#include <stdio.h>
#include <stdlib.h>
#include <string.h>
+#include <sys/select.h>
#include <sys/stat.h>
#include <sys/time.h>
#include <sys/types.h>
+#include <sys/wait.h>
#include <unistd.h>
#ifdef USE_UTEMPTER
#ifdef USE_UTMPX
# include <utmpx.h>
#endif
+#ifndef DONT_USE_X11
+# include <pthread.h>
+# include <X11/Xlib.h>
+#endif
static void sig_handler(int signal) {
sigaction(SIGQUIT, &action, NULL);
sigaction(SIGUSR1, &action, NULL);
sigaction(SIGUSR2, &action, NULL);
+}
- /* Collect zombies automatically without having to call waitpid(2). */
- signal(SIGCHLD, SIG_IGN);
+static int set_cloexec(int fd) {
+ int flags = fcntl(fd, F_GETFD);
+ if (flags == -1) {
+ return 0;
+ }
+ if (fcntl(fd, F_SETFD, flags | FD_CLOEXEC) == -1) {
+ return 0;
+ }
+ return 1;
}
-static int open_tty(void) {
+static int open_tty(int public) {
int ptm;
const char *name;
if (grantpt(ptm) != 0) {
return -1;
}
+ if (!set_cloexec(ptm)) {
+ return -1;
+ }
/* Prevent write access for other users so they can't use wall to send
* messages to this program. */
- name = ptsname(ptm);
- if (!name) {
- return -1;
- }
- if (chmod(name, S_IRUSR | S_IWUSR) != 0) {
- return -1;
+ if (!public) {
+ name = ptsname(ptm);
+ if (!name) {
+ return -1;
+ }
+ if (chmod(name, S_IRUSR | S_IWUSR) != 0) {
+ return -1;
+ }
}
if (unlockpt(ptm) != 0) {
#endif
static int login(int ptm) {
#if defined(USE_UTEMPTER)
- return utempter_add_record(ptm, NULL);
+ int result = utempter_add_record(ptm, NULL);
+ /* Exit value of utempter_*() is not correct on all systems, e.g.
+ * FreeBSD() always returns 0. Checking the utmpx database manually is
+ * difficult because we don't know the exact values for ut_id and ut_line,
+ * therefore we only check the return value on systems known to return a
+ * useful value. */
+# ifndef __linux
+ result = 1;
+# endif
+ return result;
#elif defined(USE_UTMPX)
return set_utmpx(USER_PROCESS, ptm);
#else
}
static int logout(int ptm) {
#if defined(USE_UTEMPTER)
- return utempter_remove_record(ptm);
+ int result = utempter_remove_record(ptm);
+ /* See above. */
+# ifndef __linux
+ result = 1;
+# endif
+ return result;
#elif defined(USE_UTMPX)
return set_utmpx(DEAD_PROCESS, ptm);
#else
#endif
}
+static int wait_for_write(int fd, int timeout) {
+ fd_set rfds;
+ struct timeval tv;
+ int result;
+
+ FD_ZERO(&rfds);
+ FD_SET(fd, &rfds);
+
+ tv.tv_sec = timeout;
+ tv.tv_usec = 0;
+
+ result = select(fd + 1, &rfds, NULL, NULL, &tv);
+ if (result < 0) {
+ perror("select");
+ return 0;
+ }
+ if (result == 0) {
+ /* Timeout. */
+ return 0;
+ }
+
+ /* Got more data to read. */
+ return 1;
+}
+
+#ifdef USE_UTMPX
+static void drop_privileges(void) {
+ uid_t uid, ruid, euid, suid;
+ gid_t gid, rgid, egid, sgid;
+
+ uid = getuid();
+ gid = getgid();
+
+ /* Drop all privileges. */
+ if (setresgid(gid, gid, gid) != 0) {
+ perror("setresgid");
+ exit(EXIT_FAILURE);
+ }
+ if (setresuid(uid, uid, uid) != 0) {
+ perror("setresuid");
+ exit(EXIT_FAILURE);
+ }
+
+ /* Verify all privileges were dropped. */
+ if (getresuid(&ruid, &euid, &suid) != 0) {
+ perror("getresuid");
+ exit(EXIT_FAILURE);
+ }
+ if (getresgid(&rgid, &egid, &sgid) != 0) {
+ perror("getresgid");
+ exit(EXIT_FAILURE);
+ }
+ if (uid == ruid && uid == euid && uid == suid
+ && gid == rgid && gid == egid && gid == sgid) {
+ /* Everything fine. */
+ return;
+ }
+
+ fprintf(stderr, "failed to drop privileges, aborting\n");
+ exit(EXIT_FAILURE);
+}
+#endif
+
static void pass_buffer_to_program(const char *buffer, size_t length, char **argv) {
int fds[2];
FILE *fh;
pid_t pid;
- /* Skip argv[0]. */
- argv++;
-
if (pipe(fds) != 0) {
perror("pipe");
return;
} else if (pid == 0) {
/* child */
+#ifdef USE_UTMPX
+ drop_privileges();
+#endif
+
close(fds[1]); /* write side */
/* Pass read side as stdin to the program. */
}
close(fds[0]);
- execvp(argv[0], argv);
- perror("execvp");
- exit(EXIT_FAILURE);
+ /* Double fork so `wall-notify` doesn't have to wait for the
+ * notification process to terminate. We can't just use
+ * signal(SIGCHLD, SIG_IGN); because utempter on at least FreeBSD
