2 * Pseudo-tty backend for pterm.
4 * Unlike the other backends, data for this one is not neatly
5 * encapsulated into a data structure, because it wouldn't make
6 * sense to do so - the utmp stuff has to be done before a backend
7 * is initialised, and starting a second pterm from the same
8 * process would therefore be infeasible because privileges would
9 * already have been dropped. Hence, I haven't bothered to keep the
10 * data dynamically allocated: instead, the backend handle is just
11 * a null pointer and ignored everywhere.
15 #define _XOPEN_SOURCE_EXTENDED
30 #include <sys/types.h>
32 #include <sys/ioctl.h>
45 #define UTMP_FILE "/var/run/utmp"
48 #define WTMP_FILE "/var/log/wtmp"
52 #define LASTLOG_FILE _PATH_LASTLOG
54 #define LASTLOG_FILE "/var/log/lastlog"
59 * Set up a default for vaguely sane systems. The idea is that if
60 * OMIT_UTMP is not defined, then at least one of the symbols which
61 * enable particular forms of utmp processing should be, if only so
62 * that a link error can warn you that you should have defined
63 * OMIT_UTMP if you didn't want any. Currently HAVE_PUTUTLINE is
64 * the only such symbol.
67 #if !defined HAVE_PUTUTLINE
68 #define HAVE_PUTUTLINE
72 static Config pty_cfg;
73 static int pty_master_fd;
74 static void *pty_frontend;
75 static char pty_name[FILENAME_MAX];
76 static int pty_signal_pipe[2];
77 static int pty_stamped_utmp = 0;
78 static int pty_child_pid;
79 static int pty_utmp_helper_pid, pty_utmp_helper_pipe;
80 static int pty_term_width, pty_term_height;
81 static int pty_child_dead, pty_finished;
82 static int pty_exit_code;
84 static struct utmp utmp_entry;
88 static void pty_close(void);
90 static void setup_utmp(char *ttyname, char *location)
94 struct lastlog lastlog_entry;
100 pw = getpwuid(getuid());
101 memset(&utmp_entry, 0, sizeof(utmp_entry));
102 utmp_entry.ut_type = USER_PROCESS;
103 utmp_entry.ut_pid = getpid();
104 strncpy(utmp_entry.ut_line, ttyname+5, lenof(utmp_entry.ut_line));
105 strncpy(utmp_entry.ut_id, ttyname+8, lenof(utmp_entry.ut_id));
106 strncpy(utmp_entry.ut_user, pw->pw_name, lenof(utmp_entry.ut_user));
107 strncpy(utmp_entry.ut_host, location, lenof(utmp_entry.ut_host));
108 time(&utmp_entry.ut_time);
110 #if defined HAVE_PUTUTLINE
113 pututline(&utmp_entry);
117 if ((wtmp = fopen(WTMP_FILE, "a")) != NULL) {
118 fwrite(&utmp_entry, 1, sizeof(utmp_entry), wtmp);
123 memset(&lastlog_entry, 0, sizeof(lastlog_entry));
124 strncpy(lastlog_entry.ll_line, ttyname+5, lenof(lastlog_entry.ll_line));
125 strncpy(lastlog_entry.ll_host, location, lenof(lastlog_entry.ll_host));
126 time(&lastlog_entry.ll_time);
127 if ((lastlog = fopen(LASTLOG_FILE, "r+")) != NULL) {
128 fseek(lastlog, sizeof(lastlog_entry) * getuid(), SEEK_SET);
129 fwrite(&lastlog_entry, 1, sizeof(lastlog_entry), lastlog);
134 pty_stamped_utmp = 1;
139 static void cleanup_utmp(void)
144 if (!pty_stamped_utmp)
147 utmp_entry.ut_type = DEAD_PROCESS;
148 memset(utmp_entry.ut_user, 0, lenof(utmp_entry.ut_user));
149 time(&utmp_entry.ut_time);
151 if ((wtmp = fopen(WTMP_FILE, "a")) != NULL) {
