam_conversation,
+	      pam_handle_t **pamh)
+{
+    int (*real_pam_start)(const char *, const char *,
+				 const struct pam_conv *,
+				 pam_handle_t **);
+    RESOLVE_PAM_FUNCTION(pam_start, int, (const char *, const char *,
+					  const struct pam_conv *,
+					  pam_handle_t **), PAM_ABORT);
+    return real_pam_start(service_name, user, pam_conversation, pamh);
+}
+
+int pam_end(pam_handle_t *pamh, int pam_status)
+{
+    int (*real_pam_end)(pam_handle_t *, int);
+    RESOLVE_PAM_FUNCTION(pam_end, int, (pam_handle_t *, int), PAM_ABORT);
+    return real_pam_end(pamh, pam_status);
+}
+
+int pam_set_item(pam_handle_t *pamh, int item_type, const void *item)
+{
+    int (*real_pam_set_item)(pam_handle_t *, int, const void *);
+    RESOLVE_PAM_FUNCTION(pam_set_item, int,
+			 (pam_handle_t *, int, const void *), PAM_ABORT);
+    return real_pam_set_item(pamh, item_type, item);
+}
+
+int pam_get_item(const pam_handle_t *pamh, int item_type, const void **item)
+{
+    int (*real_pam_get_item)(const pam_handle_t *, int, const void **);
+    RESOLVE_PAM_FUNCTION(pam_get_item, int,
+			 (const pam_handle_t *, int, const void **),
+			 PAM_ABORT);
+    return real_pam_get_item(pamh, item_type, item);
+}
+
+int pam_fail_delay(pam_handle_t *pamh, unsigned int musec_delay)
+{
+    int (*real_pam_fail_delay)(pam_handle_t *, unsigned int);
+    RESOLVE_PAM_FUNCTION(pam_fail_delay, int, (pam_handle_t *, unsigned int),
+			 PAM_ABORT);
+    return real_pam_fail_delay(pamh, musec_delay);
+}
+
+typedef const char * const_char_pointer;
+
+const_char_pointer pam_strerror(pam_handle_t *pamh, int errnum)
+{
+    const_char_pointer (*real_pam_strerror)(pam_handle_t *, int);
+    RESOLVE_PAM_FUNCTION(pam_strerror, const_char_pointer,
+			 (pam_handle_t *, int), NULL);
+    return real_pam_strerror(pamh, errnum);
+}
+
+int pam_putenv(pam_handle_t *pamh, const char *name_value)
+{
+    int (*real_pam_putenv)(pam_handle_t *, const char *);
+    RESOLVE_PAM_FUNCTION(pam_putenv, int, (pam_handle_t *, const char *),
+			 PAM_ABORT);
+    return real_pam_putenv(pamh, name_value);
+}
+
+const_char_pointer pam_getenv(pam_handle_t *pamh, const char *name)
+{
+    const_char_pointer (*real_pam_getenv)(pam_handle_t *, const char *);
+    RESOLVE_PAM_FUNCTION(pam_getenv, const_char_pointer,
+			 (pam_handle_t *, const char *), NULL);
+    return real_pam_getenv(pamh, name);
+}
+
+typedef char ** char_ppointer;
+char_ppointer pam_getenvlist(pam_handle_t *pamh)
+{
+    char_ppointer (*real_pam_getenvlist)(pam_handle_t *);
+    RESOLVE_PAM_FUNCTION(pam_getenvlist, char_ppointer, (pam_handle_t *),
+			 NULL);
+    return real_pam_getenvlist(pamh);
+}
+
+/* Authentication management */
+
+int pam_authenticate(pam_handle_t *pamh, int flags)
+{
+    int (*real_pam_authenticate)(pam_handle_t *, int);
+    RESOLVE_PAM_FUNCTION(pam_authenticate, int, (pam_handle_t *, int),
+			 PAM_ABORT);
+    return real_pam_authenticate(pamh, flags);
+}
+
+int pam_setcred(pam_handle_t *pamh, int flags)
+{
+    int (*real_pam_setcred)(pam_handle_t *, int);
+    RESOLVE_PAM_FUNCTION(pam_setcred, int, (pam_handle_t *, int), PAM_ABORT);
+    return real_pam_setcred(pamh, flags);
+}
+
+/* Account Management API's */
+
+int pam_acct_mgmt(pam_handle_t *pamh, int flags)
+{
+    int (*real_pam_acct_mgmt)(pam_handle_t *, int);
+    RESOLVE_PAM_FUNCTION(pam_acct_mgmt, int, (pam_handle_t *, int), PAM_ABORT);
+    return real_pam_acct_mgmt(pamh, flags);
+}
+
+/* Session Management API's */
+
+int pam_open_session(pam_handle_t *pamh, int flags)
+{
+    int (*real_pam_open_session)(pam_handle_t *, int);
+    RESOLVE_PAM_FUNCTION(pam_open_session, int, (pam_handle_t *, int),
+			 PAM_ABORT);
+    return real_pam_open_session(pamh, flags);
+}
+
+int pam_close_session(pam_handle_t *pamh, int flags)
+{
+    int (*real_pam_close_session)(pam_handle_t *, int);
+    RESOLVE_PAM_FUNCTION(pam_close_session, int, (pam_handle_t *, int),
+			 PAM_ABORT);
+    return real_pam_close_session(pamh, flags);
+}
+
+/* Password Management API's */
+
+int pam_chauthtok(pam_handle_t *pamh, int flags)
+{
+    int (*real_pam_chauthtok)(pam_handle_t *, int);
+    RESOLVE_PAM_FUNCTION(pam_chauthtok, int, (pam_handle_t *, int), PAM_ABORT);
+    return real_pam_chauthtok(pamh, flags);
+}
+#endif
diff --git a/plugin/auth-pam/pamdl.h b/plugin/auth-pam/pamdl.h
new file mode 100644
index 0000000..b10b035
--- /dev/null
+++ b/plugin/auth-pam/pamdl.h
@@ -0,0 +1,7 @@
+#if DLOPEN_PAM
+#include <security/pam_appl.h>
+
+/* Dynamically load and unload the PAM library */
+int dlopen_pam (const char *so);
+void dlclose_pam (void);
+#endif