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 signum)
  69 {
  70   if (signum == SIGTERM)
  71     fprintf(stderr, "vlock-main: Terminated!\n");
  72   else if (signum == SIGABRT)
  73     fprintf(stderr, "vlock-main: Aborted!\n");
  74
  75   exit(1);
  76 }
  77
  78 static void block_signals(void)
  79 {
  80   struct sigaction sa;
  81
  82   /* Ignore some signals. */
  83   /* These signals shouldn't be delivered anyway, because terminal signals are
  84    * disabled below. */
  85   (void) sigemptyset(&(sa.sa_mask));
  86   sa.sa_flags = SA_RESTART;
  87   sa.sa_handler = SIG_IGN;
  88   (void) sigaction(SIGINT, &sa, NULL);
  89   (void) sigaction(SIGQUIT, &sa, NULL);
  90   (void) sigaction(SIGTSTP, &sa, NULL);
  91
  92   /* Install special handler for TERM and ABRT. */
  93   sa.sa_flags = SA_RESETHAND;
  94   sa.sa_handler = terminate;
  95   (void) sigaction(SIGTERM, &sa, NULL);
  96   (void) sigaction(SIGABRT, &sa, NULL);
  97 }
  98
  99 static struct termios term;
 100 static tcflag_t lflag;
 101
 102 static void secure_terminal(void)
 103 {
 104   /* Disable terminal echoing and signals. */
 105   (void) tcgetattr(STDIN_FILENO, &term);
 106   lflag = term.c_lflag;
 107   term.c_lflag &= ~(ECHO | ISIG);
 108   (void) tcsetattr(STDIN_FILENO, TCSANOW, &term);
 109 }
 110
 111 static void restore_terminal(void)
 112 {
 113   /* Restore the terminal. */
 114   term.c_lflag = lflag;
 115   (void) tcsetattr(STDIN_FILENO, TCSANOW, &term);
 116 }
 117
 118 static void auth_loop(const char *username)
 119 {
 120   struct timespec *prompt_timeout;
 121   struct timespec *wait_timeout;
 122   char *vlock_message;
 123
 124   /* Get the vlock message from the environment. */
 125   vlock_message = getenv("VLOCK_MESSAGE");
 126
 127   if (vlock_message == NULL) {
 128     if (console_switch_locked)
 129       vlock_message = getenv("VLOCK_ALL_MESSAGE");
 130     else
 131       vlock_message = getenv("VLOCK_CURRENT_MESSAGE");
 132   }
 133
 134   /* Get the timeouts from the environment. */
 135   prompt_timeout = parse_seconds(getenv("VLOCK_PROMPT_TIMEOUT"));
 136 #ifdef USE_PLUGINS
 137   wait_timeout = parse_seconds(getenv("VLOCK_TIMEOUT"));
 138 #else
 139   wait_timeout = NULL;
 140 #endif
 141
 142   for (;;) {
 143     char c;
 144
 145     /* Print vlock message if there is one. */
 146     if (vlock_message && *vlock_message) {
 147       fputs(vlock_message, stderr);
 148       fputc('\n', stderr);
 149     }
 150
 151     /* Wait for enter or escape to be pressed. */
 152     c = wait_for_character("\n\033", wait_timeout);
 153
 154     /* Escape was pressed or the timeout occurred. */
 155     if (c == '\033' || c == 0) {
 156 #ifdef USE_PLUGINS
 157       plugin_hook("vlock_save");
 158       /* Wait for any key to be pressed. */
 159       c = wait_for_character(NULL, NULL);
 160       plugin_hook("vlock_save_abort");
 161
 162       /* Do not require enter to be pressed twice. */
 163       if (c != '\n')
 164         continue;
 165 #else
 166       continue;
 167 #endif
 168     }
 169
 170     if (auth(username, prompt_timeout))
 171       break;
 172     else
 173       sleep(1);
 174
 175 #ifndef NO_ROOT_PASS
 176     if (auth("root", prompt_timeout))
 177       break;
 178     else
 179       sleep(1);
 180 #endif
 181   }
 182
 183   /* Free timeouts memory. */
 184   free(wait_timeout);
 185   free(prompt_timeout);
 186 }
 187
 188 #ifdef USE_PLUGINS
 189 static void call_end_hook(void)
 190 {
 191   (void) plugin_hook("vlock_end");
 192 }
 193 #endif
 194
 195 /* Lock the current terminal until proper authentication is received. */
 196 int main(int argc, char *const argv[])
 197 {
 198   char *username;
 199
 200   vlock_debug = (getenv("VLOCK_DEBUG") != NULL);
 201
 202   block_signals();
 203
 204   username = get_username();
 205
 206   if (username == NULL)
 207     fatal_perror("vlock-main: could not get username");
 208
 209 #ifdef USE_PLUGINS
 210   for (int i = 1; i < argc; i++)
 211     if (!load_plugin(argv[i]))
 212       fatal_error("vlock-main: loading plugin '%s' failed: %s", argv[i], STRERROR);
 213
 214   ensure_atexit(unload_plugins);
 215
 216   if (!resolve_dependencies()) {
 217     if (errno == 0)
 218       exit(EXIT_FAILURE);
 219     else
 220       fatal_error("vlock-main: error resolving plugin dependencies: %s", STRERROR);
 221   }
 222
 223   plugin_hook("vlock_start");
 224   ensure_atexit(call_end_hook);
 225 #else /* !USE_PLUGINS */
 226   /* Emulate pseudo plugin "all". */
 227   if (argc == 2 && (strcmp(argv[1], "all") == 0)) {
 228     if (!lock_console_switch()) {
 229       if (errno == ENOTTY || errno == EINVAL)
 230         fatal_error("vlock-main: this terminal is not a virtual console");
 231       else
 232         fatal_perror("vlock-main: could not disable console switching");
 233     }
 234
 235     ensure_atexit((void (*)(void))unlock_console_switch);
 236   } else if (argc > 1) {
 237     fatal_error("vlock-main: plugin support disabled");
 238   }
 239 #endif
 240
 241   secure_terminal();
 242   ensure_atexit(restore_terminal);
 243
 244   auth_loop(username);
 245
 246   free(username);
 247
 248   exit(0);
 249 }