| /* |
| * 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 |
| pselect_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 pid_t notify_pid; |
| static int notify_pipe[2]; |
| static void |
| pselect_notify_setup(void) |
| { |
| static int initialized; |
| |
| if (initialized && notify_pid == getpid()) |
| return; |
| if (notify_pid == 0) |
| debug3_f("initializing"); |
| else { |
| debug3_f("pid changed, reinitializing"); |
| if (notify_pipe[0] != -1) |
| close(notify_pipe[0]); |
| if (notify_pipe[1] != -1) |
| close(notify_pipe[1]); |
| } |
| if (pipe(notify_pipe) == -1) { |
| error("pipe(notify_pipe) failed %s", strerror(errno)); |
| } else if (pselect_notify_setup_fd(¬ify_pipe[0]) == -1 || |
| pselect_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]); |
| notify_pid = getpid(); |
| debug3_f("pid %d saved %d pipe0 %d pipe1 %d", getpid(), |
| notify_pid, notify_pipe[0], notify_pipe[1]); |
| initialized = 1; |
| return; |
| } |
| notify_pipe[0] = -1; /* read end */ |
| notify_pipe[1] = -1; /* write end */ |
| } |
| static void |
| pselect_notify_parent(void) |
| { |
| if (notify_pipe[1] != -1) |
| (void)write(notify_pipe[1], "", 1); |
| } |
| static void |
| pselect_notify_prepare(fd_set *readset) |
| { |
| if (notify_pipe[0] != -1) |
| FD_SET(notify_pipe[0], readset); |
| } |
| static void |
| pselect_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"); |
| FD_CLR(notify_pipe[0], readset); |
| } |
| } |
| |
| /*ARGSUSED*/ |
| static void |
| pselect_sig_handler(int sig) |
| { |
| int save_errno = errno; |
| |
| pselect_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) { |
| unmasked = 1; |
| if (sa.sa_handler == pselect_sig_handler) |
| continue; |
| sa.sa_handler = pselect_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; |
| } |
| } |
| } |
| if (unmasked) { |
| pselect_notify_setup(); |
| pselect_notify_prepare(readfds); |
| nfds = MAX(nfds, notify_pipe[0] + 1); |
| } |
| |
| /* 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); |
| |
| if (unmasked) |
| pselect_notify_done(readfds); |
| errno = saved_errno; |
| return ret; |
| } |
| #endif |