152 fwrite(&utmp_entry, 1, sizeof(utmp_entry), wtmp);
156 memset(utmp_entry.ut_line, 0, lenof(utmp_entry.ut_line));
157 utmp_entry.ut_time = 0;
159 #if defined HAVE_PUTUTLINE
162 pututline(&utmp_entry);
166 pty_stamped_utmp = 0; /* ensure we never double-cleanup */
170 static void sigchld_handler(int signum)
172 write(pty_signal_pipe[1], "x", 1);
175 static void fatal_sig_handler(int signum)
177 putty_signal(signum, SIG_DFL);
183 static void pty_open_master(void)
186 const char chars1[] = "pqrstuvwxyz";
187 const char chars2[] = "0123456789abcdef";
189 char master_name[20];
192 for (p1 = chars1; *p1; p1++)
193 for (p2 = chars2; *p2; p2++) {
194 sprintf(master_name, "/dev/pty%c%c", *p1, *p2);
195 pty_master_fd = open(master_name, O_RDWR);
196 if (pty_master_fd >= 0) {
197 if (geteuid() == 0 ||
198 access(master_name, R_OK | W_OK) == 0)
200 close(pty_master_fd);
204 /* If we get here, we couldn't get a tty at all. */
205 fprintf(stderr, "pterm: unable to open a pseudo-terminal device\n");
209 strcpy(pty_name, master_name);
210 pty_name[5] = 't'; /* /dev/ptyXX -> /dev/ttyXX */
212 /* We need to chown/chmod the /dev/ttyXX device. */
213 gp = getgrnam("tty");
214 chown(pty_name, getuid(), gp ? gp->gr_gid : -1);
215 chmod(pty_name, 0600);
217 pty_master_fd = open("/dev/ptmx", O_RDWR);
219 if (pty_master_fd < 0) {
220 perror("/dev/ptmx: open");
224 if (grantpt(pty_master_fd) < 0) {
229 if (unlockpt(pty_master_fd) < 0) {
234 pty_name[FILENAME_MAX-1] = '\0';
235 strncpy(pty_name, ptsname(pty_master_fd), FILENAME_MAX-1);
240 * Pre-initialisation. This is here to get around the fact that GTK
241 * doesn't like being run in setuid/setgid programs (probably
242 * sensibly). So before we initialise GTK - and therefore before we
243 * even process the command line - we check to see if we're running
244 * set[ug]id. If so, we open our pty master _now_, chown it as
245 * necessary, and drop privileges. We can always close it again
246 * later. If we're potentially going to be doing utmp as well, we
247 * also fork off a utmp helper process and communicate with it by
248 * means of a pipe; the utmp helper will keep privileges in order
249 * to clean up utmp when we exit (i.e. when its end of our pipe
252 void pty_pre_init(void)
257 /* set the child signal handler straight away; it needs to be set
258 * before we ever fork. */
259 putty_signal(SIGCHLD, sigchld_handler);
262 if (geteuid() != getuid() || getegid() != getgid()) {
268 * Fork off the utmp helper.
270 if (pipe(pipefd) < 0) {
271 perror("pterm: pipe");
276 perror("pterm: fork");
278 } else if (pid == 0) {
279 char display[128], buffer[128];
284 * Now sit here until we receive a display name from the
285 * other end of the pipe, and then stamp utmp. Unstamp utmp
286 * again, and exit, when the pipe closes.
292 ret = read(pipefd[0], buffer, lenof(buffer));
296 } else if (!pty_stamped_utmp) {
297 if (dlen < lenof(display))
298 memcpy(display+dlen, buffer,
299 min(ret, lenof(display)-dlen));
300 if (buffer[ret-1] == '\0') {
302 * Now we have a display name. NUL-terminate
303 * it, and stamp utmp.
