/*
* Copyright (c) 2009-2011 Todd C. Miller <Todd.Miller@courtesan.com>
*
* 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 <config.h>
#include <sys/types.h>
#include <sys/param.h>
#ifdef HAVE_SYS_SYSMACROS_H
# include <sys/sysmacros.h>
#endif
#include <sys/socket.h>
#include <sys/time.h>
#include <sys/wait.h>
#include <sys/ioctl.h>
#ifdef HAVE_SYS_SELECT_H
# include <sys/select.h>
#endif /* HAVE_SYS_SELECT_H */
#include <stdio.h>
#ifdef STDC_HEADERS
# include <stdlib.h>
# include <stddef.h>
#else
# ifdef HAVE_STDLIB_H
# include <stdlib.h>
# endif
#endif /* STDC_HEADERS */
#ifdef HAVE_STRING_H
# if defined(HAVE_MEMORY_H) && !defined(STDC_HEADERS)
# include <memory.h>
# endif
# include <string.h>
#endif /* HAVE_STRING_H */
#ifdef HAVE_STRINGS_H
# include <strings.h>
#endif /* HAVE_STRINGS_H */
#ifdef HAVE_UNISTD_H
# include <unistd.h>
#endif /* HAVE_UNISTD_H */
#if TIME_WITH_SYS_TIME
# include <time.h>
#endif
#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"
#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);
}
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