src/vlock-main.c

   1 /* vlock-main.c -- main routine for vlock,
   2  *                    the VT locking program for linux
   3  *
   4  * This program is copyright (C) 2007 Frank Benkstein, and is free
   5  * software which is freely distributable under the terms of the
   6  * GNU General Public License version 2, included as the file COPYING in this
   7  * distribution.  It is NOT public domain software, and any
   8  * redistribution not permitted by the GNU General Public License is
   9  * expressly forbidden without prior written permission from
  10  * the author.
  11  *
  12  */
  13
  14 #include <stdlib.h>
  15 #include <string.h>
  16 #include <stdio.h>
  17
  18 #include <pwd.h>
  19
  20 #include <termios.h>
  21 #include <unistd.h>
  22 #include <sys/types.h>
  23 #include <signal.h>
  24 #include <errno.h>
  25 #include <time.h>
  26
  27 #include "prompt.h"
  28 #include "auth.h"
  29 #include "console_switch.h"
  30 #include "util.h"
  31
  32 #ifdef USE_PLUGINS
  33 #include "plugins.h"
  34 #endif
  35
  36 int vlock_debug = 0;
  37
  38 #define ensure_atexit(func) \
  39   do { \
  40     if (atexit(func) != 0) \
  41       fatal_perror("vlock-main: atexit() failed"); \
  42   } while (0)
  43
  44 static char *get_username(void)
  45 {
  46   uid_t uid = getuid();
  47   char *username = NULL;
  48
  49   /* Get the user name from the environment if started as root. */
  50   if (uid == 0)
  51     username = getenv("USER");
  52
  53   if (username == NULL) {
  54     struct passwd *pw;
  55
  56     /* Get the password entry. */
  57     pw = getpwuid(uid);
  58
  59     if (pw == NULL)
  60       return NULL;
  61
  62     username = pw->pw_name;
  63   }
  64
  65   return strdup(username);
  66 }
  67
  68 static void terminate(int __attribute__((unused)) signum)
  69 {
  70   fprintf(stderr, "vlock-main: Terminated!\n");
  71   exit(1);
  72 }
  73
  74 static void block_signals(void)
  75 {
  76   struct sigaction sa;
  77
  78   /* Ignore some signals. */
  79   /* These signals shouldn't be delivered anyway, because terminal signals are
  80    * disabled below. */
  81   (void) sigemptyset(&(sa.sa_mask));
  82   sa.sa_flags = SA_RESTART;
  83   sa.sa_handler = SIG_IGN;
  84   (void) sigaction(SIGINT, &sa, NULL);
  85   (void) sigaction(SIGQUIT, &sa, NULL);
  86   (void) sigaction(SIGTSTP, &sa, NULL);
  87
  88   /* Install special handler for SIGTERM. */
  89   sa.sa_flags = SA_RESETHAND;
  90   sa.sa_handler = terminate;
  91   (void) sigaction(SIGTERM, &sa, NULL);
  92 }
  93
  94 static struct termios term;
  95 static tcflag_t lflag;
  96
  97 static void secure_terminal(void)
  98 {
  99   /* Disable terminal echoing and signals. */
 100   (void) tcgetattr(STDIN_FILENO, &term);
 101   lflag = term.c_lflag;
 102   term.c_lflag &= ~(ECHO | ISIG);
 103   (void) tcsetattr(STDIN_FILENO, TCSANOW, &term);
 104 }
 105
 106 static void restore_terminal(void)
 107 {
 108   /* Restore the terminal. */
 109   term.c_lflag = lflag;
 110   (void) tcsetattr(STDIN_FILENO, TCSANOW, &term);
 111 }
 112
 113 static void auth_loop(const char *username)
 114 {
 115   struct timespec *prompt_timeout;
 116   struct timespec *wait_timeout;
 117   char *vlock_message;
 118
 119   /* Get the vlock message from the environment. */
 120   vlock_message = getenv("VLOCK_MESSAGE");
 121
 122   if (vlock_message == NULL) {
