/*
* 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) 2002-2010 OpenVPN Technologies, Inc. <sales@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 privileged down-script execution.
*/
#include <stdio.h>
#include <string.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) >= 7)
/* Command codes for foreground -> background communication */
#define COMMAND_RUN_SCRIPT 0
#define COMMAND_EXIT 1
/* Response codes for background -> foreground communication */
#define RESPONSE_INIT_SUCCEEDED 10
#define RESPONSE_INIT_FAILED 11
#define RESPONSE_SCRIPT_SUCCEEDED 12
#define RESPONSE_SCRIPT_FAILED 13
/* Background process function */
static void down_root_server (const int fd, char *command, const char *argv[], const char *envp[], const int verb);
/*
* Plugin state, used by foreground
*/
struct down_root_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;
/* down command */
char *command;
};
/*
* 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
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;
}
/*
* 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, "DOWN-ROOT: daemonization failed\n");
}
else if (fd >= 3)
{
dup2 (fd, 2);
close (fd);
}
}
}
/*
* 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);
}
/*
* convert system() return into a success/failure value
*/
int
system_ok (int stat)
{
#ifdef WIN32
return stat == 0;
#else
return stat != -1 && WIFEXITED (stat) && WEXITSTATUS (stat) == 0;
#endif
}
static char *
build_command_line (const char *argv[])
{
int size = 0;
int n = 0;
int i;
char *string;
/* precompute size */
if (argv)
{
for (i = 0; argv[i]; ++i)
{
size += (strlen (argv[i]) + 1); /* string length plus trailing space */
++n;
}
}
++size; /* for null terminator */
/* allocate memory */
string = (char *) malloc (size);
if (!string)
{
fprintf (stderr, "DOWN-ROOT: out of memory\n");
exit (1);
}
string[0] = '\0';
/* build string */
for (i = 0; i < n; ++i)
{
strcat (string, argv[i]);
if (i + 1 < n)
strcat (string, " ");
}
return string;
}
static void
free_context (struct down_root_context *context)
{
if (context)
{
if (context->command)
free (context->command);
free (context);
}
}
OPENVPN_EXPORT openvpn_plugin_handle_t
openvpn_plugin_open_v1 (unsigned int *type_mask, const char *argv[], const char *envp[])
{
struct down_root_context *context;
/*
* Allocate our context
*/
context = (struct down_root_context *) calloc (1, sizeof (struct down_root_context));
if (!context)
goto error;
context->foreground_fd = -1;
/*
* Intercept the --up and --down callbacks
*/
*type_mask = OPENVPN_PLUGIN_MASK (OPENVPN_PLUGIN_UP) | OPENVPN_PLUGIN_MASK (OPENVPN_PLUGIN_DOWN);
/*
* Make sure we have two string arguments: the first is the .so name,
* the second is the script command.
*/
if (string_array_len (argv) < 2)
{
fprintf (stderr, "DOWN-ROOT: need down script command\n");
goto error;
}
/*
* Save our argument in context
*/
context->command = build_command_line (&argv[1]);
/*
* Get verbosity level from environment
*/
{
const char *verb_string = get_env ("verb", envp);
if (verb_string)
context->verb = atoi (verb_string);
}
return (openvpn_plugin_handle_t) context;
error:
free_context (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 down_root_context *context = (struct down_root_context *) handle;
if (type == OPENVPN_PLUGIN_UP && context->foreground_fd == -1) /* fork off a process to hold onto root */
{
pid_t pid;
int fd[2];
/*
* Make a socket for foreground and background processes
* to communicate.
