Adding upstream version 1.9.13p3.upstream/1.9.13p3upstream

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 805 insertions, 0 deletions

diff --git a/src/exec_nopty.c b/src/exec_nopty.c
new file mode 100644
index 0000000..27dd045
--- /dev/null
+++ b/src/exec_nopty.c
@@ -0,0 +1,805 @@
+/*
+ * SPDX-License-Identifier: ISC
+ *
+ * Copyright (c) 2009-2022 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 <sys/types.h>
+#include <sys/socket.h>
+#include <sys/wait.h>
+#include <sys/ioctl.h>
+
+#if defined(HAVE_STDINT_H)
+# include <stdint.h>
+#elif defined(HAVE_INTTYPES_H)
+# include <inttypes.h>
+#endif
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <unistd.h>
+#include <errno.h>
+#include <fcntl.h>
+#include <signal.h>
+#include <termios.h>		/* for struct winsize on HP-UX */
+
+#include "sudo.h"
+#include "sudo_exec.h"
+#include "sudo_plugin.h"
+#include "sudo_plugin_int.h"
+
+static void handle_sigchld_nopty(struct exec_closure *ec);
+
+/*
+ * Handle window size change events.
+ */
+static void
+handle_sigwinch(struct exec_closure *ec, int fd)
+{
+    struct winsize wsize;
+    debug_decl(handle_sigwinch, SUDO_DEBUG_EXEC);
+
+    if (fd != -1 && ioctl(fd, TIOCGWINSZ, &wsize) == 0) {
+        if (wsize.ws_row != ec->rows || wsize.ws_col != ec->cols) {
+            /* Log window change event. */
+            log_winchange(ec, wsize.ws_row, wsize.ws_col);
+
+            /* Update rows/cols. */
+            ec->rows = wsize.ws_row;
+            ec->cols = wsize.ws_col;
+        }
+    }
+}
+
+/* Note: this is basically the same as mon_errpipe_cb() in exec_monitor.c */
+static void
+errpipe_cb(int fd, int what, void *v)
+{
+    struct exec_closure *ec = v;
+    ssize_t nread;
+    int errval;
+    debug_decl(errpipe_cb, SUDO_DEBUG_EXEC);
+
+    /*
+     * Read errno from child or EOF when command is executed.
+     * Note that the error pipe is *blocking*.
+     */
+    nread = read(fd, &errval, sizeof(errval));
+    switch (nread) {
+    case -1:
+	if (errno != EAGAIN && errno != EINTR) {
+	    if (ec->cstat->val == CMD_INVALID) {
+		/* XXX - need a way to distinguish non-exec error. */
+		ec->cstat->type = CMD_ERRNO;
+		ec->cstat->val = errno;
+	    }
+	    sudo_debug_printf(SUDO_DEBUG_ERROR|SUDO_DEBUG_ERRNO,
+		"%s: failed to read error pipe", __func__);
+	    sudo_ev_loopbreak(ec->evbase);
+	}
+	break;
+    default:
+	if (nread == 0) {
+	    /* The error pipe closes when the command is executed. */
+	    sudo_debug_printf(SUDO_DEBUG_INFO, "EOF on error pipe");
+	} else {
+	    /* Errno value when child is unable to execute command. */
+	    sudo_debug_printf(SUDO_DEBUG_INFO, "errno from child: %s",
+		strerror(errval));
+	    ec->cstat->type = CMD_ERRNO;
+	    ec->cstat->val = errval;
+	}
+	sudo_ev_del(ec->evbase, ec->backchannel_event);
+	close(fd);
+	break;
+    }
+    debug_return;
+}
+
+/* Signal callback */
+static void
+signal_cb_nopty(int signo, int what, void *v)
+{
+    struct sudo_ev_siginfo_container *sc = v;
+    struct exec_closure *ec = sc->closure;
+    char signame[SIG2STR_MAX];
+    pid_t si_pgrp;
+    debug_decl(signal_cb_nopty, SUDO_DEBUG_EXEC);
+
+    if (ec->cmnd_pid == -1)
+	debug_return;
+
+    if (sig2str(signo, signame) == -1)
+	(void)snprintf(signame, sizeof(signame), "%d", signo);
+    sudo_debug_printf(SUDO_DEBUG_DIAG,
+	"%s: evbase %p, command: %d, signo %s(%d), cstat %p",
+	__func__, ec->evbase, (int)ec->cmnd_pid, signame, signo, ec->cstat);
+
+    switch (signo) {
+    case SIGCHLD:
+	handle_sigchld_nopty(ec);
+	if (ec->cmnd_pid == -1) {
+	    /* Command exited or was killed, exit event loop. */
+	    sudo_ev_loopexit(ec->evbase);
+	}
+	debug_return;
+    case SIGWINCH:
+	handle_sigwinch(ec, io_fds[SFD_USERTTY]);
+	FALLTHROUGH;
+#ifdef SIGINFO
+    case SIGINFO:
+#endif
+    case SIGINT:
+    case SIGQUIT:
+    case SIGTSTP:
+	/*
+	 * Only forward user-generated signals not sent by a process other than
+	 * the command itself or a member of the command's process group (but
+	 * only when either sudo or the command is the process group leader).
