/* * Copyright (c) 2009-2011 Todd C. Miller * * Permission to use, copy, modify, and distribute this software for any * purpose with or without fee is hereby granted, provided that the above * copyright notice and this permission notice appear in all copies. * * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE. */ #include #include #include #ifdef HAVE_SYS_SYSMACROS_H # include #endif #include #include #include #include #ifdef HAVE_SYS_SELECT_H # include #endif /* HAVE_SYS_SELECT_H */ #include #ifdef STDC_HEADERS # include # include #else # ifdef HAVE_STDLIB_H # include # endif #endif /* STDC_HEADERS */ #ifdef HAVE_STRING_H # if defined(HAVE_MEMORY_H) && !defined(STDC_HEADERS) # include # endif # include #endif /* HAVE_STRING_H */ #ifdef HAVE_STRINGS_H # include #endif /* HAVE_STRINGS_H */ #ifdef HAVE_UNISTD_H # include #endif /* HAVE_UNISTD_H */ #if TIME_WITH_SYS_TIME # include #endif #include #include #include #include #include "sudo.h" #include "sudo_exec.h" #include "sudo_plugin.h" #include "sudo_plugin_int.h" #define SFD_STDIN 0 #define SFD_STDOUT 1 #define SFD_STDERR 2 #define SFD_MASTER 3 #define SFD_SLAVE 4 #define SFD_USERTTY 5 #define TERM_COOKED 0 #define TERM_RAW 1 /* Compatibility with older tty systems. */ #if !defined(TIOCGWINSZ) && defined(TIOCGSIZE) # define TIOCGWINSZ TIOCGSIZE # define TIOCSWINSZ TIOCSSIZE # define winsize ttysize #endif struct io_buffer { struct io_buffer *next; int len; /* buffer length (how much produced) */ int off; /* write position (how much already consumed) */ int rfd; /* reader (producer) */ int wfd; /* writer (consumer) */ int (*action)(const char *buf, unsigned int len); char buf[16 * 1024]; }; static char slavename[PATH_MAX]; static int foreground; static int io_fds[6] = { -1, -1, -1, -1, -1, -1}; static int pipeline = FALSE; static int tty_initialized; static int ttymode = TERM_COOKED; static pid_t ppgrp, child, child_pgrp; static sigset_t ttyblock; static struct io_buffer *iobufs; static void flush_output(void); static int exec_monitor(struct command_details *details, int backchannel); static void exec_pty(struct command_details *detail); static void sigwinch(int s); static void sync_ttysize(int src, int dst); static void deliver_signal(pid_t pid, int signo); static int safe_close(int fd); /* * Cleanup hook for error()/errorx() */ void cleanup(int gotsignal) { if (!tq_empty(&io_plugins)) term_restore(io_fds[SFD_USERTTY], 0); #ifdef HAVE_SELINUX selinux_restore_tty(); #endif utmp_logout(slavename, 0); /* XXX - only if CD_SET_UTMP */ } /* * Allocate a pty if /dev/tty is a tty. * Fills in io_fds[SFD_USERTTY], io_fds[SFD_MASTER], io_fds[SFD_SLAVE] * and slavename globals. */ void pty_setup(uid_t uid, const char *tty, const char *utmp_user) { io_fds[SFD_USERTTY] = open(_PATH_TTY, O_RDWR|O_NOCTTY, 0); if (io_fds[SFD_USERTTY] != -1) { if (!get_pty(&io_fds[SFD_MASTER], &io_fds[SFD_SLAVE], slavename, sizeof(slavename), uid)) error(1, _("unable to allocate pty")); /* Add entry to utmp/utmpx? */ if (utmp_user != NULL) utmp_login(tty, slavename, io_fds[SFD_SLAVE], utmp_user); } } /* Call I/O plugin tty input log method. */ static int log_ttyin(const char *buf, unsigned int n) { struct plugin_container *plugin; sigset_t omask; int rval = TRUE; sigprocmask(SIG_BLOCK, &ttyblock, &omask); tq_foreach_fwd(&io_plugins, plugin) { if (plugin->u.io->log_ttyin) { if (!plugin->u.io->log_ttyin(buf, n)) { rval = FALSE; break; } } } sigprocmask(SIG_SETMASK, &omask, NULL); return rval; } /* Call I/O plugin stdin log method. */ static int log_stdin(const char *buf, unsigned int n) { struct plugin_container *plugin; sigset_t omask; int rval = TRUE; sigprocmask(SIG_BLOCK, &ttyblock, &omask); tq_foreach_fwd(&io_plugins, plugin) { if (plugin->u.io->log_stdin) { if (!plugin->u.io->log_stdin(buf, n)) { rval = FALSE; break; } } } sigprocmask(SIG_SETMASK, &omask, NULL); return rval; } /* Call I/O plugin tty output log method. */ static int log_ttyout(const char *buf, unsigned int n) { struct plugin_container *plugin; sigset_t omask; int rval = TRUE; sigprocmask(SIG_BLOCK, &ttyblock, &omask); tq_foreach_fwd(&io_plugins, plugin) { if (plugin->u.io->log_ttyout) { if (!plugin->u.io->log_ttyout(buf, n)) { rval = FALSE; break; } } } sigprocmask(SIG_SETMASK, &omask, NULL); return rval; } /* Call I/O plugin stdout log method. */ static int log_stdout(const char *buf, unsigned int n) { struct plugin_container *plugin; sigset_t omask; int rval = TRUE; sigprocmask(SIG_BLOCK, &ttyblock, &omask); tq_foreach_fwd(&io_plugins, plugin) { if (plugin->u.io->log_stdout) { if (!plugin->u.io->log_stdout(buf, n)) { rval = FALSE; break; } } } sigprocmask(SIG_SETMASK, &omask, NULL); return rval; } /* Call I/O plugin stderr log method. */ static int log_stderr(const char *buf, unsigned int n) { struct plugin_container *plugin; sigset_t omask; int rval = TRUE; sigprocmask(SIG_BLOCK, &ttyblock, &omask); tq_foreach_fwd(&io_plugins, plugin) { if (plugin->u.io->log_stderr) { if (!plugin->u.io->log_stderr(buf, n)) { rval = FALSE; break; } } } sigprocmask(SIG_SETMASK, &omask, NULL); return rval; } /* * Check whether we are running in the foregroup. * Updates the foreground global and does lazy init of the * the pty slave as needed. */ static void check_foreground(void) { if (io_fds[SFD_USERTTY] != -1) { foreground = tcgetpgrp(io_fds[SFD_USERTTY]) == ppgrp; if (foreground && !tty_initialized) { if (term_copy(io_fds[SFD_USERTTY], io_fds[SFD_SLAVE])) { tty_initialized = 1; sync_ttysize(io_fds[SFD_USERTTY], io_fds[SFD_SLAVE]); } } } } /* * Suspend sudo if the underlying command is suspended. * Returns SIGCONT_FG if the child should be resume in the * foreground or SIGCONT_BG if it is a background process. */ int suspend_parent(int signo) { sigaction_t sa, osa; int n, oldmode = ttymode, rval = 0; switch (signo) { case SIGTTOU: case SIGTTIN: /* * If we are the foreground process, just resume the child. * Otherwise, re-send the signal with the handler disabled. */ if (!foreground) check_foreground(); if (foreground) { if (ttymode != TERM_RAW) { do { n = term_raw(io_fds[SFD_USERTTY], 0); } while (!n && errno == EINTR); ttymode = TERM_RAW; } rval = SIGCONT_FG; /* resume child in foreground */ break; } ttymode = TERM_RAW; /* FALLTHROUGH */ case SIGSTOP: case SIGTSTP: /* Flush any remaining output before suspending. */ flush_output(); /* Restore original tty mode before suspending. */ if (oldmode != TERM_COOKED) { do { n = term_restore(io_fds[SFD_USERTTY], 0); } while (!n && errno == EINTR); } /* Suspend self and continue child when we resume. */ sa.sa_handler = SIG_DFL; sigaction(signo, &sa, &osa); sudo_debug(8, "kill parent %d", signo); if (killpg(ppgrp, signo) != 0) warning("killpg(%d, %d)", (int)ppgrp, signo); /* Check