Annotation of embedaddon/sudo/src/exec_pty.c, revision 1.1.1.1
1.1 misho 1: /*
2: * Copyright (c) 2009-2011 Todd C. Miller <Todd.Miller@courtesan.com>
3: *
4: * Permission to use, copy, modify, and distribute this software for any
5: * purpose with or without fee is hereby granted, provided that the above
6: * copyright notice and this permission notice appear in all copies.
7: *
8: * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
9: * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
10: * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
11: * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
12: * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
13: * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
14: * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
15: */
16:
17: #include <config.h>
18:
19: #include <sys/types.h>
20: #include <sys/param.h>
21: #ifdef HAVE_SYS_SYSMACROS_H
22: # include <sys/sysmacros.h>
23: #endif
24: #include <sys/socket.h>
25: #include <sys/time.h>
26: #include <sys/wait.h>
27: #include <sys/ioctl.h>
28: #ifdef HAVE_SYS_SELECT_H
29: # include <sys/select.h>
30: #endif /* HAVE_SYS_SELECT_H */
31: #include <stdio.h>
32: #ifdef STDC_HEADERS
33: # include <stdlib.h>
34: # include <stddef.h>
35: #else
36: # ifdef HAVE_STDLIB_H
37: # include <stdlib.h>
38: # endif
39: #endif /* STDC_HEADERS */
40: #ifdef HAVE_STRING_H
41: # if defined(HAVE_MEMORY_H) && !defined(STDC_HEADERS)
42: # include <memory.h>
43: # endif
44: # include <string.h>
45: #endif /* HAVE_STRING_H */
46: #ifdef HAVE_STRINGS_H
47: # include <strings.h>
48: #endif /* HAVE_STRINGS_H */
49: #ifdef HAVE_UNISTD_H
50: # include <unistd.h>
51: #endif /* HAVE_UNISTD_H */
52: #if TIME_WITH_SYS_TIME
53: # include <time.h>
54: #endif
55: #include <errno.h>
56: #include <fcntl.h>
57: #include <signal.h>
58: #include <termios.h>
59:
60: #include "sudo.h"
61: #include "sudo_exec.h"
62: #include "sudo_plugin.h"
63: #include "sudo_plugin_int.h"
64:
65: #define SFD_STDIN 0
66: #define SFD_STDOUT 1
67: #define SFD_STDERR 2
68: #define SFD_MASTER 3
69: #define SFD_SLAVE 4
70: #define SFD_USERTTY 5
71:
72: #define TERM_COOKED 0
73: #define TERM_RAW 1
74:
75: /* Compatibility with older tty systems. */
76: #if !defined(TIOCGWINSZ) && defined(TIOCGSIZE)
77: # define TIOCGWINSZ TIOCGSIZE
78: # define TIOCSWINSZ TIOCSSIZE
79: # define winsize ttysize
80: #endif
81:
82: struct io_buffer {
83: struct io_buffer *next;
84: int len; /* buffer length (how much produced) */
85: int off; /* write position (how much already consumed) */
86: int rfd; /* reader (producer) */
87: int wfd; /* writer (consumer) */
88: int (*action)(const char *buf, unsigned int len);
89: char buf[16 * 1024];
90: };
91:
92: static char slavename[PATH_MAX];
93: static int foreground;
94: static int io_fds[6] = { -1, -1, -1, -1, -1, -1};
95: static int pipeline = FALSE;
96: static int tty_initialized;
97: static int ttymode = TERM_COOKED;
98: static pid_t ppgrp, child, child_pgrp;
99: static sigset_t ttyblock;
100: static struct io_buffer *iobufs;
101:
102: static void flush_output(void);
103: static int exec_monitor(struct command_details *details, int backchannel);
104: static void exec_pty(struct command_details *detail);
105: static void sigwinch(int s);
106: static void sync_ttysize(int src, int dst);
107: static void deliver_signal(pid_t pid, int signo);
108: static int safe_close(int fd);
109:
110: /*
111: * Cleanup hook for error()/errorx()
112: */
113: void
114: cleanup(int gotsignal)
115: {
116: if (!tq_empty(&io_plugins))
117: term_restore(io_fds[SFD_USERTTY], 0);
118: #ifdef HAVE_SELINUX
119: selinux_restore_tty();
120: #endif
121: utmp_logout(slavename, 0); /* XXX - only if CD_SET_UTMP */
122: }
123:
124: /*
125: * Allocate a pty if /dev/tty is a tty.
126: * Fills in io_fds[SFD_USERTTY], io_fds[SFD_MASTER], io_fds[SFD_SLAVE]
127: * and slavename globals.