+	 * Signals sent by the kernel may include SIGTSTP when the user presses
+	 * ^Z.  Curses programs often trap ^Z and send SIGTSTP to their own
+	 * process group, so we don't want to send an extra SIGTSTP.
+	 */
+	if (!USER_SIGNALED(sc->siginfo))
+	    debug_return;
+	if (sc->siginfo->si_pid != 0) {
+	    if (sc->siginfo->si_pid == ec->cmnd_pid)
+		debug_return;
+	    si_pgrp = getpgid(sc->siginfo->si_pid);
+	    if (si_pgrp != -1) {
+		if (si_pgrp == ec->cmnd_pid || si_pgrp == ec->sudo_pid)
+		    debug_return;
+	    }
+	}
+	break;
+    default:
+	/*
+	 * Do not forward signals sent by the command itself or a member of the
+	 * command's process group (but only when either sudo or the command is
+	 * the process group leader).  We don't want the command to indirectly
+	 * kill itself.  For example, this can happen with some versions of
+	 * reboot that call kill(-1, SIGTERM) to kill all other processes.
+	 */
+	if (USER_SIGNALED(sc->siginfo) && sc->siginfo->si_pid != 0) {
+	    if (sc->siginfo->si_pid == ec->cmnd_pid)
+		debug_return;
+	    si_pgrp = getpgid(sc->siginfo->si_pid);
+	    if (si_pgrp != -1) {
+		if (si_pgrp == ec->cmnd_pid || si_pgrp == ec->sudo_pid)
+		    debug_return;
+	    }
+	}
+	break;
+    }
+
+    /* Send signal to command. */
+    if (signo == SIGALRM) {
+	terminate_command(ec->cmnd_pid, false);
+    } else if (kill(ec->cmnd_pid, signo) != 0) {
+	sudo_warn("kill(%d, SIG%s)", (int)ec->cmnd_pid, signame);
+    }
+
+    debug_return;
+}
+
+
+/*
+ * Fill in the exec closure and setup initial exec events.
+ * Allocates events for the signal pipe and error pipe.
+ */
+static void
+fill_exec_closure(struct exec_closure *ec,
+    struct command_status *cstat, struct command_details *details, int errfd)
+{
+    debug_decl(fill_exec_closure, SUDO_DEBUG_EXEC);
+
+    /* Fill in the non-event part of the closure. */
+    ec->sudo_pid = getpid();
+    ec->ppgrp = getpgrp();
+    ec->cstat = cstat;
+    ec->details = details;
+    ec->rows = user_details.ts_rows;
+    ec->cols = user_details.ts_cols;
+
+    /* Setup event base and events. */
+    ec->evbase = details->evbase;
+    details->evbase = NULL;
+
+    /* Event for command status via errfd. */
+    ec->backchannel_event = sudo_ev_alloc(errfd,
+	SUDO_EV_READ|SUDO_EV_PERSIST, errpipe_cb, ec);
+    if (ec->backchannel_event == NULL)
+	sudo_fatalx(U_("%s: %s"), __func__, U_("unable to allocate memory"));
+    if (sudo_ev_add(ec->evbase, ec->backchannel_event, NULL, false) == -1)
+	sudo_fatal("%s", U_("unable to add event to queue"));
+    sudo_debug_printf(SUDO_DEBUG_INFO, "error pipe fd %d\n", errfd);
+
+    /* Events for local signals. */
+    ec->sigint_event = sudo_ev_alloc(SIGINT,
+	SUDO_EV_SIGINFO, signal_cb_nopty, ec);
+    if (ec->sigint_event == NULL)
+	sudo_fatalx(U_("%s: %s"), __func__, U_("unable to allocate memory"));
+    if (sudo_ev_add(ec->evbase, ec->sigint_event, NULL, false) == -1)