+ * doesn't work if SIGCHLD is ignored. */
+ pid = fork();
+ if (pid < 0) {
+ perror("fork");
+ exit(EXIT_FAILURE);
+ } else if (pid == 0) {
+ execvp(argv[0], argv);
+ perror("execvp");
+ exit(EXIT_FAILURE);
+ }
+
+ exit(EXIT_SUCCESS);
}
/* father */
out:
close(fds[0]); /* read side */
fclose(fh);
+
+ if (waitpid(pid, NULL, 0) < 0) {
+ perror("waitpid");
+ }
}
static void handle_wall(int fd, char **argv) {
char buffer[4096];
ssize_t r;
+ assert(SSIZE_MAX <= SIZE_MAX);
while ((r = read(fd, buffer, sizeof(buffer))) > 0) {
- assert(SSIZE_MAX <= SIZE_MAX);
+ size_t space;
+ ssize_t r2;
+
+ /* To prevent partial messages (sometimes it takes multiple reads to
+ * get the complete message) wait for a short time to get the rest of
+ * the message. */
+ space = sizeof(buffer) - (size_t)r;
+ while (space > 0 && wait_for_write(fd, 1 /* second */)) {
+ r2 = read(fd, buffer + r, space);
+ if (r2 <= 0) {
+ break;
+ }
+ r += r2;
+ space -= (size_t)r2;
+ }
+
pass_buffer_to_program(buffer, (size_t)r, argv);
}
}
+#ifndef DONT_USE_X11
+static void *x11_event_loop_thread(void *unused) {
+ Display *display;
+ XEvent event;
+
+ (void)unused;
+
+ pthread_detach(pthread_self());
+
+ display = XOpenDisplay(NULL);
+ if (!display) {
+ fprintf(stderr, "failed to connect to X server\n");
+ exit(EXIT_FAILURE);
+ }
+
+ /* Do nothing. We just want to die if the X11 session is closed. */
+ while (1) {
+ XNextEvent(display, &event);
+ }
+}
+#endif
+
+static void usage(const char *argv0) {
+ fprintf(stderr, "usage: %s [-X] [-m] [-v] <cmd args..>\n", argv0);
+ fprintf(stderr, "Pass wall messages to <cmd args..>.\n");
+ fprintf(stderr, "\n");
+ fprintf(stderr, "-X quit when the current X session terminates\n");
+ fprintf(stderr, "-m allow messages from normal users (like `mesg y`)\n");
+ fprintf(stderr, "-v display version\n");
+#ifdef DONT_USE_X11
+ fprintf(stderr, "\n");
+ fprintf(stderr, "compiled without X11 support, -X disabled\n");
+#endif
+ exit(EXIT_FAILURE);
+}
int main(int argc, char **argv) {
+ int option, enable_x11, mesg_yes;
int ptm, pts;
char *name;
- if (argc < 2) {
- fprintf(stderr, "usage: %s <cmd args..>\n", argv[0]);
- exit(EXIT_FAILURE);
+ /* Don't display error messages for unknown options. */
+ opterr = 0;
+
+ enable_x11 = 0;
+ mesg_yes = 0;
+
+ /*
+ * Glibc violates POSIX by default and skips over non-option arguments and
+ * parses later arguments which look like options as well. But we want to
+ * pass everything except the options unmodified to execvp(). Prefixing
+ * the optstring with "+" fixes this behaver. This is not POSIX
+ * compatible, but the option should be ignored on other systems.
+ */
+ while ((option = getopt(argc, argv, "+Xmhv")) != -1) {
+ switch (option) {
+ case 'X':
+ enable_x11 = 1;
+ break;
+ case 'm':
+ mesg_yes = 1;
+ break;
+ case 'h':
+ usage(argv[0]);
+ break;
+ case 'v':
+ printf("%s%s\n",
+ PACKAGE_STRING,
+ strlen(GIT_VERSION) ? " (Git " GIT_VERSION ")" : "");
+ exit(0);
+ break;
+ default:
+ fprintf(stderr, "%s: unknown option '%s'!\n\n",
+ argv[0], argv[optind - 1]);
+ usage(argv[0]);
+ break;
+ }
+ }
+
+ /* No arguments remaining, abort. */
+ if (!argv[optind]) {
+ usage(argv[0]);
}
+ /* Arguments for notification program. */
+ argv += optind;
- ptm = open_tty();
+ ptm = open_tty(mesg_yes);
if (ptm < 0) {
perror("open_tty");
exit(EXIT_FAILURE);
/* We need to open the slave or reading from the master yields EOF after
* the first wall write to it. */
- pts = open(name, O_RDWR);
+ pts = open(name, O_RDWR | O_CLOEXEC);
if (pts < 0) {
perror(name);
exit(EXIT_FAILURE);
}
+ /* Start a thread which connects to X11. This way we die if the user logs
+ * out of its X11 session. */
+ if (enable_x11) {
+#ifdef DONT_USE_X11
+ fprintf(stderr, "%s: option -X is disabled!\n\n", argv0);
+ usage(argv0);
+#else
+ pthread_t tid;
+
+ if (pthread_create(&tid, NULL, x11_event_loop_thread, NULL) != 0) {
+ perror("pthread_create");
+ exit(EXIT_FAILURE);
+ }
+#endif
+ }
+
/* Cleanup on signals. Necessary before login(). */
setup_signals();
ruderich.org/simon / wall-notify / wall-notify.git / blobdiff