/*	$OpenBSD: posix_spawn.c,v 1.10 2019/06/28 13:32:41 deraadt Exp $	*/
/*-
 * Copyright (c) 2008 Ed Schouten <ed@FreeBSD.org>
 * All rights reserved.
 *
 * 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 AND CONTRIBUTORS ``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 OR CONTRIBUTORS 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 <sys/queue.h>

#include <errno.h>
#include <fcntl.h>
#include <sched.h>
#include <spawn.h>
#include <signal.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>

struct __posix_spawnattr {
	short			sa_flags;
	pid_t			sa_pgroup;
	struct sched_param	sa_schedparam;
	int			sa_schedpolicy;
	sigset_t		sa_sigdefault;
	sigset_t		sa_sigmask;
};

struct __posix_spawn_file_actions {
	SIMPLEQ_HEAD(, __posix_spawn_file_actions_entry) fa_list;
};

typedef struct __posix_spawn_file_actions_entry {
	SIMPLEQ_ENTRY(__posix_spawn_file_actions_entry) fae_list;
	enum { FAE_OPEN, FAE_DUP2, FAE_CLOSE } fae_action;

	int fae_fildes;
	union {
		struct {
			char *path;
#define fae_path	fae_data.open.path
			int oflag;
#define fae_oflag	fae_data.open.oflag
			mode_t mode;
#define fae_mode	fae_data.open.mode
		} open;
		struct {
			int newfildes;
#define fae_newfildes	fae_data.dup2.newfildes
		} dup2;
	} fae_data;
} posix_spawn_file_actions_entry_t;

/*
 * Spawn routines
 */

static int
process_spawnattr(const posix_spawnattr_t sa)
{
	struct sigaction sigact;
	int i;

	memset(&sigact, 0, sizeof(sigact));
	sigact.sa_handler = SIG_DFL;

	/*
	 * POSIX doesn't really describe in which order everything
	 * should be set. We'll just set them in the order in which they
	 * are mentioned.
	 */

	/* Set process group */
	if (sa->sa_flags & POSIX_SPAWN_SETPGROUP) {
		if (setpgid(0, sa->sa_pgroup) != 0)
			return (errno);
	}

#if 0 /* NOT IMPLEMENTED */
	/* Set scheduler policy */
	if (sa->sa_flags & POSIX_SPAWN_SETSCHEDULER) {
		if (sched_setscheduler(0, sa->sa_schedpolicy,
		    &sa->sa_schedparam) != 0)
			return (errno);
	} else if (sa->sa_flags & POSIX_SPAWN_SETSCHEDPARAM) {
		if (sched_setparam(0, &sa->sa_schedparam) != 0)
			return (errno);
	}
#endif

	/* Reset user ID's */
	if (sa->sa_flags & POSIX_SPAWN_RESETIDS) {
		if (setegid(getgid()) != 0)
			return (errno);
		if (seteuid(getuid()) != 0)
			return (errno);
	}

	/* Set signal masks/defaults */
	if (sa->sa_flags & POSIX_SPAWN_SETSIGMASK) {
		WRAP(sigprocmask)(SIG_SETMASK, &sa->sa_sigmask, NULL);
	}

	if (sa->sa_flags & POSIX_SPAWN_SETSIGDEF) {
		for (i = 1; i < _NSIG; i++) {
			/* silently ignore attempts to alter SIGTHR */
			if (sigismember(&sa->sa_sigdefault, i) && i != SIGTHR)
				if (sigaction(i, &sigact, NULL) != 0)
					return (errno);
		}
	}

	return (0);
}

static int
process_file_actions_entry(posix_spawn_file_actions_entry_t *fae)
{
	int fd;

	switch (fae->fae_action) {
	case FAE_OPEN:
		/* Perform an open(), make it use the right fd */
		fd = open(fae->fae_path, fae->fae_oflag, fae->fae_mode);
		if (fd == -1)
			return (errno);
		if (fd != fae->fae_fildes) {
			if (dup2(fd, fae->fae_fildes) == -1)
				return (errno);
			if (close(fd) != 0) {
				if (errno == EBADF)
					return (EBADF);
			}
		}
		break;
	case FAE_DUP2:
		/*
		 * Perform a dup2(), making sure the FD_CLOEXEC flag is clear
		 */
		fd = fae->fae_fildes;
		if (fd == fae->fae_newfildes) {
			int flags = fcntl(fd, F_GETFD);