+	sudo_fatal("%s", U_("unable to add event to queue"));
+
+    ec->sigquit_event = sudo_ev_alloc(SIGQUIT,
+	SUDO_EV_SIGINFO, signal_cb_nopty, ec);
+    if (ec->sigquit_event == NULL)
+	sudo_fatalx(U_("%s: %s"), __func__, U_("unable to allocate memory"));
+    if (sudo_ev_add(ec->evbase, ec->sigquit_event, NULL, false) == -1)
+	sudo_fatal("%s", U_("unable to add event to queue"));
+
+    ec->sigtstp_event = sudo_ev_alloc(SIGTSTP,
+	SUDO_EV_SIGINFO, signal_cb_nopty, ec);
+    if (ec->sigtstp_event == NULL)
+	sudo_fatalx(U_("%s: %s"), __func__, U_("unable to allocate memory"));
+    if (sudo_ev_add(ec->evbase, ec->sigtstp_event, NULL, false) == -1)
+	sudo_fatal("%s", U_("unable to add event to queue"));
+
+    ec->sigterm_event = sudo_ev_alloc(SIGTERM,
+	SUDO_EV_SIGINFO, signal_cb_nopty, ec);
+    if (ec->sigterm_event == NULL)
+	sudo_fatalx(U_("%s: %s"), __func__, U_("unable to allocate memory"));
+    if (sudo_ev_add(ec->evbase, ec->sigterm_event, NULL, false) == -1)
+	sudo_fatal("%s", U_("unable to add event to queue"));
+
+    ec->sighup_event = sudo_ev_alloc(SIGHUP,
+	SUDO_EV_SIGINFO, signal_cb_nopty, ec);
+    if (ec->sighup_event == NULL)
+	sudo_fatalx(U_("%s: %s"), __func__, U_("unable to allocate memory"));
+    if (sudo_ev_add(ec->evbase, ec->sighup_event, NULL, false) == -1)
+	sudo_fatal("%s", U_("unable to add event to queue"));
+
+    ec->sigalrm_event = sudo_ev_alloc(SIGALRM,
+	SUDO_EV_SIGINFO, signal_cb_nopty, ec);
+    if (ec->sigalrm_event == NULL)
+	sudo_fatalx(U_("%s: %s"), __func__, U_("unable to allocate memory"));
+    if (sudo_ev_add(ec->evbase, ec->sigalrm_event, NULL, false) == -1)
+	sudo_fatal("%s", U_("unable to add event to queue"));
+
+    ec->sigpipe_event = sudo_ev_alloc(SIGPIPE,
+	SUDO_EV_SIGINFO, signal_cb_nopty, ec);
+    if (ec->sigpipe_event == NULL)
+	sudo_fatalx(U_("%s: %s"), __func__, U_("unable to allocate memory"));
+    if (sudo_ev_add(ec->evbase, ec->sigpipe_event, NULL, false) == -1)
+	sudo_fatal("%s", U_("unable to add event to queue"));
+
+    ec->sigusr1_event = sudo_ev_alloc(SIGUSR1,
+	SUDO_EV_SIGINFO, signal_cb_nopty, ec);
+    if (ec->sigusr1_event == NULL)
+	sudo_fatalx(U_("%s: %s"), __func__, U_("unable to allocate memory"));
+    if (sudo_ev_add(ec->evbase, ec->sigusr1_event, NULL, false) == -1)
+	sudo_fatal("%s", U_("unable to add event to queue"));
+
+    ec->sigusr2_event = sudo_ev_alloc(SIGUSR2,
+	SUDO_EV_SIGINFO, signal_cb_nopty, ec);
+    if (ec->sigusr2_event == NULL)
+	sudo_fatalx(U_("%s: %s"), __func__, U_("unable to allocate memory"));
+    if (sudo_ev_add(ec->evbase, ec->sigusr2_event, NULL, false) == -1)
+	sudo_fatal("%s", U_("unable to add event to queue"));
+
+    ec->sigchld_event = sudo_ev_alloc(SIGCHLD,
+	SUDO_EV_SIGINFO, signal_cb_nopty, ec);
+    if (ec->sigchld_event == NULL)
+	sudo_fatalx(U_("%s: %s"), __func__, U_("unable to allocate memory"));
+    if (sudo_ev_add(ec->evbase, ec->sigchld_event, NULL, false) == -1)