foreground/background status on resume. */ check_foreground(); /* * Only modify term if we are foreground process and either * the old tty mode was not cooked or child got SIGTT{IN,OU} */ sudo_debug(8, "parent is in %s, ttymode %d -> %d", foreground ? "foreground" : "background", oldmode, ttymode); if (ttymode != TERM_COOKED) { if (foreground) { /* Set raw mode. */ do { n = term_raw(io_fds[SFD_USERTTY], 0); } while (!n && errno == EINTR); } else { /* Background process, no access to tty. */ ttymode = TERM_COOKED; } } sigaction(signo, &osa, NULL); rval = ttymode == TERM_RAW ? SIGCONT_FG : SIGCONT_BG; break; } return rval; } /* * Kill child with increasing urgency. */ void terminate_child(pid_t pid, int use_pgrp) { /* * Note that SIGCHLD will interrupt the sleep() */ if (use_pgrp) { killpg(pid, SIGHUP); killpg(pid, SIGTERM); sleep(2); killpg(pid, SIGKILL); } else { kill(pid, SIGHUP); kill(pid, SIGTERM); sleep(2); kill(pid, SIGKILL); } } static struct io_buffer * io_buf_new(int rfd, int wfd, int (*action)(const char *, unsigned int), struct io_buffer *head) { struct io_buffer *iob; iob = emalloc(sizeof(*iob)); zero_bytes(iob, sizeof(*iob)); iob->rfd = rfd; iob->wfd = wfd; iob->action = action; iob->next = head; return iob; } /* * Read/write iobufs depending on fdsr and fdsw. * Returns the number of errors. */ int perform_io(fd_set *fdsr, fd_set *fdsw, struct command_status *cstat) { struct io_buffer *iob; int n, errors = 0; for (iob = iobufs; iob; iob = iob->next) { if (iob->rfd != -1 && FD_ISSET(iob->rfd, fdsr)) { do { n = read(iob->rfd, iob->buf + iob->len, sizeof(iob->buf) - iob->len); } while (n == -1 && errno == EINTR); switch (n) { case -1: if (errno == EAGAIN) break; if (errno != ENXIO && errno != EBADF) { errors++; break; } /* FALLTHROUGH */ case 0: /* got EOF or pty has gone away */ safe_close(iob->rfd); iob->rfd = -1; break; default: if (!iob->action(iob->buf + iob->len, n)) terminate_child(child, TRUE); iob->len += n; break; } } if (iob->wfd != -1 && FD_ISSET(iob->wfd, fdsw)) { do { n = write(iob->wfd, iob->buf + iob->off, iob->len - iob->off); } while (n == -1 && errno == EINTR); if (n == -1) { if (errno == EPIPE || errno == ENXIO || errno == EBADF) { /* other end of pipe closed or pty revoked */ if (iob->rfd != -1) { safe_close(iob->rfd); iob->rfd = -1; } safe_close(iob->wfd); iob->wfd = -1; continue; } if (errno != EAGAIN) errors++; } else { iob->off += n; } } } if (errors && cstat != NULL) { cstat->type = CMD_ERRNO; cstat->val = errno; } return errors; } /* * Fork a monitor process which runs the actual command as its own child * process with std{in,out,err} hooked up to the pty or pipes as appropriate. * Returns the child pid. */ int fork_pty(struct command_details *details, int sv[], int *maxfd) { struct command_status cstat; struct io_buffer *iob; int io_pipe[3][2], n; sigaction_t sa; ppgrp = getpgrp(); /* parent's pgrp, so child can signal us */ zero_bytes(&sa, sizeof(sa)); sigemptyset(&sa.sa_mask); if (io_fds[SFD_USERTTY] != -1) { sa.sa_flags = SA_RESTART; sa.sa_handler = sigwinch; sigaction(SIGWINCH, &sa, NULL); } /* So we can block tty-generated signals */ sigemptyset(&ttyblock); sigaddset(&ttyblock, SIGINT); sigaddset(&ttyblock, SIGQUIT); sigaddset(&ttyblock, SIGTSTP); sigaddset(&ttyblock, SIGTTIN); sigaddset(&ttyblock, SIGTTOU); /* * Setup