 123     if (console_switch_locked)
 124       vlock_message = getenv("VLOCK_ALL_MESSAGE");
 125     else
 126       vlock_message = getenv("VLOCK_CURRENT_MESSAGE");
 127   }
 128
 129   /* Get the timeouts from the environment. */
 130   prompt_timeout = parse_seconds(getenv("VLOCK_PROMPT_TIMEOUT"));
 131 #ifdef USE_PLUGINS
 132   wait_timeout = parse_seconds(getenv("VLOCK_TIMEOUT"));
 133 #else
 134   wait_timeout = NULL;
 135 #endif
 136
 137   for (;;) {
 138     char c;
 139
 140     /* Print vlock message if there is one. */
 141     if (vlock_message && *vlock_message) {
 142       fputs(vlock_message, stderr);
 143       fputc('\n', stderr);
 144     }
 145
 146     /* Wait for enter or escape to be pressed. */
 147     c = wait_for_character("\n\033", wait_timeout);
 148
 149     /* Escape was pressed or the timeout occurred. */
 150     if (c == '\033' || c == 0) {
 151 #ifdef USE_PLUGINS
 152       plugin_hook("vlock_save");
 153       /* Wait for any key to be pressed. */
 154       c = wait_for_character(NULL, NULL);
 155       plugin_hook("vlock_save_abort");
 156
 157       /* Do not require enter to be pressed twice. */
 158       if (c != '\n')
 159         continue;
 160 #else
 161       continue;
 162 #endif
 163     }
 164
 165     if (auth(username, prompt_timeout))
 166       break;
 167     else
 168       sleep(1);
 169
 170 #ifndef NO_ROOT_PASS
 171     if (auth("root", prompt_timeout))
 172       break;
 173     else
 174       sleep(1);
 175 #endif
 176   }
 177
 178   /* Free timeouts memory. */
 179   free(wait_timeout);
 180   free(prompt_timeout);
 181 }
 182
 183 #ifdef USE_PLUGINS
 184 static void call_end_hook(void)
 185 {
 186   (void) plugin_hook("vlock_end");
 187 }
 188 #endif
 189
 190 /* Lock the current terminal until proper authentication is received. */
 191 int main(int argc, char *const argv[])
 192 {
 193   char *username;
 194
 195   vlock_debug = (getenv("VLOCK_DEBUG") != NULL);
 196
 197   block_signals();
 198
 199   username = get_username();
 200
 201   if (username == NULL)
 202     fatal_perror("vlock-main: could not get username");
 203
 204 #ifdef USE_PLUGINS
 205   for (int i = 1; i < argc; i++)
 206     if (!load_plugin(argv[i]))
 207       fatal_error("vlock-main: loading plugin '%s' failed: %s", argv[i], STRERROR);
 208
 209   ensure_atexit(unload_plugins);
 210
 211   if (!resolve_dependencies()) {
 212     if (errno == 0)
 213       exit(EXIT_FAILURE);
 214     else
 215       fatal_error("vlock-main: error resolving plugin dependencies: %s", STRERROR);
 216   }
 217
 218   plugin_hook("vlock_start");
 219   ensure_atexit(call_end_hook);
 220 #else /* !USE_PLUGINS */
 221   /* Emulate pseudo plugin "all". */
 222   if (argc == 2 && (strcmp(argv[1], "all") == 0)) {
 223     if (!lock_console_switch()) {
 224       if (errno == ENOTTY || errno == EINVAL)
 225         fatal_error("vlock-main: this terminal is not a virtual console");
 226       else
 227         fatal_perror("vlock-main: could not disable console switching");
 228     }
 229
 230     ensure_atexit((void (*)(void))unlock_console_switch);
 231   } else if (argc > 1) {
 232     fatal_error("vlock-main: plugin support disabled");
 233   }
 234 #endif
 235
 236   secure_terminal();
 237   ensure_atexit(restore_terminal);
 238
 239   auth_loop(username);
 240
 241   free(username);
 242
 243   exit(0);
 244 }