+	sudo_fatal("%s", U_("unable to add event to queue"));
+
+    ec->sigcont_event = sudo_ev_alloc(SIGCONT,
+	SUDO_EV_SIGINFO, signal_cb_nopty, ec);
+    if (ec->sigcont_event == NULL)
+	sudo_fatalx(U_("%s: %s"), __func__, U_("unable to allocate memory"));
+    if (sudo_ev_add(ec->evbase, ec->sigcont_event, NULL, false) == -1)
+	sudo_fatal("%s", U_("unable to add event to queue"));
+
+#ifdef SIGINFO
+    ec->siginfo_event = sudo_ev_alloc(SIGINFO,
+	SUDO_EV_SIGINFO, signal_cb_nopty, ec);
+    if (ec->siginfo_event == NULL)
+	sudo_fatalx(U_("%s: %s"), __func__, U_("unable to allocate memory"));
+    if (sudo_ev_add(ec->evbase, ec->siginfo_event, NULL, false) == -1)
+	sudo_fatal("%s", U_("unable to add event to queue"));
+#endif
+
+    ec->sigwinch_event = sudo_ev_alloc(SIGWINCH,
+	SUDO_EV_SIGINFO, signal_cb_nopty, ec);
+    if (ec->sigwinch_event == NULL)
+	sudo_fatalx(U_("%s: %s"), __func__, U_("unable to allocate memory"));
+    if (sudo_ev_add(ec->evbase, ec->sigwinch_event, NULL, false) == -1)
+	sudo_fatal("%s", U_("unable to add event to queue"));
+
+    /* Set the default event base. */
+    sudo_ev_base_setdef(ec->evbase);
+
+    debug_return;
+}
+
+/*
+ * Read an iobuf that is ready.
+ */
+static void
+read_callback(int fd, int what, void *v)
+{
+    struct io_buffer *iob = v;
+    struct sudo_event_base *evbase = sudo_ev_get_base(iob->revent);
+    ssize_t n;
+    debug_decl(read_callback, SUDO_DEBUG_EXEC);
+
+    n = read(fd, iob->buf + iob->len, sizeof(iob->buf) - iob->len);
+    switch (n) {
+	case -1:
+	    if (errno == EAGAIN || errno == EINTR) {
+		/* Not an error, retry later. */
+		break;
+	    }
+	    /* Treat read error as fatal and close the fd. */
+	    sudo_debug_printf(SUDO_DEBUG_ERROR,
+		"error reading fd %d: %s", fd, strerror(errno));
+	    FALLTHROUGH;
+	case 0:
+	    /* got EOF */
+	    if (n == 0) {
+		sudo_debug_printf(SUDO_DEBUG_INFO,
+		    "read EOF from fd %d", fd);
+	    }
+	    safe_close(fd);
+	    ev_free_by_fd(evbase, fd);
+	    /* If writer already consumed the buffer, close it too. */
+	    if (iob->wevent != NULL && iob->off == iob->len) {
+		safe_close(sudo_ev_get_fd(iob->wevent));
+		ev_free_by_fd(evbase, sudo_ev_get_fd(iob->wevent));
+		iob->off = iob->len = 0;
+	    }
+	    break;
+	default:
+	    sudo_debug_printf(SUDO_DEBUG_INFO,
+		"read %zd bytes from fd %d", n, fd);
+	    if (!iob->action(iob->buf + iob->len, n, iob)) {
+		terminate_command(iob->ec->cmnd_pid, false);
+		iob->ec->cmnd_pid = -1;
+	    }
+	    iob->len += n;
+	    /* Disable reader if buffer is full. */
+	    if (iob->len == sizeof(iob->buf))
+		sudo_ev_del(evbase, iob->revent);
+	    /* Enable writer now that there is new data in the buffer. */
+	    if (iob->wevent != NULL) {
+		if (sudo_ev_add(evbase, iob->wevent, NULL, false) == -1)
+		    sudo_fatal("%s", U_("unable to add event to queue"));
+	    }
+	    break;
+    }
+
+    debug_return;
+}
+
+/*
+ * Write an iobuf that is ready.