stdin/stdout/stderr for child, to be duped after forking. * In background mode there is no stdin. */ if (!ISSET(details->flags, CD_BACKGROUND)) io_fds[SFD_STDIN] = io_fds[SFD_SLAVE]; io_fds[SFD_STDOUT] = io_fds[SFD_SLAVE]; io_fds[SFD_STDERR] = io_fds[SFD_SLAVE]; if (io_fds[SFD_USERTTY] != -1) { /* Read from /dev/tty, write to pty master */ if (!ISSET(details->flags, CD_BACKGROUND)) { iobufs = io_buf_new(io_fds[SFD_USERTTY], io_fds[SFD_MASTER], log_ttyin, iobufs); } /* Read from pty master, write to /dev/tty */ iobufs = io_buf_new(io_fds[SFD_MASTER], io_fds[SFD_USERTTY], log_ttyout, iobufs); /* Are we the foreground process? */ foreground = tcgetpgrp(io_fds[SFD_USERTTY]) == ppgrp; } /* * If either stdin, stdout or stderr is not a tty we use a pipe * to interpose ourselves instead of duping the pty fd. */ memset(io_pipe, 0, sizeof(io_pipe)); if (io_fds[SFD_STDIN] == -1 || !isatty(STDIN_FILENO)) { pipeline = TRUE; if (pipe(io_pipe[STDIN_FILENO]) != 0) error(1, _("unable to create pipe")); iobufs = io_buf_new(STDIN_FILENO, io_pipe[STDIN_FILENO][1], log_stdin, iobufs); io_fds[SFD_STDIN] = io_pipe[STDIN_FILENO][0]; } if (io_fds[SFD_STDOUT] == -1 || !isatty(STDOUT_FILENO)) { pipeline = TRUE; if (pipe(io_pipe[STDOUT_FILENO]) != 0) error(1, _("unable to create pipe")); iobufs = io_buf_new(io_pipe[STDOUT_FILENO][0], STDOUT_FILENO, log_stdout, iobufs); io_fds[SFD_STDOUT] = io_pipe[STDOUT_FILENO][1]; } if (io_fds[SFD_STDERR] == -1 || !isatty(STDERR_FILENO)) { if (pipe(io_pipe[STDERR_FILENO]) != 0) error(1, _("unable to create pipe")); iobufs = io_buf_new(io_pipe[STDERR_FILENO][0], STDERR_FILENO, log_stderr, iobufs); io_fds[SFD_STDERR] = io_pipe[STDERR_FILENO][1]; } /* Job control signals to relay from parent to child. */ sa.sa_flags = SA_INTERRUPT; /* do not restart syscalls */ sa.sa_handler = handler; sigaction(SIGTSTP, &sa, NULL); if (foreground) { /* Copy terminal attrs from user tty -> pty slave. */ if (term_copy(io_fds[SFD_USERTTY], io_fds[SFD_SLAVE])) { tty_initialized = 1; sync_ttysize(io_fds[SFD_USERTTY], io_fds[SFD_SLAVE]); } /* Start out in raw mode if we are not part of a pipeline. */ if (!pipeline) { ttymode = TERM_RAW; do { n = term_raw(io_fds[SFD_USERTTY], 0); } while (!n && errno == EINTR); if (!n) error(1, _("unable to set terminal to raw mode")); } } child = fork(); switch (child) { case -1: error(1, _("unable to fork")); break; case 0: /* child */ close(sv[0]); close(signal_pipe[0]); close(signal_pipe[1]); fcntl(sv[1], F_SETFD, FD_CLOEXEC); if (exec_setup(details, slavename, io_fds[SFD_SLAVE]) == TRUE) { /* Close the other end of the stdin/stdout/stderr pipes and exec. */ if (io_pipe[STDIN_FILENO][1]) close(io_pipe[STDIN_FILENO][1]); if (io_pipe[STDOUT_FILENO][0]) close(io_pipe[STDOUT_FILENO][0]); if (io_pipe[STDERR_FILENO][0]) close(io_pipe[STDERR_FILENO][0]); exec_monitor(details, sv[1]); } cstat.type = CMD_ERRNO; cstat.val = errno; send(sv[1], &cstat, sizeof(cstat), 0); _exit(1); } /* Close the other end of the stdin/stdout/stderr pipes. */ if (io_pipe[STDIN_FILENO][0]) close(io_pipe[STDIN_FILENO][0]); if (io_pipe[STDOUT_FILENO][1]) close(io_pipe[STDOUT_FILENO][1]); if (io_pipe[STDERR_FILENO][1]) close(io_pipe[STDERR_FILENO][1]); for (iob = iobufs; iob; iob = iob->next) { /* Determine maxfd */ if (iob->rfd > *maxfd) *maxfd = iob->rfd; if (iob->wfd > *maxfd) *maxfd = iob->wfd; /* Set