			if (flags == -1 ||
			    ((flags & FD_CLOEXEC) &&
			    fcntl(fd, F_SETFD, flags & ~FD_CLOEXEC) == -1))
				return (errno);
		} else if (dup2(fd, fae->fae_newfildes) == -1)
			return (errno);
		break;
	case FAE_CLOSE:
		/* Perform a close(), do not fail if already closed */
		(void)close(fae->fae_fildes);
		break;
	}
	return (0);
}

static int
process_file_actions(const posix_spawn_file_actions_t fa)
{
	posix_spawn_file_actions_entry_t *fae;
	int error;

	/* Replay all file descriptor modifications */
	SIMPLEQ_FOREACH(fae, &fa->fa_list, fae_list) {
		error = process_file_actions_entry(fae);
		if (error)
			return (error);
	}
	return (0);	
}

static int
do_posix_spawn(pid_t *pid, const char *path,
    const posix_spawn_file_actions_t *fa,
    const posix_spawnattr_t *sa,
    char *const argv[], char *const envp[], int use_env_path)
{
	pid_t p;
	
	p = fork();
	switch (p) {
	case -1:
		return (errno);
	case 0: {
		int error;
		if (sa != NULL) {
			error = process_spawnattr(*sa);
			if (error)
				_exit(127);
		}
		if (fa != NULL) {
			error = process_file_actions(*fa);
			if (error)
				_exit(127);
		}
		if (use_env_path)
			execvpe(path, argv, envp != NULL ? envp : environ);
		else
			execve(path, argv, envp != NULL ? envp : environ);
		_exit(127);
	}
	default:
		if (pid != NULL)
			*pid = p;
		return (0);
	}
}

int
posix_spawn(pid_t *pid, const char *path,
    const posix_spawn_file_actions_t *fa,
    const posix_spawnattr_t *sa,
    char *const argv[], char *const envp[])
{
	return do_posix_spawn(pid, path, fa, sa, argv, envp, 0);
}

int
posix_spawnp(pid_t *pid, const char *path,
    const posix_spawn_file_actions_t *fa,
    const posix_spawnattr_t *sa,
    char *const argv[], char *const envp[])
{
	return do_posix_spawn(pid, path, fa, sa, argv, envp, 1);
}

/*
 * File descriptor actions
 */

int
posix_spawn_file_actions_init(posix_spawn_file_actions_t *ret)
{
	posix_spawn_file_actions_t fa;

	fa = malloc(sizeof(struct __posix_spawn_file_actions));
	if (fa == NULL)
		return (errno);

	SIMPLEQ_INIT(&fa->fa_list);
	*ret = fa;
	return (0);
}

int
posix_spawn_file_actions_destroy(posix_spawn_file_actions_t *fa)
{
	posix_spawn_file_actions_entry_t *fae;

	while ((fae = SIMPLEQ_FIRST(&(*fa)->fa_list)) != NULL) {
		/* Remove file action entry from the queue */
		SIMPLEQ_REMOVE_HEAD(&(*fa)->fa_list, fae_list);

		/* Deallocate file action entry */
		if (fae->fae_action == FAE_OPEN)
			free(fae->fae_path);
		free(fae);
	}

	free(*fa);
	return (0);
}

int
posix_spawn_file_actions_addopen(posix_spawn_file_actions_t *__restrict fa,
    int fildes, const char *__restrict path, int oflag, mode_t mode)
{
	posix_spawn_file_actions_entry_t *fae;
	int error;

	if (fildes < 0)
		return (EBADF);

	/* Allocate object */
	fae = malloc(sizeof(posix_spawn_file_actions_entry_t));
	if (fae == NULL)
		return (errno);

	/* Set values and store in queue */
	fae->fae_action = FAE_OPEN;
	fae->fae_path = strdup(path);
	if (fae->fae_path == NULL) {
		error = errno;
		free(fae);
		return (error);
	}
	fae->fae_fildes = fildes;
	fae->fae_oflag = oflag;
	fae->fae_mode = mode;

