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;
87 int use_pty_argv = TRUE;
89 static void pty_close(void);
91 static void setup_utmp(char *ttyname, char *location)
95 struct lastlog lastlog_entry;
101 pw = getpwuid(getuid());
102 memset(&utmp_entry, 0, sizeof(utmp_entry));
103 utmp_entry.ut_type = USER_PROCESS;
104 utmp_entry.ut_pid = getpid();
105 strncpy(utmp_entry.ut_line, ttyname+5, lenof(utmp_entry.ut_line));
106 strncpy(utmp_entry.ut_id, ttyname+8, lenof(utmp_entry.ut_id));
107 strncpy(utmp_entry.ut_user, pw->pw_name, lenof(utmp_entry.ut_user));
108 strncpy(utmp_entry.ut_host, location, lenof(utmp_entry.ut_host));
109 time(&utmp_entry.ut_time);
111 #if defined HAVE_PUTUTLINE
114 pututline(&utmp_entry);
118 if ((wtmp = fopen(WTMP_FILE, "a")) != NULL) {
119 fwrite(&utmp_entry, 1, sizeof(utmp_entry), wtmp);
124 memset(&lastlog_entry, 0, sizeof(lastlog_entry));
125 strncpy(lastlog_entry.ll_line, ttyname+5, lenof(lastlog_entry.ll_line));
126 strncpy(lastlog_entry.ll_host, location, lenof(lastlog_entry.ll_host));
127 time(&lastlog_entry.ll_time);
128 if ((lastlog = fopen(LASTLOG_FILE, "r+")) != NULL) {
129 fseek(lastlog, sizeof(lastlog_entry) * getuid(), SEEK_SET);
130 fwrite(&lastlog_entry, 1, sizeof(lastlog_entry), lastlog);
135 pty_stamped_utmp = 1;
140 static void cleanup_utmp(void)
145 if (!pty_stamped_utmp)
148 utmp_entry.ut_type = DEAD_PROCESS;
149 memset(utmp_entry.ut_user, 0, lenof(utmp_entry.ut_user));
150 time(&utmp_entry.ut_time);
152 if ((wtmp = fopen(WTMP_FILE, "a")) != NULL) {
153 fwrite(&utmp_entry, 1, sizeof(utmp_entry), wtmp);
157 memset(utmp_entry.ut_line, 0, lenof(utmp_entry.ut_line));
158 utmp_entry.ut_time = 0;
160 #if defined HAVE_PUTUTLINE
163 pututline(&utmp_entry);
167 pty_stamped_utmp = 0; /* ensure we never double-cleanup */
171 static void sigchld_handler(int signum)
173 write(pty_signal_pipe[1], "x", 1);
176 static void fatal_sig_handler(int signum)
178 putty_signal(signum, SIG_DFL);
184 static void pty_open_master(void)
187 const char chars1[] = "pqrstuvwxyz";
188 const char chars2[] = "0123456789abcdef";
190 char master_name[20];
193 for (p1 = chars1; *p1; p1++)
194 for (p2 = chars2; *p2; p2++) {
195 sprintf(master_name, "/dev/pty%c%c", *p1, *p2);
196 pty_master_fd = open(master_name, O_RDWR);
197 if (pty_master_fd >= 0) {
198 if (geteuid() == 0 ||
199 access(master_name, R_OK | W_OK) == 0)
201 close(pty_master_fd);
205 /* If we get here, we couldn't get a tty at all. */
206 fprintf(stderr, "pterm: unable to open a pseudo-terminal device\n");
210 strcpy(pty_name, master_name);
211 pty_name[5] = 't'; /* /dev/ptyXX -> /dev/ttyXX */
213 /* We need to chown/chmod the /dev/ttyXX device. */
214 gp = getgrnam("tty");
215 chown(pty_name, getuid(), gp ? gp->gr_gid : -1);
216 chmod(pty_name, 0600);
218 pty_master_fd = open("/dev/ptmx", O_RDWR);
220 if (pty_master_fd < 0) {
221 perror("/dev/ptmx: open");
225 if (grantpt(pty_master_fd) < 0) {
230 if (unlockpt(pty_master_fd) < 0) {
235 pty_name[FILENAME_MAX-1] = '\0';
236 strncpy(pty_name, ptsname(pty_master_fd), FILENAME_MAX-1);
241 * Pre-initialisation. This is here to get around the fact that GTK
242 * doesn't like being run in setuid/setgid programs (probably
243 * sensibly). So before we initialise GTK - and therefore before we
244 * even process the command line - we check to see if we're running
245 * set[ug]id. If so, we open our pty master _now_, chown it as
246 * necessary, and drop privileges. We can always close it again
247 * later. If we're potentially going to be doing utmp as well, we
248 * also fork off a utmp helper process and communicate with it by
249 * means of a pipe; the utmp helper will keep privileges in order
250 * to clean up utmp when we exit (i.e. when its end of our pipe
253 void pty_pre_init(void)
258 /* set the child signal handler straight away; it needs to be set
259 * before we ever fork. */
260 putty_signal(SIGCHLD, sigchld_handler);
263 if (geteuid() != getuid() || getegid() != getgid()) {
269 * Fork off the utmp helper.