non-blocking mode. */ n = fcntl(iob->rfd, F_GETFL, 0); if (n != -1 && !ISSET(n, O_NONBLOCK)) (void) fcntl(iob->rfd, F_SETFL, n | O_NONBLOCK); n = fcntl(iob->wfd, F_GETFL, 0); if (n != -1 && !ISSET(n, O_NONBLOCK)) (void) fcntl(iob->wfd, F_SETFL, n | O_NONBLOCK); } return child; } void pty_close(struct command_status *cstat) { int n; /* Flush any remaining output (the plugin already got it) */ if (io_fds[SFD_USERTTY] != -1) { n = fcntl(io_fds[SFD_USERTTY], F_GETFL, 0); if (n != -1 && ISSET(n, O_NONBLOCK)) { CLR(n, O_NONBLOCK); (void) fcntl(io_fds[SFD_USERTTY], F_SETFL, n); } } flush_output(); if (io_fds[SFD_USERTTY] != -1) { do { n = term_restore(io_fds[SFD_USERTTY], 0); } while (!n && errno == EINTR); } /* If child was signalled, write the reason to stdout like the shell. */ if (cstat->type == CMD_WSTATUS && WIFSIGNALED(cstat->val)) { int signo = WTERMSIG(cstat->val); if (signo && signo != SIGINT && signo != SIGPIPE) { const char *reason = strsignal(signo); n = io_fds[SFD_USERTTY] != -1 ? io_fds[SFD_USERTTY] : STDOUT_FILENO; if (write(n, reason, strlen(reason)) != -1) { if (WCOREDUMP(cstat->val)) { if (write(n, " (core dumped)", 14) == -1) /* shut up glibc */; } if (write(n, "\n", 1) == -1) /* shut up glibc */; } } } utmp_logout(slavename, cstat->type == CMD_WSTATUS ? cstat->val : 0); /* XXX - only if CD_SET_UTMP */ } /* * Fill in fdsr and fdsw based on the io buffers list. * Called prior to select(). */ void fd_set_iobs(fd_set *fdsr, fd_set *fdsw) { struct io_buffer *iob; for (iob = iobufs; iob; iob = iob->next) { if (iob->rfd == -1 && iob->wfd == -1) continue; if (iob->off == iob->len) { iob->off = iob->len = 0; /* Forward the EOF from reader to writer. */ if (iob->rfd == -1) { safe_close(iob->wfd); iob->wfd = -1; } } /* Don't read/write /dev/tty if we are not in the foreground. */ if (iob->rfd != -1 && (ttymode == TERM_RAW || iob->rfd != io_fds[SFD_USERTTY])) { if (iob->len != sizeof(iob->buf)) FD_SET(iob->rfd, fdsr); } if (iob->wfd != -1 && (foreground || iob->wfd != io_fds[SFD_USERTTY])) { if (iob->len > iob->off) FD_SET(iob->wfd, fdsw); } } } static void deliver_signal(pid_t pid, int signo) { int status; /* Handle signal from parent. */ sudo_debug(8, "signal %d from parent", signo); switch (signo) { case SIGALRM: terminate_child(pid, TRUE); break; case SIGCONT_FG: /* Continue in foreground, grant it controlling tty. */ do { status = tcsetpgrp(io_fds[SFD_SLAVE], child_pgrp); } while (status == -1 && errno == EINTR); killpg(pid, SIGCONT); break; case SIGCONT_BG: /* Continue in background, I take controlling tty. */ do { status = tcsetpgrp(io_fds[SFD_SLAVE], getpid()); } while (status == -1 && errno == EINTR); killpg(pid, SIGCONT); break; case SIGKILL: _exit(1); /* XXX */ /* NOTREACHED */ default: /* Relay signal to child. */ killpg(pid, signo); break; } } /* * Send status to parent over socketpair. * Return value is the same as send(2). */ static int send_status(int fd, struct command_status *cstat) { int n = -1; if (cstat->type != CMD_INVALID) { do { n = send(fd, cstat, sizeof(*cstat), 0); } while (n == -1 && errno == EINTR); if (n != sizeof(*cstat)) { sudo_debug(8, "unable to send status to parent: %s", strerror(errno)); } else { sudo_debug(8, "sent status to parent"); } cstat->type = CMD_INVALID; /* prevent re-sending */ } return n; } /* * Wait for child status after receiving SIGCHLD. * If