diff options
Diffstat (limited to 'src/exec_pty.c')
| -rw-r--r-- | src/exec_pty.c | 1897 |
1 files changed, 1897 insertions, 0 deletions
diff --git a/src/exec_pty.c b/src/exec_pty.c new file mode 100644 index 0000000..cfe4929 --- /dev/null +++ b/src/exec_pty.c @@ -0,0 +1,1897 @@ +/* + * SPDX-License-Identifier: ISC + * + * Copyright (c) 2009-2021 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/stat.h> +#include <sys/socket.h> +#include <sys/wait.h> +#include <sys/ioctl.h> +#include <stdio.h> +#include <stdlib.h> +#include <string.h> +#include <unistd.h> +#include <errno.h> +#include <fcntl.h> +#include <signal.h> +#include <termios.h> /* for struct winsize on HP-UX */ + +#include "sudo.h" +#include "sudo_exec.h" +#include "sudo_plugin.h" +#include "sudo_plugin_int.h" + +/* Evaluates to true if the event has /dev/tty as its fd. */ +#define USERTTY_EVENT(_ev) (sudo_ev_get_fd((_ev)) == io_fds[SFD_USERTTY]) + +#define TERM_COOKED 0 +#define TERM_RAW 1 + +/* Tail queue of messages to send to the monitor. */ +struct monitor_message { + TAILQ_ENTRY(monitor_message) entries; + struct command_status cstat; +}; +TAILQ_HEAD(monitor_message_list, monitor_message); + +struct exec_closure_pty { + pid_t monitor_pid; + pid_t cmnd_pid; + pid_t ppgrp; + short rows; + short cols; + struct command_status *cstat; + struct command_details *details; + struct sudo_event_base *evbase; + struct sudo_event *backchannel_event; + struct sudo_event *fwdchannel_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 *sigalrm_event; + struct sudo_event *sigusr1_event; + struct sudo_event *sigusr2_event; + struct sudo_event *sigchld_event; + struct sudo_event *sigwinch_event; + struct monitor_message_list monitor_messages; +}; + +/* + * I/O buffer with associated read/write events and a logging action. + * Used to, e.g. pass data from the pty to the user's terminal + * and any I/O logging plugins. + */ +struct io_buffer; +typedef bool (*sudo_io_action_t)(const char *, unsigned int, struct io_buffer *); +struct io_buffer { + SLIST_ENTRY(io_buffer) entries; + struct exec_closure_pty *ec; + struct sudo_event *revent; + struct sudo_event *wevent; + sudo_io_action_t action; + int len; /* buffer length (how much produced) */ + int off; /* write position (how much already consumed) */ + char buf[64 * 1024]; +}; +SLIST_HEAD(io_buffer_list, io_buffer); + +static char ptyname[PATH_MAX]; +int io_fds[6] = { -1, -1, -1, -1, -1, -1}; +static bool foreground, pipeline; +static int ttymode = TERM_COOKED; +static sigset_t ttyblock; +static struct io_buffer_list iobufs; +static const char *utmp_user; + +static void del_io_events(bool nonblocking); +static void sync_ttysize(struct exec_closure_pty *ec); +static int safe_close(int fd); +static void ev_free_by_fd(struct sudo_event_base *evbase, int fd); +static pid_t check_foreground(struct exec_closure_pty *ec); +static void add_io_events(struct sudo_event_base *evbase); +static void schedule_signal(struct exec_closure_pty *ec, int signo); + +/* + * Cleanup hook for sudo_fatal()/sudo_fatalx() + */ +void +pty_cleanup(void) +{ + debug_decl(cleanup, SUDO_DEBUG_EXEC); + + if (io_fds[SFD_USERTTY] != -1) + sudo_term_restore(io_fds[SFD_USERTTY], false); + if (utmp_user != NULL) + utmp_logout(ptyname, 0); + + debug_return; +} + +/* + * Allocate a pty if /dev/tty is a tty. + * Fills in io_fds[SFD_USERTTY], io_fds[SFD_LEADER], io_fds[SFD_FOLLOWER] + * and ptyname globals. + */ +static bool +pty_setup(struct command_details *details, const char *tty) +{ + debug_decl(pty_setup, SUDO_DEBUG_EXEC); + + io_fds[SFD_USERTTY] = open(_PATH_TTY, O_RDWR); + if (io_fds[SFD_USERTTY] == -1) { + sudo_debug_printf(SUDO_DEBUG_INFO, "%s: no %s, not allocating a pty", + __func__, _PATH_TTY); + debug_return_bool(false); + } + + if (!get_pty(&io_fds[SFD_LEADER], &io_fds[SFD_FOLLOWER], + ptyname, sizeof(ptyname), details->cred.euid)) + sudo_fatal("%s", U_("unable to allocate pty")); + + /* Update tty name in command details (used by SELinux and AIX). */ + details->tty = ptyname; + + /* Add entry to utmp/utmpx? */ + if (ISSET(details->flags, CD_SET_UTMP)) { + utmp_user = + details->utmp_user ? details->utmp_user : user_details.username; + utmp_login(tty, ptyname, io_fds[SFD_FOLLOWER], utmp_user); + } + + sudo_debug_printf(SUDO_DEBUG_INFO, + "%s: %s fd %d, pty leader fd %d, pty follower fd %d", + __func__, _PATH_TTY, io_fds[SFD_USERTTY], io_fds[SFD_LEADER], + io_fds[SFD_FOLLOWER]); + + debug_return_bool(true); +} + +/* + * Make the tty follower the controlling tty. + * This is only used by the monitor but ptyname[] is static. + */ +int +pty_make_controlling(void) +{ + if (io_fds[SFD_FOLLOWER] != -1) { +#ifdef TIOCSCTTY + if (ioctl(io_fds[SFD_FOLLOWER], TIOCSCTTY, NULL) != 0) + return -1; +#else + /* Set controlling tty by reopening pty follower. */ + int fd = open(ptyname, O_RDWR); + if (fd == -1) + return -1; + close(fd); +#endif + } + return 0; +} + +/* Call I/O plugin tty input log method. */ +static bool +log_ttyin(const char *buf, unsigned int n, struct io_buffer *iob) +{ + struct plugin_container *plugin; + const char *errstr = NULL; + sigset_t omask; + bool ret = true; + debug_decl(log_ttyin, SUDO_DEBUG_EXEC); + + sigprocmask(SIG_BLOCK, &ttyblock, &omask); + TAILQ_FOREACH(plugin, &io_plugins, entries) { + if (plugin->u.io->log_ttyin) { + int rc; + + sudo_debug_set_active_instance(plugin->debug_instance); + rc = plugin->u.io->log_ttyin(buf, n, &errstr); + if (rc <= 0) { + if (rc < 0) { + /* Error: disable plugin's I/O function. */ + plugin->u.io->log_ttyin = NULL; + audit_error(plugin->name, SUDO_IO_PLUGIN, + errstr ? errstr : _("I/O plugin error"), + iob->ec->details->info); + } else { + audit_reject(plugin->name, SUDO_IO_PLUGIN, + errstr ? errstr : _("command rejected by I/O plugin"), + iob->ec->details->info); + } + ret = false; + break; + } + } + } + sudo_debug_set_active_instance(sudo_debug_instance); + sigprocmask(SIG_SETMASK, &omask, NULL); + + debug_return_bool(ret); +} + +/* Call I/O plugin stdin log method. */ +static bool +log_stdin(const char *buf, unsigned int n, struct io_buffer *iob) +{ + struct plugin_container *plugin; + const char *errstr = NULL; + sigset_t omask; + bool ret = true; + debug_decl(log_stdin, SUDO_DEBUG_EXEC); + + sigprocmask(SIG_BLOCK, &ttyblock, &omask); + TAILQ_FOREACH(plugin, &io_plugins, entries) { + if (plugin->u.io->log_stdin) { + int rc; + + sudo_debug_set_active_instance(plugin->debug_instance); + rc = plugin->u.io->log_stdin(buf, n, &errstr); + if (rc <= 0) { + if (rc < 0) { + /* Error: disable plugin's I/O function. */ + plugin->u.io->log_stdin = NULL; + audit_error(plugin->name, SUDO_IO_PLUGIN, + errstr ? errstr : _("I/O plugin error"), + iob->ec->details->info); + } else { + audit_reject(plugin->name, SUDO_IO_PLUGIN, + errstr ? errstr : _("command rejected