271 if (pipe(pipefd) < 0) {
272 perror("pterm: pipe");
277 perror("pterm: fork");
279 } else if (pid == 0) {
280 char display[128], buffer[128];
285 * Now sit here until we receive a display name from the
286 * other end of the pipe, and then stamp utmp. Unstamp utmp
287 * again, and exit, when the pipe closes.
293 ret = read(pipefd[0], buffer, lenof(buffer));
297 } else if (!pty_stamped_utmp) {
298 if (dlen < lenof(display))
299 memcpy(display+dlen, buffer,
300 min(ret, lenof(display)-dlen));
301 if (buffer[ret-1] == '\0') {
303 * Now we have a display name. NUL-terminate
304 * it, and stamp utmp.
306 display[lenof(display)-1] = '\0';
308 * Trap as many fatal signals as we can in the
309 * hope of having the best possible chance to
310 * clean up utmp before termination. We are
311 * unfortunately unprotected against SIGKILL,
314 putty_signal(SIGHUP, fatal_sig_handler);
315 putty_signal(SIGINT, fatal_sig_handler);
316 putty_signal(SIGQUIT, fatal_sig_handler);
317 putty_signal(SIGILL, fatal_sig_handler);
318 putty_signal(SIGABRT, fatal_sig_handler);
319 putty_signal(SIGFPE, fatal_sig_handler);
320 putty_signal(SIGPIPE, fatal_sig_handler);
321 putty_signal(SIGALRM, fatal_sig_handler);
322 putty_signal(SIGTERM, fatal_sig_handler);
323 putty_signal(SIGSEGV, fatal_sig_handler);
324 putty_signal(SIGUSR1, fatal_sig_handler);
325 putty_signal(SIGUSR2, fatal_sig_handler);
327 putty_signal(SIGBUS, fatal_sig_handler);
330 putty_signal(SIGPOLL, fatal_sig_handler);
333 putty_signal(SIGPROF, fatal_sig_handler);
336 putty_signal(SIGSYS, fatal_sig_handler);
339 putty_signal(SIGTRAP, fatal_sig_handler);
342 putty_signal(SIGVTALRM, fatal_sig_handler);
345 putty_signal(SIGXCPU, fatal_sig_handler);
348 putty_signal(SIGXFSZ, fatal_sig_handler);
351 putty_signal(SIGIO, fatal_sig_handler);
353 setup_utmp(pty_name, display);
359 pty_utmp_helper_pid = pid;
360 pty_utmp_helper_pipe = pipefd[1];
366 int gid = getgid(), uid = getuid();
367 #ifndef HAVE_NO_SETRESUID
368 int setresgid(gid_t, gid_t, gid_t);
369 int setresuid(uid_t, uid_t, uid_t);
370 setresgid(gid, gid, gid);
371 setresuid(uid, uid, uid);
379 int pty_select_result(int fd, int event)
383 int finished = FALSE;
385 if (fd == pty_master_fd && event == 1) {
387 ret = read(pty_master_fd, buf, sizeof(buf));
390 * Clean termination condition is that either ret == 0, or ret
391 * < 0 and errno == EIO. Not sure why the latter, but it seems
394 if (ret == 0 || (ret < 0 && errno == EIO)) {
396 * We assume a clean exit if the pty has closed but the
397 * actual child process hasn't. The only way I can
398 * imagine this happening is if it detaches itself from
399 * the pty and goes daemonic - in which case the
400 * expected usage model would precisely _not_ be for
401 * the pterm window to hang around!