the child was stopped, the status is send back to the parent. * Otherwise, cstat is filled in but not sent. * Returns TRUE if child is still alive, else FALSE. */ static int handle_sigchld(int backchannel, struct command_status *cstat) { int status, alive = TRUE; pid_t pid; /* read child status */ do { pid = waitpid(child, &status, WUNTRACED|WNOHANG); } while (pid == -1 && errno == EINTR); if (pid == child) { if (cstat->type != CMD_ERRNO) { cstat->type = CMD_WSTATUS; cstat->val = status; if (WIFSTOPPED(status)) { sudo_debug(8, "command stopped, signal %d", WSTOPSIG(status)); do { child_pgrp = tcgetpgrp(io_fds[SFD_SLAVE]); } while (child_pgrp == -1 && errno == EINTR); if (send_status(backchannel, cstat) == -1) return alive; /* XXX */ } else if (WIFSIGNALED(status)) { sudo_debug(8, "command killed, signal %d", WTERMSIG(status)); } else { sudo_debug(8, "command exited: %d", WEXITSTATUS(status)); } } if (!WIFSTOPPED(status)) alive = FALSE; } return alive; } /* * Monitor process that creates a new session with the controlling tty, * resets signal handlers and forks a child to call exec_pty(). * Waits for status changes from the command and relays them to the * parent and relays signals from the parent to the command. * Returns an error if fork(2) fails, else calls _exit(2). */ static int exec_monitor(struct command_details *details, int backchannel) { struct command_status cstat; struct timeval tv; fd_set *fdsr; sigaction_t sa; int errpipe[2], maxfd, n, status; int alive = TRUE; unsigned char signo; /* Close unused fds. */ if (io_fds[SFD_MASTER] != -1) close(io_fds[SFD_MASTER]); if (io_fds[SFD_USERTTY] != -1) close(io_fds[SFD_USERTTY]); /* * We use a pipe to atomically handle signal notification within * the select() loop. */ if (pipe_nonblock(signal_pipe) != 0) error(1, _("unable to create pipe")); /* Reset SIGWINCH and SIGALRM. */ zero_bytes(&sa, sizeof(sa)); sigemptyset(&sa.sa_mask); sa.sa_flags = SA_RESTART; sa.sa_handler = SIG_DFL; sigaction(SIGWINCH, &sa, NULL); sigaction(SIGALRM, &sa, NULL); /* Ignore any SIGTTIN or SIGTTOU we get. */ sa.sa_handler = SIG_IGN; sigaction(SIGTTIN, &sa, NULL); sigaction(SIGTTOU, &sa, NULL); /* Note: HP-UX select() will not be interrupted if SA_RESTART set */ sa.sa_flags = SA_INTERRUPT; sa.sa_handler = handler; sigaction(SIGCHLD, &sa, NULL); /* * Start a new session with the parent as the session leader * and the slave pty as the controlling terminal. * This allows us to be notified when the child has been suspended. */ if (setsid() == -1) { warning("setsid"); goto bad; } if (io_fds[SFD_SLAVE] != -1) { #ifdef TIOCSCTTY if (ioctl(io_fds[SFD_SLAVE], TIOCSCTTY, NULL) != 0) error(1, _("unable to set controlling tty")); #else /* Set controlling tty by reopening slave. */ if ((n = open(slavename, O_RDWR)) >= 0) close(n); #endif } /* * If stdin/stdout is not a tty, start command in the background * since it might be part of a pipeline that reads from /dev/tty. * In this case, we rely on the command receiving SIGTTOU or SIGTTIN * when it needs access to the controlling tty. */ if (pipeline) foreground = 0; /* Start command and wait for it to stop or exit */ if (pipe(errpipe) == -1) error(1, _("unable to create pipe")); child = fork(); if (child == -1) { warning(_("unable to fork")); goto bad; } if (child == 0) { /* We pass errno back to our parent via pipe on exec