305 display[lenof(display)-1] = '\0';
307 * Trap as many fatal signals as we can in the
308 * hope of having the best possible chance to
309 * clean up utmp before termination. We are
310 * unfortunately unprotected against SIGKILL,
313 putty_signal(SIGHUP, fatal_sig_handler);
314 putty_signal(SIGINT, fatal_sig_handler);
315 putty_signal(SIGQUIT, fatal_sig_handler);
316 putty_signal(SIGILL, fatal_sig_handler);
317 putty_signal(SIGABRT, fatal_sig_handler);
318 putty_signal(SIGFPE, fatal_sig_handler);
319 putty_signal(SIGPIPE, fatal_sig_handler);
320 putty_signal(SIGALRM, fatal_sig_handler);
321 putty_signal(SIGTERM, fatal_sig_handler);
322 putty_signal(SIGSEGV, fatal_sig_handler);
323 putty_signal(SIGUSR1, fatal_sig_handler);
324 putty_signal(SIGUSR2, fatal_sig_handler);
326 putty_signal(SIGBUS, fatal_sig_handler);
329 putty_signal(SIGPOLL, fatal_sig_handler);
332 putty_signal(SIGPROF, fatal_sig_handler);
335 putty_signal(SIGSYS, fatal_sig_handler);
338 putty_signal(SIGTRAP, fatal_sig_handler);
341 putty_signal(SIGVTALRM, fatal_sig_handler);
344 putty_signal(SIGXCPU, fatal_sig_handler);
347 putty_signal(SIGXFSZ, fatal_sig_handler);
350 putty_signal(SIGIO, fatal_sig_handler);
352 setup_utmp(pty_name, display);
358 pty_utmp_helper_pid = pid;
359 pty_utmp_helper_pipe = pipefd[1];
365 int gid = getgid(), uid = getuid();
366 #ifndef HAVE_NO_SETRESUID
367 int setresgid(gid_t, gid_t, gid_t);
368 int setresuid(uid_t, uid_t, uid_t);
369 setresgid(gid, gid, gid);
370 setresuid(uid, uid, uid);
378 int pty_select_result(int fd, int event)
382 int finished = FALSE;
384 if (fd == pty_master_fd && event == 1) {
386 ret = read(pty_master_fd, buf, sizeof(buf));
389 * Clean termination condition is that either ret == 0, or ret
390 * < 0 and errno == EIO. Not sure why the latter, but it seems
393 if (ret == 0 || (ret < 0 && errno == EIO)) {
395 * We assume a clean exit if the pty has closed but the
396 * actual child process hasn't. The only way I can
397 * imagine this happening is if it detaches itself from
398 * the pty and goes daemonic - in which case the
399 * expected usage model would precisely _not_ be for
400 * the pterm window to hang around!
405 } else if (ret < 0) {
406 perror("read pty master");
408 } else if (ret > 0) {
409 from_backend(pty_frontend, 0, buf, ret);
411 } else if (fd == pty_signal_pipe[0]) {
416 read(pty_signal_pipe[0], c, 1); /* ignore its value; it'll be `x' */
419 pid = waitpid(-1, &status, WNOHANG);
420 if (pid == pty_child_pid &&
421 (WIFEXITED(status) || WIFSIGNALED(status))) {
423 * The primary child process died. We could keep
424 * the terminal open for remaining subprocesses to
425 * output to, but conventional wisdom seems to feel
426 * that that's the Wrong Thing for an xterm-alike,
427 * so we bail out now (though we don't necessarily
428 * _close_ the window, depending on the state of
429 * Close On Exit). This would be easy enough to
430 * change or make configurable if necessary.
432 pty_exit_code = status;
433 pty_child_dead = TRUE;
439 if (finished && !pty_finished) {
440 uxsel_del(pty_master_fd);
447 * This is a slight layering-violation sort of hack: only
448 * if we're not closing on exit (COE is set to Never, or to
449 * Only On Clean and it wasn't a clean exit) do we output a
450 * `terminated' message.
452 if (pty_cfg.close_on_exit == FORCE_OFF ||
453 (pty_cfg.close_on_exit == AUTO && pty_exit_code != 0)) {
455 if (WIFEXITED(pty_exit_code))
456 sprintf(message, "\r\n[pterm: process terminated with exit"
457 " code %d]\r\n", WEXITSTATUS(pty_exit_code));
458 else if (WIFSIGNALED(pty_exit_code))
459 #ifdef HAVE_NO_STRSIGNAL
460 sprintf(message, "\r\n[pterm: process terminated on signal"
461 " %d]\r\n", WTERMSIG(pty_exit_code));
463 sprintf(message, "\r\n[pterm: process terminated on signal"
464 " %d (%.400s)]\r\n", WTERMSIG(pty_exit_code),
465 strsignal(WTERMSIG(pty_exit_code)));
467 from_backend(pty_frontend, 0, message, strlen(message));
473 static void pty_uxsel_setup(void)
475 uxsel_set(pty_master_fd, 1, pty_select_result);
476 uxsel_set(pty_signal_pipe[0], 1, pty_select_result);
480 * Called to set up the pty.
482 * Returns an error message, or NULL on success.
484 * Also places the canonical host name into `realhost'. It must be
485 * freed by the caller.
487 static char *pty_init(void *frontend, void **backend_handle, Config *cfg,
488 char *host, int port, char **realhost, int nodelay)
494 pty_frontend = frontend;
495 *backend_handle = NULL; /* we can't sensibly use this, sadly */
497 pty_cfg = *cfg; /* structure copy */
498 pty_term_width = cfg->width;
499 pty_term_height = cfg->height;
501 if (pty_master_fd < 0)
505 * Set the backspace character to be whichever of ^H and ^? is
506 * specified by bksp_is_delete.
