/*-
 * SPDX-License-Identifier: BSD-2-Clause
 *
 * Copyright (c) 2012 The FreeBSD Foundation
 * Copyright (c) 2015 Mariusz Zaborski <oshogbo@FreeBSD.org>
 * Copyright (c) 2017 Robert N. M. Watson
 *
 * This software was developed by Pawel Jakub Dawidek under sponsorship from
 * the FreeBSD Foundation.
 *
 * All rights reserved.
 * This software was developed by SRI International and the University of
 * Cambridge Computer Laboratory under DARPA/AFRL contract (FA8750-10-C-0237)
 * ("CTSRD"), as part of the DARPA CRASH research programme.
 *
 * 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 AUTHORS 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 AUTHORS 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/types.h>
#include <sys/capsicum.h>
#include <sys/procdesc.h>
#include <sys/socket.h>
#include <sys/nv.h>

#include <assert.h>
#include <err.h>
#include <errno.h>
#include <stdbool.h>
#include <stdlib.h>
#include <strings.h>
#include <unistd.h>

#include "libcasper_impl.h"
#include "zygote.h"

/* Zygote info. */
static int      zygote_sock = -1;

#define ZYGOTE_SERVICE_EXECUTE  1

int
zygote_clone(uint64_t funcidx, int *chanfdp, int *procfdp)
{
        nvlist_t *nvl;
        int error;

        if (zygote_sock == -1) {
                /* Zygote didn't start. */
                errno = ENXIO;
                return (-1);
        }

        nvl = nvlist_create(0);
        nvlist_add_number(nvl, "funcidx", funcidx);
        nvl = nvlist_xfer(zygote_sock, nvl, 0);
        if (nvl == NULL)
                return (-1);
        if (nvlist_exists_number(nvl, "error")) {
                error = (int)nvlist_get_number(nvl, "error");
                nvlist_destroy(nvl);
                errno = error;
                return (-1);
        }

        *chanfdp = nvlist_take_descriptor(nvl, "chanfd");
        *procfdp = nvlist_take_descriptor(nvl, "procfd");

        nvlist_destroy(nvl);
        return (0);
}

int
zygote_clone_service_execute(int *chanfdp, int *procfdp)
{

        return (zygote_clone(ZYGOTE_SERVICE_EXECUTE, chanfdp, procfdp));
}

/*
 * This function creates sandboxes on-demand whoever has access to it via
 * 'sock' socket. Function sends two descriptors to the caller: process
 * descriptor of the sandbox and socket pair descriptor for communication
 * between sandbox and its owner.
 */
static void
zygote_main(int *sockp)
{
        int error, procfd;
        int chanfd[2];
        nvlist_t *nvlin, *nvlout;
        uint64_t funcidx;
        zygote_func_t *func;
        pid_t pid;

        fd_fix_environment(sockp);

        assert(*sockp > STDERR_FILENO);

        setproctitle("zygote");

        for (;;) {
                nvlin = nvlist_recv(*sockp, 0);
                if (nvlin == NULL) {
                        if (errno == ENOTCONN) {
                                /* Casper exited. */
                                _exit(0);
                        }
                        continue;
                }
                funcidx = nvlist_get_number(nvlin, "funcidx");
                nvlist_destroy(nvlin);

                switch (funcidx) {
                case ZYGOTE_SERVICE_EXECUTE:
                        func = service_execute;
                        break;
                default:
                        _exit(0);
                }

                /*
                 * Someone is requesting a new process, create one.
                 */
                procfd = -1;
                chanfd[0] = -1;
                chanfd[1] = -1;
                error = 0;
                if (socketpair(PF_UNIX, SOCK_STREAM | SOCK_NONBLOCK, 0,
                    chanfd) == -1) {
                        error = errno;
                        goto send;
                }
                pid = pdfork(&procfd, 0);
                switch (pid) {
                case -1:
                        /* Failure. */
                        error = errno;
                        break;
                case 0:
                        /* Child. */
                        close(*sockp);
                        close(chanfd[0]);
                        func(chanfd[1]);
                        /* NOTREACHED */
                        _exit(1);
                default:
                        /* Parent. */
                        close(chanfd[1]);
                        break;
                }
send:
                nvlout = nvlist_create(0);
                if (error != 0) {
                        nvlist_add_number(nvlout, "error", (uint64_t)error);
                        if (chanfd[0] >= 0)
                                close(chanfd[0]);
                        if (procfd >= 0)
                                close(procfd);
                } else {
                        nvlist_move_descriptor(nvlout, "chanfd", chanfd[0]);
                        nvlist_move_descriptor(nvlout, "procfd", procfd);
                }
                (void)nvlist_send(*sockp, nvlout);
                nvlist_destroy(nvlout);
        }
        /* NOTREACHED */
}

int
zygote_init(void)
{
        int serrno, sp[2];
        pid_t pid;

        if (socketpair(PF_UNIX, SOCK_STREAM | SOCK_NONBLOCK, 0, sp) == -1)
                return (-1);

        pid = fork();
        switch (pid) {
        case -1:
                /* Failure. */
                serrno = errno;
                close(sp[0]);
                close(sp[1]);
                errno = serrno;
                return (-1);
        case 0:
                /* Child. */
                close(sp[0]);
                zygote_main(&sp[1]);
                /* NOTREACHED */
                abort();
        default:
                /* Parent. */
                zygote_sock = sp[0];
                close(sp[1]);
                return (0);
        }
        /* NOTREACHED */
}