128: */
129: void
130: pty_setup(uid_t uid, const char *tty, const char *utmp_user)
131: {
132: io_fds[SFD_USERTTY] = open(_PATH_TTY, O_RDWR|O_NOCTTY, 0);
133: if (io_fds[SFD_USERTTY] != -1) {
134: if (!get_pty(&io_fds[SFD_MASTER], &io_fds[SFD_SLAVE],
135: slavename, sizeof(slavename), uid))
136: error(1, _("unable to allocate pty"));
137: /* Add entry to utmp/utmpx? */
138: if (utmp_user != NULL)
139: utmp_login(tty, slavename, io_fds[SFD_SLAVE], utmp_user);
140: }
141: }
142:
143: /* Call I/O plugin tty input log method. */
144: static int
145: log_ttyin(const char *buf, unsigned int n)
146: {
147: struct plugin_container *plugin;
148: sigset_t omask;
149: int rval = TRUE;
150:
151: sigprocmask(SIG_BLOCK, &ttyblock, &omask);
152:
153: tq_foreach_fwd(&io_plugins, plugin) {
154: if (plugin->u.io->log_ttyin) {
155: if (!plugin->u.io->log_ttyin(buf, n)) {
156: rval = FALSE;
157: break;
158: }
159: }
160: }
161:
162: sigprocmask(SIG_SETMASK, &omask, NULL);
163: return rval;
164: }
165:
166: /* Call I/O plugin stdin log method. */
167: static int
168: log_stdin(const char *buf, unsigned int n)
169: {
170: struct plugin_container *plugin;
171: sigset_t omask;
172: int rval = TRUE;
173:
174: sigprocmask(SIG_BLOCK, &ttyblock, &omask);
175:
176: tq_foreach_fwd(&io_plugins, plugin) {
177: if (plugin->u.io->log_stdin) {
178: if (!plugin->u.io->log_stdin(buf, n)) {
179: rval = FALSE;
180: break;
181: }
182: }
183: }
184:
185: sigprocmask(SIG_SETMASK, &omask, NULL);
186: return rval;
187: }
188:
189: /* Call I/O plugin tty output log method. */
190: static int
191: log_ttyout(const char *buf, unsigned int n)
192: {
193: struct plugin_container *plugin;
194: sigset_t omask;
195: int rval = TRUE;
196:
197: sigprocmask(SIG_BLOCK, &ttyblock, &omask);
198:
199: tq_foreach_fwd(&io_plugins, plugin) {
200: if (plugin->u.io->log_ttyout) {
201: if (!plugin->u.io->log_ttyout(buf, n)) {
202: rval = FALSE;
203: break;
204: }
205: }
206: }
207:
208: sigprocmask(SIG_SETMASK, &omask, NULL);
209: return rval;
210: }
211:
212: /* Call I/O plugin stdout log method. */
213: static int
214: log_stdout(const char *buf, unsigned int n)
215: {
216: struct plugin_container *plugin;
217: sigset_t omask;
218: int rval = TRUE;
219:
220: sigprocmask(SIG_BLOCK, &ttyblock, &omask);
221:
222: tq_foreach_fwd(&io_plugins, plugin) {
223: if (plugin->u.io->log_stdout) {
224: if (!plugin->u.io->log_stdout(buf, n)) {
225: rval = FALSE;
226: break;
227: }
228: }
229: }
230:
231: sigprocmask(SIG_SETMASK, &omask, NULL);
232: return rval;
233: }
234:
235: /* Call I/O plugin stderr log method. */
236: static int
237: log_stderr(const char *buf, unsigned int n)
238: {
239: struct plugin_container *plugin;
240: sigset_t omask;
241: int rval = TRUE;
242:
243: sigprocmask(SIG_BLOCK, &ttyblock, &omask);
244:
245: tq_foreach_fwd(&io_plugins, plugin) {
246: if (plugin->u.io->log_stderr) {
247: if (!plugin->u.io->log_stderr(buf, n)) {
248: rval = FALSE;
249: break;
250: }
251: }
252: }
253:
254: sigprocmask(SIG_SETMASK, &omask, NULL);
255: return rval;
256: }
257:
258: /*
259: * Check whether we are running in the foregroup.
260: * Updates the foreground global and does lazy init of the
261: * the pty slave as needed.
262: */
263: static void
264: check_foreground(void)
265: {
266: if (io_fds[SFD_USERTTY] != -1) {
267: foreground = tcgetpgrp(io_fds[SFD_USERTTY]) == ppgrp;
268: if (foreground && !tty_initialized) {
269: if (term_copy(io_fds[SFD_USERTTY], io_fds[SFD_SLAVE])) {
270: tty_initialized = 1;
271: sync_ttysize(io_fds[SFD_USERTTY], io_fds[SFD_SLAVE]);
272: }
273: }
274: }
275: }
276:
277: /*
278: * Suspend sudo if the underlying command is suspended.
279: * Returns SIGCONT_FG if the child should be resume in the
280: * foreground or SIGCONT_BG if it is a background process.
281: */
282: int
283: suspend_parent(int signo)
284: {
285: sigaction_t sa, osa;
286: int n, oldmode = ttymode, rval = 0;
287:
288: switch (signo) {
289: case SIGTTOU:
290: case SIGTTIN:
291: /*
292: * If we are the foreground process, just resume the child.
293: * Otherwise, re-send the signal with the handler disabled.
