diff options
Diffstat (limited to 'src/exec_monitor.c')
| -rw-r--r-- | src/exec_monitor.c | 731 |
1 files changed, 731 insertions, 0 deletions
diff --git a/src/exec_monitor.c b/src/exec_monitor.c new file mode 100644 index 0000000..a92ed40 --- /dev/null +++ b/src/exec_monitor.c @@ -0,0 +1,731 @@ +/* + * SPDX-License-Identifier: ISC + * + * Copyright (c) 2009-2022 Todd C. Miller <Todd.Miller@sudo.ws> + * + * 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. + */ + +/* + * This is an open source non-commercial project. Dear PVS-Studio, please check it. + * PVS-Studio Static Code Analyzer for C, C++ and C#: http://www.viva64.com + */ + +#include <config.h> + +#include <sys/types.h> +#include <sys/ioctl.h> +#include <sys/socket.h> +#include <sys/wait.h> +#include <stdio.h> +#include <stdlib.h> +#include <string.h> +#include <unistd.h> +#include <time.h> +#include <errno.h> +#include <fcntl.h> +#include <signal.h> +#include <termios.h> + +#include "sudo.h" +#include "sudo_exec.h" +#include "sudo_plugin.h" +#include "sudo_plugin_int.h" + +struct monitor_closure { + struct command_details *details; + struct sudo_event_base *evbase; + struct sudo_event *errpipe_event; + struct sudo_event *backchannel_event; + struct sudo_event *sigint_event; + struct sudo_event *sigquit_event; + struct sudo_event *sigtstp_event; + struct sudo_event *sigterm_event; + struct sudo_event *sighup_event; + struct sudo_event *sigusr1_event; + struct sudo_event *sigusr2_event; + struct sudo_event *sigchld_event; + struct command_status *cstat; + pid_t cmnd_pid; + pid_t cmnd_pgrp; + pid_t mon_pgrp; + int backchannel; +}; + +static bool tty_initialized; + +/* + * Deliver a signal to the running command. + * The signal was either forwarded to us by the parent sudo process + * or was received by the monitor itself. + * + * There are two "special" signals, SIGCONT_FG and SIGCONT_BG that + * also specify whether the command should have the controlling tty. + */ +static void +deliver_signal(struct monitor_closure *mc, int signo, bool from_parent) +{ + char signame[SIG2STR_MAX]; + debug_decl(deliver_signal, SUDO_DEBUG_EXEC); + + /* Avoid killing more than a single process or process group. */ + if (mc->cmnd_pid <= 0) + debug_return; + + if (signo == SIGCONT_FG) + (void)strlcpy(signame, "CONT_FG", sizeof(signame)); + else if (signo == SIGCONT_BG) + (void)strlcpy(signame, "CONT_BG", sizeof(signame)); + else if (sig2str(signo, signame) == -1) + (void)snprintf(signame, sizeof(signame), "%d", signo); + + /* Handle signal from parent or monitor. */ + sudo_debug_printf(SUDO_DEBUG_INFO, "received SIG%s%s", + signame, from_parent ? " from parent" : ""); + switch (signo) { + case SIGALRM: + terminate_command(mc->cmnd_pid, true); + break; + case SIGCONT_FG: + /* Continue in foreground, grant it controlling tty. */ + if (tcsetpgrp(io_fds[SFD_FOLLOWER], mc->cmnd_pgrp) == -1) { + sudo_debug_printf(SUDO_DEBUG_ERROR|SUDO_DEBUG_ERRNO, + "%s: unable to set foreground pgrp to %d (command)", + __func__, (int)mc->cmnd_pgrp); + } + /* Lazily initialize the pty if needed. */ + if (!tty_initialized) { + if (sudo_term_copy(io_fds[SFD_USERTTY], io_fds[SFD_FOLLOWER])) + tty_initialized = true; + } + killpg(mc->cmnd_pid, SIGCONT); + break; + case