2 * Receive wall messages and pass them to a notification program via stdin.
4 * Copyright (C) 2014 Simon Ruderich
6 * This program is free software: you can redistribute it and/or modify
7 * it under the terms of the GNU General Public License as published by
8 * the Free Software Foundation, either version 3 of the License, or
9 * (at your option) any later version.
11 * This program is distributed in the hope that it will be useful,
12 * but WITHOUT ANY WARRANTY; without even the implied warranty of
13 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
14 * GNU General Public License for more details.
16 * You should have received a copy of the GNU General Public License
17 * along with this program. If not, see <http://www.gnu.org/licenses/>.
32 #include <sys/select.h>
35 #include <sys/types.h>
40 # include <utempter.h>
47 # include <X11/Xlib.h>
51 static void sig_handler(int signal) {
54 static void setup_signals(void) {
55 struct sigaction action;
57 memset(&action, 0, sizeof(action));
58 sigemptyset(&action.sa_mask);
59 action.sa_handler = sig_handler;
61 /* Handle all important signals which might be sent to us so we break out
62 * of the read()-loop below and can perform our cleanup. */
63 sigaction(SIGHUP, &action, NULL);
64 sigaction(SIGINT, &action, NULL);
65 sigaction(SIGQUIT, &action, NULL);
66 sigaction(SIGUSR1, &action, NULL);
67 sigaction(SIGUSR2, &action, NULL);
70 static int open_tty(void) {
74 ptm = posix_openpt(O_RDWR);
78 if (grantpt(ptm) != 0) {
82 /* Prevent write access for other users so they can't use wall to send
83 * messages to this program. */
88 if (chmod(name, S_IRUSR | S_IWUSR) != 0) {
92 if (unlockpt(ptm) != 0) {
100 static const char *skip_prefix(const char *string, const char *prefix) {
101 size_t length = strlen(prefix);
103 if (!strncmp(string, prefix, length)) {
104 return string + length;
109 static int set_utmpx(short type, int ptm) {
112 const char *tty, *user, *id, *line;
115 user = getpwuid(getuid())->pw_name;
116 gettimeofday(&now, NULL);
123 id = skip_prefix(tty, "/dev/pts/");
124 line = skip_prefix(tty, "/dev/");
126 /* Create utmp entry for the given terminal. */
127 memset(&entry, 0, sizeof(entry));
129 snprintf(entry.ut_user, sizeof(entry.ut_user), "%s", user);
130 snprintf(entry.ut_id, sizeof(entry.ut_id), "%s", id);
131 snprintf(entry.ut_line, sizeof(entry.ut_line), "%s", line);
133 entry.ut_pid = getpid();
134 entry.ut_type = type;
135 entry.ut_tv.tv_sec = now.tv_sec;
136 entry.ut_tv.tv_usec = now.tv_usec;
138 /* Write the entry to the utmp file. */
140 if (!pututxline(&entry)) {
148 static int login(int ptm) {
149 #if defined(USE_UTEMPTER)
150 int result = utempter_add_record(ptm, NULL);
151 /* Exit value of utempter_*() is not correct on all systems, e.g.
152 * FreeBSD() always returns 0. Checking the utmpx database manually is
153 * difficult because we don't know the exact values for ut_id and ut_line,
154 * therefore we only check the return value on systems known to return a
160 #elif defined(USE_UTMPX)
161 return set_utmpx(USER_PROCESS, ptm);
163 # error "neither USE_UTEMPTER nor USE_UTMPX defined"
166 static int logout(int ptm) {
167 #if defined(USE_UTEMPTER)
168 int result = utempter_remove_record(ptm);
174 #elif defined(USE_UTMPX)
175 return set_utmpx(DEAD_PROCESS, ptm);
177 # error "neither USE_UTEMPTER nor USE_UTMPX defined"
181 static int wait_for_write(int fd, int timeout) {
192 result = select(fd + 1, &rfds, NULL, NULL, &tv);
202 /* Got more data to read. */
206 static void pass_buffer_to_program(const char *buffer, size_t length, char **argv) {
212 if (pipe(fds) != 0) {
217 fh = fdopen(fds[1] /* write side */, "w");
229 } else if (pid == 0) {
232 close(fds[1]); /* write side */
234 /* Pass read side as stdin to the program. */
235 if (dup2(fds[0], STDIN_FILENO) < 0) {
241 /* Double fork so `wall-notify` doesn't have to wait for the
242 * notification process to terminate. We can't just use
243 * signal(SIGCHLD, SIG_IGN); because utempter on at least FreeBSD
244 * doesn't work if SIGCHLD is ignored. */
249 } else if (pid == 0) {
250 execvp(argv[0], argv);
259 if (fwrite(buffer, 1, length, fh) != length) {
261 /* continue to perform cleanup */
265 close(fds[0]); /* read side */
268 if (waitpid(pid, NULL, 0) < 0) {
272 static void handle_wall(int fd, char **argv) {
276 assert(SSIZE_MAX <= SIZE_MAX);
277 while ((r = read(fd, buffer, sizeof(buffer))) > 0) {
281 /* To prevent partial messages (sometimes it takes multiple reads to
282 * get the complete message) wait for a short time to get the rest of
284 space = sizeof(buffer) - (size_t)r;
285 while (space > 0 && wait_for_write(fd, 1 /* second */)) {
286 r2 = read(fd, buffer + r, space);
294 pass_buffer_to_program(buffer, (size_t)r, argv);
298 static void *x11_event_loop_thread(void *unused) {
304 pthread_detach(pthread_self());
306 display = XOpenDisplay(NULL);
308 fprintf(stderr, "failed to connect to X server\n");
312 /* Do nothing. We just want to die if the X11 session is closed. */
314 XNextEvent(display, &event);
319 static void usage(const char *argv0) {
320 fprintf(stderr, "usage: %s <cmd args..>\n", argv0);
325 int main(int argc, char **argv) {
331 /* Don't pass our argv[0] to the notification program. */
350 printf("%s\n", name);
353 /* We need to open the slave or reading from the master yields EOF after
354 * the first wall write to it. */
355 pts = open(name, O_RDWR);
362 /* Start a thread which connects to X11. This way we die if the user logs
363 * out of its X11 session. */
367 if (pthread_create(&tid, NULL, x11_event_loop_thread, NULL) != 0) {
368 perror("pthread_create");
374 /* Cleanup on signals. Necessary before login(). */
382 /* Main loop. Handle all wall messages sent to our PTY. */
383 handle_wall(ptm, argv);