+ */
+static void
+write_callback(int fd, int what, void *v)
+{
+    struct io_buffer *iob = v;
+    struct sudo_event_base *evbase = sudo_ev_get_base(iob->wevent);
+    ssize_t n;
+    debug_decl(write_callback, SUDO_DEBUG_EXEC);
+
+    n = write(fd, iob->buf + iob->off, iob->len - iob->off);
+    if (n == -1) {
+	switch (errno) {
+	case EPIPE:
+	case EBADF:
+	    /* other end of pipe closed */
+	    sudo_debug_printf(SUDO_DEBUG_INFO,
+		"unable to write %d bytes to fd %d",
+		iob->len - iob->off, fd);
+	    /* Close reader if there is one. */
+	    if (iob->revent != NULL) {
+		safe_close(sudo_ev_get_fd(iob->revent));
+		ev_free_by_fd(evbase, sudo_ev_get_fd(iob->revent));
+	    }
+	    safe_close(fd);
+	    ev_free_by_fd(evbase, fd);
+	    break;
+	case EINTR:
+	case EAGAIN:
+	    /* Not an error, retry later. */
+	    break;
+	default:
+	    /* XXX - need a way to distinguish non-exec error. */
+	    iob->ec->cstat->type = CMD_ERRNO;
+	    iob->ec->cstat->val = errno;
+	    sudo_debug_printf(SUDO_DEBUG_ERROR,
+		"error writing fd %d: %s", fd, strerror(errno));
+	    sudo_ev_loopbreak(evbase);
+	    break;
+	}
+    } else {
+	sudo_debug_printf(SUDO_DEBUG_INFO,
+	    "wrote %zd bytes to fd %d", n, fd);
+	iob->off += n;
+	/* Disable writer and reset the buffer if fully consumed. */
+	if (iob->off == iob->len) {
+	    iob->off = iob->len = 0;
+	    sudo_ev_del(evbase, iob->wevent);
+	    /* Forward the EOF from reader to writer. */
+	    if (iob->revent == NULL) {
+		safe_close(fd);
+		ev_free_by_fd(evbase, fd);
+	    }
+	}
+	/*
+	 * Enable reader if buffer is not full but avoid reading
+	 * /dev/tty if the command is no longer running.
+	 */
+	if (iob->revent != NULL && iob->len != sizeof(iob->buf)) {
+	    if (!USERTTY_EVENT(iob->revent) || iob->ec->cmnd_pid != -1) {
+		if (sudo_ev_add(evbase, iob->revent, NULL, false) == -1)
+		    sudo_fatal("%s", U_("unable to add event to queue"));
+	    }
+	}
+    }
+
+    debug_return;
+}
+
+/*
+ * If std{in,out,err} are not connected to a terminal, interpose
+ * ourselves using a pipe.  Fills in io_pipe[][].
+ */
+static void
+interpose_pipes(struct exec_closure *ec, int io_pipe[3][2])
+{
+    bool interpose[3] = { false, false, false };
+    struct plugin_container *plugin;
+    bool want_winch = false;
+    debug_decl(interpose_pipes, SUDO_DEBUG_EXEC);
+
+    /*
+     * Determine whether any of std{in,out,err} or window size changes
+     * should be logged.
+     */
+    TAILQ_FOREACH(plugin, &io_plugins, entries) {
+	if (plugin->u.io->log_stdin)
+	    interpose[STDIN_FILENO] = true;
+	if (plugin->u.io->log_stdout)
+	    interpose[STDOUT_FILENO] = true;
+	if (plugin->u.io->log_stderr)
+	    interpose[STDERR_FILENO] = true;
+	if (plugin->u.io->version >= SUDO_API_MKVERSION(1, 12)) {
+	    if (plugin->u.io->change_winsize)
+		want_winch = true;
+	}
+    }
+
+    /*
+     * If stdin, stdout or stderr is not a tty and logging is enabled,
+     * use a pipe to interpose ourselves.
