Move signal code into its own source file and add sudo_sigaction()
wrapper that has an extra flag to check the saved_signals list to only install the handler if the signal is not already ignored. Bump plugin API version for the new front-end signal behavior.
This commit is contained in:
Todd C. Miller
167
src/signal.c
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167
src/signal.c
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@@ -0,0 +1,167 @@
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/*
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* Copyright (c) 2009-2012 Todd C. Miller <Todd.Miller@courtesan.com>
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*
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* Permission to use, copy, modify, and distribute this software for any
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* purpose with or without fee is hereby granted, provided that the above
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* copyright notice and this permission notice appear in all copies.
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*
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* THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
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* WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
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* MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
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* ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
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* WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
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* ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
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* OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
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*/
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#include <config.h>
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#include <sys/types.h>
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#include <stdio.h>
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#ifdef STDC_HEADERS
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# include <stdlib.h>
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# include <stddef.h>
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#else
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# ifdef HAVE_STDLIB_H
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# include <stdlib.h>
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# endif
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#endif /* STDC_HEADERS */
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#ifdef HAVE_STRING_H
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# include <string.h>
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#endif /* HAVE_STRING_H */
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#ifdef HAVE_STRINGS_H
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# include <strings.h>
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#endif /* HAVE_STRINGS_H */
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#ifdef HAVE_UNISTD_H
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# include <unistd.h>
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#endif /* HAVE_UNISTD_H */
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#include <errno.h>
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#include <signal.h>
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#include "sudo.h"
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int signal_pipe[2];
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static struct signal_state {
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int signo;
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sigaction_t sa;
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} saved_signals[] = {
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{ SIGALRM }, /* SAVED_SIGALRM */
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{ SIGCHLD }, /* SAVED_SIGCHLD */
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{ SIGCONT }, /* SAVED_SIGCONT */
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{ SIGHUP }, /* SAVED_SIGHUP */
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{ SIGINT }, /* SAVED_SIGINT */
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{ SIGPIPE }, /* SAVED_SIGPIPE */
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{ SIGQUIT }, /* SAVED_SIGQUIT */
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{ SIGTERM }, /* SAVED_SIGTERM */
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{ SIGTSTP }, /* SAVED_SIGTSTP */
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{ SIGTTIN }, /* SAVED_SIGTTIN */
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{ SIGTTOU }, /* SAVED_SIGTTOU */
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{ SIGUSR1 }, /* SAVED_SIGUSR1 */
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{ SIGUSR2 }, /* SAVED_SIGUSR2 */
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{ -1 }
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};
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/*
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* Save signal handler state so it can be restored before exec.
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*/
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void
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save_signals(void)
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{
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struct signal_state *ss;
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debug_decl(save_signals, SUDO_DEBUG_MAIN)
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for (ss = saved_signals; ss->signo != -1; ss++)
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sigaction(ss->signo, NULL, &ss->sa);
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debug_return;
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}
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/*
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* Restore signal handlers to initial state for exec.
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*/
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void
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restore_signals(void)
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{
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struct signal_state *ss;
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debug_decl(restore_signals, SUDO_DEBUG_MAIN)
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for (ss = saved_signals; ss->signo != -1; ss++)
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sigaction(ss->signo, &ss->sa, NULL);
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debug_return;
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}
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static void
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sudo_handler(int signo)
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{
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/*
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* The pipe is non-blocking, if we overflow the kernel's pipe
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* buffer we drop the signal. This is not a problem in practice.
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*/
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ignore_result(write(signal_pipe[1], &signo, sizeof(signo)));
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}
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/*
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* Trap tty-generated (and other) signals so we can't be killed before
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* calling the policy close function. The signal pipe will be drained
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* in sudo_execute() before running the command and new handlers will
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* be installed in the parent.
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*/
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void
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init_signals(void)
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{
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struct sigaction sa;
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struct signal_state *ss;
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debug_decl(init_signals, SUDO_DEBUG_MAIN)
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/*
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* We use a pipe to atomically handle signal notification within
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* the select() loop without races (we may not have pselect()).
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*/
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if (pipe_nonblock(signal_pipe) != 0)
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error(1, _("unable to create pipe"));
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memset(&sa, 0, sizeof(sa));
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sigfillset(&sa.sa_mask);
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sa.sa_flags = SA_RESTART;
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sa.sa_handler = sudo_handler;
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for (ss = saved_signals; ss->signo > 0; ss++) {
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switch (ss->signo) {
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case SIGCHLD:
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case SIGCONT:
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case SIGPIPE:
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case SIGTTIN:
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case SIGTTOU:
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/* Don't install these until exec time. */
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break;
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default:
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if (ss->sa.sa_handler != SIG_IGN)
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sigaction(ss->signo, &sa, NULL);
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break;
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}
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}
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debug_return;
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}
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/*
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* Like sigaction() but includes an udpate_only flag.
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* In update-only mode, don't override SIG_IGN.
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*/
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int
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sudo_sigaction(int signo, struct sigaction *sa, struct sigaction *osa, bool update_only)
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{
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/* Don't override SIG_IGN if the update_only flag is set. */
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if (update_only) {
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struct signal_state *ss;
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for (ss = saved_signals; ss->signo > 0; ss++) {
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if (ss->signo == signo) {
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if (ss->sa.sa_handler == SIG_IGN)
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return 0;
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break;
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}
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}
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}
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return sigaction(signo, sa, osa);
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}
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