by I/O plugin"), + iob->ec->details->info); + } + ret = false; + break; + } + } + } + sudo_debug_set_active_instance(sudo_debug_instance); + sigprocmask(SIG_SETMASK, &omask, NULL); + + debug_return_bool(ret); +} + +/* Call I/O plugin tty output log method. */ +static bool +log_ttyout(const char *buf, unsigned int n, struct io_buffer *iob) +{ + struct plugin_container *plugin; + const char *errstr = NULL; + sigset_t omask; + bool ret = true; + debug_decl(log_ttyout, SUDO_DEBUG_EXEC); + + sigprocmask(SIG_BLOCK, &ttyblock, &omask); + TAILQ_FOREACH(plugin, &io_plugins, entries) { + if (plugin->u.io->log_ttyout) { + int rc; + + sudo_debug_set_active_instance(plugin->debug_instance); + rc = plugin->u.io->log_ttyout(buf, n, &errstr); + if (rc <= 0) { + if (rc < 0) { + /* Error: disable plugin's I/O function. */ + plugin->u.io->log_ttyout = NULL; + audit_error(plugin->name, SUDO_IO_PLUGIN, + errstr ? errstr : _("I/O plugin error"), + iob->ec->details->info); + } else { + audit_reject(plugin->name, SUDO_IO_PLUGIN, + errstr ? errstr : _("command rejected by I/O plugin"), + iob->ec->details->info); + } + ret = false; + break; + } + } + } + sudo_debug_set_active_instance(sudo_debug_instance); + if (!ret) { + /* + * I/O plugin rejected the output, delete the write event + * (user's tty) so we do not display the rejected output. + */ + sudo_debug_printf(SUDO_DEBUG_INFO, + "%s: deleting and freeing devtty wevent %p", __func__, iob->wevent); + sudo_ev_free(iob->wevent); + iob->wevent = NULL; + iob->off = iob->len = 0; + } + sigprocmask(SIG_SETMASK, &omask, NULL); + + debug_return_bool(ret); +} + +/* Call I/O plugin stdout log method. */ +static bool +log_stdout(const char *buf, unsigned int n, struct io_buffer *iob) +{ + struct plugin_container *plugin; + const char *errstr = NULL; + sigset_t omask; + bool ret = true; + debug_decl(log_stdout, SUDO_DEBUG_EXEC); + + sigprocmask(SIG_BLOCK, &ttyblock, &omask); + TAILQ_FOREACH(plugin, &io_plugins, entries) { + if (plugin->u.io->log_stdout) { + int rc; + + sudo_debug_set_active_instance(plugin->debug_instance); + rc = plugin->u.io->log_stdout(buf, n, &errstr); + if (rc <= 0) { + if (rc < 0) { + /* Error: disable plugin's I/O function. */ + plugin->u.io->log_stdout = NULL; + audit_error(plugin->name, SUDO_IO_PLUGIN, + errstr ? errstr : _("I/O plugin error"), + iob->ec->details->info); + } else { + audit_reject(plugin->name, SUDO_IO_PLUGIN, + errstr ? errstr : _("command rejected by I/O plugin"), + iob->ec->details->info); + } + ret = false; + break; + } + } + } + sudo_debug_set_active_instance(sudo_debug_instance); + if (!ret) { + /* + * I/O plugin rejected the output, delete the write event + * (user's stdout) so we do not display the rejected output. + */ + sudo_debug_printf(SUDO_DEBUG_INFO, + "%s: deleting and freeing stdout wevent %p", __func__, iob->wevent); + sudo_ev_free(iob->wevent); + iob->wevent = NULL; + iob->off = iob->len = 0; + } + sigprocmask(SIG_SETMASK, &omask, NULL); + + debug_return_bool(ret); +} + +/* Call I/O plugin stderr log method. */ +static bool +log_stderr(const char *buf, unsigned int n, struct io_buffer *iob) +{ + struct plugin_container *plugin; + const char *errstr = NULL; + sigset_t omask; + bool ret = true; + debug_decl(log_stderr, SUDO_DEBUG_EXEC); + + sigprocmask(SIG_BLOCK, &ttyblock, &omask); + TAILQ_FOREACH(plugin, &io_plugins, entries) { + if (plugin->u.io->log_stderr) { + int rc; + + sudo_debug_set_active_instance(plugin->debug_instance); + rc = plugin->u.io->log_stderr(buf, n, &errstr); + if (rc <= 0) { + if (rc < 0) { + /* Error: disable plugin's I/O function. */ + plugin->u.io->log_stderr = NULL; + audit_error(plugin->name, SUDO_IO_PLUGIN, + errstr ? errstr : _("I/O plugin error"), + iob->ec->details->info); + } else { + audit_reject(plugin->name, SUDO_IO_PLUGIN, + errstr ? errstr : _("command rejected by I/O plugin"), + iob->ec->details->info); + } + ret = false; + break; + } + } + } + sudo_debug_set_active_instance(sudo_debug_instance); + if (!ret) { + /* + * I/O plugin rejected the output, delete the write event + * (user's stderr) so we do not display the rejected output. + */ + sudo_debug_printf(SUDO_DEBUG_INFO, + "%s: deleting and freeing stderr wevent %p", __func__, iob->wevent); + sudo_ev_free(iob->wevent); + iob->wevent = NULL; + iob->off = iob->len = 0; + } + sigprocmask(SIG_SETMASK, &omask, NULL); + + debug_return_bool(ret); +} + +/* Call I/O plugin suspend log method. */ +static void +log_suspend(struct exec_closure_pty *ec, int signo) +{ + struct plugin_container *plugin; + const char *errstr = NULL; + sigset_t omask; + debug_decl(log_suspend, SUDO_DEBUG_EXEC); + + sigprocmask(SIG_BLOCK, &ttyblock, &omask); + TAILQ_FOREACH(plugin, &io_plugins, entries) { + if (plugin->u.io->version < SUDO_API_MKVERSION(1, 13)) + continue; + if (plugin->u.io->log_suspend) { + int rc; + + sudo_debug_set_active_instance(plugin->debug_instance); + rc = plugin->u.io->log_suspend(signo, &errstr); + if (rc <= 0) { + /* Error: disable plugin's I/O function. */ + plugin->u.io->log_suspend = NULL; + audit_error(plugin->name, SUDO_IO_PLUGIN, + errstr ? errstr : _("error logging suspend"), + ec->details->info); + break; + } + } + } + sudo_debug_set_active_instance(sudo_debug_instance); + sigprocmask(SIG_SETMASK, &omask, NULL); + + debug_return; +} + +/* Call I/O plugin window change log method. */ +static void +log_winchange(struct exec_closure_pty *ec, unsigned int rows, unsigned int cols) +{ + struct plugin_container *plugin; + const char *errstr = NULL; + sigset_t omask; + debug_decl(log_winchange, SUDO_DEBUG_EXEC); + + sigprocmask(SIG_BLOCK, &ttyblock, &omask); + TAILQ_FOREACH(plugin, &io_plugins, entries) { + if (plugin->u.io->version < SUDO_API_MKVERSION(1, 12)) + continue; + if (plugin->u.io->change_winsize) { + int rc; + + sudo_debug_set_active_instance(plugin->debug_instance); + rc = plugin->u.io->change_winsize(rows, cols, &errstr); + if (rc <= 0) { + /* Error: disable plugin's I/O function. */ + plugin->u.io->change_winsize = NULL; + audit_error(plugin->name, SUDO_IO_PLUGIN, + errstr ? errstr : _("error changing window size"), + ec->details->info); + break; + } + } + } + sudo_debug_set_active_instance(sudo_debug_instance); + sigprocmask(SIG_SETMASK, &omask, NULL); + + debug_return; +} + +/* + * Check whether we are running in the foregroup. + * Updates the foreground global and updates the window size. + * Returns 0 if there is no tty, the foreground process group ID + * on success, or -1 on failure (tty revoked). + */ +static pid_t +check_foreground(struct exec_closure_pty *ec) +{ + int ret = 0; + debug_decl(check_foreground, SUDO_DEBUG_EXEC); + + if (io_fds[SFD_USERTTY] != -1) { + if ((ret = tcgetpgrp(io_fds[SFD_USERTTY])) != -1) { + foreground = ret == ec->ppgrp; + + /* Also check for window size changes. */ + sync_ttysize(ec); + } + } + debug_return_int(ret); +} + +/* + * Suspend sudo if the underlying command is suspended. + * Returns SIGCONT_FG if the command should be resumed in the + * foreground or SIGCONT_BG if it is a background process. + */ +static int +suspend_sudo(struct exec_closure_pty *ec, int signo) +{ + char signame[SIG2STR_MAX]; + struct sigaction sa, osa; + int ret = 0; + debug_decl(suspend_sudo, SUDO_DEBUG_EXEC); + + switch (signo) { + case SIGTTOU: + case SIGTTIN: + /* + * If sudo is already the foreground process, just resume the command + * in the foreground. If not, we'll suspend sudo and resume later. + */ + if (!foreground) { + if (check_foreground(ec) == -1) { + /* User's tty was revoked. */ + break; + } + } + if (foreground) { + if (ttymode != TERM_RAW) { + if (sudo_term_raw(io_fds[SFD_USERTTY], 0)) + ttymode = TERM_RAW; + } + ret = SIGCONT_FG; /* resume command in foreground */ + break; + } + FALLTHROUGH; + case SIGSTOP: + case SIGTSTP: + /* Flush any remaining output and deschedule I/O events. */ + del_io_events(true); + + /* Restore original tty mode before suspending. */ + if (ttymode != TERM_COOKED) + sudo_term_restore(io_fds[SFD_USERTTY], false); + + /* Log the suspend event. */ + log_suspend(ec, signo); + + if (sig2str(signo, signame) == -1) + (void)snprintf(signame, sizeof(signame), "%d", signo); + + /* Suspend self and continue command when we resume. */ + if (signo != SIGSTOP) { + memset(&sa, 0, sizeof(sa)); + sigemptyset(&sa.sa_mask); + sa.sa_flags = SA_RESTART; + sa.sa_handler = SIG_DFL; + if (sudo_sigaction(signo, &sa, &osa) != 0) + sudo_warn(U_("unable to set handler for signal %d"), signo); + } + sudo_debug_printf(SUDO_DEBUG_INFO, "kill parent SIG%s", signame); + if (killpg(ec->ppgrp, signo) != 0) + sudo_warn("killpg(%d, SIG%s)", (int)ec->ppgrp, signame); + + /* Log the resume event. */ + log_suspend(ec, SIGCONT); + + /* Check foreground/background status on resume. */ + if (check_foreground(ec) == -1) { + /* User's tty was revoked. */ + break; + } + + /* + * We always resume the command in the foreground if sudo itself + * is the foreground process. This helps work around poorly behaved + * programs that catch SIGTTOU/SIGTTIN but suspend themselves with + * SIGSTOP. At worst, sudo will go into the background but upon + * resume the command will be runnable. Otherwise, we can get into + * a situation where the command will immediately suspend itself. + */ + sudo_debug_printf(SUDO_DEBUG_INFO, "parent is in %s, ttymode %d -> %d", + foreground ? "foreground" : "background", ttymode, + foreground ? TERM_RAW : TERM_COOKED); + + if (foreground) { + /* Foreground process, set tty to raw mode. */ + if (sudo_term_raw(io_fds[SFD_USERTTY], 0)) + ttymode = TERM_RAW; + } else { + /* Background process, no access to tty. */ + ttymode = TERM_COOKED; + } + + if (signo != SIGSTOP) { + if (sudo_sigaction(signo, &osa, NULL) != 0) + sudo_warn(U_("unable to restore handler for signal %d"), signo); + } + + ret = ttymode == TERM_RAW ? SIGCONT_FG : SIGCONT_BG; + break; + } + + debug_return_int(ret); +} + +/* + * SIGTTIN signal handler for read_callback that just sets a flag. + */ +static volatile sig_atomic_t got_sigttin; + +static void +sigttin(int signo) +{ + got_sigttin = 1; +} + +/* + * Read an iobuf that is ready. + */ +static void +read_callback(int fd, int what, void *v) +{ + struct io_buffer *iob = v; + struct sudo_event_base *evbase = sudo_ev_get_base(iob->revent); + struct sigaction sa, osa; + int saved_errno; + ssize_t n; + debug_decl(read_callback, SUDO_DEBUG_EXEC); + + /* + * We ignore SIGTTIN by default but we need to handle it when reading + * from the terminal. A signal event won't work here because the + * read() would be restarted, preventing the callback from running. + */ + memset(&sa, 0, sizeof(sa)); + sigemptyset(&sa.sa_mask); + sa.sa_handler = sigttin; + got_sigttin = 0; + sigaction(SIGTTIN, &sa, &osa); + n = read(fd, iob->buf + iob->len, sizeof(iob->buf) - iob->len); + saved_errno = errno; + sigaction(SIGTTIN, &osa, NULL); + errno = saved_errno; + + switch (n) { + case -1: + if (got_sigttin) { + /* Schedule SIGTTIN to be forwarded to the command. */ + schedule_signal(iob->ec, SIGTTIN); + } + if (errno == EAGAIN || errno == EINTR) + break; + /* treat read error as fatal and close the fd */ + sudo_debug_printf(SUDO_DEBUG_ERROR, + "error reading fd %d: %s", fd, strerror(errno)); + FALLTHROUGH; + case 0: + /* got EOF or pty has gone away */ + if (n == 0) { + sudo_debug_printf(SUDO_DEBUG_INFO, + "read EOF from fd %d", fd); + } + safe_close(fd); + ev_free_by_fd(evbase, fd); + /* If writer already consumed the buffer, close it too. */ + if (iob->wevent != NULL && iob->off == iob->len) { + safe_close(sudo_ev_get_fd(iob->wevent)); + ev_free_by_fd(evbase, sudo_ev_get_fd(iob->wevent)); + iob->off = iob->len = 0; + } + break; + default: + sudo_debug_printf(SUDO_DEBUG_INFO, + "read %zd bytes from fd %d", n, fd); + if (!iob->action(iob->buf + iob->len, n, iob)) { + terminate_command(iob->ec->cmnd_pid, true); + iob->ec->cmnd_pid = -1; + } + iob->len += n; + /* Enable writer now that there is data in the buffer. */ + if (iob->wevent != NULL) { + if (sudo_ev_add(evbase, iob->wevent, NULL, false) == -1) + sudo_fatal("%s", U_("unable to add event to queue")); + } + /* Re-enable reader if buffer is not full. */ + if (iob->len != sizeof(iob->buf)) { + if (sudo_ev_add(evbase, iob->revent, NULL, false) == -1) + sudo_fatal("%s", U_("unable to add event to queue")); + } + break; + } +} + +/* + * SIGTTOU signal handler for write_callback that just sets a flag. + */ +static volatile sig_atomic_t got_sigttou; + +static void +sigttou(int signo) +{ + got_sigttou = 1; +} + +/* + * Write an iobuf that is ready. + */ +static void +write_callback(int fd, int what, void *v) +{ + struct io_buffer *iob = v; + struct sudo_event_base *evbase = sudo_ev_get_base(iob->wevent); + struct sigaction sa, osa; + int saved_errno; + ssize_t n; + debug_decl(write_callback, SUDO_DEBUG_EXEC); + + /* + * We ignore SIGTTOU by default but we need to handle it when writing + * to the terminal. A signal event won't work here because the + * write() would be restarted, preventing the callback from running. + */ + memset(&sa, 0, sizeof(sa)); + sigemptyset(&sa.sa_mask); + sa.sa_handler = sigttou; + got_sigttou = 0; + sigaction(SIGTTOU, &sa, &osa); + n = write(fd, iob->buf + iob->off, iob->len - iob->off); + saved_errno = errno; + sigaction(SIGTTOU, &osa, NULL); + errno = saved_errno; + + if (n == -1) { + switch (errno) { + case EPIPE: + case ENXIO: + case EIO: + case EBADF: + /* other end of pipe closed or pty revoked */ + sudo_debug_printf(SUDO_DEBUG_INFO, + "unable to write %d bytes to fd %d", + iob->len - iob->off, fd); + /* Close reader if there is one. */ + if (iob->revent != NULL) { + safe_close(sudo_ev_get_fd(iob->revent)); + ev_free_by_fd(evbase, sudo_ev_get_fd(iob->revent)); + } + safe_close(fd); + ev_free_by_fd(evbase, fd); + break; + case EINTR: + if (got_sigttou) { + /* Schedule SIGTTOU to be forwarded to the command. */ + schedule_signal(iob->ec, SIGTTOU); + } + FALLTHROUGH; + case EAGAIN: + /* not an error */ + break; + default: + /* XXX - need a way to distinguish non-exec error. */ + iob->ec->cstat->type = CMD_ERRNO; + iob->ec->cstat->val = errno; + sudo_debug_printf(SUDO_DEBUG_ERROR, + "error writing fd %d: %s", fd, strerror(errno)); + sudo_ev_loopbreak(evbase); + break; + } + } else { + sudo_debug_printf(SUDO_DEBUG_INFO, + "wrote %zd bytes to fd %d", n, fd); + iob->off += n; + /* Reset buffer if fully consumed. */ + if (iob->off == iob->len) { + iob->off = iob->len = 0; + /* Forward the EOF from reader to writer. */ + if (iob->revent == NULL) { + safe_close(fd); + ev_free_by_fd(evbase, fd); + } + } + /* Re-enable writer if buffer is not empty. */ + if (iob->len > iob->off) { + if (sudo_ev_add(evbase, iob->wevent, NULL, false) == -1) + sudo_fatal("%s", U_("unable to add event to queue")); + } + /* Enable reader if buffer is not full. */ + if (iob->revent != NULL && + (ttymode == TERM_RAW || !USERTTY_EVENT(iob->revent))) { + if (iob->len != sizeof(iob->buf)) { + if (sudo_ev_add(evbase, iob->revent, NULL, false) == -1) + sudo_fatal("%s", U_("unable to add event to queue")); + } + } + } +} + +static void +io_buf_new(int rfd, int wfd, + bool (*action)(const char *, unsigned int, struct io_buffer *), + struct exec_closure_pty *ec, struct io_buffer_list *head) +{ + int n; + struct io_buffer *iob; + debug_decl(io_buf_new, SUDO_DEBUG_EXEC); + + /* Set non-blocking mode. */ + n = fcntl(rfd, F_GETFL, 0); + if (n != -1 && !ISSET(n, O_NONBLOCK)) + (void) fcntl(rfd, F_SETFL, n | O_NONBLOCK); + n = fcntl(wfd, F_GETFL, 0); + if (n != -1 && !ISSET(n, O_NONBLOCK)) + (void) fcntl(wfd, F_SETFL, n | O_NONBLOCK); + + /* Allocate and add to head of list. */ + if ((iob = malloc(sizeof(*iob))) == NULL) + sudo_fatalx(U_("%s: %s"), __func__, U_("unable to allocate memory")); + iob->ec = ec; + iob->revent = sudo_ev_alloc(rfd, SUDO_EV_READ, read_callback, iob); + iob->wevent = sudo_ev_alloc(wfd, SUDO_EV_WRITE, write_callback, iob); + iob->len = 0; + iob->off = 0; + iob->action = action; + iob->buf[0] = '\0'; + if (iob->revent == NULL || iob->wevent == NULL) + sudo_fatalx(U_("%s: %s"), __func__, U_("unable to allocate memory")); + SLIST_INSERT_HEAD(head, iob, entries); + + debug_return; +} + +/* + * We already closed the follower so reads from the leader will not block. + */ +static void +pty_finish(struct command_status *cstat) +{ + struct io_buffer *iob; + int n; + debug_decl(pty_finish, SUDO_DEBUG_EXEC); + + /* 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); + } + } + del_io_events(false); + + /* Free I/O buffers. */ + while ((iob = SLIST_FIRST(&iobufs)) != NULL) { + SLIST_REMOVE_HEAD(&iobufs, entries); + if (iob->revent != NULL) + sudo_ev_free(iob->revent); + if (iob->wevent != NULL) + sudo_ev_free(iob->wevent); + free(iob); + } + + /* Restore terminal settings. */ + if (io_fds[SFD_USERTTY] != -1) + sudo_term_restore(io_fds[SFD_USERTTY], false); + + /* Update utmp */ + if (utmp_user != NULL) + utmp_logout(ptyname, cstat->type == CMD_WSTATUS ? cstat->val : 0); + + debug_return; +} + +/* + * Send command status to the monitor (signal or window size change). + */ +static void +send_command_status(struct exec_closure_pty *ec, int type, int val) +{ + struct monitor_message *msg; + debug_decl(send_command, SUDO_DEBUG_EXEC); + + if ((msg = calloc(1, sizeof(*msg))) == NULL) + sudo_fatalx(U_("%s: %s"), __func__, U_("unable to allocate memory")); + msg->cstat.type = type; + msg->cstat.val = val; + TAILQ_INSERT_TAIL(&ec->monitor_messages, msg, entries); + + if (sudo_ev_add(ec->evbase, ec->fwdchannel_event, NULL, true) == -1) + sudo_fatal("%s", U_("unable to add event to queue")); + + /* Restart event loop to send the command immediately. */ + sudo_ev_loopcontinue(ec->evbase); + + debug_return; +} + +/* + * Schedule a signal to be forwarded. + */ +static void +schedule_signal(struct exec_closure_pty *ec, int signo) +{ + char signame[SIG2STR_MAX]; + debug_decl(schedule_signal, SUDO_DEBUG_EXEC); + + if (signo == 0) + debug_return; + + if (signo == SIGCONT_FG) + strlcpy(signame, "CONT_FG", sizeof(signame)); + else if (signo == SIGCONT_BG) + strlcpy(signame, "CONT_BG", sizeof(signame)); + else if (sig2str(signo, signame) == -1) + (void)snprintf(signame, sizeof(signame), "%d", signo); + sudo_debug_printf(SUDO_DEBUG_DIAG, "scheduled SIG%s for command", signame); + + send_command_status(ec, CMD_SIGNO, signo); + + debug_return; +} + +static void +backchannel_cb(int fd, int what, void *v) +{ + struct exec_closure_pty *ec = v; + struct command_status cstat; + ssize_t nread; + debug_decl(backchannel_cb, SUDO_DEBUG_EXEC); + + /* + * Read command status from the monitor. + * Note that the backchannel is a *blocking* socket. + */ + nread = recv(fd, &cstat, sizeof(cstat), MSG_WAITALL); + switch (nread) { + case -1: + switch (errno) { + case EINTR: + case EAGAIN: + /* Nothing ready. */ + break; + default: + if (ec->cstat->val == CMD_INVALID) { + ec->cstat->type = CMD_ERRNO; + ec->cstat->val = errno; + sudo_debug_printf(SUDO_DEBUG_ERROR, + "%s: failed to read command status: %s", + __func__, strerror(errno)); + sudo_ev_loopbreak(ec->evbase); + } + break; + } + break; + case 0: + /* EOF, monitor exited or was killed. */ + sudo_debug_printf(SUDO_DEBUG_INFO, + "EOF on backchannel, monitor dead?"); + if (ec->cstat->type == CMD_INVALID) { + /* XXX - need new CMD_ type for monitor errors. */ + ec->cstat->type = CMD_ERRNO; + ec->cstat->val = ECONNRESET; + } + sudo_ev_loopexit(ec->evbase); + break; + case sizeof(cstat): + /* Check command status. */ + switch (cstat.type) { + case CMD_PID: + ec->cmnd_pid = cstat.val; + sudo_debug_printf(SUDO_DEBUG_INFO, "executed %s, pid %d", + ec->details->command, (int)ec->cmnd_pid); + break; + case CMD_WSTATUS: + if (WIFSTOPPED(cstat.val)) { + int signo; + + /* Suspend parent and tell monitor how to resume on return. */ + sudo_debug_printf(SUDO_DEBUG_INFO, + "command stopped, suspending parent"); + signo = suspend_sudo(ec, WSTOPSIG(cstat.val)); + schedule_signal(ec, signo); + /* Re-enable I/O events */ + add_io_events(ec->evbase); + } else { + /* Command exited or was killed, either way we are done. */ + sudo_debug_printf(SUDO_DEBUG_INFO, "command exited or was killed"); + sudo_ev_loopexit(ec->evbase); + } + *ec->cstat = cstat; + break; + case CMD_ERRNO: + /* Monitor was unable to execute command or broken pipe. */ + sudo_debug_printf(SUDO_DEBUG_INFO, "errno from monitor: %s", + strerror(cstat.val)); + sudo_ev_loopbreak(ec->evbase); + *ec->cstat = cstat; + break; + } + /* Keep reading command status messages until EAGAIN or EOF. */ + break; + default: + /* Short read, should not happen. */ + if (ec->cstat->val == CMD_INVALID) { + ec->cstat->type = CMD_ERRNO; + ec->cstat->val = EIO; + sudo_debug_printf(SUDO_DEBUG_ERROR, + "%s: failed to read command status: short read", __func__); + sudo_ev_loopbreak(ec->evbase); + } + break; + } + debug_return; +} + +/* + * Handle changes to the monitors's status (SIGCHLD). + */ +static void +handle_sigchld_pty(struct exec_closure_pty *ec) +{ + int n, status; + pid_t pid; + debug_decl(handle_sigchld_pty, SUDO_DEBUG_EXEC); + + /* + * Monitor process was signaled; wait for it as needed. + */ + do { + pid = waitpid(ec->monitor_pid, &status, WUNTRACED|WNOHANG); + } while (pid == -1 && errno == EINTR); + switch (pid) { + case 0: + errno = ECHILD; + FALLTHROUGH; + case -1: + sudo_warn(U_("%s: %s"), __func__, "waitpid"); + debug_return; + } + + /* + * If the monitor dies we get notified via backchannel_cb(). + * If it was stopped, we should stop too (the command keeps + * running in its pty) and continue it when we come back. + */ + if (WIFSTOPPED(status)) { + sudo_debug_printf(SUDO_DEBUG_INFO, + "monitor stopped, suspending sudo"); + n = suspend_sudo(ec, WSTOPSIG(status)); + kill(pid, SIGCONT); + schedule_signal(ec, n); + /* Re-enable I/O events */ + add_io_events(ec->evbase); + } else if (WIFSIGNALED(status)) { + char signame[SIG2STR_MAX]; + if (sig2str(WTERMSIG(status), signame) == -1) + (void)snprintf(signame, sizeof(signame), "%d", WTERMSIG(status)); + sudo_debug_printf(SUDO_DEBUG_INFO, "%s: monitor (%d) killed, SIG%s", + __func__, (int)ec->monitor_pid, signame); + ec->monitor_pid = -1; + } else { + sudo_debug_printf(SUDO_DEBUG_INFO, + "%s: monitor exited, status %d", __func__, WEXITSTATUS(status)); + ec->monitor_pid = -1; + } + debug_return; +} + +/* Signal callback */ +static void +signal_cb_pty(int signo, int what, void *v) +{ + struct sudo_ev_siginfo_container *sc = v; + struct exec_closure_pty *ec = sc->closure; + char signame[SIG2STR_MAX]; + debug_decl(signal_cb_pty, SUDO_DEBUG_EXEC); + + if (ec->monitor_pid == -1) + debug_return; + + if (sig2str(signo, signame) == -1) + (void)snprintf(signame, sizeof(signame), "%d", signo); + sudo_debug_printf(SUDO_DEBUG_DIAG, + "%s: evbase %p, monitor: %d, signo %s(%d), cstat %p", __func__, + ec->evbase, (int)ec->monitor_pid, signame, signo, ec->cstat); + + switch (signo) { + case SIGCHLD: + handle_sigchld_pty(ec); + break; + case SIGWINCH: + sync_ttysize(ec); + break; + default: + /* + * Do not forward signals sent by a process in the command's process + * group, as we don't want the command to indirectly kill itself. + * For example, this can happen with some 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 = getpgid(sc->siginfo->si_pid); + if (si_pgrp != -1) { + if (si_pgrp == ec->ppgrp || si_pgrp == ec->cmnd_pid) + debug_return; + } else if (sc->siginfo->si_pid == ec->cmnd_pid) { + debug_return; + } + } + /* Schedule signal to be forwarded to the command. */ + schedule_signal(ec, signo); + break; + } + + debug_return; +} + +/* + * Forward signals in monitor_messages to the monitor so it can + * deliver them to the command. + */ +static void +fwdchannel_cb(int sock, int what, void *v) +{ + struct exec_closure_pty *ec = v; + char signame[SIG2STR_MAX]; + struct monitor_message *msg; + ssize_t nsent; + debug_decl(fwdchannel_cb, SUDO_DEBUG_EXEC); + + while ((msg = TAILQ_FIRST(&ec->monitor_messages)) != NULL) { + switch (msg->cstat.type) { + case CMD_SIGNO: + if (msg->cstat.val == SIGCONT_FG) + strlcpy(signame, "CONT_FG", sizeof(signame)); + else if (msg->cstat.val == SIGCONT_BG) + strlcpy(signame, "CONT_BG", sizeof(signame)); + else if (sig2str(msg->cstat.val, signame) == -1) + (void)snprintf(signame, sizeof(signame), "%d", msg->cstat.val); + sudo_debug_printf(SUDO_DEBUG_INFO, + "sending SIG%s to monitor over backchannel", signame); + break; + case CMD_TTYWINCH: + sudo_debug_printf(SUDO_DEBUG_INFO, "sending window size change " + "to monitor over backchannelL %d x %d", + msg->cstat.val & 0xffff, (msg->cstat.val >> 16) & 0xffff); + break; + default: + sudo_debug_printf(SUDO_DEBUG_INFO, + "sending cstat type %d, value %d to monitor over backchannel", + msg->cstat.type, msg->cstat.val); + break; + } + TAILQ_REMOVE(&ec->monitor_messages, msg, entries); + nsent = send(sock, &msg->cstat, sizeof(msg->cstat), 0); + if (nsent != sizeof(msg->cstat)) { + if (errno == EPIPE) { + sudo_debug_printf(SUDO_DEBUG_ERROR, + "broken pipe writing to monitor over backchannel"); + /* Other end of socket gone, empty out monitor_messages. */ + free(msg); + while ((msg = TAILQ_FIRST(&ec->monitor_messages)) != NULL) { + TAILQ_REMOVE(&ec->monitor_messages, msg, entries); + free(msg); + } + /* XXX - need new CMD_ type for monitor errors. */ + ec->cstat->type = CMD_ERRNO; + ec->cstat->val = errno; + sudo_ev_loopbreak(ec->evbase); + } + break; + } + free(msg); + } +} + +/* + * Fill in the exec closure and setup initial exec events. + * Allocates events for the signal pipe and backchannel. + * Forwarded signals on the backchannel are enabled on demand. + */ +static void +fill_exec_closure_pty(struct exec_closure_pty *ec, struct command_status *cstat, + struct command_details *details, pid_t ppgrp, int backchannel) +{ + debug_decl(fill_exec_closure_pty, SUDO_DEBUG_EXEC); + + /* Fill in the non-event part of the closure. */ + ec->cmnd_pid = -1; + ec->ppgrp = ppgrp; + ec->cstat = cstat; + ec->details = details; + ec->rows = user_details.ts_rows; + ec->cols = user_details.ts_cols; + TAILQ_INIT(&ec->monitor_messages); + + /* Reset cstat for running the command. */ + cstat->type = CMD_INVALID; + cstat->val = 0; + + /* Setup event base and events. */ + ec->evbase = details->evbase; + details->evbase = NULL; + + /* Event for command status via backchannel. */ + ec->backchannel_event = sudo_ev_alloc(backchannel, + SUDO_EV_READ|SUDO_EV_PERSIST, backchannel_cb, ec); + if (ec->backchannel_event == NULL) + sudo_fatalx(U_("%s: %s"), __func__, U_("unable to allocate memory")); + if (sudo_ev_add(ec->evbase, ec->backchannel_event, NULL, false) == -1) + sudo_fatal("%s", U_("unable to add event to queue")); + sudo_debug_printf(SUDO_DEBUG_INFO, "backchannel fd %d\n", backchannel); + + /* Events for local signals. */ + ec->sigint_event = sudo_ev_alloc(SIGINT, + SUDO_EV_SIGINFO, signal_cb_pty, ec); + if (ec->sigint_event == NULL) + sudo_fatalx(U_("%s: %s"), __func__, U_("unable to allocate memory")); + if (sudo_ev_add(ec->evbase, ec->sigint_event, NULL, false) == -1) + sudo_fatal("%s", U_("unable to add event to queue")); + + ec->sigquit_event = sudo_ev_alloc(SIGQUIT, + SUDO_EV_SIGINFO, signal_cb_pty, ec); + if (ec->sigquit_event == NULL) + sudo_fatalx(U_("%s: %s"), __func__, U_("unable to allocate memory")); + if (sudo_ev_add(ec->evbase, ec->sigquit_event, NULL, false) == -1) + sudo_fatal("%s", U_("unable to add event to queue")); + + ec->sigtstp_event = sudo_ev_alloc(SIGTSTP, + SUDO_EV_SIGINFO, signal_cb_pty, ec); + if (ec->sigtstp_event == NULL) + sudo_fatalx(U_("%s: %s"), __func__, U_("unable to allocate memory")); + if (sudo_ev_add(ec->evbase, ec->sigtstp_event, NULL, false) == -1) + sudo_fatal("%s", U_("unable to add event to queue")); + + ec->sigterm_event = sudo_ev_alloc(SIGTERM, + SUDO_EV_SIGINFO, signal_cb_pty, ec); + if (ec->sigterm_event == NULL) + sudo_fatalx(U_("%s: %s"), __func__, U_("unable to allocate memory")); + if (sudo_ev_add(ec->evbase, ec->sigterm_event, NULL, false) == -1) + sudo_fatal("%s", U_("unable to add event to queue")); + + ec->sighup_event = sudo_ev_alloc(SIGHUP, + SUDO_EV_SIGINFO, signal_cb_pty, ec); + if (ec->sighup_event == NULL) + sudo_fatalx(U_("%s: %s"), __func__, U_("unable to allocate memory")); + if (sudo_ev_add(ec->evbase, ec->sighup_event, NULL, false) == -1) + sudo_fatal("%s", U_("unable to add event to queue")); + + ec->sigalrm_event = sudo_ev_alloc(SIGALRM, + SUDO_EV_SIGINFO, signal_cb_pty, ec); + if (ec->sigalrm_event == NULL) + sudo_fatalx(U_("%s: %s"), __func__, U_("unable to allocate memory")); + if (sudo_ev_add(ec->evbase, ec->sigalrm_event, NULL, false) == -1) + sudo_fatal("%s", U_("unable to add event to queue")); + + ec->sigusr1_event = sudo_ev_alloc(SIGUSR1, + SUDO_EV_SIGINFO, signal_cb_pty, ec); + if (ec->sigusr1_event == NULL) + sudo_fatalx(U_("%s: %s"), __func__, U_("unable to allocate memory")); + if (sudo_ev_add(ec->evbase, ec->sigusr1_event, NULL, false) == -1) + sudo_fatal("%s", U_("unable to add event to queue")); + + ec->sigusr2_event = sudo_ev_alloc(SIGUSR2, + SUDO_EV_SIGINFO, signal_cb_pty, ec); + if (ec->sigusr2_event == NULL) + sudo_fatalx(U_("%s: %s"), __func__, U_("unable to allocate memory")); + if (sudo_ev_add(ec->evbase, ec->sigusr2_event, NULL, false) == -1) + sudo_fatal("%s", U_("unable to add event to queue")); + + ec->sigchld_event = sudo_ev_alloc(SIGCHLD, + SUDO_EV_SIGINFO, signal_cb_pty, ec); + if (ec->sigchld_event == NULL) + sudo_fatalx(U_("%s: %s"), __func__, U_("unable to allocate memory")); + if (sudo_ev_add(ec->evbase, ec->sigchld_event, NULL, false) == -1) + sudo_fatal("%s", U_("unable to add event to queue")); + + ec->sigwinch_event = sudo_ev_alloc(SIGWINCH, + SUDO_EV_SIGINFO, signal_cb_pty, ec); + if (ec->sigwinch_event == NULL) + sudo_fatalx(U_("%s: %s"), __func__, U_("unable to allocate memory")); + if (sudo_ev_add(ec->evbase, ec->sigwinch_event, NULL, false) == -1) + sudo_fatal("%s", U_("unable to add event to queue")); + + /* The signal forwarding event gets added on demand. */ + ec->fwdchannel_event = sudo_ev_alloc(backchannel, + SUDO_EV_WRITE, fwdchannel_cb, ec); + if (ec->fwdchannel_event == NULL) + sudo_fatalx(U_("%s: %s"), __func__, U_("unable to allocate memory")); + + /* Set the default event base. */ + sudo_ev_base_setdef(ec->evbase); + + debug_return; +} + +/* + * Free the dynamically-allocated contents of the exec closure. + */ +static void +free_exec_closure_pty(struct exec_closure_pty *ec) +{ + struct monitor_message *msg; + debug_decl(free_exec_closure_pty, SUDO_DEBUG_EXEC); + + sudo_ev_base_free(ec->evbase); + sudo_ev_free(ec->backchannel_event); + sudo_ev_free(ec->fwdchannel_event); + sudo_ev_free(ec->sigint_event); + sudo_ev_free(ec->sigquit_event); + sudo_ev_free(ec->sigtstp_event); + sudo_ev_free(ec->sigterm_event); + sudo_ev_free(ec->sighup_event); + sudo_ev_free(ec->sigalrm_event); + sudo_ev_free(ec->sigusr1_event); + sudo_ev_free(ec->sigusr2_event); + sudo_ev_free(ec->sigchld_event); + sudo_ev_free(ec->sigwinch_event); + + while ((msg = TAILQ_FIRST(&ec->monitor_messages)) != NULL) { + TAILQ_REMOVE(&ec->monitor_messages, msg, entries); + free(msg); + } + + debug_return; +} + +/* + * Execute a command in a pty, potentially with I/O logging, and + * wait for it to finish. + * This is a little bit tricky due to how POSIX job control works and + * we fact that we have two different controlling terminals to deal with. + */ +bool +exec_pty(struct command_details *details, struct command_status *cstat) +{ + int io_pipe[3][2] = { { -1, -1 }, { -1, -1 }, { -1, -1 } }; + bool interpose[3] = { false, false, false }; + struct exec_closure_pty ec = { 0 }; + struct plugin_container *plugin; + int evloop_retries = -1; + sigset_t set, oset; + struct sigaction sa; + struct stat sb; + pid_t ppgrp; + int sv[2]; + debug_decl(exec_pty, SUDO_DEBUG_EXEC); + + /* + * Allocate a pty. + */ + if (!pty_setup(details, user_details.tty)) { + if (TAILQ_EMPTY(&io_plugins)) { + /* Not logging I/O and didn't allocate a pty. */ + debug_return_bool(false); + } + } + + /* + * We communicate with the monitor over a bi-directional pair of sockets. + * Parent sends signal info to monitor and monitor sends back wait status. + */ + if (socketpair(PF_UNIX, SOCK_STREAM, 0, sv) == -1 || + fcntl(sv[0], F_SETFD, FD_CLOEXEC) == -1 || + fcntl(sv[1], F_SETFD, FD_CLOEXEC) == -1) + sudo_fatal("%s", U_("unable to create sockets")); + + /* + * We don't want to receive SIGTTIN/SIGTTOU. + * XXX - this affects tcsetattr() and tcsetpgrp() too. + */ + 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); + + /* + * The policy plugin's session init must be run before we fork + * or certain pam modules won't be able to track their state. + */ + if (policy_init_session(details) != true) + sudo_fatalx("%s", U_("policy plugin failed session initialization")); + + /* + * Child will run the command in the pty, parent will pass data + * to and from pty. + */ + + /* So we can block tty-generated signals */ + sigemptyset(&ttyblock); + sigaddset(&ttyblock, SIGINT); + sigaddset(&ttyblock, SIGQUIT); + sigaddset(&ttyblock, SIGTSTP); + sigaddset(&ttyblock, SIGTTIN); + sigaddset(&ttyblock, SIGTTOU); + + ppgrp = getpgrp(); /* parent's pgrp, so child can signal us */ + + /* Determine whether any of std{in,out,err} should be logged. */ + TAILQ_FOREACH(plugin, &io_plugins, entries) { + if (plugin->u.io->log_stdin) + interpose[STDIN_FILENO] = true; + if (plugin->u.io->log_stdout) + interpose[STDOUT_FILENO] = true; + if (plugin->u.io->log_stderr) + interpose[STDERR_FILENO] = true; + } + + /* + * Setup stdin/stdout/stderr for command, 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_FOLLOWER]; + io_fds[SFD_STDOUT] = io_fds[SFD_FOLLOWER]; + io_fds[SFD_STDERR] = io_fds[SFD_FOLLOWER]; + + if (io_fds[SFD_USERTTY] != -1) { + /* Read from /dev/tty, write to pty leader */ + if (!ISSET(details->flags, CD_BACKGROUND)) { + io_buf_new(io_fds[SFD_USERTTY], io_fds[SFD_LEADER], + log_ttyin, &ec, &iobufs); + } + + /* Read from pty leader, write to /dev/tty */ + io_buf_new(io_fds[SFD_LEADER], io_fds[SFD_USERTTY], + log_ttyout, &ec, &iobufs); + + /* Are