diff options
Diffstat (limited to '')
| -rw-r--r-- | src/exec_nopty.c | 573 |
1 files changed, 573 insertions, 0 deletions
diff --git a/src/exec_nopty.c b/src/exec_nopty.c new file mode 100644 index 0000000..0df79f0 --- /dev/null +++ b/src/exec_nopty.c @@ -0,0 +1,573 @@ +/* + * Copyright (c) 2009-2017 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/wait.h> +#include <stdio.h> +#include <stdlib.h> +#ifdef HAVE_STRING_H +# include <string.h> +#endif /* HAVE_STRING_H */ +#ifdef HAVE_STRINGS_H +# include <strings.h> +#endif /* HAVE_STRINGS_H */ +#include <unistd.h> +#include <errno.h> +#include <fcntl.h> +#include <signal.h> + +#include "sudo.h" +#include "sudo_exec.h" +#include "sudo_event.h" +#include "sudo_plugin.h" +#include "sudo_plugin_int.h" + +struct exec_closure_nopty { + pid_t cmnd_pid; + pid_t ppgrp; + struct command_status *cstat; + struct command_details *details; + struct sudo_event_base *evbase; + struct sudo_event *errpipe_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 *sigpipe_event; + struct sudo_event *sigusr1_event; + struct sudo_event *sigusr2_event; + struct sudo_event *sigchld_event; + struct sudo_event *sigcont_event; + struct sudo_event *siginfo_event; +}; + +static void handle_sigchld_nopty(struct exec_closure_nopty *ec); + +/* Note: this is basically the same as mon_errpipe_cb() in exec_monitor.c */ +static void +errpipe_cb(int fd, int what, void *v) +{ + struct exec_closure_nopty *ec = v; + ssize_t nread; + int errval; + debug_decl(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 (ec->cstat->val == CMD_INVALID) { + /* XXX - need a way to distinguish non-exec error. */ + ec->cstat->type = CMD_ERRNO; + ec->cstat->val = errno; + } + sudo_debug_printf(SUDO_DEBUG_ERROR|SUDO_DEBUG_ERRNO, + "%s: failed to read error pipe", __func__); + sudo_ev_loopbreak(ec->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)); + ec->cstat->type = CMD_ERRNO; + ec->cstat->val = errval; + } + sudo_ev_del(ec->evbase, ec->errpipe_event); + close(fd); + break; + } + debug_return; +} + +/* Signal callback */ +static void +signal_cb_nopty(int signo, int what, void *v) +{ + struct sudo_ev_siginfo_container *sc = v; + struct exec_closure_nopty *ec = sc->closure; + char signame[SIG2STR_MAX]; + debug_decl(signal_cb_nopty, SUDO_DEBUG_EXEC) + + if (ec->cmnd_pid == -1) + debug_return; + + if (sig2str(signo, signame) == -1) + snprintf(signame, sizeof(signame), "%d", signo); + sudo_debug_printf(SUDO_DEBUG_DIAG, + "%s: evbase %p, command: %d, signo %s(%d), cstat %p", + __func__, ec->evbase, (int)ec->cmnd_pid, signame, signo, ec->cstat); + + switch (signo) { + case SIGCHLD: + handle_sigchld_nopty(ec); + if (ec->cmnd_pid == -1) { + /* Command exited or was killed, exit event loop. */ + sudo_ev_loopexit(ec->evbase); + } + debug_return; +#ifdef SIGINFO + case SIGINFO: +#endif + case SIGINT: + case SIGQUIT: + case SIGTSTP: + /* + * Only forward user-generated signals not sent by a process in + * the command's own process group. Signals sent by the kernel + * may include SIGTSTP when the user presses ^Z. Curses programs + * often trap ^Z and send SIGTSTP to their own pgrp, so we don't + * want to send an extra SIGTSTP. + */ + if (!USER_SIGNALED(sc->siginfo)) + debug_return; + if (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; + } + } + 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; + } + } + break; + } + + /* Send signal to command. */ + if (signo == SIGALRM) { + terminate_command(ec->cmnd_pid, false); + } else if (kill(ec->cmnd_pid, signo) != 0) { + sudo_warn("kill(%d, SIG%s)", (int)ec->cmnd_pid, signame); + } + + debug_return; +} + + +/* + * Fill in the exec closure and setup initial exec events. + * Allocates events for the signal pipe and error pipe. + */ +static void +fill_exec_closure_nopty(struct exec_closure_nopty *ec, + struct command_status *cstat, struct command_details *details, int errfd) +{ + debug_decl(fill_exec_closure_nopty, SUDO_DEBUG_EXEC) + + /* Fill in the non-event part of the closure. */ + ec->ppgrp = getpgrp(); + ec->cstat = cstat; + ec->details = details; + + /* Setup event base and events. */ + ec->evbase = sudo_ev_base_alloc(); + if (ec->evbase == NULL) + sudo_fatalx(U_("%s: %s"), __func__, U_("unable to allocate memory")); + + /* Event for command status via errfd. */ + ec->errpipe_event = sudo_ev_alloc(errfd, + SUDO_EV_READ|SUDO_EV_PERSIST, errpipe_cb, ec); + if (ec->errpipe_event == NULL) + sudo_fatalx(U_("%s: %s"), __func__, U_("unable to allocate memory")); + if (sudo_ev_add(ec->evbase, ec->errpipe_event, NULL, false) == -1) + sudo_fatal(U_("unable to add event to queue")); + sudo_debug_printf(SUDO_DEBUG_INFO, "error pipe fd %d\n", errfd); + + /* Events for local signals. */ + ec->sigint_event = sudo_ev_alloc(SIGINT, + SUDO_EV_SIGINFO, signal_cb_nopty, 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(U_("unable to add event to queue")); + + ec->sigquit_event = sudo_ev_alloc(SIGQUIT, + SUDO_EV_SIGINFO, signal_cb_nopty, 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(U_("unable to add event to queue")); + + ec->sigtstp_event = sudo_ev_alloc(SIGTSTP, + SUDO_EV_SIGINFO, signal_cb_nopty, 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(U_("unable to add event to queue")); + + ec->sigterm_event = sudo_ev_alloc(SIGTERM, + SUDO_EV_SIGINFO, signal_cb_nopty, 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(U_("unable to add event to queue")); + + ec->sighup_event = sudo_ev_alloc(SIGHUP, + SUDO_EV_SIGINFO, signal_cb_nopty, 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(U_("unable to add event to queue")); + + ec->sigalrm_event = sudo_ev_alloc(SIGALRM, + SUDO_EV_SIGINFO, signal_cb_nopty, 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(U_("unable to add event to queue")); + + ec->sigpipe_event = sudo_ev_alloc(SIGPIPE, + SUDO_EV_SIGINFO, signal_cb_nopty, ec); + if (ec->sigpipe_event == NULL) + sudo_fatalx(U_("%s: %s"), __func__, U_("unable to allocate memory")); + if (sudo_ev_add(ec->evbase, ec->sigpipe_event, NULL, false) == -1) + sudo_fatal(U_("unable to add event to queue")); + + ec->sigusr1_event = sudo_ev_alloc(SIGUSR1, + SUDO_EV_SIGINFO, signal_cb_nopty, 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(U_("unable to add event to queue")); + + ec->sigusr2_event = sudo_ev_alloc(SIGUSR2, + SUDO_EV_SIGINFO, signal_cb_nopty, 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(U_("unable to add