191 lines
5.3 KiB
C
191 lines
5.3 KiB
C
/*
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* Copyright (c) 2001 Markus Friedl. All rights reserved.
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* Copyright (c) 2021 Darren Tucker (dtucker at dtucker net).
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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* 1. Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* 2. Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in the
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* documentation and/or other materials provided with the distribution.
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*
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* THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
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* IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
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* OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
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* IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
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* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
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* NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
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* DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
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* THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
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* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
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* THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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*/
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#include "includes.h"
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#ifndef HAVE_PSELECT
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#include <sys/types.h>
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#include <sys/time.h>
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#ifdef HAVE_SYS_SELECT_H
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# include <sys/select.h>
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#endif
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#include <errno.h>
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#include <fcntl.h>
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#include <signal.h>
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#include <stdlib.h>
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#include <string.h>
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#include <unistd.h>
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#include "log.h"
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#include "misc.h" /* for set_nonblock */
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#ifndef HAVE_SIGHANDLER_T
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typedef void (*sighandler_t)(int);
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#endif
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static sighandler_t saved_sighandler[_NSIG];
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/*
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* Set up the descriptors. Because they are close-on-exec, in the case
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* where sshd's re-exec fails notify_pipe will still point to a descriptor
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* that was closed by the exec attempt but if that descriptor has been
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* reopened then we'll attempt to use that. Ensure that notify_pipe is
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* outside of the range used by sshd re-exec but within NFDBITS (so we don't
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* need to expand the fd_sets).
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*/
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#define REEXEC_MIN_FREE_FD (STDERR_FILENO + 4)
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static int
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notify_setup_fd(int *fd)
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{
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int r;
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if ((r = fcntl(*fd, F_DUPFD, REEXEC_MIN_FREE_FD)) < 0 ||
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fcntl(r, F_SETFD, FD_CLOEXEC) < 0 || r >= FD_SETSIZE)
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return -1;
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(void)close(*fd);
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return (*fd = r);
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}
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/*
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* we write to this pipe if a SIGCHLD is caught in order to avoid
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* the race between select() and child_terminated
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*/
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static int notify_pipe[2];
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static void
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notify_setup(void)
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{
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static int initialized;
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if (initialized)
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return;
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if (pipe(notify_pipe) == -1) {
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error("pipe(notify_pipe) failed %s", strerror(errno));
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} else if (notify_setup_fd(¬ify_pipe[0]) == -1 ||
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notify_setup_fd(¬ify_pipe[1]) == -1) {
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error("fcntl(notify_pipe, ...) failed %s", strerror(errno));
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close(notify_pipe[0]);
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close(notify_pipe[1]);
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} else {
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set_nonblock(notify_pipe[0]);
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set_nonblock(notify_pipe[1]);
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initialized = 1;
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return;
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}
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notify_pipe[0] = -1; /* read end */
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notify_pipe[1] = -1; /* write end */
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}
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static void
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notify_parent(void)
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{
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if (notify_pipe[1] != -1)
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(void)write(notify_pipe[1], "", 1);
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}
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static void
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notify_prepare(fd_set *readset)
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{
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if (notify_pipe[0] != -1)
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FD_SET(notify_pipe[0], readset);
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}
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static void
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notify_done(fd_set *readset)
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{
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char c;
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if (notify_pipe[0] != -1 && FD_ISSET(notify_pipe[0], readset)) {
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while (read(notify_pipe[0], &c, 1) != -1)
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debug2_f("reading");
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FD_CLR(notify_pipe[0], readset);
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}
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}
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/*ARGSUSED*/
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static void
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sig_handler(int sig)
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{
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int save_errno = errno;
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notify_parent();
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if (saved_sighandler[sig] != NULL)
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(*saved_sighandler[sig])(sig); /* call original handler */
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errno = save_errno;
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}
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/*
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* A minimal implementation of pselect(2), built on top of select(2).
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*/
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int
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pselect(int nfds, fd_set *readfds, fd_set *writefds, fd_set *exceptfds,
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const struct timespec *timeout, const sigset_t *mask)
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{
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int ret, sig, saved_errno, unmasked = 0;
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sigset_t osig;
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struct sigaction sa, osa;
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struct timeval tv, *tvp = NULL;
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if (timeout != NULL) {
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tv.tv_sec = timeout->tv_sec;
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tv.tv_usec = timeout->tv_nsec / 1000;
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tvp = &tv;
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}
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if (mask == NULL) /* no signal mask, just call select */
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return select(nfds, readfds, writefds, exceptfds, tvp);
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/* For each signal we're unmasking, install our handler if needed. */
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for (sig = 0; sig < _NSIG; sig++) {
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if (sig == SIGKILL || sig == SIGSTOP || sigismember(mask, sig))
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continue;
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if (sigaction(sig, NULL, &sa) == 0 &&
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sa.sa_handler != SIG_IGN && sa.sa_handler != SIG_DFL &&
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sa.sa_handler != sig_handler) {
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sa.sa_handler = sig_handler;
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if (sigaction(sig, &sa, &osa) == 0) {
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debug3_f("installing signal handler for %s, "
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"previous %p", strsignal(sig),
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osa.sa_handler);
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saved_sighandler[sig] = osa.sa_handler;
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unmasked = 1;
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}
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}
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}
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if (unmasked) {
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notify_setup();
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notify_prepare(readfds);
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nfds = MAX(nfds, notify_pipe[0]);
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}
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/* Unmask signals, call select then restore signal mask. */
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sigprocmask(SIG_SETMASK, mask, &osig);
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ret = select(nfds, readfds, writefds, exceptfds, tvp);
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saved_errno = errno;
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sigprocmask(SIG_SETMASK, &osig, NULL);
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notify_done(readfds);
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errno = saved_errno;
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return ret;
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}
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#endif
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