SIGCONT_BG: + /* Continue in background, I take controlling tty. */ + if (tcsetpgrp(io_fds[SFD_FOLLOWER], mc->mon_pgrp) == -1) { + sudo_debug_printf(SUDO_DEBUG_ERROR|SUDO_DEBUG_ERRNO, + "%s: unable to set foreground pgrp to %d (monitor)", + __func__, (int)mc->mon_pgrp); + } + killpg(mc->cmnd_pid, SIGCONT); + break; + case SIGKILL: + _exit(EXIT_FAILURE); /* XXX */ + /* NOTREACHED */ + default: + /* Relay signal to command. */ + killpg(mc->cmnd_pid, signo); + break; + } + debug_return; +} + +/* + * Unpack rows and cols from a CMD_TTYWINCH value, set the new window + * size on the pty follower and inform the command of the change. + */ +static void +handle_winch(struct monitor_closure *mc, unsigned int wsize_packed) +{ + struct winsize wsize, owsize; + debug_decl(handle_winch, SUDO_DEBUG_EXEC); + + /* Rows and columns are stored as two shorts packed into a single int. */ + wsize.ws_row = wsize_packed & 0xffff; + wsize.ws_col = (wsize_packed >> 16) & 0xffff; + + if (ioctl(io_fds[SFD_FOLLOWER], TIOCGWINSZ, &owsize) == 0 && + (wsize.ws_row != owsize.ws_row || wsize.ws_col != owsize.ws_col)) { + + sudo_debug_printf(SUDO_DEBUG_INFO, + "window size change %dx%d -> %dx%d", + owsize.ws_col, owsize.ws_row, wsize.ws_col, wsize.ws_row); + + (void)ioctl(io_fds[SFD_FOLLOWER], TIOCSWINSZ, &wsize); + deliver_signal(mc, SIGWINCH, true); + } + + debug_return; +} + +/* + * 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; + debug_decl(send_status, SUDO_DEBUG_EXEC); + + if (cstat->type != CMD_INVALID) { + sudo_debug_printf(SUDO_DEBUG_INFO, + "sending status message to parent: [%d, %d]", + cstat->type, cstat->val); + n = send(fd, cstat, sizeof(*cstat), 0); + if (n != sizeof(*cstat)) { + sudo_debug_printf(SUDO_DEBUG_ERROR|SUDO_DEBUG_ERRNO, + "%s: unable to send status to parent", __func__); + } + cstat->type = CMD_INVALID; /* prevent re-sending */ + } + debug_return_int(n); +} + +/* + * Wait for command status after receiving SIGCHLD. + * If the command was stopped, the status is send back to the parent. + * Otherwise, cstat is filled in but not sent. + */ +static void +mon_handle_sigchld(struct monitor_closure *mc) +{ + char signame[SIG2STR_MAX]; + int status; + pid_t pid; + debug_decl(mon_handle_sigchld, SUDO_DEBUG_EXEC); + + /* Read command status. */ + do { + pid = waitpid(mc->cmnd_pid, &status, WUNTRACED|WNOHANG); + } while (pid == -1 && errno == EINTR); + switch (pid) { + case -1: + if (errno != ECHILD) { + sudo_warn(U_("%s: %s"), __func__, "waitpid"); + debug_return; + } + FALLTHROUGH; + case 0: + /* Nothing to wait for. */ + sudo_debug_printf(SUDO_DEBUG_INFO, "%s: no process to wait for", + __func__); + debug_return; + } + + if (WIFSTOPPED(status)) { + if (sig2str(WSTOPSIG(status), signame) == -1) + (void)snprintf(signame, sizeof(signame), "%d", WSTOPSIG(status)); + sudo_debug_printf(SUDO_DEBUG_INFO, "%s: command (%d) stopped, SIG%s", + __func__, (int)mc->cmnd_pid, signame); + } else if (WIFSIGNALED(status)) { + if (sig2str(WTERMSIG(status), signame) == -1) + (void)snprintf(signame, sizeof(signame), "%d", WTERMSIG(status)); + sudo_debug_printf(SUDO_DEBUG_INFO, "%s: command (%d) killed, SIG%s", + __func__, (int)mc->cmnd_pid, signame); + mc->cmnd_pid = -1; + } else if (WIFEXITED(status)) { + sudo_debug_printf(SUDO_DEBUG_INFO, "%s: command (%d) exited: %d", + __func__, (int)mc->cmnd_pid, WEXITSTATUS(status)); + mc->cmnd_pid = -1; + } else { + sudo_debug_printf(SUDO_DEBUG_WARN, + "%s: unexpected wait status 0x%x for command (%d)", + __func__, status, (int)mc->cmnd_pid); + } + + /* Don't overwrite execve() failure with child exit status. */ + if (mc->cstat->type == CMD_INVALID) { + /* + * Store wait status in cstat and forward to parent if stopped. + */ + mc->cstat->type = CMD_WSTATUS; + mc->cstat->val = status; + if (WIFSTOPPED(status)) { + /* Save the foreground pgid so we can restore it later. */ + pid = tcgetpgrp(io_fds[SFD_FOLLOWER]); + if (pid != mc->mon_pgrp) + mc->cmnd_pgrp = pid; + send_status(mc->backchannel, mc->cstat); + } + } else { + sudo_debug_printf(SUDO_DEBUG_WARN, + "%s: not overwriting command status %d,%d with %d,%d", + __func__, mc->cstat->type, mc->cstat->val, CMD_WSTATUS, status); + } + + debug_return; +} + +static void +mon_signal_cb(int signo, int what, void *v) +{ + struct sudo_ev_siginfo_container *sc = v; + struct monitor_closure *mc = sc->closure; + debug_decl(mon_signal_cb, SUDO_DEBUG_EXEC); + + /* + * Handle SIGCHLD specially and deliver other signals + * directly to the command. + */ + if (signo == SIGCHLD) { + mon_handle_sigchld(mc); + if (mc->cmnd_pid == -1) { + /* Command exited or was killed, exit event loop. */ + sudo_ev_loopexit(mc->evbase); + } + } else { + /* + * If the signal came from the process group of the command we ran, + * do not forward it as we don't want the child to indirectly kill + * itself. This can happen with, e.g., BSD-derived versions of + * reboot that call kill(-1, SIGTERM) to kill all other processes. + */ + if (USER_SIGNALED(sc->siginfo) && sc->siginfo->si_pid != 0) { + pid_t si_pgrp; + + if (sc->siginfo->si_pid == mc->cmnd_pid) + debug_return; + si_pgrp = getpgid(sc->siginfo->si_pid); + if (si_pgrp != -1) { + if (si_pgrp == mc->cmnd_pgrp) + debug_return; + } + } + deliver_signal(mc, signo, false); + } + debug_return; +} + +/* Note: this is basically the same as errpipe_cb() in exec_nopty.c */ +static void +mon_errpipe_cb(int fd, int what, void *v) +{ + struct monitor_closure *mc = v; + ssize_t nread; + int errval; + debug_decl(mon_errpipe_cb, SUDO_DEBUG_EXEC); + + /* + * Read errno from child or EOF when command is executed. + * Note that the error pipe is *blocking*. + */ + nread = read(fd, &errval, sizeof(errval)); + switch (nread) { + case -1: + if (errno != EAGAIN && errno != EINTR) { + if (mc->cstat->val == CMD_INVALID) { + /* XXX - need a way to distinguish non-exec error. */ + mc->cstat->type = CMD_ERRNO; + mc->cstat->val = errno; + } + sudo_debug_printf(SUDO_DEBUG_ERROR|SUDO_DEBUG_ERRNO, + "%s: failed to read error pipe", __func__); + sudo_ev_loopbreak(mc->evbase); + } + break; + default: + if (nread == 0) { + /* The error pipe closes when the command is executed. */ + sudo_debug_printf(SUDO_DEBUG_INFO, "EOF on error pipe"); + } else { + /* Errno value when child is unable to execute command. */ + sudo_debug_printf(SUDO_DEBUG_INFO, "errno from child: %s", + strerror(errval)); + mc->cstat->type = CMD_ERRNO; + mc->cstat->val = errval; + } + sudo_ev_del(mc->evbase, mc->errpipe_event); + close(fd); + break; + } + debug_return; +} + +static void +mon_backchannel_cb(int fd, int what, void *v) +{ + struct monitor_closure *mc = v; + struct command_status cstmp; + ssize_t n; + debug_decl(mon_backchannel_cb, SUDO_DEBUG_EXEC); + + /* + * Read command from backchannel, should be a signal. + * Note that the backchannel is a *blocking* socket. + */ + n = recv(fd, &cstmp, sizeof(cstmp), MSG_WAITALL); + if (n != sizeof(cstmp)) { + if (n == -1) { + if (errno == EINTR || errno == EAGAIN) + debug_return; + sudo_warn("%s", U_("error reading from socketpair")); + } else { + /* short read or EOF, parent process died? */ + } + /* XXX - need a way to distinguish non-exec error. */ + mc->cstat->type = CMD_ERRNO; + mc->cstat->val = n ? EIO : ECONNRESET; + sudo_ev_loopbreak(mc->evbase); + } else { + switch (cstmp.type) { + case CMD_TTYWINCH: + handle_winch(mc, cstmp.val); + break; + case CMD_SIGNO: + deliver_signal(mc, cstmp.val, true); + break; + default: + sudo_warnx(U_("unexpected reply type on backchannel: %d"), cstmp.type); + break; + } + } + debug_return; +} + +/* + * Sets up std{in,out,err} and executes the actual command. + * Returns only if execve() fails. + */ +static void +exec_cmnd_pty(struct command_details *details, sigset_t *mask, + bool foreground, int intercept_fd, int errfd) +{ + volatile pid_t self = getpid(); + debug_decl(exec_cmnd_pty, SUDO_DEBUG_EXEC); + + /* Register cleanup function */ + sudo_fatal_callback_register(pty_cleanup); + + /* Set command process group here too to avoid a race. */ + setpgid(0, self); + + /* Wire up standard fds, note that stdout/stderr may be pipes. */ + if (dup3(io_fds[SFD_STDIN], STDIN_FILENO, 0) == -1) + sudo_fatal("dup3"); + if (io_fds[SFD_STDIN] != io_fds[SFD_FOLLOWER]) + close(io_fds[SFD_STDIN]); + if (dup3(io_fds[SFD_STDOUT], STDOUT_FILENO, 0) == -1) + sudo_fatal("dup3"); + if (io_fds[SFD_STDOUT] != io_fds[SFD_FOLLOWER]) + close(io_fds[SFD_STDOUT]); + if (dup3(io_fds[SFD_STDERR], STDERR_FILENO, 0) == -1) + sudo_fatal("dup3"); + if (io_fds[SFD_STDERR] != io_fds[SFD_FOLLOWER]) + close(io_fds[SFD_STDERR]); + + /* Wait for parent to grant us the tty if we are foreground. */ + if (foreground && !ISSET(details->flags, CD_EXEC_BG)) { + struct timespec ts = { 0, 1000 }; /* 1us */ + sudo_debug_printf(SUDO_DEBUG_DEBUG, "%s: waiting for controlling tty", + __func__); + while (tcgetpgrp(io_fds[SFD_FOLLOWER]) != self) + nanosleep(&ts, NULL); + sudo_debug_printf(SUDO_DEBUG_DEBUG, "%s: got controlling tty", + __func__); + } + + /* Done with the pty follower, don't leak it. */ + if (io_fds[SFD_FOLLOWER] != -1) + close(io_fds[SFD_FOLLOWER]); + + /* Execute command; only returns on error. */ + sudo_debug_printf(SUDO_DEBUG_INFO, "executing %s in the %s", + details->command, foreground ? "foreground" : "background"); + exec_cmnd(details, mask, intercept_fd, errfd); + + debug_return; +} + +/* + * Fill in the monitor closure and setup initial events. + * Allocates read events for the signal pipe, error pipe and backchannel. + */ +static void +fill_exec_closure_monitor(struct monitor_closure *mc, + struct command_details *details, struct command_status *cstat, + int errfd, int backchannel) +{ + debug_decl(fill_exec_closure_monitor, SUDO_DEBUG_EXEC); + + /* Fill in the non-event part of the closure. */ + mc->details = details; + mc->cstat = cstat; + mc->backchannel = backchannel; + mc->mon_pgrp = getpgrp(); + + /* Setup event base and events. */ + mc->evbase = sudo_ev_base_alloc(); + if (mc->evbase == NULL) + sudo_fatalx(U_("%s: %s"), __func__, U_("unable to allocate memory")); + + /* Event for command status via errfd. */ + mc->errpipe_event = sudo_ev_alloc(errfd, + SUDO_EV_READ|SUDO_EV_PERSIST, mon_errpipe_cb, mc); + if (mc->errpipe_event == NULL) + sudo_fatalx(U_("%s: %s"), __func__, U_("unable to allocate memory")); + if (sudo_ev_add(mc->evbase, mc->errpipe_event, NULL, false) == -1) + sudo_fatal("%s", U_("unable to add event to queue")); + + /* Event for forwarded signals via backchannel. */ + mc->backchannel_event = sudo_ev_alloc(backchannel, + SUDO_EV_READ|SUDO_EV_PERSIST, mon_backchannel_cb, mc); + if (mc->backchannel_event == NULL) + sudo_fatalx(U_("%s: %s"), __func__, U_("unable to allocate memory")); + if (sudo_ev_add(mc->evbase, mc->backchannel_event, NULL, false) == -1) + sudo_fatal("%s", U_("unable to add event to queue")); + + /* Events for local signals. */ + mc->sigint_event = sudo_ev_alloc(SIGINT, + SUDO_EV_SIGINFO, mon_signal_cb, mc); + if (mc->sigint_event == NULL) + sudo_fatalx(U_("%s: %s"), __func__, U_("unable to allocate memory")); + if (sudo_ev_add(mc->evbase, mc->sigint_event, NULL, false) == -1) + sudo_fatal("%s", U_("unable to add event to queue")); + + mc->sigquit_event = sudo_ev_alloc(SIGQUIT, + SUDO_EV_SIGINFO, mon_signal_cb, mc); + if (mc->sigquit_event == NULL) + sudo_fatalx(U_("%s: %s"), __func__, U_("unable to allocate memory")); + if (sudo_ev_add(mc->evbase, mc->sigquit_event, NULL, false) == -1) + sudo_fatal("%s", U_("unable to add event to queue")); + + mc->sigtstp_event = sudo_ev_alloc(SIGTSTP, + SUDO_EV_SIGINFO, mon_signal_cb, mc); + if (mc->sigtstp_event == NULL) + sudo_fatalx(U_("%s: %s"), __func__, U_("unable to allocate memory")); + if (sudo_ev_add(mc->evbase, mc->sigtstp_event, NULL, false) == -1) + sudo_fatal("%s", U_("unable to add event to queue")); + + mc->sigterm_event = sudo_ev_alloc(SIGTERM, + SUDO_EV_SIGINFO, mon_signal_cb, mc); + if (mc->sigterm_event == NULL) + sudo_fatalx(U_("%s: %s"), __func__, U_("unable to allocate memory")); + if (sudo_ev_add(mc->evbase, mc->sigterm_event, NULL, false) == -1) + sudo_fatal("%s", U_("unable to add event to queue")); + + mc->sighup_event = sudo_ev_alloc(SIGHUP, + SUDO_EV_SIGINFO, mon_signal_cb, mc); + if (mc->sighup_event == NULL) + sudo_fatalx(U_("%s: %s"), __func__, U_("unable to allocate memory")); + if (sudo_ev_add(mc->evbase, mc->sighup_event, NULL, false) == -1) + sudo_fatal("%s", U_("unable to add event to queue")); + + mc->sigusr1_event = sudo_ev_alloc(SIGUSR1, + SUDO_EV_SIGINFO, mon_signal_cb, mc); + if (mc->sigusr1_event == NULL) + sudo_fatalx(U_("%s: %s"), __func__, U_("unable to allocate memory")); + if (sudo_ev_add(mc->evbase, mc->sigusr1_event, NULL, false) == -1) + sudo_fatal("%s", U_("unable to add event to queue")); + + mc->sigusr2_event = sudo_ev_alloc(SIGUSR2, + SUDO_EV_SIGINFO, mon_signal_cb, mc); + if (mc->sigusr2_event == NULL) + sudo_fatalx(U_("%s: %s"), __func__, U_("unable to allocate memory")); + if (sudo_ev_add(mc->evbase, mc->sigusr2_event, NULL, false) == -1) + sudo_fatal("%s", U_("unable to add event to queue")); + + mc->sigchld_event = sudo_ev_alloc(SIGCHLD, + SUDO_EV_SIGINFO, mon_signal_cb, mc); + if (mc->sigchld_event == NULL) + sudo_fatalx(U_("%s: %s"), __func__, U_("unable to allocate memory")); + if (sudo_ev_add(mc->evbase, mc->sigchld_event, NULL, false) == -1) + sudo_fatal("%s", U_("unable to add event to queue")); + + /* Clear the default event base. */ + sudo_ev_base_setdef(NULL); + + debug_return; +} + +/* + * Monitor process that creates a new session with the controlling tty, + * resets signal handlers and forks a child to call exec_cmnd_pty(). + * Waits for status changes from the command and relays them to the + * parent and relays signals from the parent to the command. + * Must be called with signals blocked and the old signal mask in oset. + * Returns an error if fork(2) fails, else calls _exit(2). + */ +int +exec_monitor(struct command_details *details, sigset_t *oset, + bool foreground, int backchannel, int intercept_fd) +{ + struct monitor_closure mc = { 0 }; + struct command_status cstat; + struct sigaction sa; + int errpipe[2]; + debug_decl(exec_monitor, SUDO_DEBUG_EXEC); + + /* The pty leader is not used by the monitor. */ + if (io_fds[SFD_LEADER] != -1) + close(io_fds[SFD_LEADER]); + + /* Ignore any SIGTTIN or SIGTTOU we receive (shouldn't be possible). */ + memset(&sa, 0, sizeof(sa)); + sigemptyset(&sa.sa_mask); + sa.sa_flags = SA_RESTART; + sa.sa_handler = SIG_IGN; + if (sudo_sigaction(SIGTTIN, &sa, NULL) != 0) + sudo_warn(U_("unable to set handler for signal %d"), SIGTTIN); + if (sudo_sigaction(SIGTTOU, &sa, NULL) != 0) + sudo_warn(U_("unable to set handler for signal %d"), SIGTTOU); + + /* If we are starting in the foreground, the pty was already initialized. */ + if (foreground) + tty_initialized = true; + + /* + * Start a new session with the parent as the session leader + * and the follower device as the controlling terminal. + * This allows us to be notified when the command has been suspended. + */ + if (setsid() == -1) { + sudo_warn("setsid"); + goto bad; + } + if (pty_make_controlling() == -1) { + sudo_warn("%s", U_("unable to set controlling tty")); + goto bad; + } + + /* + * We use a pipe to get errno if execve(2) fails in the child. + */ + if (pipe2(errpipe, O_CLOEXEC) != 0) { + sudo_warn("%s", U_("unable to create pipe")); + goto bad; + } + + /* + * Before forking, wait for the main sudo process to tell us to go. + * Avoids race conditions when the command exits quickly. + */ + while (recv(backchannel, &cstat, sizeof(cstat), MSG_WAITALL) == -1) { + if (errno != EINTR && errno != EAGAIN) { + sudo_warn("%s", U_("unable to receive message from parent")); + goto bad; + } + } + +#ifdef HAVE_SELINUX + if (ISSET(details->flags, CD_RBAC_ENABLED)) { + if (selinux_relabel_tty(details->tty, io_fds[SFD_FOLLOWER]) == -1) + goto bad; + selinux_audit_role_change(); + } +#endif + + mc.cmnd_pid = sudo_debug_fork(); + switch (mc.cmnd_pid) { + case -1: + sudo_warn("%s", U_("unable to fork")); +#ifdef HAVE_SELINUX + if (ISSET(details->flags, CD_RBAC_ENABLED)) { + if (selinux_restore_tty() != 0) + sudo_warnx("%s", U_("unable to restore tty label")); + } +#endif + goto bad; + case 0: + /* child */ + close(backchannel); + close(errpipe[0]); + if (io_fds[SFD_USERTTY] != -1) + close(io_fds[SFD_USERTTY]); + /* setup tty and exec command */ + exec_cmnd_pty(details, oset, foreground, intercept_fd, errpipe[1]); + if (write(errpipe[1], &errno, sizeof(int)) == -1) + sudo_warn(U_("unable to execute %s"), details->command); + _exit(EXIT_FAILURE); + } + close(errpipe[1]); + if (intercept_fd != -1) + close(intercept_fd); + + /* No longer need execfd. */ + if (details->execfd != -1) { + close(details->execfd); + details->execfd = -1; + } + + /* Send the command's pid to main sudo process. */ + cstat.type = CMD_PID; + cstat.val = mc.cmnd_pid; + send_status(backchannel, &cstat); + + /* + * Create new event base and register read events for the + * signal pipe, error pipe, and backchannel. + */ + fill_exec_closure_monitor(&mc, details, &cstat, errpipe[0], backchannel); + + /* Restore signal mask now that signal handlers are setup. */ + sigprocmask(SIG_SETMASK, oset, NULL); + + /* If any of stdin/stdout/stderr are pipes, close them in parent. */ + if (io_fds[SFD_STDIN] != io_fds[SFD_FOLLOWER]) + close(io_fds[SFD_STDIN]); + if (io_fds[SFD_STDOUT] != io_fds[SFD_FOLLOWER]) + close(io_fds[SFD_STDOUT]); + if (io_fds[SFD_STDERR] != io_fds[SFD_FOLLOWER]) + close(io_fds[SFD_STDERR]); + + /* Put command in its own process group. */ + mc.cmnd_pgrp = mc.cmnd_pid; + setpgid(mc.cmnd_pid, mc.cmnd_pgrp); + + /* Make the command the foreground process for the pty follower. */ + if (foreground && !ISSET(details->flags, CD_EXEC_BG)) { + if (tcsetpgrp(io_fds[SFD_FOLLOWER], mc.cmnd_pgrp) == -1) { + sudo_debug_printf(SUDO_DEBUG_ERROR|SUDO_DEBUG_ERRNO, + "%s: unable to set foreground pgrp to %d (command)", + __func__, (int)mc.cmnd_pgrp); + } + } + + /* + * Wait for errno on pipe, signal on backchannel or for SIGCHLD. + * The event loop ends when the child is no longer running and + * the error pipe is closed. + */ + cstat.type = CMD_INVALID; + cstat.val = 0; + (void) sudo_ev_dispatch(mc.evbase); + if (mc.cmnd_pid != -1) { + pid_t pid; + + /* Command still running, did the parent die? */ + sudo_debug_printf(SUDO_DEBUG_ERROR, + "Command still running after event loop exit, terminating"); + terminate_command(mc.cmnd_pid, true); + do { + pid = waitpid(mc.cmnd_pid, NULL, 0); + } while (pid == -1 && errno == EINTR); + /* XXX - update cstat with wait status? */ + } + + /* + * Take the controlling tty. This prevents processes spawned by the + * command from receiving SIGHUP when the session leader (us) exits. + */ + if (tcsetpgrp(io_fds[SFD_FOLLOWER], mc.mon_pgrp) == -1) { + sudo_debug_printf(SUDO_DEBUG_ERROR|SUDO_DEBUG_ERRNO, + "%s: unable to set foreground pgrp to %d (monitor)", + __func__, (int)mc.mon_pgrp); + } + + /* Send parent status. */ + send_status(backchannel, &cstat); + +#ifdef HAVE_SELINUX + if (ISSET(details->flags, CD_RBAC_ENABLED)) { + if (selinux_restore_tty() != 0) + sudo_warnx("%s", U_("unable to restore tty label")); + } +#endif + sudo_debug_exit_int(__func__, __FILE__, __LINE__, sudo_debug_subsys, 1); + _exit(EXIT_FAILURE); + +bad: + debug_return_int(-1); +} |