406 } else if (ret < 0) {
407 perror("read pty master");
409 } else if (ret > 0) {
410 from_backend(pty_frontend, 0, buf, ret);
412 } else if (fd == pty_signal_pipe[0]) {
417 read(pty_signal_pipe[0], c, 1); /* ignore its value; it'll be `x' */
420 pid = waitpid(-1, &status, WNOHANG);
421 if (pid == pty_child_pid &&
422 (WIFEXITED(status) || WIFSIGNALED(status))) {
424 * The primary child process died. We could keep
425 * the terminal open for remaining subprocesses to
426 * output to, but conventional wisdom seems to feel
427 * that that's the Wrong Thing for an xterm-alike,
428 * so we bail out now (though we don't necessarily
429 * _close_ the window, depending on the state of
430 * Close On Exit). This would be easy enough to
431 * change or make configurable if necessary.
433 pty_exit_code = status;
434 pty_child_dead = TRUE;
440 if (finished && !pty_finished) {
441 uxsel_del(pty_master_fd);
448 * This is a slight layering-violation sort of hack: only
449 * if we're not closing on exit (COE is set to Never, or to
450 * Only On Clean and it wasn't a clean exit) do we output a
451 * `terminated' message.
453 if (pty_cfg.close_on_exit == FORCE_OFF ||
454 (pty_cfg.close_on_exit == AUTO && pty_exit_code != 0)) {
456 if (WIFEXITED(pty_exit_code))
457 sprintf(message, "\r\n[pterm: process terminated with exit"
458 " code %d]\r\n", WEXITSTATUS(pty_exit_code));
459 else if (WIFSIGNALED(pty_exit_code))
460 #ifdef HAVE_NO_STRSIGNAL
461 sprintf(message, "\r\n[pterm: process terminated on signal"
462 " %d]\r\n", WTERMSIG(pty_exit_code));
464 sprintf(message, "\r\n[pterm: process terminated on signal"
465 " %d (%.400s)]\r\n", WTERMSIG(pty_exit_code),
466 strsignal(WTERMSIG(pty_exit_code)));
468 from_backend(pty_frontend, 0, message, strlen(message));
474 static void pty_uxsel_setup(void)
476 uxsel_set(pty_master_fd, 1, pty_select_result);
477 uxsel_set(pty_signal_pipe[0], 1, pty_select_result);
481 * Called to set up the pty.
483 * Returns an error message, or NULL on success.
485 * Also places the canonical host name into `realhost'. It must be
486 * freed by the caller.
488 static char *pty_init(void *frontend, void **backend_handle, Config *cfg,
489 char *host, int port, char **realhost, int nodelay)
495 pty_frontend = frontend;
496 *backend_handle = NULL; /* we can't sensibly use this, sadly */
498 pty_cfg = *cfg; /* structure copy */
499 pty_term_width = cfg->width;
500 pty_term_height = cfg->height;
502 if (pty_master_fd < 0)
506 * Set the backspace character to be whichever of ^H and ^? is
507 * specified by bksp_is_delete.
510 struct termios attrs;
511 tcgetattr(pty_master_fd, &attrs);
512 attrs.c_cc[VERASE] = cfg->bksp_is_delete ? '\177' : '\010';
513 tcsetattr(pty_master_fd, TCSANOW, &attrs);
517 * Stamp utmp (that is, tell the utmp helper process to do so),
520 if (!cfg->stamp_utmp)
521 close(pty_utmp_helper_pipe); /* just let the child process die */
523 char *location = get_x_display(pty_frontend);
524 int len = strlen(location)+1, pos = 0; /* +1 to include NUL */
526 int ret = write(pty_utmp_helper_pipe, location+pos, len - pos);
528 perror("pterm: writing to utmp helper process");
529 close(pty_utmp_helper_pipe); /* arrgh, just give up */
536 windowid = get_windowid(pty_frontend);
539 * Fork and execute the command.
