/*
* 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;
}