294: */
295: if (!foreground)
296: check_foreground();
297: if (foreground) {
298: if (ttymode != TERM_RAW) {
299: do {
300: n = term_raw(io_fds[SFD_USERTTY], 0);
301: } while (!n && errno == EINTR);
302: ttymode = TERM_RAW;
303: }
304: rval = SIGCONT_FG; /* resume child in foreground */
305: break;
306: }
307: ttymode = TERM_RAW;
308: /* FALLTHROUGH */
309: case SIGSTOP:
310: case SIGTSTP:
311: /* Flush any remaining output before suspending. */
312: flush_output();
313:
314: /* Restore original tty mode before suspending. */
315: if (oldmode != TERM_COOKED) {
316: do {
317: n = term_restore(io_fds[SFD_USERTTY], 0);
318: } while (!n && errno == EINTR);
319: }
320:
321: /* Suspend self and continue child when we resume. */
322: sa.sa_handler = SIG_DFL;
323: sigaction(signo, &sa, &osa);
324: sudo_debug(8, "kill parent %d", signo);
325: if (killpg(ppgrp, signo) != 0)
326: warning("killpg(%d, %d)", (int)ppgrp, signo);
327:
328: /* Check foreground/background status on resume. */
329: check_foreground();
330:
331: /*
332: * Only modify term if we are foreground process and either
333: * the old tty mode was not cooked or child got SIGTT{IN,OU}
334: */
335: sudo_debug(8, "parent is in %s, ttymode %d -> %d",
336: foreground ? "foreground" : "background", oldmode, ttymode);
337:
338: if (ttymode != TERM_COOKED) {
339: if (foreground) {
340: /* Set raw mode. */
341: do {
342: n = term_raw(io_fds[SFD_USERTTY], 0);
343: } while (!n && errno == EINTR);
344: } else {
345: /* Background process, no access to tty. */
346: ttymode = TERM_COOKED;
347: }
348: }
349:
350: sigaction(signo, &osa, NULL);
351: rval = ttymode == TERM_RAW ? SIGCONT_FG : SIGCONT_BG;
352: break;
353: }
354:
355: return rval;
356: }
357:
358: /*
359: * Kill child with increasing urgency.
360: */
361: void
362: terminate_child(pid_t pid, int use_pgrp)
363: {
364: /*
365: * Note that SIGCHLD will interrupt the sleep()
366: */
367: if (use_pgrp) {
368: killpg(pid, SIGHUP);
369: killpg(pid, SIGTERM);
370: sleep(2);
371: killpg(pid, SIGKILL);
372: } else {
373: kill(pid, SIGHUP);
374: kill(pid, SIGTERM);
375: sleep(2);
376: kill(pid, SIGKILL);
377: }
378: }
379:
380: static struct io_buffer *
381: io_buf_new(int rfd, int wfd, int (*action)(const char *, unsigned int),
382: struct io_buffer *head)
383: {
384: struct io_buffer *iob;
385:
386: iob = emalloc(sizeof(*iob));
387: zero_bytes(iob, sizeof(*iob));
388: iob->rfd = rfd;
389: iob->wfd = wfd;
390: iob->action = action;
391: iob->next = head;
392: return iob;
393: }
394:
395: /*
396: * Read/write iobufs depending on fdsr and fdsw.
397: * Returns the number of errors.
398: */
399: int
400: perform_io(fd_set *fdsr, fd_set *fdsw, struct command_status *cstat)
401: {
402: struct io_buffer *iob;
403: int n, errors = 0;
404:
405: for (iob = iobufs; iob; iob = iob->next) {
406: if (iob->rfd != -1 && FD_ISSET(iob->rfd, fdsr)) {
407: do {
408: n = read(iob->rfd, iob->buf + iob->len,
409: sizeof(iob->buf) - iob->len);
410: } while (n == -1 && errno == EINTR);
411: switch (n) {
412: case -1:
413: if (errno == EAGAIN)
414: break;
415: if (errno != ENXIO && errno != EBADF) {
416: errors++;
417: break;
418: }
419: /* FALLTHROUGH */
420: case 0:
421: /* got EOF or pty has gone away */
422: safe_close(iob->rfd);
423: iob->rfd = -1;
424: break;
425: default:
426: if (!iob->action(iob->buf + iob->len, n))
427: terminate_child(child, TRUE);
428: iob->len += n;
429: break;
430: }
431: }
432: if (iob->wfd != -1 && FD_ISSET(iob->wfd, fdsw)) {
433: do {
434: n = write(iob->wfd, iob->buf + iob->off,
435: iob->len - iob->off);
436: } while (n == -1 && errno == EINTR);
437: if (n == -1) {
438: if (errno == EPIPE || errno == ENXIO || errno == EBADF) {
439: /* other end of pipe closed or pty revoked */
440: if (iob->rfd != -1) {
441: safe_close(iob->rfd);
442: iob->rfd = -1;
443: }
444: safe_close(iob->wfd);
445: iob->wfd = -1;
446: continue;
447: }
448: if (errno != EAGAIN)
449: errors++;
450: } else {
451: iob->off += n;
452: }
453: }
454: }
455: if (errors && cstat != NULL) {
456: cstat->type = CMD_ERRNO;
457: cstat->val = errno;
458: }
459: return errors;
460: }
461:
462: /*
463: * Fork a monitor process which runs the actual command as its own child
464: * process with std{in,out,err} hooked up to the pty or pipes as appropriate.
465: * Returns the child pid.
466: */
467: int
468: fork_pty(struct command_details *details, int sv[], int *maxfd)
469: {
470: struct command_status cstat;
471: struct io_buffer *iob;
472: int io_pipe[3][2], n;
473: sigaction_t sa;
474:
475: ppgrp = getpgrp(); /* parent's pgrp, so child can signal us */
476:
477: zero_bytes(&sa, sizeof(sa));
478: sigemptyset(&sa.sa_mask);
479:
480: if (io_fds[SFD_USERTTY] != -1) {
481: sa.sa_flags = SA_RESTART;
482: sa.sa_handler = sigwinch;
483: sigaction(SIGWINCH, &sa, NULL);
484: }
485:
486: /* So we can block tty-generated signals */
487: sigemptyset(&ttyblock);
488: sigaddset(&ttyblock, SIGINT);
489: sigaddset(&ttyblock, SIGQUIT);
490: sigaddset(&ttyblock, SIGTSTP);
491: sigaddset(&ttyblock, SIGTTIN);
492: sigaddset(&ttyblock, SIGTTOU);
493:
494: /*
495: * Setup stdin/stdout/stderr for child, to be duped after forking.