+     */
+    if (interpose[STDIN_FILENO]) {
+	if (!isatty(STDIN_FILENO)) {
+	    sudo_debug_printf(SUDO_DEBUG_INFO,
+		"stdin not a tty, creating a pipe");
+	    if (pipe2(io_pipe[STDIN_FILENO], O_CLOEXEC) != 0)
+		sudo_fatal("%s", U_("unable to create pipe"));
+	    io_buf_new(STDIN_FILENO, io_pipe[STDIN_FILENO][1],
+		log_stdin, read_callback, write_callback, ec, &iobufs);
+	}
+    }
+    if (interpose[STDOUT_FILENO]) {
+	if (!isatty(STDOUT_FILENO)) {
+	    sudo_debug_printf(SUDO_DEBUG_INFO,
+		"stdout not a tty, creating a pipe");
+	    if (pipe2(io_pipe[STDOUT_FILENO], O_CLOEXEC) != 0)
+		sudo_fatal("%s", U_("unable to create pipe"));
+	    io_buf_new(io_pipe[STDOUT_FILENO][0], STDOUT_FILENO,
+		log_stdout, read_callback, write_callback, ec, &iobufs);
+	}
+    }
+    if (interpose[STDERR_FILENO]) {
+	if (!isatty(STDERR_FILENO)) {
+	    sudo_debug_printf(SUDO_DEBUG_INFO,
+		"stderr not a tty, creating a pipe");
+	    if (pipe2(io_pipe[STDERR_FILENO], O_CLOEXEC) != 0)
+		sudo_fatal("%s", U_("unable to create pipe"));
+	    io_buf_new(io_pipe[STDERR_FILENO][0], STDERR_FILENO,
+		log_stderr, read_callback, write_callback, ec, &iobufs);
+	}
+    }
+    if (want_winch) {
+	/* Need /dev/tty for SIGWINCH handling. */
+	io_fds[SFD_USERTTY] = open(_PATH_TTY, O_RDWR);
+    }
+}
+
+/*
+ * Execute a command and wait for it to finish.
+ */
+void
+exec_nopty(struct command_details *details, struct command_status *cstat)
+{
+    int io_pipe[3][2] = { { -1, -1 }, { -1, -1 }, { -1, -1 } };
+    int errpipe[2], intercept_sv[2] = { -1, -1 };
+    struct exec_closure ec = { 0 };
+    sigset_t set, oset;
+    debug_decl(exec_nopty, SUDO_DEBUG_EXEC);
+
+    /*
+     * The policy plugin's session init must be run before we fork
+     * or certain pam modules won't be able to track their state.
+     */
+    if (policy_init_session(details) != true)
+	sudo_fatalx("%s", U_("policy plugin failed session initialization"));
+
+    /*
+     * We use a pipe to get errno if execve(2) fails in the child.
+     */
+    if (pipe2(errpipe, O_CLOEXEC) != 0)
+	sudo_fatal("%s", U_("unable to create pipe"));
+
+    if (ISSET(details->flags, CD_INTERCEPT|CD_LOG_SUBCMDS)) {
+	if (!ISSET(details->flags, CD_USE_PTRACE)) {
+	    /*
+	     * Allocate a socketpair for communicating with sudo_intercept.so.
+	     * This must be inherited across exec, hence no FD_CLOEXEC.
+	     */
+	    if (socketpair(PF_UNIX, SOCK_STREAM, 0, intercept_sv) == -1)
+		sudo_fatal("%s", U_("unable to create sockets"));
+	}
+    }
+
+    /* Interpose std{in,out,err} with pipes if logging I/O. */
+    interpose_pipes(&ec, io_pipe);
+
+    /*
+     * Block signals until we have our handlers setup in the parent so
+     * we don't miss SIGCHLD if the command exits immediately.