*/
if (socketpair (PF_UNIX, SOCK_DGRAM, 0, fd) == -1)
{
fprintf (stderr, "DOWN-ROOT: socketpair call failed\n");
return OPENVPN_PLUGIN_FUNC_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, "DOWN-ROOT: 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_FUNC_SUCCESS;
}
}
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 ();
/* Daemonize if --daemon option is set. */
daemonize (envp);
/* execute the event loop */
down_root_server (fd[1], context->command, argv, envp, context->verb);
close (fd[1]);
exit (0);
return 0; /* NOTREACHED */
}
}
else if (type == OPENVPN_PLUGIN_DOWN && context->foreground_fd >= 0)
{
if (send_control (context->foreground_fd, COMMAND_RUN_SCRIPT) == -1)
{
fprintf (stderr, "DOWN-ROOT: Error sending script execution signal to background process\n");
}
else
{
const int status = recv_control (context->foreground_fd);
if (status == RESPONSE_SCRIPT_SUCCEEDED)
return OPENVPN_PLUGIN_FUNC_SUCCESS;
if (status == -1)
fprintf (stderr, "DOWN-ROOT: Error receiving script execution confirmation from background process\n");
}
}
return OPENVPN_PLUGIN_FUNC_ERROR;
}
OPENVPN_EXPORT void
openvpn_plugin_close_v1 (openvpn_plugin_handle_t handle)
{
struct down_root_context *context = (struct down_root_context *) handle;
if (DEBUG (context->verb))
fprintf (stderr, "DOWN-ROOT: close\n");
if (context->foreground_fd >= 0)
{
/* tell background process to exit */
if (send_control (context->foreground_fd, COMMAND_EXIT) == -1)
fprintf (stderr, "DOWN-ROOT: 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 (context);
}
OPENVPN_EXPORT void
openvpn_plugin_abort_v1 (openvpn_plugin_handle_t handle)
{
struct down_root_context *context = (struct down_root_context *) handle;
if (context && context->foreground_fd >= 0)
{
/* tell background process to exit */
send_control (context->foreground_fd, COMMAND_EXIT);
close (context->foreground_fd);
context->foreground_fd = -1;
}
}
/*
* Background process -- runs with privilege.
*/
static void
down_root_server (const int fd, char *command, const char *argv[], const char *envp[], const int verb)
{
const char *p[3];
char *command_line = NULL;
char *argv_cat = NULL;
int i;
/*
* Do initialization
*/
if (DEBUG (verb))
fprintf (stderr, "DOWN-ROOT: BACKGROUND: INIT command='%s'\n", command);
/*
* Tell foreground that we initialized successfully
*/
if (send_control (fd, RESPONSE_INIT_SUCCEEDED) == -1)
{
fprintf (stderr, "DOWN-ROOT: BACKGROUND: write error on response socket [1]\n");
goto done;
}
/*
* Build command line
*/
if (string_array_len (argv) >= 2)
argv_cat = build_command_line (&argv[1]);
else
argv_cat = build_command_line (NULL);
p[0] = command;
p[1] = argv_cat;
p[2] = NULL;
command_line = build_command_line (p);
/*
* Save envp in environment
*/
for (i = 0; envp[i]; ++i)
{
putenv ((char *)envp[i]);
}
/*
* Event loop
*/
while (1)
{
int command_code;
int status;
/* get a command from foreground process */
command_code = recv_control (fd);
if (DEBUG (verb))
fprintf (stderr, "DOWN-ROOT: BACKGROUND: received command code: %d\n", command_code);
switch (command_code)
{
case COMMAND_RUN_SCRIPT:
status = system (command_line);
if (system_ok (status)) /* Succeeded */
{
if (send_control (fd, RESPONSE_SCRIPT_SUCCEEDED) == -1)
{
fprintf (stderr, "DOWN-ROOT: BACKGROUND: write error on response socket [2]\n");
goto done;
}
}
else /* Failed */
{
if (send_control (fd, RESPONSE_SCRIPT_FAILED) == -1)
{
fprintf (stderr, "DOWN-ROOT: BACKGROUND: write error on response socket [3]\n");
goto done;
}
}
break;
case COMMAND_EXIT:
goto done;
case -1:
fprintf (stderr, "DOWN-ROOT: BACKGROUND: read error on command channel\n");
goto done;
default:
fprintf (stderr, "DOWN-ROOT: BACKGROUND: unknown command code: code=%d, exiting\n",
command_code);
goto done;
}
}
done:
if (argv_cat)
free (argv_cat);
if (command_line)
free (command_line);
if (DEBUG (verb))
fprintf (stderr, "DOWN-ROOT: BACKGROUND: EXIT\n");
return;
}