496: * In background mode there is no stdin.
497: */
498: if (!ISSET(details->flags, CD_BACKGROUND))
499: io_fds[SFD_STDIN] = io_fds[SFD_SLAVE];
500: io_fds[SFD_STDOUT] = io_fds[SFD_SLAVE];
501: io_fds[SFD_STDERR] = io_fds[SFD_SLAVE];
502:
503: if (io_fds[SFD_USERTTY] != -1) {
504: /* Read from /dev/tty, write to pty master */
505: if (!ISSET(details->flags, CD_BACKGROUND)) {
506: iobufs = io_buf_new(io_fds[SFD_USERTTY], io_fds[SFD_MASTER],
507: log_ttyin, iobufs);
508: }
509:
510: /* Read from pty master, write to /dev/tty */
511: iobufs = io_buf_new(io_fds[SFD_MASTER], io_fds[SFD_USERTTY],
512: log_ttyout, iobufs);
513:
514: /* Are we the foreground process? */
515: foreground = tcgetpgrp(io_fds[SFD_USERTTY]) == ppgrp;
516: }
517:
518: /*
519: * If either stdin, stdout or stderr is not a tty we use a pipe
520: * to interpose ourselves instead of duping the pty fd.
521: */
522: memset(io_pipe, 0, sizeof(io_pipe));
523: if (io_fds[SFD_STDIN] == -1 || !isatty(STDIN_FILENO)) {
524: pipeline = TRUE;
525: if (pipe(io_pipe[STDIN_FILENO]) != 0)
526: error(1, _("unable to create pipe"));
527: iobufs = io_buf_new(STDIN_FILENO, io_pipe[STDIN_FILENO][1],
528: log_stdin, iobufs);
529: io_fds[SFD_STDIN] = io_pipe[STDIN_FILENO][0];
530: }
531: if (io_fds[SFD_STDOUT] == -1 || !isatty(STDOUT_FILENO)) {
532: pipeline = TRUE;
533: if (pipe(io_pipe[STDOUT_FILENO]) != 0)
534: error(1, _("unable to create pipe"));
535: iobufs = io_buf_new(io_pipe[STDOUT_FILENO][0], STDOUT_FILENO,
536: log_stdout, iobufs);
537: io_fds[SFD_STDOUT] = io_pipe[STDOUT_FILENO][1];
538: }
539: if (io_fds[SFD_STDERR] == -1 || !isatty(STDERR_FILENO)) {
540: if (pipe(io_pipe[STDERR_FILENO]) != 0)
541: error(1, _("unable to create pipe"));
542: iobufs = io_buf_new(io_pipe[STDERR_FILENO][0], STDERR_FILENO,
543: log_stderr, iobufs);
544: io_fds[SFD_STDERR] = io_pipe[STDERR_FILENO][1];
545: }
546:
547: /* Job control signals to relay from parent to child. */
548: sa.sa_flags = SA_INTERRUPT; /* do not restart syscalls */
549: sa.sa_handler = handler;
550: sigaction(SIGTSTP, &sa, NULL);
551:
552: if (foreground) {
553: /* Copy terminal attrs from user tty -> pty slave. */
554: if (term_copy(io_fds[SFD_USERTTY], io_fds[SFD_SLAVE])) {
555: tty_initialized = 1;
556: sync_ttysize(io_fds[SFD_USERTTY], io_fds[SFD_SLAVE]);
557: }
558:
559: /* Start out in raw mode if we are not part of a pipeline. */
560: if (!pipeline) {
561: ttymode = TERM_RAW;
562: do {
563: n = term_raw(io_fds[SFD_USERTTY], 0);
564: } while (!n && errno == EINTR);
565: if (!n)
566: error(1, _("unable to set terminal to raw mode"));
567: }
568: }
569:
570: child = fork();
571: switch (child) {
572: case -1:
573: error(1, _("unable to fork"));
574: break;
575: case 0:
576: /* child */
577: close(sv[0]);
578: close(signal_pipe[0]);
579: close(signal_pipe[1]);
580: fcntl(sv[1], F_SETFD, FD_CLOEXEC);
581: if (exec_setup(details, slavename, io_fds[SFD_SLAVE]) == TRUE) {
582: /* Close the other end of the stdin/stdout/stderr pipes and exec. */
583: if (io_pipe[STDIN_FILENO][1])
584: close(io_pipe[STDIN_FILENO][1]);
585: if (io_pipe[STDOUT_FILENO][0])
586: close(io_pipe[STDOUT_FILENO][0]);
587: if (io_pipe[STDERR_FILENO][0])
588: close(io_pipe[STDERR_FILENO][0]);
589: exec_monitor(details, sv[1]);
590: }
591: cstat.type = CMD_ERRNO;
592: cstat.val = errno;
593: send(sv[1], &cstat, sizeof(cstat), 0);
594: _exit(1);
595: }
596:
597: /* Close the other end of the stdin/stdout/stderr pipes. */
598: if (io_pipe[STDIN_FILENO][0])
599: close(io_pipe[STDIN_FILENO][0]);
600: if (io_pipe[STDOUT_FILENO][1])
601: close(io_pipe[STDOUT_FILENO][1]);
602: if (io_pipe[STDERR_FILENO][1])
603: close(io_pipe[STDERR_FILENO][1]);
604:
