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
29 #include <sys/types.h>
31 #include <sys/ioctl.h>
43 #define UTMP_FILE "/var/run/utmp"
46 #define WTMP_FILE "/var/log/wtmp"
50 #define LASTLOG_FILE _PATH_LASTLOG
52 #define LASTLOG_FILE "/var/log/lastlog"
57 * Set up a default for vaguely sane systems. The idea is that if
58 * OMIT_UTMP is not defined, then at least one of the symbols which
59 * enable particular forms of utmp processing should be, if only so
60 * that a link error can warn you that you should have defined
61 * OMIT_UTMP if you didn't want any. Currently HAVE_PUTUTLINE is
62 * the only such symbol.
65 #if !defined HAVE_PUTUTLINE
66 #define HAVE_PUTUTLINE
71 static char pty_name
[FILENAME_MAX
];
72 static int pty_stamped_utmp
= 0;
73 static int pty_child_pid
;
74 static int pty_utmp_helper_pid
, pty_utmp_helper_pipe
;
75 static int pty_term_width
, pty_term_height
;
76 static sig_atomic_t pty_child_dead
;
77 static int pty_exit_code
;
79 static struct utmp utmp_entry
;
83 static void setup_utmp(char *ttyname
, char *location
)
87 struct lastlog lastlog_entry
;
93 pw
= getpwuid(getuid());
94 memset(&utmp_entry
, 0, sizeof(utmp_entry
));
95 utmp_entry
.ut_type
= USER_PROCESS
;
96 utmp_entry
.ut_pid
= getpid();
97 strncpy(utmp_entry
.ut_line
, ttyname
+5, lenof(utmp_entry
.ut_line
));
98 strncpy(utmp_entry
.ut_id
, ttyname
+8, lenof(utmp_entry
.ut_id
));
99 strncpy(utmp_entry
.ut_user
, pw
->pw_name
, lenof(utmp_entry
.ut_user
));
100 strncpy(utmp_entry
.ut_host
, location
, lenof(utmp_entry
.ut_host
));
101 time(&utmp_entry
.ut_time
);
103 #if defined HAVE_PUTUTLINE
106 pututline(&utmp_entry
);
110 if ((wtmp
= fopen(WTMP_FILE
, "a")) != NULL
) {
111 fwrite(&utmp_entry
, 1, sizeof(utmp_entry
), wtmp
);
116 memset(&lastlog_entry
, 0, sizeof(lastlog_entry
));
117 strncpy(lastlog_entry
.ll_line
, ttyname
+5, lenof(lastlog_entry
.ll_line
));
118 strncpy(lastlog_entry
.ll_host
, location
, lenof(lastlog_entry
.ll_host
));
119 time(&lastlog_entry
.ll_time
);
120 if ((lastlog
= fopen(LASTLOG_FILE
, "r+")) != NULL
) {
121 fseek(lastlog
, sizeof(lastlog_entry
) * getuid(), SEEK_SET
);
122 fwrite(&lastlog_entry
, 1, sizeof(lastlog_entry
), lastlog
);
127 pty_stamped_utmp
= 1;
132 static void cleanup_utmp(void)
137 if (!pty_stamped_utmp
)
140 utmp_entry
.ut_type
= DEAD_PROCESS
;
141 memset(utmp_entry
.ut_user
, 0, lenof(utmp_entry
.ut_user
));
142 time(&utmp_entry
.ut_time
);
144 if ((wtmp
= fopen(WTMP_FILE
, "a")) != NULL
) {
145 fwrite(&utmp_entry
, 1, sizeof(utmp_entry
), wtmp
);
149 memset(utmp_entry
.ut_line
, 0, lenof(utmp_entry
.ut_line
));
150 utmp_entry
.ut_time
= 0;
152 #if defined HAVE_PUTUTLINE
155 pututline(&utmp_entry
);
159 pty_stamped_utmp
= 0; /* ensure we never double-cleanup */
163 static void sigchld_handler(int signum
)
167 pid
= waitpid(-1, &status
, WNOHANG
);
168 if (pid
== pty_child_pid
&& (WIFEXITED(status
) || WIFSIGNALED(status
))) {
169 pty_exit_code
= status
;
170 pty_child_dead
= TRUE
;
174 static void fatal_sig_handler(int signum
)
176 signal(signum
, SIG_DFL
);
182 static void pty_open_master(void)
185 const char chars1
[] = "pqrstuvwxyz";
186 const char chars2
[] = "0123456789abcdef";
188 char master_name
[20];
191 for (p1
= chars1
; *p1
; p1
++)
192 for (p2
= chars2
; *p2
; p2
++) {
193 sprintf(master_name
, "/dev/pty%c%c", *p1
, *p2
);
194 pty_master_fd
= open(master_name
, O_RDWR
);
195 if (pty_master_fd
>= 0) {
196 if (geteuid() == 0 ||
197 access(master_name
, R_OK
| W_OK
) == 0)
199 close(pty_master_fd
);
203 /* If we get here, we couldn't get a tty at all. */
204 fprintf(stderr