event to queue")); + + ec->sigchld_event = sudo_ev_alloc(SIGCHLD, + SUDO_EV_SIGINFO, signal_cb_nopty, 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(U_("unable to add event to queue")); + + ec->sigcont_event = sudo_ev_alloc(SIGCONT, + SUDO_EV_SIGINFO, signal_cb_nopty, ec); + if (ec->sigcont_event == NULL) + sudo_fatalx(U_("%s: %s"), __func__, U_("unable to allocate memory")); + if (sudo_ev_add(ec->evbase, ec->sigcont_event, NULL, false) == -1) + sudo_fatal(U_("unable to add event to queue")); + +#ifdef SIGINFO + ec->siginfo_event = sudo_ev_alloc(SIGINFO, + SUDO_EV_SIGINFO, signal_cb_nopty, ec); + if (ec->siginfo_event == NULL) + sudo_fatalx(U_("%s: %s"), __func__, U_("unable to allocate memory")); + if (sudo_ev_add(ec->evbase, ec->siginfo_event, NULL, false) == -1) + sudo_fatal(U_("unable to add event to queue")); +#endif + + /* 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_nopty(struct exec_closure_nopty *ec) +{ + debug_decl(free_exec_closure_nopty, SUDO_DEBUG_EXEC) + + sudo_ev_base_free(ec->evbase); + sudo_ev_free(ec->errpipe_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->sigpipe_event); + sudo_ev_free(ec->sigusr1_event); + sudo_ev_free(ec->sigusr2_event); + sudo_ev_free(ec->sigchld_event); + sudo_ev_free(ec->sigcont_event); + sudo_ev_free(ec->siginfo_event); + + debug_return; +} + +/* + * Execute a command and wait for it to finish. + */ +void +exec_nopty(struct command_details *details, struct command_status *cstat) +{ + struct exec_closure_nopty ec = { 0 }; + sigset_t set, oset; + int errpipe[2]; + debug_decl(exec_nopty, SUDO_DEBUG_EXEC) + + /* + * 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(U_("policy plugin failed session initialization")); + + /* + * We use a pipe to get errno if execve(2) fails in the child. + */ + if (pipe2(errpipe, O_CLOEXEC) != 0) + sudo_fatal(U_("unable to create pipe")); + + /* + * 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; + } + + ec.cmnd_pid = sudo_debug_fork(); + switch (ec.cmnd_pid) { + case -1: + sudo_fatal(U_("unable to fork")); + break; + case 0: + /* child */ + sigprocmask(SIG_SETMASK, &oset, NULL); + close(errpipe[0]); + exec_cmnd(details, errpipe[1]); + while (write(errpipe[1], &errno, sizeof(int)) == -1) { + if (errno != EINTR) + break; + } + sudo_debug_exit_int(__func__, __FILE__, __LINE__, sudo_debug_subsys, 1); + _exit(1); + } + sudo_debug_printf(SUDO_DEBUG_INFO, "executed %s, pid %d", details->command, + (int)ec.cmnd_pid); + close(errpipe[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 error pipe event. + */ + fill_exec_closure_nopty(&ec, cstat, details, errpipe[0]); + + /* Restore signal mask now that signal handlers are setup. */ + sigprocmask(SIG_SETMASK, &oset, NULL); + + /* + * Non-pty event loop. + * Wait for command to exit, handles signals and the error pipe. + */ + if (sudo_ev_dispatch(ec.evbase) == -1) + sudo_warn(U_("error in event loop")); + if (sudo_ev_got_break(ec.evbase)) { + /* error from callback */ + sudo_debug_printf(SUDO_DEBUG_ERROR, "event loop exited prematurely"); + /* kill command */ + terminate_command(ec.cmnd_pid, true); + } + +#ifdef HAVE_SELINUX + if (ISSET(details->flags, CD_RBAC_ENABLED)) { + if (selinux_restore_tty() != 