605: for (iob = iobufs; iob; iob = iob->next) {
606: /* Determine maxfd */
607: if (iob->rfd > *maxfd)
608: *maxfd = iob->rfd;
609: if (iob->wfd > *maxfd)
610: *maxfd = iob->wfd;
611:
612: /* Set non-blocking mode. */
613: n = fcntl(iob->rfd, F_GETFL, 0);
614: if (n != -1 && !ISSET(n, O_NONBLOCK))
615: (void) fcntl(iob->rfd, F_SETFL, n | O_NONBLOCK);
616: n = fcntl(iob->wfd, F_GETFL, 0);
617: if (n != -1 && !ISSET(n, O_NONBLOCK))
618: (void) fcntl(iob->wfd, F_SETFL, n | O_NONBLOCK);
619: }
620:
621: return child;
622: }
623:
624: void
625: pty_close(struct command_status *cstat)
626: {
627: int n;
628:
629: /* Flush any remaining output (the plugin already got it) */
630: if (io_fds[SFD_USERTTY] != -1) {
631: n = fcntl(io_fds[SFD_USERTTY], F_GETFL, 0);
632: if (n != -1 && ISSET(n, O_NONBLOCK)) {
633: CLR(n, O_NONBLOCK);
634: (void) fcntl(io_fds[SFD_USERTTY], F_SETFL, n);
635: }
636: }
637: flush_output();
638:
639: if (io_fds[SFD_USERTTY] != -1) {
640: do {
641: n = term_restore(io_fds[SFD_USERTTY], 0);
642: } while (!n && errno == EINTR);
643: }
644:
645: /* If child was signalled, write the reason to stdout like the shell. */
646: if (cstat->type == CMD_WSTATUS && WIFSIGNALED(cstat->val)) {
647: int signo = WTERMSIG(cstat->val);
648: if (signo && signo != SIGINT && signo != SIGPIPE) {
649: const char *reason = strsignal(signo);
650: n = io_fds[SFD_USERTTY] != -1 ?
651: io_fds[SFD_USERTTY] : STDOUT_FILENO;
652: if (write(n, reason, strlen(reason)) != -1) {
653: if (WCOREDUMP(cstat->val)) {
654: if (write(n, " (core dumped)", 14) == -1)
655: /* shut up glibc */;
656: }
657: if (write(n, "\n", 1) == -1)
658: /* shut up glibc */;
659: }
660: }
661: }
662: utmp_logout(slavename, cstat->type == CMD_WSTATUS ? cstat->val : 0); /* XXX - only if CD_SET_UTMP */
663: }
664:
665: /*
666: * Fill in fdsr and fdsw based on the io buffers list.
667: * Called prior to select().
668: */
669: void
670: fd_set_iobs(fd_set *fdsr, fd_set *fdsw)
671: {
672: struct io_buffer *iob;
673:
674: for (iob = iobufs; iob; iob = iob->next) {
675: if (iob->rfd == -1 && iob->wfd == -1)
676: continue;
677: if (iob->off == iob->len) {
678: iob->off = iob->len = 0;
679: /* Forward the EOF from reader to writer. */
680: if (iob->rfd == -1) {
681: safe_close(iob->wfd);
682: iob->wfd = -1;
683: }
684: }
685: /* Don't read/write /dev/tty if we are not in the foreground. */
686: if (iob->rfd != -1 &&
687: (ttymode == TERM_RAW || iob->rfd != io_fds[SFD_USERTTY])) {
688: if (iob->len != sizeof(iob->buf))
689: FD_SET(iob->rfd, fdsr);
690: }
691: if (iob->wfd != -1 &&
692: (foreground || iob->wfd != io_fds[SFD_USERTTY])) {
693: if (iob->len > iob->off)
694: FD_SET(iob->wfd, fdsw);
695: }
696: }
697: }
698:
699: static void
700: deliver_signal(pid_t pid, int signo)
701: {
702: int status;
703:
704: /* Handle signal from parent. */
705: sudo_debug(8, "signal %d from parent", signo);
706: switch (signo) {
707: case SIGALRM:
708: terminate_child(pid, TRUE);
709: break;
710: case SIGCONT_FG:
711: /* Continue in foreground, grant it controlling tty. */
712: do {
713: status = tcsetpgrp(io_fds[SFD_SLAVE], child_pgrp);
714: } while (status == -1 && errno == EINTR);
715: killpg(pid, SIGCONT);
716: break;
717: case SIGCONT_BG:
718: /* Continue in background, I take controlling tty. */
719: do {
720: status = tcsetpgrp(io_fds[SFD_SLAVE], getpid());
721: } while (status == -1 && errno == EINTR);
722: killpg(pid, SIGCONT);
723: break;
724: case SIGKILL:
725: _exit(1); /* XXX */
726: /* NOTREACHED */
727: default:
728: /* Relay signal to child. */
729: killpg(pid, signo);
730: break;
731: }
732: }
733:
734: /*
735: * Send status to parent over socketpair.
736: * Return value is the same as send(2).