509 struct termios attrs;
510 tcgetattr(pty_master_fd, &attrs);
511 attrs.c_cc[VERASE] = cfg->bksp_is_delete ? '\177' : '\010';
512 tcsetattr(pty_master_fd, TCSANOW, &attrs);
516 * Stamp utmp (that is, tell the utmp helper process to do so),
519 if (!cfg->stamp_utmp)
520 close(pty_utmp_helper_pipe); /* just let the child process die */
522 char *location = get_x_display(pty_frontend);
523 int len = strlen(location)+1, pos = 0; /* +1 to include NUL */
525 int ret = write(pty_utmp_helper_pipe, location+pos, len - pos);
527 perror("pterm: writing to utmp helper process");
528 close(pty_utmp_helper_pipe); /* arrgh, just give up */
535 windowid = get_windowid(pty_frontend);
538 * Fork and execute the command.
552 slavefd = open(pty_name, O_RDWR);
554 perror("slave pty: open");
558 close(pty_master_fd);
559 fcntl(slavefd, F_SETFD, 0); /* don't close on exec */
564 ioctl(slavefd, TIOCSCTTY, 1);
566 tcsetpgrp(slavefd, pgrp);
568 close(open(pty_name, O_WRONLY, 0));
570 /* Close everything _else_, for tidiness. */
571 for (i = 3; i < 1024; i++)
574 char term_env_var[10 + sizeof(cfg->termtype)];
575 sprintf(term_env_var, "TERM=%s", cfg->termtype);
576 putenv(term_env_var);
579 char windowid_env_var[40];
580 sprintf(windowid_env_var, "WINDOWID=%ld", windowid);
581 putenv(windowid_env_var);
584 * SIGINT and SIGQUIT may have been set to ignored by our
585 * parent, particularly by things like sh -c 'pterm &' and
586 * some window managers. Reverse this for our child process.
588 putty_signal(SIGINT, SIG_DFL);
589 putty_signal(SIGQUIT, SIG_DFL);
591 execvp(pty_argv[0], pty_argv);
593 char *shell = getenv("SHELL");
595 if (cfg->login_shell) {
596 char *p = strrchr(shell, '/');
597 shellname = snewn(2+strlen(shell), char);
599 sprintf(shellname, "-%s", p);
602 execl(getenv("SHELL"), shellname, NULL);
606 * If we're here, exec has gone badly foom.
612 pty_child_dead = FALSE;
613 pty_finished = FALSE;
616 if (pipe(pty_signal_pipe) < 0) {
626 * Stub routine (we don't have any need to reconfigure this backend).
628 static void pty_reconfig(void *handle, Config *cfg)
633 * Stub routine (never called in pterm
635 static void pty_free(void *handle)
641 * Called to send data down the pty.
643 static int pty_send(void *handle, char *buf, int len)
645 if (pty_master_fd < 0)
646 return 0; /* ignore all writes if fd closed */
649 int ret = write(pty_master_fd, buf, len);
651 perror("write pty master");
660 static void pty_close(void)
662 if (pty_master_fd >= 0) {
663 close(pty_master_fd);
666 close(pty_utmp_helper_pipe); /* this causes utmp to be cleaned up */
670 * Called to query the current socket sendability status.
672 static int pty_sendbuffer(void *handle)
678 * Called to set the size of the window
680 static void pty_size(void *handle, int width, int height)
684 pty_term_width = width;
685 pty_term_height = height;
687 size.ws_row = (unsigned short)pty_term_height;
688 size.ws_col = (unsigned short)pty_term_width;
689 size.ws_xpixel = (unsigned short) pty_term_width *
690 font_dimension(pty_frontend, 0);
691 size.ws_ypixel = (unsigned short) pty_term_height *
692 font_dimension(pty_frontend, 1);
693 ioctl(pty_master_fd, TIOCSWINSZ, (void *)&size);
698 * Send special codes.
700 static void pty_special(void *handle, Telnet_Special code)
706 static Socket pty_socket(void *handle)
708 return NULL; /* shouldn't ever be needed */
711 static int pty_sendok(void *handle)
716 static void pty_unthrottle(void *handle, int backlog)
721 static int pty_ldisc(void *handle, int option)
723 return 0; /* neither editing nor echoing */
726 static void pty_provide_ldisc(void *handle, void *ldisc)
728 /* This is a stub. */
731 static void pty_provide_logctx(void *handle, void *logctx)
733 /* This is a stub. */
736 static int pty_exitcode(void *handle)
739 return -1; /* not dead yet */
741 return pty_exit_code;
744 Backend pty_backend = {