X-Git-Url: https://ruderich.org/simon/gitweb/?p=wall-notify%2Fwall-notify.git;a=blobdiff_plain;f=src%2Fwall-notify.c;h=57ec37f00a60cef695e28b536055551716c4f391;hp=24afb7a1f90295f3cf69e80e6815dbbbb189e10a;hb=d28191ac3e71802b939721c1f7b8b4fe509bde53;hpb=ebdd9b1bfc90722e80fcd25f7121888fc57507cf diff --git a/src/wall-notify.c b/src/wall-notify.c index 24afb7a..57ec37f 100644 --- a/src/wall-notify.c +++ b/src/wall-notify.c @@ -42,6 +42,10 @@ #ifdef USE_UTMPX # include #endif +#ifndef DONT_USE_X11 +# include +# include +#endif static void sig_handler(int signal) { @@ -63,7 +67,18 @@ static void setup_signals(void) { sigaction(SIGUSR2, &action, NULL); } -static int open_tty(void) { +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(int public) { int ptm; const char *name; @@ -74,15 +89,20 @@ static int open_tty(void) { 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) { @@ -199,15 +219,50 @@ static int wait_for_write(int fd, int timeout) { 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; @@ -228,6 +283,10 @@ static void pass_buffer_to_program(const char *buffer, size_t length, char **arg } else if (pid == 0) { /* child */ +#ifdef USE_UTMPX + drop_privileges(); +#endif + close(fds[1]); /* write side */ /* Pass read side as stdin to the program. */ @@ -293,22 +352,94 @@ static void handle_wall(int fd, char **argv) { 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 \n", argv0); + fprintf(stderr, "usage: %s [-X] [-m] [-v] \n", argv0); + fprintf(stderr, "Pass wall messages to .\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) { + /* 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); @@ -325,12 +456,28 @@ int main(int argc, char **argv) { /* 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();