553 slavefd = open(pty_name, O_RDWR);
555 perror("slave pty: open");
559 close(pty_master_fd);
560 fcntl(slavefd, F_SETFD, 0); /* don't close on exec */
565 ioctl(slavefd, TIOCSCTTY, 1);
567 tcsetpgrp(slavefd, pgrp);
569 close(open(pty_name, O_WRONLY, 0));
571 /* Close everything _else_, for tidiness. */
572 for (i = 3; i < 1024; i++)
575 char term_env_var[10 + sizeof(cfg->termtype)];
576 sprintf(term_env_var, "TERM=%s", cfg->termtype);
577 putenv(term_env_var);
580 char windowid_env_var[40];
581 sprintf(windowid_env_var, "WINDOWID=%ld", windowid);
582 putenv(windowid_env_var);
585 * SIGINT and SIGQUIT may have been set to ignored by our
586 * parent, particularly by things like sh -c 'pterm &' and
587 * some window managers. Reverse this for our child process.
589 putty_signal(SIGINT, SIG_DFL);
590 putty_signal(SIGQUIT, SIG_DFL);
592 execvp(pty_argv[0], pty_argv);
594 char *shell = getenv("SHELL");
596 if (cfg->login_shell) {
597 char *p = strrchr(shell, '/');
598 shellname = snewn(2+strlen(shell), char);
600 sprintf(shellname, "-%s", p);
603 execl(getenv("SHELL"), shellname, NULL);
607 * If we're here, exec has gone badly foom.
613 pty_child_dead = FALSE;
614 pty_finished = FALSE;
617 if (pipe(pty_signal_pipe) < 0) {
626 static void pty_reconfig(void *handle, Config *cfg)
629 * We don't have much need to reconfigure this backend, but
630 * unfortunately we do need to pick up the setting of Close On
631 * Exit so we know whether to give a `terminated' message.
633 pty_cfg = *cfg; /* structure copy */
637 * Stub routine (never called in pterm).
639 static void pty_free(void *handle)
644 * Called to send data down the pty.
646 static int pty_send(void *handle, char *buf, int len)
648 if (pty_master_fd < 0)
649 return 0; /* ignore all writes if fd closed */
652 int ret = write(pty_master_fd, buf, len);
654 perror("write pty master");
663 static void pty_close(void)
665 if (pty_master_fd >= 0) {
666 close(pty_master_fd);
669 close(pty_utmp_helper_pipe); /* this causes utmp to be cleaned up */
673 * Called to query the current socket sendability status.
675 static int pty_sendbuffer(void *handle)
681 * Called to set the size of the window
683 static void pty_size(void *handle, int width, int height)
687 pty_term_width = width;
688 pty_term_height = height;
690 size.ws_row = (unsigned short)pty_term_height;
691 size.ws_col = (unsigned short)pty_term_width;
692 size.ws_xpixel = (unsigned short) pty_term_width *
693 font_dimension(pty_frontend, 0);
694 size.ws_ypixel = (unsigned short) pty_term_height *
695 font_dimension(pty_frontend, 1);
696 ioctl(pty_master_fd, TIOCSWINSZ, (void *)&size);
701 * Send special codes.
703 static void pty_special(void *handle, Telnet_Special code)
710 * Return a list of the special codes that make sense in this
713 static const struct telnet_special *pty_get_specials(void *handle)
716 * Hmm. When I get round to having this actually usable, it
717 * might be quite nice to have the ability to deliver a few
718 * well chosen signals to the child process - SIGINT, SIGTERM,
724 static Socket pty_socket(void *handle)
726 return NULL; /* shouldn't ever be needed */
729 static int pty_sendok(void *handle)
734 static void pty_unthrottle(void *handle, int backlog)
739 static int pty_ldisc(void *handle, int option)
741 return 0; /* neither editing nor echoing */
744 static void pty_provide_ldisc(void *handle, void *ldisc)
746 /* This is a stub. */
749 static void pty_provide_logctx(void *handle, void *logctx)
751 /* This is a stub. */
754 static int pty_exitcode(void *handle)
757 return -1; /* not dead yet */
759 return pty_exit_code;
762 Backend pty_backend = {