	SIMPLEQ_INSERT_TAIL(&(*fa)->fa_list, fae, fae_list);
	return (0);
}

int
posix_spawn_file_actions_adddup2(posix_spawn_file_actions_t *fa,
    int fildes, int newfildes)
{
	posix_spawn_file_actions_entry_t *fae;

	if (fildes < 0 || newfildes < 0)
		return (EBADF);

	/* Allocate object */
	fae = malloc(sizeof(posix_spawn_file_actions_entry_t));
	if (fae == NULL)
		return (errno);

	/* Set values and store in queue */
	fae->fae_action = FAE_DUP2;
	fae->fae_fildes = fildes;
	fae->fae_newfildes = newfildes;

	SIMPLEQ_INSERT_TAIL(&(*fa)->fa_list, fae, fae_list);
	return (0);
}

int
posix_spawn_file_actions_addclose(posix_spawn_file_actions_t *fa,
    int fildes)
{
	posix_spawn_file_actions_entry_t *fae;

	if (fildes < 0)
		return (EBADF);

	/* Allocate object */
	fae = malloc(sizeof(posix_spawn_file_actions_entry_t));
	if (fae == NULL)
		return (errno);

	/* Set values and store in queue */
	fae->fae_action = FAE_CLOSE;
	fae->fae_fildes = fildes;

	SIMPLEQ_INSERT_TAIL(&(*fa)->fa_list, fae, fae_list);
	return (0);
}

/*
 * Spawn attributes
 */

int
posix_spawnattr_init(posix_spawnattr_t *ret)
{
	posix_spawnattr_t sa;

	sa = calloc(1, sizeof(struct __posix_spawnattr));
	if (sa == NULL)
		return (errno);

	/* Set defaults as specified by POSIX, cleared above */
	*ret = sa;
	return (0);
}

int
posix_spawnattr_destroy(posix_spawnattr_t *sa)
{
	free(*sa);
	return (0);
}

int
posix_spawnattr_getflags(const posix_spawnattr_t *__restrict sa,
    short *__restrict flags)
{
	*flags = (*sa)->sa_flags;
	return (0);
}

int
posix_spawnattr_getpgroup(const posix_spawnattr_t *__restrict sa,
    pid_t *__restrict pgroup)
{
	*pgroup = (*sa)->sa_pgroup;
	return (0);
}

int
posix_spawnattr_getschedparam(const posix_spawnattr_t *__restrict sa,
    struct sched_param *__restrict schedparam)
{
	*schedparam = (*sa)->sa_schedparam;
	return (0);
}

int
posix_spawnattr_getschedpolicy(const posix_spawnattr_t *__restrict sa,
    int *__restrict schedpolicy)
{
	*schedpolicy = (*sa)->sa_schedpolicy;
	return (0);
}

int
posix_spawnattr_getsigdefault(const posix_spawnattr_t *__restrict sa,
    sigset_t *__restrict sigdefault)
{
	*sigdefault = (*sa)->sa_sigdefault;
	return (0);
}

int
posix_spawnattr_getsigmask(const posix_spawnattr_t *__restrict sa,
    sigset_t *__restrict sigmask)
{
	*sigmask = (*sa)->sa_sigmask;
	return (0);
}

int
posix_spawnattr_setflags(posix_spawnattr_t *sa, short flags)
{
	(*sa)->sa_flags = flags;
	return (0);
}

int
posix_spawnattr_setpgroup(posix_spawnattr_t *sa, pid_t pgroup)
{
	(*sa)->sa_pgroup = pgroup;
	return (0);
}

int
posix_spawnattr_setschedparam(posix_spawnattr_t *__restrict sa,
    const struct sched_param *__restrict schedparam)
{
	(*sa)->sa_schedparam = *schedparam;
	return (0);
}

int
posix_spawnattr_setschedpolicy(posix_spawnattr_t *sa, int schedpolicy)
{
	(*sa)->sa_schedpolicy = schedpolicy;
	return (0);
}

int
posix_spawnattr_setsigdefault(posix_spawnattr_t *__restrict sa,
    const sigset_t *__restrict sigdefault)
{
	(*sa)->sa_sigdefault = *sigdefault;
	return (0);
}

int
posix_spawnattr_setsigmask(posix_spawnattr_t *__restrict sa,
    const sigset_t *__restrict sigmask)
{
	(*sa)->sa_sigmask = *sigmask;
	return (0);
}