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