+     */
+    sigfillset(&set);
+    sigprocmask(SIG_BLOCK, &set, &oset);
+
+    /* Check for early termination or suspend signals before we fork. */
+    if (sudo_terminated(cstat)) {
+	sigprocmask(SIG_SETMASK, &oset, NULL);
+	debug_return;
+    }
+
+#ifdef HAVE_SELINUX
+    if (ISSET(details->flags, CD_RBAC_ENABLED)) {
+        if (selinux_relabel_tty(details->tty, -1) == -1) {
+	    cstat->type = CMD_ERRNO;
+	    cstat->val = errno;
+	    debug_return;
+	}
+	selinux_audit_role_change();
+    }
+#endif
+
+    ec.cmnd_pid = sudo_debug_fork();
+    switch (ec.cmnd_pid) {
+    case -1:
+	sudo_fatal("%s", U_("unable to fork"));
+	break;
+    case 0:
+	/* child */
+	close(errpipe[0]);
+	if (intercept_sv[0] != -1)
+	    close(intercept_sv[0]);
+	/* Replace stdin/stdout/stderr with pipes as needed and exec. */
+	if (io_pipe[STDIN_FILENO][0] != -1) {
+	    if (dup3(io_pipe[STDIN_FILENO][0], STDIN_FILENO, 0) == -1)
+		sudo_fatal("dup3");
+	    close(io_pipe[STDIN_FILENO][0]);
+	    close(io_pipe[STDIN_FILENO][1]);
+	}
+	if (io_pipe[STDOUT_FILENO][0] != -1) {
+	    if (dup3(io_pipe[STDOUT_FILENO][1], STDOUT_FILENO, 0) == -1)
+		sudo_fatal("dup3");
+	    close(io_pipe[STDOUT_FILENO][0]);
+	    close(io_pipe[STDOUT_FILENO][1]);
+	}
+	if (io_pipe[STDERR_FILENO][0] != -1) {
+	    if (dup3(io_pipe[STDERR_FILENO][1], STDERR_FILENO, 0) == -1)
+		sudo_fatal("dup3");
+	    close(io_pipe[STDERR_FILENO][0]);
+	    close(io_pipe[STDERR_FILENO][1]);
+	}
+	exec_cmnd(details, &oset, intercept_sv[1], errpipe[1]);
+	while (write(errpipe[1], &errno, sizeof(int)) == -1) {
+	    if (errno != EINTR)
+		break;
+	}
+	sudo_debug_exit_int(__func__, __FILE__, __LINE__, sudo_debug_subsys, 1);
+	_exit(EXIT_FAILURE);
+    }
+    sudo_debug_printf(SUDO_DEBUG_INFO, "executed %s, pid %d", details->command,
+	(int)ec.cmnd_pid);
+    /* Close the other end of the pipes and socketpairs. */
+    if (io_pipe[STDIN_FILENO][0] != -1)
+        close(io_pipe[STDIN_FILENO][0]);
+    if (io_pipe[STDOUT_FILENO][1] != -1)
+        close(io_pipe[STDOUT_FILENO][1]);
+    if (io_pipe[STDERR_FILENO][1] != -1)
+        close(io_pipe[STDERR_FILENO][1]);
+    close(errpipe[1]);
+    if (intercept_sv[1] != -1)
+        close(intercept_sv[1]);
+
+    /* No longer need execfd. */
+    if (details->execfd != -1) {
+	close(details->execfd);
+	details->execfd = -1;
+    }
+
+    /* Set command timeout if specified. */
+    if (ISSET(details->flags, CD_SET_TIMEOUT))
+	alarm(details->timeout);
+
+    /*
+     * Fill in exec closure, allocate event base, signal events and
+     * the error pipe event.
+     */
+    fill_exec_closure(&ec, cstat, details, errpipe[0]);
+
+    if (ISSET(details->flags, CD_INTERCEPT|CD_LOG_SUBCMDS)) {
+	int rc = 1;
+
+	/* Create event and closure for intercept mode. */
+	ec.intercept = intercept_setup(intercept_sv[0], ec.evbase, details);
+	if (ec.intercept == NULL) {
+	    rc = -1;
+	} else if (ISSET(details->flags, CD_USE_PTRACE)) {
+	    /* Try to seize control of the command using ptrace(2). */
+	    rc = exec_ptrace_seize(ec.cmnd_pid);
+	    if (rc == 0) {
+		/* There is another tracer present. */
+		CLR(details->flags, CD_INTERCEPT|CD_LOG_SUBCMDS|CD_USE_PTRACE);
+	    }
+	}
+	if (rc == -1)
+	    terminate_command(ec.cmnd_pid, false);
+    }
+
+    /* Enable any I/O log events. */
+    add_io_events(ec.evbase);
+
+    /* Restore signal mask now that signal handlers are setup. */
+    sigprocmask(SIG_SETMASK, &oset, NULL);
+
+    /*
+     * Non-pty event loop.
+     * Wait for command to exit, handles signals and the error pipe.