failure. */ close(backchannel); close(signal_pipe[0]); close(signal_pipe[1]); close(errpipe[0]); fcntl(errpipe[1], F_SETFD, FD_CLOEXEC); restore_signals(); /* setup tty and exec command */ exec_pty(details); cstat.type = CMD_ERRNO; cstat.val = errno; if (write(errpipe[1], &cstat, sizeof(cstat)) == -1) /* shut up glibc */; _exit(1); } close(errpipe[1]); /* If any of stdin/stdout/stderr are pipes, close them in parent. */ if (io_fds[SFD_STDIN] != io_fds[SFD_SLAVE]) close(io_fds[SFD_STDIN]); if (io_fds[SFD_STDOUT] != io_fds[SFD_SLAVE]) close(io_fds[SFD_STDOUT]); if (io_fds[SFD_STDERR] != io_fds[SFD_SLAVE]) close(io_fds[SFD_STDERR]); /* * Put child in its own process group. If we are starting the command * in the foreground, assign its pgrp to the tty. */ child_pgrp = child; setpgid(child, child_pgrp); if (foreground) { do { status = tcsetpgrp(io_fds[SFD_SLAVE], child_pgrp); } while (status == -1 && errno == EINTR); } /* Wait for errno on pipe, signal on backchannel or for SIGCHLD */ maxfd = MAX(MAX(errpipe[0], signal_pipe[0]), backchannel); fdsr = (fd_set *)emalloc2(howmany(maxfd + 1, NFDBITS), sizeof(fd_mask)); zero_bytes(fdsr, howmany(maxfd + 1, NFDBITS) * sizeof(fd_mask)); zero_bytes(&cstat, sizeof(cstat)); tv.tv_sec = 0; tv.tv_usec = 0; for (;;) { /* Check for signal on backchannel or errno on errpipe. */ FD_SET(backchannel, fdsr); FD_SET(signal_pipe[0], fdsr); if (errpipe[0] != -1) FD_SET(errpipe[0], fdsr); maxfd = MAX(MAX(errpipe[0], signal_pipe[0]), backchannel); /* If command exited we just poll, there may be data on errpipe. */ n = select(maxfd + 1, fdsr, NULL, NULL, alive ? NULL : &tv); if (n <= 0) { if (n == 0) goto done; if (errno == EINTR) continue; error(1, _("select failed")); } if (FD_ISSET(signal_pipe[0], fdsr)) { n = read(signal_pipe[0], &signo, sizeof(signo)); if (n == -1) { if (errno == EINTR || errno == EAGAIN) continue; warning(_("error reading from signal pipe")); goto done; } /* * Handle SIGCHLD specially and deliver other signals * directly to the child. */ if (signo == SIGCHLD) alive = handle_sigchld(backchannel, &cstat); else deliver_signal(child, signo); continue; } if (errpipe[0] != -1 && FD_ISSET(errpipe[0], fdsr)) { /* read errno or EOF from command pipe */ n = read(errpipe[0], &cstat, sizeof(cstat)); if (n == -1) { if (errno == EINTR) continue; warning(_("error reading from pipe")); goto done; } /* Got errno or EOF, either way we are done with errpipe. */ FD_CLR(errpipe[0], fdsr); close(errpipe[0]); errpipe[0] = -1; } if (FD_ISSET(backchannel, fdsr)) { struct command_status cstmp; /* read command from backchannel, should be a signal */ n = recv(backchannel, &cstmp, sizeof(cstmp), 0); if (n == -1) { if (errno == EINTR) continue; warning(_("error reading from socketpair")); goto done; } if (cstmp.type != CMD_SIGNO) { warningx(_("unexpected reply type on backchannel: %d"), cstmp.type); continue; } deliver_signal(child, cstmp.val); } } done: if (alive) { /* XXX An error occurred, should send an error back. */ kill(child, SIGKILL); } else { /* Send parent status. */ send_status(backchannel, &cstat); } _exit(1); bad: return errno; } /* * Flush any output buffered in iobufs or readable from the fds. * Does not read from /dev/tty. */ static void flush_output(void) { struct io_buffer *iob; struct timeval tv; fd_set *fdsr, *fdsw; int nready, nwriters, maxfd = -1; /* Determine