737: */
738: static int
739: send_status(int fd, struct command_status *cstat)
740: {
741: int n = -1;
742:
743: if (cstat->type != CMD_INVALID) {
744: do {
745: n = send(fd, cstat, sizeof(*cstat), 0);
746: } while (n == -1 && errno == EINTR);
747: if (n != sizeof(*cstat)) {
748: sudo_debug(8, "unable to send status to parent: %s",
749: strerror(errno));
750: } else {
751: sudo_debug(8, "sent status to parent");
752: }
753: cstat->type = CMD_INVALID; /* prevent re-sending */
754: }
755: return n;
756: }
757:
758: /*
759: * Wait for child status after receiving SIGCHLD.
760: * If the child was stopped, the status is send back to the parent.
761: * Otherwise, cstat is filled in but not sent.
762: * Returns TRUE if child is still alive, else FALSE.
763: */
764: static int
765: handle_sigchld(int backchannel, struct command_status *cstat)
766: {
767: int status, alive = TRUE;
768: pid_t pid;
769:
770: /* read child status */
771: do {
772: pid = waitpid(child, &status, WUNTRACED|WNOHANG);
773: } while (pid == -1 && errno == EINTR);
774: if (pid == child) {
775: if (cstat->type != CMD_ERRNO) {
776: cstat->type = CMD_WSTATUS;
777: cstat->val = status;
778: if (WIFSTOPPED(status)) {
779: sudo_debug(8, "command stopped, signal %d", WSTOPSIG(status));
780: do {
781: child_pgrp = tcgetpgrp(io_fds[SFD_SLAVE]);
782: } while (child_pgrp == -1 && errno == EINTR);
783: if (send_status(backchannel, cstat) == -1)
784: return alive; /* XXX */
785: } else if (WIFSIGNALED(status)) {
786: sudo_debug(8, "command killed, signal %d", WTERMSIG(status));
787: } else {
788: sudo_debug(8, "command exited: %d", WEXITSTATUS(status));
789: }
790: }
791: if (!WIFSTOPPED(status))
792: alive = FALSE;
793: }
794: return alive;
795: }
796:
797: /*
798: * Monitor process that creates a new session with the controlling tty,
799: * resets signal handlers and forks a child to call exec_pty().
800: * Waits for status changes from the command and relays them to the
801: * parent and relays signals from the parent to the command.
802: * Returns an error if fork(2) fails, else calls _exit(2).
803: */
804: static int
805: exec_monitor(struct command_details *details, int backchannel)
806: {
807: struct command_status cstat;
808: struct timeval tv;
809: fd_set *fdsr;
810: sigaction_t sa;
811: int errpipe[2], maxfd, n, status;
812: int alive = TRUE;
813: unsigned char signo;
814:
815: /* Close unused fds. */
816: if (io_fds[SFD_MASTER] != -1)
817: close(io_fds[SFD_MASTER]);
818: if (io_fds[SFD_USERTTY] != -1)
819: close(io_fds[SFD_USERTTY]);
820:
821: /*
822: * We use a pipe to atomically handle signal notification within
823: * the select() loop.
824: */
825: if (pipe_nonblock(signal_pipe) != 0)
826: error(1, _("unable to create pipe"));
827:
828: /* Reset SIGWINCH and SIGALRM. */
829: zero_bytes(&sa, sizeof(sa));
830: sigemptyset(&sa.sa_mask);
831: sa.sa_flags = SA_RESTART;
832: sa.sa_handler = SIG_DFL;
833: sigaction(SIGWINCH, &sa, NULL);
834: sigaction(SIGALRM, &sa, NULL);
835:
836: /* Ignore any SIGTTIN or SIGTTOU we get. */
837: sa.sa_handler = SIG_IGN;
838: sigaction(SIGTTIN, &sa, NULL);
839: sigaction(SIGTTOU, &sa, NULL);
840:
841: /* Note: HP-UX select() will not be interrupted if SA_RESTART set */
842: sa.sa_flags = SA_INTERRUPT;
843: sa.sa_handler = handler;
844: sigaction(SIGCHLD, &sa, NULL);
845:
846: /*
847: * Start a new session with the parent as the session leader
848: * and the slave pty as the controlling terminal.
849: * This allows us to be notified when the child has been suspended.
850: */
851: if (setsid() == -1) {
852: warning("setsid");
853: goto bad;
854: }
855: if (io_fds[SFD_SLAVE] != -1) {
856: #ifdef TIOCSCTTY
857: if (ioctl(io_fds[SFD_SLAVE], TIOCSCTTY, NULL) != 0)
858: error(1, _("unable to set controlling tty"));
859: #else
860: /* Set controlling tty by reopening slave. */
861: if ((n = open(slavename, O_RDWR)) >= 0)
862: close(n);
863: #endif
864: }
865:
866: /*
867: * If stdin/stdout is not a tty, start command in the background
868: * since it might be part of a pipeline that reads from /dev/tty.
869: * In this case, we rely on the command receiving SIGTTOU or SIGTTIN
870: * when it needs access to the controlling tty.