, "pterm: unable to open a pseudo-terminal device\n");
208 strcpy(pty_name
, master_name
);
209 pty_name
[5] = 't'; /* /dev/ptyXX -> /dev/ttyXX */
211 /* We need to chown/chmod the /dev/ttyXX device. */
212 gp
= getgrnam("tty");
213 chown(pty_name
, getuid(), gp ? gp
->gr_gid
: -1);
214 chmod(pty_name
, 0600);
216 pty_master_fd
= open("/dev/ptmx", O_RDWR
);
218 if (pty_master_fd
< 0) {
219 perror("/dev/ptmx: open");
223 if (grantpt(pty_master_fd
) < 0) {
228 if (unlockpt(pty_master_fd
) < 0) {
233 pty_name
[FILENAME_MAX
-1] = '\0';
234 strncpy(pty_name
, ptsname(pty_master_fd
), FILENAME_MAX
-1);
239 * Pre-initialisation. This is here to get around the fact that GTK
240 * doesn't like being run in setuid/setgid programs (probably
241 * sensibly). So before we initialise GTK - and therefore before we
242 * even process the command line - we check to see if we're running
243 * set[ug]id. If so, we open our pty master _now_, chown it as
244 * necessary, and drop privileges. We can always close it again
245 * later. If we're potentially going to be doing utmp as well, we
246 * also fork off a utmp helper process and communicate with it by
247 * means of a pipe; the utmp helper will keep privileges in order
248 * to clean up utmp when we exit (i.e. when its end of our pipe
251 void pty_pre_init(void)
258 if (geteuid() != getuid() || getegid() != getgid()) {
264 * Fork off the utmp helper.
266 if (pipe(pipefd
) < 0) {
267 perror("pterm: pipe");
272 perror("pterm: fork");
274 } else if (pid
== 0) {
275 char display
[128], buffer
[128];
280 * Now sit here until we receive a display name from the
281 * other end of the pipe, and then stamp utmp. Unstamp utmp
282 * again, and exit, when the pipe closes.
288 ret
= read(pipefd
[0], buffer
, lenof(buffer
));
292 } else if (!pty_stamped_utmp
) {
293 if (dlen
< lenof(display
))
294 memcpy(display
+dlen
, buffer
,
295 min(ret
, lenof(display
)-dlen
));
296 if (buffer
[ret
-1] == '\0') {
298 * Now we have a display name. NUL-terminate
299 * it, and stamp utmp.
301 display
[lenof(display
)-1] = '\0';
303 * Trap as many fatal signals as we can in the
304 * hope of having the best possible chance to
305 * clean up utmp before termination. We are
306 * unfortunately unprotected against SIGKILL,
309 signal(SIGHUP
, fatal_sig_handler
);
310 signal(SIGINT
, fatal_sig_handler
);
311 signal(SIGQUIT
, fatal_sig_handler
);
312 signal(SIGILL
, fatal_sig_handler
);
313 signal(SIGABRT
, fatal_sig_handler
);
314 signal(SIGFPE
, fatal_sig_handler
);
315 signal(SIGPIPE
, fatal_sig_handler
);
316 signal(SIGALRM
, fatal_sig_handler
);
317 signal(SIGTERM
, fatal_sig_handler
);
318 signal(SIGSEGV
, fatal_sig_handler
);
319 signal(SIGUSR1
, fatal_sig_handler
);
320 signal(SIGUSR2
, fatal_sig_handler
);
322 signal(SIGBUS
, fatal_sig_handler
);
325 signal(SIGPOLL
, fatal_sig_handler
);
328 signal(SIGPROF
, fatal_sig_handler
);
331 signal(SIGSYS
, fatal_sig_handler
);
334 signal(SIGTRAP
, fatal_sig_handler
);
337 signal(SIGVTALRM
, fatal_sig_handler
);
340 signal(SIGXCPU
, fatal_sig_handler
);
343 signal(SIGXFSZ
, fatal_sig_handler
);
346 signal(SIGIO
, fatal_sig_handler
);
348 /* Also clean up utmp on normal exit. */
349 atexit(cleanup_utmp
);
350 setup_utmp(pty_name
, display
);
356 pty_utmp_helper_pid
= pid
;
357 pty_utmp_helper_pipe
= pipefd
[1];
358 signal(SIGCHLD
, sigchld_handler
);
364 int gid
= getgid(), uid
= getuid();
365 #ifndef HAVE_NO_SETRESUID
366 int setresgid(gid_t
, gid_t
, gid_t
);
367 int setresuid(uid_t
, uid_t
, uid_t
);
368 setresgid(gid
, gid
, gid
);
369 setresuid(uid
, uid
, uid
);
378 * Called to set up the pty.
