diff options
Diffstat (limited to '')
| -rw-r--r-- | src/suspend_parent.c | 170 |
1 files changed, 170 insertions, 0 deletions
diff --git a/src/suspend_parent.c b/src/suspend_parent.c new file mode 100644 index 0000000..af6957f --- /dev/null +++ b/src/suspend_parent.c @@ -0,0 +1,170 @@ +/* + * SPDX-License-Identifier: ISC + * + * Copyright (c) 2009-2023 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 <stdio.h> +#include <string.h> +#include <unistd.h> +#include <errno.h> +#include <fcntl.h> +#include <signal.h> + +#include <pathnames.h> +#include <sudo_debug.h> +#include <sudo_fatal.h> +#include <sudo_gettext.h> +#include <sudo_exec.h> + +static volatile sig_atomic_t got_sigttou; + +/* + * SIGTTOU signal handler for tcsetpgrp_nobg() that just sets a flag. + */ +static void +sigttou(int signo) +{ + got_sigttou = 1; +} + +/* + * Like tcsetpgrp() but restarts on EINTR _except_ for SIGTTOU. + * Returns 0 on success or -1 on failure, setting errno. + * Sets got_sigttou on failure if interrupted by SIGTTOU. + */ +static int +tcsetpgrp_nobg(int fd, pid_t pgrp_id) +{ + struct sigaction sa, osa; + int rc; + debug_decl(tcsetpgrp_nobg, SUDO_DEBUG_UTIL); + + /* + * If we receive SIGTTOU from tcsetpgrp() it means we are + * not in the foreground process group. + * This avoid a TOCTOU race compared to using tcgetpgrp(). + */ + memset(&sa, 0, sizeof(sa)); + sigemptyset(&sa.sa_mask); + sa.sa_flags = 0; /* do not restart syscalls */ + sa.sa_handler = sigttou; + got_sigttou = 0; + (void)sigaction(SIGTTOU, &sa, &osa); + do { + rc = tcsetpgrp(fd, pgrp_id); + } while (rc != 0 && errno == EINTR && !got_sigttou); + (void)sigaction(SIGTTOU, &osa, NULL); + + debug_return_int(rc); +} + +/* + * Suspend the main process in response to an interactive child process + * being suspended. + */ +void +sudo_suspend_parent(int signo, pid_t my_pid, pid_t my_pgrp, pid_t cmnd_pid, + void *closure, void (*callback)(void *, int)) +{ + struct sigaction sa, osa; + pid_t saved_pgrp = -1; + int fd; + debug_decl(sudo_suspend_parent, SUDO_DEBUG_EXEC); + + /* + * Save the controlling terminal's process group so we can restore + * it after we resume, if needed. Most well-behaved shells change + * the pgrp back to its original value before suspending so we must + * not try to restore in that case, lest we race with the command + * upon resume, potentially stopping sudo with SIGTTOU while the + * command continues to run. + */ + fd = open(_PATH_TTY, O_RDWR); + if (fd != -1) { + saved_pgrp = tcgetpgrp(fd); + if (saved_pgrp == -1) { + close(fd); + fd = -1; + } + } + + if (saved_pgrp != -1) { + /* + * Command was stopped trying to access the controlling + * terminal. If the command has a different pgrp and we + * own the controlling terminal, give it to the command's + * pgrp and let it continue. + */ + if (signo == SIGTTOU || signo == SIGTTIN) { + if (saved_pgrp == my_pgrp) { + pid_t cmnd_pgrp = getpgid(cmnd_pid); + if (cmnd_pgrp != my_pgrp) { + if (tcsetpgrp_nobg(fd, cmnd_pgrp) == 0) { + if (killpg(cmnd_pgrp, SIGCONT) != 0) + sudo_warn("kill(%d, SIGCONT)", (int)cmnd_pgrp); + close(fd); + debug_return; + } + } + } + } + } + + /* Run callback before we suspend. */ + if (callback != NULL) + callback(closure, signo); + + if (signo == SIGTSTP) { + memset(&sa, 0, sizeof(sa)); + sigemptyset(&sa.sa_mask); + sa.sa_flags = SA_RESTART; + sa.sa_handler = SIG_DFL; + if (sigaction(SIGTSTP, &sa, &osa) != 0) + sudo_warn(U_("unable to set handler for signal %d"), SIGTSTP); + } + if (kill(my_pid, signo) != 0) + sudo_warn("kill(%d, %d)", (int)my_pid, signo); + if (signo == SIGTSTP) { + if (sigaction(SIGTSTP, &osa, NULL) != 0) + sudo_warn(U_("unable to restore handler for signal %d"), SIGTSTP); + } + + /* Run callback on resume. */ + if (callback != NULL) + callback(closure, SIGCONT); + + if (saved_pgrp != -1) { + /* + * On resume, restore foreground process group, if different. + * Otherwise, we cannot resume some shells (pdksh). + * + * It is possible that we are no longer the foreground process, + * use tcsetpgrp_nobg() to prevent sudo from receiving SIGTTOU. + */ + if (saved_pgrp != my_pgrp) + tcsetpgrp_nobg(fd, saved_pgrp); + close(fd); + } + + debug_return; +} |