871: */
872: if (pipeline)
873: foreground = 0;
874:
875: /* Start command and wait for it to stop or exit */
876: if (pipe(errpipe) == -1)
877: error(1, _("unable to create pipe"));
878: child = fork();
879: if (child == -1) {
880: warning(_("unable to fork"));
881: goto bad;
882: }
883: if (child == 0) {
884: /* We pass errno back to our parent via pipe on exec failure. */
885: close(backchannel);
886: close(signal_pipe[0]);
887: close(signal_pipe[1]);
888: close(errpipe[0]);
889: fcntl(errpipe[1], F_SETFD, FD_CLOEXEC);
890: restore_signals();
891:
892: /* setup tty and exec command */
893: exec_pty(details);
894: cstat.type = CMD_ERRNO;
895: cstat.val = errno;
896: if (write(errpipe[1], &cstat, sizeof(cstat)) == -1)
897: /* shut up glibc */;
898: _exit(1);
899: }
900: close(errpipe[1]);
901:
902: /* If any of stdin/stdout/stderr are pipes, close them in parent. */
903: if (io_fds[SFD_STDIN] != io_fds[SFD_SLAVE])
904: close(io_fds[SFD_STDIN]);
905: if (io_fds[SFD_STDOUT] != io_fds[SFD_SLAVE])
906: close(io_fds[SFD_STDOUT]);
907: if (io_fds[SFD_STDERR] != io_fds[SFD_SLAVE])
908: close(io_fds[SFD_STDERR]);
909:
910: /*
911: * Put child in its own process group. If we are starting the command
912: * in the foreground, assign its pgrp to the tty.
913: */
914: child_pgrp = child;
915: setpgid(child, child_pgrp);
916: if (foreground) {
917: do {
918: status = tcsetpgrp(io_fds[SFD_SLAVE], child_pgrp);
919: } while (status == -1 && errno == EINTR);
920: }
921:
922: /* Wait for errno on pipe, signal on backchannel or for SIGCHLD */
923: maxfd = MAX(MAX(errpipe[0], signal_pipe[0]), backchannel);
924: fdsr = (fd_set *)emalloc2(howmany(maxfd + 1, NFDBITS), sizeof(fd_mask));
925: zero_bytes(fdsr, howmany(maxfd + 1, NFDBITS) * sizeof(fd_mask));
926: zero_bytes(&cstat, sizeof(cstat));
927: tv.tv_sec = 0;
928: tv.tv_usec = 0;
929: for (;;) {
930: /* Check for signal on backchannel or errno on errpipe. */
931: FD_SET(backchannel, fdsr);
932: FD_SET(signal_pipe[0], fdsr);
933: if (errpipe[0] != -1)
934: FD_SET(errpipe[0], fdsr);
935: maxfd = MAX(MAX(errpipe[0], signal_pipe[0]), backchannel);
936:
937: /* If command exited we just poll, there may be data on errpipe. */
938: n = select(maxfd + 1, fdsr, NULL, NULL, alive ? NULL : &tv);
939: if (n <= 0) {
940: if (n == 0)
941: goto done;
942: if (errno == EINTR)
943: continue;
944: error(1, _("select failed"));
945: }
946:
947: if (FD_ISSET(signal_pipe[0], fdsr)) {
948: n = read(signal_pipe[0], &signo, sizeof(signo));
949: if (n == -1) {
950: if (errno == EINTR || errno == EAGAIN)
951: continue;
952: warning(_("error reading from signal pipe"));
953: goto done;
954: }
955: /*
956: * Handle SIGCHLD specially and deliver other signals
957: * directly to the child.
958: */
959: if (signo == SIGCHLD)
960: alive = handle_sigchld(backchannel, &cstat);
961: else
962: deliver_signal(child, signo);
963: continue;
964: }
965: if (errpipe[0] != -1 && FD_ISSET(errpipe[0], fdsr)) {
966: /* read errno or EOF from command pipe */
967: n = read(errpipe[0], &cstat, sizeof(cstat));
968: if (n == -1) {
969: if (errno == EINTR)
970: continue;
971: warning(_("error reading from pipe"));
972: goto done;
973: }
974: /* Got errno or EOF, either way we are done with errpipe. */
975: FD_CLR(errpipe[0], fdsr);
976: close(errpipe[0]);
977: errpipe[0] = -1;
978: }
979: if (FD_ISSET(backchannel, fdsr)) {
980: struct command_status cstmp;
981:
982: /* read command from backchannel, should be a signal */
983: n = recv(backchannel, &cstmp, sizeof(cstmp), 0);
984: if (n == -1) {
985: if (errno == EINTR)
986: continue;
987: warning(_("error reading from socketpair"));
988: goto done;
989: }
990: if (cstmp.type != CMD_SIGNO) {
991: warningx(_("unexpected reply type on backchannel: %d"),
992: cstmp.type);
993: continue;
994: }
995: deliver_signal(child, cstmp.val);
996: }
997: }
998:
999: done:
1000: if (alive) {
1001: /* XXX An error occurred, should send an error back. */
1002: kill(child, SIGKILL);
1003: } else {
1004: /* Send parent status. */
1005: send_status(backchannel, &cstat);
1006: }
1007: _exit(1);
1008:
1009: bad:
1010: return errno;
1011: }
1012:
1013: /*
1014: * Flush any output buffered in iobufs or readable from the fds.
1015: * Does not read from /dev/tty.