380 * Returns an error message, or NULL on success.
382 * Also places the canonical host name into `realhost'. It must be
383 * freed by the caller.
385 static char *pty_init(void *frontend
, void **backend_handle
,
386 char *host
, int port
, char **realhost
, int nodelay
)
391 *backend_handle
= NULL
; /* we can't sensibly use this, sadly */
393 pty_term_width
= cfg
.width
;
394 pty_term_height
= cfg
.height
;
396 if (pty_master_fd
< 0)
400 * Set the backspace character to be whichever of ^H and ^? is
401 * specified by bksp_is_delete.
404 struct termios attrs
;
405 tcgetattr(pty_master_fd
, &attrs
);
406 attrs
.c_cc
[VERASE
] = cfg
.bksp_is_delete ?
'\177' : '\010';
407 tcsetattr(pty_master_fd
, TCSANOW
, &attrs
);
411 * Stamp utmp (that is, tell the utmp helper process to do so),
415 close(pty_utmp_helper_pipe
); /* just let the child process die */
417 char *location
= get_x_display();
418 int len
= strlen(location
)+1, pos
= 0; /* +1 to include NUL */
420 int ret
= write(pty_utmp_helper_pipe
, location
+pos
, len
- pos
);
422 perror("pterm: writing to utmp helper process");
423 close(pty_utmp_helper_pipe
); /* arrgh, just give up */
431 * Fork and execute the command.
445 slavefd
= open(pty_name
, O_RDWR
);
447 perror("slave pty: open");
451 close(pty_master_fd
);
452 fcntl(slavefd
, F_SETFD
, 0); /* don't close on exec */
457 ioctl(slavefd
, TIOCSCTTY
, 1);
459 tcsetpgrp(slavefd
, pgrp
);
461 close(open(pty_name
, O_WRONLY
, 0));
463 /* Close everything _else_, for tidiness. */
464 for (i
= 3; i
< 1024; i
++)
467 char term_env_var
[10 + sizeof(cfg
.termtype
)];
468 sprintf(term_env_var
, "TERM=%s", cfg
.termtype
);
469 putenv(term_env_var
);
472 * SIGINT and SIGQUIT may have been set to ignored by our
473 * parent, particularly by things like sh -c 'pterm &' and
474 * some window managers. Reverse this for our child process.
476 signal(SIGINT
, SIG_DFL
);
477 signal(SIGQUIT
, SIG_DFL
);
479 execvp(pty_argv
[0], pty_argv
);
481 char *shell
= getenv("SHELL");
483 if (cfg
.login_shell
) {
484 char *p
= strrchr(shell
, '/');
485 shellname
= smalloc(2+strlen(shell
));
487 sprintf(shellname
, "-%s", p
);
490 execl(getenv("SHELL"), shellname
, NULL
);
494 * If we're here, exec has gone badly foom.
501 pty_child_dead
= FALSE
;
502 signal(SIGCHLD
, sigchld_handler
);
509 * Called to send data down the pty.
511 static int pty_send(void *handle
, char *buf
, int len
)
513 if (pty_master_fd
< 0)
514 return 0; /* ignore all writes if fd closed */
517 int ret
= write(pty_master_fd
, buf
, len
);
519 perror("write pty master");
530 if (pty_master_fd
>= 0) {
531 close(pty_master_fd
);
534 close(pty_utmp_helper_pipe
); /* this causes utmp to be cleaned up */
538 * Called to query the current socket sendability status.
540 static int pty_sendbuffer(void *handle
)
546 * Called to set the size of the window
548 static void pty_size(void *handle
, int width
, int height
)
552 pty_term_width
= width
;
553 pty_term_height
= height
;
555 size
.ws_row
= (unsigned short)pty_term_height
;
556 size
.ws_col
= (unsigned short)pty_term_width
;
557 size
.ws_xpixel
= (unsigned short) pty_term_width
* font_dimension(0);
558 size
.ws_ypixel
= (unsigned short) pty_term_height
* font_dimension(1);
559 ioctl(pty_master_fd
, TIOCSWINSZ
, (void *)&size
);
564 * Send special codes.
566 static void pty_special(void *handle
, Telnet_Special code
)
572 static Socket
pty_socket(void *handle
)
574 return NULL
; /* shouldn't ever be needed */
577 static int pty_sendok(void *handle
)
582 static void pty_unthrottle(void *handle
, int backlog
)
587 static int pty_ldisc(void *handle
, int option
)
589 return 0; /* neither editing nor echoing */
592 static int pty_exitcode(void *handle
)
595 return -1; /* not dead yet */
597 return pty_exit_code
;
600 Backend pty_backend
= {