maxfd */ for (iob = iobufs; iob; iob = iob->next) { if (iob->rfd > maxfd) maxfd = iob->rfd; if (iob->wfd > maxfd) maxfd = iob->wfd; } if (maxfd == -1) return; fdsr = (fd_set *)emalloc2(howmany(maxfd + 1, NFDBITS), sizeof(fd_mask)); fdsw = (fd_set *)emalloc2(howmany(maxfd + 1, NFDBITS), sizeof(fd_mask)); for (;;) { zero_bytes(fdsw, howmany(maxfd + 1, NFDBITS) * sizeof(fd_mask)); zero_bytes(fdsr, howmany(maxfd + 1, NFDBITS) * sizeof(fd_mask)); nwriters = 0; for (iob = iobufs; iob; iob = iob->next) { /* Don't read from /dev/tty while flushing. */ if (io_fds[SFD_USERTTY] != -1 && iob->rfd == io_fds[SFD_USERTTY]) continue; if (iob->rfd == -1 && iob->wfd == -1) continue; if (iob->off == iob->len) { iob->off = iob->len = 0; /* Forward the EOF from reader to writer. */ if (iob->rfd == -1) { safe_close(iob->wfd); iob->wfd = -1; } } if (iob->rfd != -1) { if (iob->len != sizeof(iob->buf)) FD_SET(iob->rfd, fdsr); } if (iob->wfd != -1) { if (iob->len > iob->off) { nwriters++; FD_SET(iob->wfd, fdsw); } } } /* Don't sleep in select if there are no buffers that need writing. */ tv.tv_sec = 0; tv.tv_usec = 0; nready = select(maxfd + 1, fdsr, fdsw, NULL, nwriters ? NULL : &tv); if (nready <= 0) { if (nready == 0) break; /* all I/O flushed */ if (errno == EINTR) continue; error(1, _("select failed")); } if (perform_io(fdsr, fdsw, NULL) != 0) break; } efree(fdsr); efree(fdsw); } /* * Sets up std{in,out,err} and executes the actual command. * Returns only if execve() fails. */ static void exec_pty(struct command_details *details) { pid_t self = getpid(); /* Set child process group here too to avoid a race. */ setpgid(0, self); /* Wire up standard fds, note that stdout/stderr may be pipes. */ if (dup2(io_fds[SFD_STDIN], STDIN_FILENO) == -1 || dup2(io_fds[SFD_STDOUT], STDOUT_FILENO) == -1 || dup2(io_fds[SFD_STDERR], STDERR_FILENO) == -1) error(1, "dup2"); /* Wait for parent to grant us the tty if we are foreground. */ if (foreground) { while (tcgetpgrp(io_fds[SFD_SLAVE]) != self) ; /* spin */ } /* We have guaranteed that the slave fd is > 2 */ if (io_fds[SFD_SLAVE] != -1) close(io_fds[SFD_SLAVE]); if (io_fds[SFD_STDIN] != io_fds[SFD_SLAVE]) close(io_fds[SFD_STDIN]); if (io_fds[SFD_STDOUT] != io_fds[SFD_SLAVE]) close(io_fds[SFD_STDOUT]); if (io_fds[SFD_STDERR] != io_fds[SFD_SLAVE]) close(io_fds[SFD_STDERR]); if (details->closefrom >= 0) closefrom(details->closefrom); #ifdef HAVE_SELINUX if (ISSET(details->flags, CD_RBAC_ENABLED)) selinux_execve(details->command, details->argv, details->envp); else #endif my_execve(details->command, details->argv, details->envp); } /* * Propagates tty size change signals to pty being used by the command. */ static void sync_ttysize(int src, int dst) { #ifdef TIOCGWINSZ struct winsize wsize; pid_t pgrp; if (ioctl(src, TIOCGWINSZ, &wsize) == 0) { ioctl(dst, TIOCSWINSZ, &wsize); if ((pgrp = tcgetpgrp(dst)) != -1) killpg(pgrp, SIGWINCH); } #endif } /* * Handler for SIGWINCH in parent. */ static void sigwinch(int s) { int serrno = errno; sync_ttysize(io_fds[SFD_USERTTY], io_fds[SFD_SLAVE]); errno = serrno; } /* * Only close the fd if it is not /dev/tty or std{in,out,err}. * Return value is the same as send(2). */ static int safe_close(int fd) { /* Avoid closing /dev/tty or std{in,out,err}. */ if (fd < 3 || fd == io_fds[SFD_USERTTY]) { errno = EINVAL; return -1; } return close(fd); }