1016: */
1017: static void
1018: flush_output(void)
1019: {
1020: struct io_buffer *iob;
1021: struct timeval tv;
1022: fd_set *fdsr, *fdsw;
1023: int nready, nwriters, maxfd = -1;
1024:
1025: /* Determine maxfd */
1026: for (iob = iobufs; iob; iob = iob->next) {
1027: if (iob->rfd > maxfd)
1028: maxfd = iob->rfd;
1029: if (iob->wfd > maxfd)
1030: maxfd = iob->wfd;
1031: }
1032: if (maxfd == -1)
1033: return;
1034:
1035: fdsr = (fd_set *)emalloc2(howmany(maxfd + 1, NFDBITS), sizeof(fd_mask));
1036: fdsw = (fd_set *)emalloc2(howmany(maxfd + 1, NFDBITS), sizeof(fd_mask));
1037: for (;;) {
1038: zero_bytes(fdsw, howmany(maxfd + 1, NFDBITS) * sizeof(fd_mask));
1039: zero_bytes(fdsr, howmany(maxfd + 1, NFDBITS) * sizeof(fd_mask));
1040:
1041: nwriters = 0;
1042: for (iob = iobufs; iob; iob = iob->next) {
1043: /* Don't read from /dev/tty while flushing. */
1044: if (io_fds[SFD_USERTTY] != -1 && iob->rfd == io_fds[SFD_USERTTY])
1045: continue;
1046: if (iob->rfd == -1 && iob->wfd == -1)
1047: continue;
1048: if (iob->off == iob->len) {
1049: iob->off = iob->len = 0;
1050: /* Forward the EOF from reader to writer. */
1051: if (iob->rfd == -1) {
1052: safe_close(iob->wfd);
1053: iob->wfd = -1;
1054: }
1055: }
1056: if (iob->rfd != -1) {
1057: if (iob->len != sizeof(iob->buf))
1058: FD_SET(iob->rfd, fdsr);
1059: }
1060: if (iob->wfd != -1) {
1061: if (iob->len > iob->off) {
1062: nwriters++;
1063: FD_SET(iob->wfd, fdsw);
1064: }
1065: }
1066: }
1067:
1068: /* Don't sleep in select if there are no buffers that need writing. */
1069: tv.tv_sec = 0;
1070: tv.tv_usec = 0;
1071: nready = select(maxfd + 1, fdsr, fdsw, NULL, nwriters ? NULL : &tv);
1072: if (nready <= 0) {
1073: if (nready == 0)
1074: break; /* all I/O flushed */
1075: if (errno == EINTR)
1076: continue;
1077: error(1, _("select failed"));
1078: }
1079: if (perform_io(fdsr, fdsw, NULL) != 0)
1080: break;
1081: }
1082: efree(fdsr);
1083: efree(fdsw);
1084: }
1085:
1086: /*
1087: * Sets up std{in,out,err} and executes the actual command.
1088: * Returns only if execve() fails.
1089: */
1090: static void
1091: exec_pty(struct command_details *details)
1092: {
1093: pid_t self = getpid();
1094:
1095: /* Set child process group here too to avoid a race. */
1096: setpgid(0, self);
1097:
1098: /* Wire up standard fds, note that stdout/stderr may be pipes. */
1099: if (dup2(io_fds[SFD_STDIN], STDIN_FILENO) == -1 ||
1100: dup2(io_fds[SFD_STDOUT], STDOUT_FILENO) == -1 ||
1101: dup2(io_fds[SFD_STDERR], STDERR_FILENO) == -1)
1102: error(1, "dup2");
1103:
1104: /* Wait for parent to grant us the tty if we are foreground. */
1105: if (foreground) {
1106: while (tcgetpgrp(io_fds[SFD_SLAVE]) != self)
1107: ; /* spin */
1108: }
1109:
1110: /* We have guaranteed that the slave fd is > 2 */
1111: if (io_fds[SFD_SLAVE] != -1)
1112: close(io_fds[SFD_SLAVE]);
1113: if (io_fds[SFD_STDIN] != io_fds[SFD_SLAVE])
1114: close(io_fds[SFD_STDIN]);
1115: if (io_fds[SFD_STDOUT] != io_fds[SFD_SLAVE])
1116: close(io_fds[SFD_STDOUT]);
1117: if (io_fds[SFD_STDERR] != io_fds[SFD_SLAVE])
1118: close(io_fds[SFD_STDERR]);
1119:
1120: if (details->closefrom >= 0)
1121: closefrom(details->closefrom);
1122: #ifdef HAVE_SELINUX
1123: if (ISSET(details->flags, CD_RBAC_ENABLED))
1124: selinux_execve(details->command, details->argv, details->envp);
1125: else
1126: #endif
1127: my_execve(details->command, details->argv, details->envp);
1128: }
1129:
1130: /*
1131: * Propagates tty size change signals to pty being used by the command.
1132: */
1133: static void
1134: sync_ttysize(int src, int dst)
1135: {
1136: #ifdef TIOCGWINSZ
1137: struct winsize wsize;
1138: pid_t pgrp;
1139:
1140: if (ioctl(src, TIOCGWINSZ, &wsize) == 0) {
1141: ioctl(dst, TIOCSWINSZ, &wsize);
1142: if ((pgrp = tcgetpgrp(dst)) != -1)
1143: killpg(pgrp, SIGWINCH);
1144: }
1145: #endif
1146: }
1147:
1148: /*
1149: * Handler for SIGWINCH in parent.
1150: */
1151: static void
1152: sigwinch(int s)
1153: {
1154: int serrno = errno;
1155:
1156: sync_ttysize(io_fds[SFD_USERTTY], io_fds[SFD_SLAVE]);
1157: errno = serrno;
1158: }
1159:
1160: /*
1161: * Only close the fd if it is not /dev/tty or std{in,out,err}.
1162: * Return value is the same as send(2).
1163: */
1164: static int
1165: safe_close(int fd)
1166: {
1167: /* Avoid closing /dev/tty or std{in,out,err}. */
1168: if (fd < 3 || fd == io_fds[SFD_USERTTY]) {
1169: errno = EINVAL;
1170: return -1;
1171: }
1172: return close(fd);
1173: }
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