we the foreground process? */ + foreground = tcgetpgrp(io_fds[SFD_USERTTY]) == ppgrp; + } + + /* + * If stdin, stdout or stderr is not a tty and logging is enabled, + * use a pipe to interpose ourselves instead of using the pty fd. + */ + if (io_fds[SFD_STDIN] == -1 || !isatty(STDIN_FILENO)) { + if (!interpose[STDIN_FILENO]) { + /* Not logging stdin, do not interpose. */ + sudo_debug_printf(SUDO_DEBUG_INFO, + "stdin not a tty, not logging"); + if (fstat(STDIN_FILENO, &sb) == 0 && S_ISFIFO(sb.st_mode)) + pipeline = true; + io_fds[SFD_STDIN] = dup(STDIN_FILENO); + if (io_fds[SFD_STDIN] == -1) + sudo_fatal("dup"); + } else { + sudo_debug_printf(SUDO_DEBUG_INFO, + "stdin not a tty, creating a pipe"); + pipeline = true; + if (pipe2(io_pipe[STDIN_FILENO], O_CLOEXEC) != 0) + sudo_fatal("%s", U_("unable to create pipe")); + io_buf_new(STDIN_FILENO, io_pipe[STDIN_FILENO][1], + log_stdin, &ec, &iobufs); + io_fds[SFD_STDIN] = io_pipe[STDIN_FILENO][0]; + } + } + if (io_fds[SFD_STDOUT] == -1 || !isatty(STDOUT_FILENO)) { + if (!interpose[STDOUT_FILENO]) { + /* Not logging stdout, do not interpose. */ + sudo_debug_printf(SUDO_DEBUG_INFO, + "stdout not a tty, not logging"); + if (fstat(STDOUT_FILENO, &sb) == 0 && S_ISFIFO(sb.st_mode)) + pipeline = true; + io_fds[SFD_STDOUT] = dup(STDOUT_FILENO); + if (io_fds[SFD_STDOUT] == -1) + sudo_fatal("dup"); + } else { + sudo_debug_printf(SUDO_DEBUG_INFO, + "stdout not a tty, creating a pipe"); + pipeline = true; + if (pipe2(io_pipe[STDOUT_FILENO], O_CLOEXEC) != 0) + sudo_fatal("%s", U_("unable to create pipe")); + io_buf_new(io_pipe[STDOUT_FILENO][0], STDOUT_FILENO, + log_stdout, &ec, &iobufs); + io_fds[SFD_STDOUT] = io_pipe[STDOUT_FILENO][1]; + } + } + if (io_fds[SFD_STDERR] == -1 || !isatty(STDERR_FILENO)) { + if (!interpose[STDERR_FILENO]) { + /* Not logging stderr, do not interpose. */ + sudo_debug_printf(SUDO_DEBUG_INFO, + "stderr not a tty, not logging"); + if (fstat(STDERR_FILENO, &sb) == 0 && S_ISFIFO(sb.st_mode)) + pipeline = true; + io_fds[SFD_STDERR] = dup(STDERR_FILENO); + if (io_fds[SFD_STDERR] == -1) + sudo_fatal("dup"); + } else { + sudo_debug_printf(SUDO_DEBUG_INFO, + "stderr not a tty, creating a pipe"); + if (pipe2(io_pipe[STDERR_FILENO], O_CLOEXEC) != 0) + sudo_fatal("%s", U_("unable to create pipe")); + io_buf_new(io_pipe[STDERR_FILENO][0], STDERR_FILENO, + log_stderr, &ec, &iobufs); + io_fds[SFD_STDERR] = io_pipe[STDERR_FILENO][1]; + } + } + + if (foreground) { + /* Copy terminal attrs from user tty -> pty follower. */ + if (!sudo_term_copy(io_fds[SFD_USERTTY], io_fds[SFD_FOLLOWER])) { + sudo_debug_printf(SUDO_DEBUG_ERROR|SUDO_DEBUG_ERRNO, + "%s: unable to copy terminal settings to pty", __func__); + foreground = false; + } else { + /* Start in raw mode unless part of a pipeline or backgrounded. */ + if (!pipeline && !ISSET(details->flags, CD_EXEC_BG)) { + if (sudo_term_raw(io_fds[SFD_USERTTY], 0)) + ttymode = TERM_RAW; + } + } + } + + /* + * Block signals until we have our handlers setup in the parent so + * we don't miss SIGCHLD if the command exits immediately. + */ + sigfillset(&set); + sigprocmask(SIG_BLOCK, &set, &oset); + + /* Check for early termination or suspend signals before we fork. */ + if (sudo_terminated(cstat)) { + sigprocmask(SIG_SETMASK, &oset, NULL); + debug_return_int(true); + } + + ec.monitor_pid = sudo_debug_fork(); + switch (ec.monitor_pid) { + case -1: + sudo_fatal("%s", U_("unable to fork")); + break; + case 0: + /* child */ + close(sv[0]); + /* Close the other end of the stdin/stdout/stderr pipes and exec. */ + if (io_pipe[STDIN_FILENO][1] != -1) + close(io_pipe[STDIN_FILENO][1]); + if (io_pipe[STDOUT_FILENO][0] != -1) + close(io_pipe[STDOUT_FILENO][0]); + if (io_pipe[STDERR_FILENO][0] != -1) + close(io_pipe[STDERR_FILENO][0]); + /* + * 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. + */ + exec_monitor(details, &oset, foreground && !pipeline, sv[1]); + cstat->type = CMD_ERRNO; + cstat->val = errno; + if (send(sv[1], cstat, sizeof(*cstat), 0) == -1) { + sudo_debug_printf(SUDO_DEBUG_ERROR|SUDO_DEBUG_ERRNO, + "%s: unable to send status to parent", __func__); + } + _exit(EXIT_FAILURE); + } + + /* + * We close the pty follower so only the monitor and command have a + * reference to it. This ensures that we can don't block reading + * from the leader when the command and monitor have exited. + */ + if (io_fds[SFD_FOLLOWER] != -1) { + close(io_fds[SFD_FOLLOWER]); + io_fds[SFD_FOLLOWER] = -1; + } + + /* Tell the monitor to continue now that the follower is closed. */ + cstat->type = CMD_SIGNO; + cstat->val = 0; + while (send(sv[0], cstat, sizeof(*cstat), 0) == -1) { + if (errno != EINTR && errno != EAGAIN) + sudo_fatal("%s", U_("unable to send message to monitor process")); + } + + /* Close the other end of the stdin/stdout/stderr pipes and socketpair. */ + if (io_pipe[STDIN_FILENO][0] != -1) + close(io_pipe[STDIN_FILENO][0]); + if (io_pipe[STDOUT_FILENO][1] != -1) + close(io_pipe[STDOUT_FILENO][1]); + if (io_pipe[STDERR_FILENO][1] != -1) + close(io_pipe[STDERR_FILENO][1]); + close(sv[1]); + + /* No longer need execfd. */ + if (details->execfd != -1) { + close(details->execfd); + details->execfd = -1; + } + + /* Set command timeout if specified. */ + if (ISSET(details->flags, CD_SET_TIMEOUT)) + alarm(details->timeout); + + /* + * Fill in exec closure, allocate event base, signal events and + * the backchannel event. + */ + fill_exec_closure_pty(&ec, cstat, details, ppgrp, sv[0]); + + /* Restore signal mask now that signal handlers are setup. */ + sigprocmask(SIG_SETMASK, &oset, NULL); + + /* + * I/O logging must be in the C locale for floating point numbers + * to be logged consistently. + */ + setlocale(LC_ALL, "C"); + + /* + * In the event loop we pass input from user tty to leader + * and pass output from leader to stdout and IO plugin. + * Try to recover on ENXIO, it means the tty was revoked. + */ + add_io_events(ec.evbase); + do { + if (sudo_ev_dispatch(ec.evbase) == -1) + sudo_warn("%s", U_("error in event loop")); + if (sudo_ev_got_break(ec.evbase)) { + /* error from callback or monitor died */ + sudo_debug_printf(SUDO_DEBUG_ERROR, "event loop exited prematurely"); + /* XXX: no good way to know if we should terminate the command. */ + if (cstat->val == CMD_INVALID && ec.cmnd_pid != -1) { + /* no status message, kill command */ + terminate_command(ec.cmnd_pid, true); + ec.cmnd_pid = -1; + /* TODO: need way to pass an error to the sudo front end */ + cstat->type = CMD_WSTATUS; + cstat->val = W_EXITCODE(1, SIGKILL); + } + } else if (!sudo_ev_got_exit(ec.evbase)) { + switch (errno) { + case ENXIO: + case EIO: + case EBADF: + /* /dev/tty was revoked, remove tty events and retry (once) */ + if (evloop_retries == -1 && io_fds[SFD_USERTTY] != -1) { + ev_free_by_fd(ec.evbase, io_fds[SFD_USERTTY]); + evloop_retries = 1; + } + break; + } + } + } while (evloop_retries-- > 0); + + /* Flush any remaining output, free I/O bufs and events, do logout. */ + pty_finish(cstat); + + /* Free things up. */ + free_exec_closure_pty(&ec); + + debug_return_bool(true); +} + +/* + * Schedule I/O events before starting the main event loop or + * resuming from suspend. + */ +static void +add_io_events(struct sudo_event_base *evbase) +{ + struct io_buffer *iob; + debug_decl(add_io_events, SUDO_DEBUG_EXEC); + + /* + * Schedule all readers as long as the buffer is not full. + * Schedule writers that contain buffered data. + * Normally, write buffers are added on demand when data is read. + */ + SLIST_FOREACH(iob, &iobufs, entries) { + /* Don't read from /dev/tty if we are not in the foreground. */ + if (iob->revent != NULL && + (ttymode == TERM_RAW || !USERTTY_EVENT(iob->revent))) { + if (iob->len != sizeof(iob->buf)) { + sudo_debug_printf(SUDO_DEBUG_INFO, + "added I/O revent %p, fd %d, events %d", + iob->revent, iob->revent->fd, iob->revent->events); + if (sudo_ev_add(evbase, iob->revent, NULL, false) == -1) + sudo_fatal("%s", U_("unable to add event to queue")); + } + } + if (iob->wevent != NULL) { + /* Enable writer if buffer is not empty. */ + if (iob->len > iob->off) { + sudo_debug_printf(SUDO_DEBUG_INFO, + "added I/O wevent %p, fd %d, events %d", + iob->wevent, iob->wevent->fd, iob->wevent->events); + if (sudo_ev_add(evbase, iob->wevent, NULL, false) == -1) + sudo_fatal("%s", U_("unable to add event to queue")); + } + } + } + debug_return; +} + +/* + * Flush any output buffered in iobufs or readable from fds other + * than /dev/tty. Removes I/O events from the event base when done. + */ +static void +del_io_events(bool nonblocking) +{ + struct io_buffer *iob; + struct sudo_event_base *evbase; + debug_decl(del_io_events, SUDO_DEBUG_EXEC); + + /* Remove iobufs from existing event base. */ + SLIST_FOREACH(iob, &iobufs, entries) { + if (iob->revent != NULL) { + sudo_debug_printf(SUDO_DEBUG_INFO, + "deleted I/O revent %p, fd %d, events %d", + iob->revent, iob->revent->fd, iob->revent->events); + sudo_ev_del(NULL, iob->revent); + } + if (iob->wevent != NULL) { + sudo_debug_printf(SUDO_DEBUG_INFO, + "deleted I/O wevent %p, fd %d, events %d", + iob->wevent, iob->wevent->fd, iob->wevent->events); + sudo_ev_del(NULL, iob->wevent); + } + } + + /* Create temporary event base for flushing. */ + evbase = sudo_ev_base_alloc(); + if (evbase == NULL) + sudo_fatalx(U_("%s: %s"), __func__, U_("unable to allocate memory")); + + /* Avoid reading from /dev/tty, just flush existing data. */ + SLIST_FOREACH(iob, &iobufs, entries) { + /* Don't read from /dev/tty while flushing. */ + if (iob->revent != NULL && !USERTTY_EVENT(iob->revent)) { + if (iob->len != sizeof(iob->buf)) { + if (sudo_ev_add(evbase, iob->revent, NULL, false) == -1) + sudo_fatal("%s", U_("unable to add event to queue")); + } + } + /* Flush any write buffers with data in them. */ + if (iob->wevent != NULL) { + if (iob->len > iob->off) { + if (sudo_ev_add(evbase, iob->wevent, NULL, false) == -1) + sudo_fatal("%s", U_("unable to add event to queue")); + } + } + } + sudo_debug_printf(SUDO_DEBUG_INFO, + "%s: flushing remaining I/O buffers (nonblocking)", __func__); + (void) sudo_ev_loop(evbase, SUDO_EVLOOP_NONBLOCK); + + /* + * If not in non-blocking mode, make sure we flush write buffers. + * We don't want to read from the pty or stdin since that might block + * and the command is no longer running anyway. + */ + if (!nonblocking) { + /* Clear out iobufs from event base. */ + SLIST_FOREACH(iob, &iobufs, entries) { + if (iob->revent != NULL && !USERTTY_EVENT(iob->revent)) + sudo_ev_del(evbase, iob->revent); + if (iob->wevent != NULL) + sudo_ev_del(evbase, iob->wevent); + } + + SLIST_FOREACH(iob, &iobufs, entries) { + /* Flush any write buffers with data in them. */ + if (iob->wevent != NULL) { + if (iob->len > iob->off) { + if (sudo_ev_add(evbase, iob->wevent, NULL, false) == -1) + sudo_fatal("%s", U_("unable to add event to queue")); + } + } + } + sudo_debug_printf(SUDO_DEBUG_INFO, + "%s: flushing remaining write buffers (blocking)", __func__); + (void) sudo_ev_dispatch(evbase); + + /* We should now have flushed all write buffers. */ + SLIST_FOREACH(iob, &iobufs, entries) { + if (iob->wevent != NULL) { + if (iob->len > iob->off) { + sudo_debug_printf(SUDO_DEBUG_ERROR, + "unflushed data: wevent %p, fd %d, events %d", + iob->wevent, iob->wevent->fd, iob->wevent->events); + } + } + } + } + + /* Free temporary event base, removing its events. */ + sudo_ev_base_free(evbase); + + debug_return; +} + +/* + * Check for tty size changes. + * Passes the new window size to the I/O plugin and to the monitor. + */ +static void +sync_ttysize(struct exec_closure_pty *ec) +{ + struct winsize wsize; + debug_decl(sync_ttysize, SUDO_DEBUG_EXEC); + + if (ioctl(io_fds[SFD_USERTTY], TIOCGWINSZ, &wsize) == 0) { + if (wsize.ws_row != ec->rows || wsize.ws_col != ec->cols) { + const unsigned int wsize_packed = (wsize.ws_row & 0xffff) | + ((wsize.ws_col & 0xffff) << 16); + + /* Log window change event. */ + log_winchange(ec, wsize.ws_row, wsize.ws_col); + + /* Send window change event to monitor process. */ + send_command_status(ec, CMD_TTYWINCH, wsize_packed); + + /* Update rows/cols. */ + ec->rows = wsize.ws_row; + ec->cols = wsize.ws_col; + } + } + + debug_return; +} + +/* + * Remove and free any events associated with the specified + * file descriptor present in the I/O buffers list. + */ +static void +ev_free_by_fd(struct sudo_event_base *evbase, int fd) +{ + struct io_buffer *iob; + debug_decl(ev_free_by_fd, SUDO_DEBUG_EXEC); + + /* Deschedule any users of the fd and free up the events. */ + SLIST_FOREACH(iob, &iobufs, entries) { + if (iob->revent != NULL) { + if (sudo_ev_get_fd(iob->revent) == fd) { + sudo_debug_printf(SUDO_DEBUG_INFO, + "%s: deleting and freeing revent %p with fd %d", + __func__, iob->revent, fd); + sudo_ev_free(iob->revent); + iob->revent = NULL; + } + } + if (iob->wevent != NULL) { + if (sudo_ev_get_fd(iob->wevent) == fd) { + sudo_debug_printf(SUDO_DEBUG_INFO, + "%s: deleting and freeing wevent %p with fd %d", + __func__, iob->wevent, fd); + sudo_ev_free(iob->wevent); + iob->wevent = NULL; + } + } + } + debug_return; +} + +/* + * Only close the fd if it is not /dev/tty or std{in,out,err}. + * Return value is the same as close(2). + */ +static int +safe_close(int fd) +{ + debug_decl(safe_close, SUDO_DEBUG_EXEC); + + /* Avoid closing /dev/tty or std{in,out,err}. */ + if (fd < 3 || fd == io_fds[SFD_USERTTY]) { + sudo_debug_printf(SUDO_DEBUG_INFO, + "%s: not closing fd %d (%s)", __func__, fd, _PATH_TTY); + errno = EINVAL; + debug_return_int(-1); + } + sudo_debug_printf(SUDO_DEBUG_INFO, "%s: closing fd %d", __func__, fd); + debug_return_int(close(fd)); +} |