diff options
Diffstat (limited to 'src/signal.c')
| -rw-r--r-- | src/signal.c | 196 |
1 files changed, 196 insertions, 0 deletions
diff --git a/src/signal.c b/src/signal.c new file mode 100644 index 0000000..59cb5f4 --- /dev/null +++ b/src/signal.c @@ -0,0 +1,196 @@ +/* + * SPDX-License-Identifier: ISC + * + * Copyright (c) 2009-2016 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 <string.h> +#include <errno.h> +#include <signal.h> + +#include <sudo.h> +#include <sudo_exec.h> + +static struct signal_state { + int signo; + int restore; + struct sigaction sa; +} saved_signals[] = { + { SIGALRM }, /* SAVED_SIGALRM */ + { SIGCHLD }, /* SAVED_SIGCHLD */ + { SIGCONT }, /* SAVED_SIGCONT */ + { SIGHUP }, /* SAVED_SIGHUP */ + { SIGINT }, /* SAVED_SIGINT */ + { SIGPIPE }, /* SAVED_SIGPIPE */ + { SIGQUIT }, /* SAVED_SIGQUIT */ + { SIGTERM }, /* SAVED_SIGTERM */ + { SIGTSTP }, /* SAVED_SIGTSTP */ + { SIGTTIN }, /* SAVED_SIGTTIN */ + { SIGTTOU }, /* SAVED_SIGTTOU */ + { SIGUSR1 }, /* SAVED_SIGUSR1 */ + { SIGUSR2 }, /* SAVED_SIGUSR2 */ + { -1 } +}; + +static sig_atomic_t pending_signals[NSIG]; + +static void +sudo_handler(int signo) +{ + /* Mark signal as pending. */ + pending_signals[signo] = 1; +} + +bool +signal_pending(int signo) +{ + return pending_signals[signo] == 1; +} + +/* + * Save signal handler state so it can be restored before exec. + */ +void +save_signals(void) +{ + struct signal_state *ss; + debug_decl(save_signals, SUDO_DEBUG_MAIN); + + for (ss = saved_signals; ss->signo != -1; ss++) { + if (sigaction(ss->signo, NULL, &ss->sa) != 0) + sudo_warn(U_("unable to save handler for signal %d"), ss->signo); + } + + debug_return; +} + +/* + * Restore signal handlers to initial state for exec. + */ +void +restore_signals(void) +{ + struct signal_state *ss; + debug_decl(restore_signals, SUDO_DEBUG_MAIN); + + for (ss = saved_signals; ss->signo != -1; ss++) { + if (ss->restore) { + sudo_debug_printf(SUDO_DEBUG_INFO, + "restoring handler for signal %d: %s", ss->signo, + ss->sa.sa_handler == SIG_IGN ? "SIG_IGN" : + ss->sa.sa_handler == SIG_DFL ? "SIG_DFL" : "???"); + if (sigaction(ss->signo, &ss->sa, NULL) != 0) { + sudo_warn(U_("unable to restore handler for signal %d"), + ss->signo); + } + } + } + + debug_return; +} + +/* + * Trap tty-generated (and other) signals so we can't be killed before + * calling the policy close function. The signal pipe will be drained + * in sudo_execute() before running the command and new handlers will + * be installed in the parent. + */ +void +init_signals(void) +{ + struct sigaction sa; + struct signal_state *ss; + debug_decl(init_signals, SUDO_DEBUG_MAIN); + + memset(&sa, 0, sizeof(sa)); + sigfillset(&sa.sa_mask); + sa.sa_flags = SA_RESTART; + sa.sa_handler = sudo_handler; + + for (ss = saved_signals; ss->signo > 0; ss++) { + switch (ss->signo) { + case SIGCONT: + case SIGPIPE: + case SIGTTIN: + case SIGTTOU: + /* Don't install these until exec time. */ + break; + case SIGCHLD: + /* Sudo needs to be able to catch SIGCHLD. */ + if (ss->sa.sa_handler == SIG_IGN) { + sudo_debug_printf(SUDO_DEBUG_INFO, + "will restore signal %d on exec", SIGCHLD); + ss->restore = true; + } + if (sigaction(SIGCHLD, &sa, NULL) != 0) { + sudo_warn(U_("unable to set handler for signal %d"), + SIGCHLD); + } + break; + default: + if (ss->sa.sa_handler != SIG_IGN) { + if (sigaction(ss->signo, &sa, NULL) != 0) { + sudo_warn(U_("unable to set handler for signal %d"), + ss->signo); + } + } + break; + } + } + /* Ignore SIGPIPE until exec. */ + if (saved_signals[SAVED_SIGPIPE].sa.sa_handler != SIG_IGN) { + sudo_debug_printf(SUDO_DEBUG_INFO, + "will restore signal %d on exec", SIGPIPE); + saved_signals[SAVED_SIGPIPE].restore = true; + sa.sa_handler = SIG_IGN; + if (sigaction(SIGPIPE, &sa, NULL) != 0) + sudo_warn(U_("unable to set handler for signal %d"), SIGPIPE); + } + + debug_return; +} + +/* + * Like sigaction() but sets restore flag in saved_signals[] + * if needed. + */ +int +sudo_sigaction(int signo, struct sigaction *sa, struct sigaction *osa) +{ + struct signal_state *ss; + int ret; + debug_decl(sudo_sigaction, SUDO_DEBUG_MAIN); + + for (ss = saved_signals; ss->signo > 0; ss++) { + if (ss->signo == signo) { + /* If signal was or now is ignored, restore old handler on exec. */ + if (ss->sa.sa_handler == SIG_IGN || sa->sa_handler == SIG_IGN) { + sudo_debug_printf(SUDO_DEBUG_INFO, + "will restore signal %d on exec", signo); + ss->restore = true; + } + break; + } + } + ret = sigaction(signo, sa, osa); + + debug_return_int(ret); +} |