0) + sudo_warnx(U_("unable to restore tty label")); + } +#endif + + /* Free things up. */ + free_exec_closure_nopty(&ec); + debug_return; +} + +/* + * Wait for command status after receiving SIGCHLD. + * If the command exits, fill in cstat and stop the event loop. + * If the command stops, save the tty pgrp, suspend sudo, then restore + * the tty pgrp when sudo resumes. + */ +static void +handle_sigchld_nopty(struct exec_closure_nopty *ec) +{ + pid_t pid; + int status; + char signame[SIG2STR_MAX]; + debug_decl(handle_sigchld_nopty, SUDO_DEBUG_EXEC) + + /* Read command status. */ + do { + pid = waitpid(ec->cmnd_pid, &status, WUNTRACED|WNOHANG); + } while (pid == -1 && errno == EINTR); + switch (pid) { + case 0: + /* waitpid() will return 0 for SIGCONT, which we don't care about */ + debug_return; + case -1: + sudo_warn(U_("%s: %s"), __func__, "waitpid"); + debug_return; + } + + if (WIFSTOPPED(status)) { + /* + * 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. + */ + struct sigaction sa, osa; + pid_t saved_pgrp = -1; + int fd, signo = WSTOPSIG(status); + + if (sig2str(signo, signame) == -1) + snprintf(signame, sizeof(signame), "%d", signo); + sudo_debug_printf(SUDO_DEBUG_INFO, "%s: command (%d) stopped, SIG%s", + __func__, (int)ec->cmnd_pid, signame); + + 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 == ec->ppgrp) { + pid_t cmnd_pgrp = getpgid(ec->cmnd_pid); + if (cmnd_pgrp != ec->ppgrp) { + if (tcsetpgrp_nobg(fd, cmnd_pgrp) == 0) { + if (killpg(cmnd_pgrp, SIGCONT) != 0) { + sudo_warn("kill(%d, SIGCONT)", + (int)cmnd_pgrp); + } + close(fd); + goto done; + } + } + } + } + } + if (signo == SIGTSTP) { + memset(&sa, 0, sizeof(sa)); + sigemptyset(&sa.sa_mask); + sa.sa_flags = SA_RESTART; + sa.sa_handler = SIG_DFL; + if (sudo_sigaction(SIGTSTP, &sa, &osa) != 0) { + sudo_warn(U_("unable to set handler for signal %d"), + SIGTSTP); + } + } + if (kill(getpid(), signo) != 0) + sudo_warn("kill(%d, SIG%s)", (int)getpid(), signame); + if (signo == SIGTSTP) { + if (sudo_sigaction(SIGTSTP, &osa, NULL) != 0) { + sudo_warn(U_("unable to restore handler for signal %d"), + SIGTSTP); + } + } + 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 so + * use tcsetpgrp_nobg() to prevent sudo from receiving SIGTTOU. + */ + if (saved_pgrp != ec->ppgrp) + tcsetpgrp_nobg(fd, saved_pgrp); + close(fd); + } + } else { + /* Command has exited or been killed, we are done. */ + if (WIFSIGNALED(status)) { + if (sig2str(WTERMSIG(status), signame) == -1) + snprintf(signame, sizeof(signame), "%d", WTERMSIG(status)); + sudo_debug_printf(SUDO_DEBUG_INFO, "%s: command (%d) killed, SIG%s", + __func__, (int)ec->cmnd_pid, signame); + } else { + sudo_debug_printf(SUDO_DEBUG_INFO, "%s: command (%d) exited: %d", + __func__, (int)ec->cmnd_pid, WEXITSTATUS(status)); + } + /* Don't overwrite execve() failure with command exit status. */ + if (ec->cstat->type == CMD_INVALID) { + ec->cstat->type = CMD_WSTATUS; + ec->cstat->val = status; + } else { + sudo_debug_printf(SUDO_DEBUG_WARN, + "%s: not overwriting command status %d,%d with %d,%d", + __func__, ec->cstat->type, ec->cstat->val, CMD_WSTATUS, status); + } + ec->cmnd_pid = -1; + } +done: + debug_return; +} |