+     */
+    if (sudo_ev_dispatch(ec.evbase) == -1)
+	sudo_warn("%s", U_("error in event loop"));
+    if (sudo_ev_got_break(ec.evbase)) {
+	/* error from callback */
+	sudo_debug_printf(SUDO_DEBUG_ERROR, "event loop exited prematurely");
+	/* kill command */
+	terminate_command(ec.cmnd_pid, false);
+	ec.cmnd_pid = -1;
+    }
+
+#ifdef HAVE_SELINUX
+    if (ISSET(details->flags, CD_RBAC_ENABLED)) {
+	if (selinux_restore_tty() != 0)
+	    sudo_warnx("%s", U_("unable to restore tty label"));
+    }
+#endif
+
+    /* Flush any remaining output. */
+    del_io_events(true);
+
+    /* Free things up. */
+    free_io_bufs();
+    free_exec_closure(&ec);
+
+    debug_return;
+}
+
+/*
+ * Wait for command status after receiving SIGCHLD.
+ * If the command exits, fill in cstat and stop the event loop.
+ * If the command stops, save the tty pgrp, suspend sudo, then restore
+ * the tty pgrp when sudo resumes.
+ */
+static void
+handle_sigchld_nopty(struct exec_closure *ec)
+{
+    pid_t pid;
+    int status;
+    char signame[SIG2STR_MAX];
+    debug_decl(handle_sigchld_nopty, SUDO_DEBUG_EXEC);
+
+    /* There may be multiple children in intercept mode. */
+    for (;;) {
+	do {
+	    pid = waitpid(-1, &status, __WALL|WUNTRACED|WNOHANG);
+	} while (pid == -1 && errno == EINTR);
+	switch (pid) {
+	case -1:
+	    if (errno != ECHILD) {
+		sudo_warn(U_("%s: %s"), __func__, "waitpid");
+		debug_return;
+	    }
+	    FALLTHROUGH;
+	case 0:
+	    /* Nothing left to wait for. */
+	    debug_return;
+	}
+
+	if (WIFSTOPPED(status)) {
+	    const int signo = WSTOPSIG(status);
+
+	    if (sig2str(signo, signame) == -1)
+		(void)snprintf(signame, sizeof(signame), "%d", signo);
+	    sudo_debug_printf(SUDO_DEBUG_INFO,
+		"%s: process %d stopped, SIG%s", __func__, (int)pid, signame);
+
+	    if (ISSET(ec->details->flags, CD_USE_PTRACE)) {
+		/* If not a group-stop signal, just continue. */
+		if (!exec_ptrace_stopped(pid, status, ec->intercept))
+		    continue;
+	    }
+
+	    /* If the main command is suspended, suspend sudo too. */
+	    if (pid == ec->cmnd_pid) {
+		suspend_sudo_nopty(ec, signo, ec->sudo_pid, ec->ppgrp,
+		    ec->cmnd_pid);
+	    }
+	} else {
+	    if (WIFSIGNALED(status)) {
+		if (sig2str(WTERMSIG(status), signame) == -1) {
+		    (void)snprintf(signame, sizeof(signame), "%d",
+			WTERMSIG(status));
+		}
+		sudo_debug_printf(SUDO_DEBUG_INFO,
+		    "%s: process %d killed, SIG%s", __func__,
+		    (int)pid, signame);
+	    } else if (WIFEXITED(status)) {
+		sudo_debug_printf(SUDO_DEBUG_INFO,
+		    "%s: process %d exited: %d", __func__,
+		    (int)pid, WEXITSTATUS(status));
+	    } else {
+		sudo_debug_printf(SUDO_DEBUG_WARN,
+		    "%s: unexpected wait status 0x%x for process %d",
+		    __func__, status, (int)pid);
+	    }
+
+	    /* Only store exit status of the main command. */
+	    if (pid != ec->cmnd_pid)
+		continue;
+
+	    /* Don't overwrite execve() failure with command exit status. */
+	    if (ec->cstat->type == CMD_INVALID) {
+		ec->cstat->type = CMD_WSTATUS;
+		ec->cstat->val = status;
+	    } else {
+		sudo_debug_printf(SUDO_DEBUG_WARN,
+		    "%s: not overwriting command status %d,%d with %d,%d",
+		    __func__, ec->cstat->type, ec->cstat->val,
+		    CMD_WSTATUS, status);
+	    }
+	    ec->cmnd_pid = -1;
+	}
+    }
+}