/*      $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);
}