/*-
 * SPDX-License-Identifier: BSD-2-Clause
 *
 * Copyright (c) 2013 The FreeBSD Foundation
 * Copyright (c) 2015 Mariusz Zaborski <oshogbo@FreeBSD.org>
 * All rights reserved.
 *
 * This software was developed by Pawel Jakub Dawidek under sponsorship from
 * the FreeBSD Foundation.
 *
 * 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/queue.h>
#include <sys/socket.h>
#include <sys/nv.h>

#include <assert.h>
#include <dirent.h>
#include <err.h>
#include <errno.h>
#include <fcntl.h>
#include <paths.h>
#include <stdbool.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <strings.h>
#include <unistd.h>

#include "libcasper.h"
#include "libcasper_impl.h"

/*
 * Currently there is only one service_connection per service.
 * In the future we may want multiple connections from multiple clients
 * per one service instance, but it has to be carefully designed.
 * The problem is that we may restrict/sandbox service instance according
 * to the limits provided. When new connection comes in with different
 * limits we won't be able to access requested resources.
 * Not to mention one process will serve to multiple mutually untrusted
 * clients and compromise of this service instance by one of its clients
 * can lead to compromise of the other clients.
 */

/*
 * Client connections to the given service.
 */
#define SERVICE_CONNECTION_MAGIC        0x5e91c0ec
struct service_connection {
        int              sc_magic;
        cap_channel_t   *sc_chan;
        nvlist_t        *sc_limits;
        TAILQ_ENTRY(service_connection) sc_next;
};

#define SERVICE_MAGIC   0x5e91ce
struct service {
        int                      s_magic;
        char                    *s_name;
        uint64_t                 s_flags;
        service_limit_func_t    *s_limit;
        service_command_func_t  *s_command;
        TAILQ_HEAD(, service_connection) s_connections;
};

struct service *
service_alloc(const char *name, service_limit_func_t *limitfunc,
    service_command_func_t *commandfunc, uint64_t flags)
{
        struct service *service;

        service = malloc(sizeof(*service));
        if (service == NULL)
                return (NULL);
        service->s_name = strdup(name);
        if (service->s_name == NULL) {
                free(service);
                return (NULL);
        }
        service->s_limit = limitfunc;
        service->s_command = commandfunc;
        service->s_flags = flags;
        TAILQ_INIT(&service->s_connections);
        service->s_magic = SERVICE_MAGIC;

        return (service);
}

void
service_free(struct service *service)
{
        struct service_connection *sconn;

        assert(service->s_magic == SERVICE_MAGIC);

        service->s_magic = 0;
        while ((sconn = service_connection_first(service)) != NULL)
                service_connection_remove(service, sconn);
        free(service->s_name);
        free(service);
}

struct service_connection *
service_connection_add(struct service *service, int sock,
    const nvlist_t *limits)
{
        struct service_connection *sconn;
        int serrno;

        assert(service->s_magic == SERVICE_MAGIC);

        sconn = malloc(sizeof(*sconn));
        if (sconn == NULL)
                return (NULL);
        sconn->sc_chan = cap_wrap(sock,
            service_get_channel_flags(service));
        if (sconn->sc_chan == NULL) {
                serrno = errno;
                free(sconn);
                errno = serrno;
                return (NULL);
        }
        if (limits == NULL) {
                sconn->sc_limits = NULL;
        } else {
                sconn->sc_limits = nvlist_clone(limits);
                if (sconn->sc_limits == NULL) {
                        serrno = errno;
                        (void)cap_unwrap(sconn->sc_chan, NULL);
                        free(sconn);
                        errno = serrno;
                        return (NULL);
                }
        }
        sconn->sc_magic = SERVICE_CONNECTION_MAGIC;
        TAILQ_INSERT_TAIL(&service->s_connections, sconn, sc_next);
        return (sconn);
}

void
service_connection_remove(struct service *service,
    struct service_connection *sconn)
{

        assert(service->s_magic == SERVICE_MAGIC);
        assert(sconn->sc_magic == SERVICE_CONNECTION_MAGIC);

        TAILQ_REMOVE(&service->s_connections, sconn, sc_next);
        sconn->sc_magic = 0;
        nvlist_destroy(sconn->sc_limits);
        cap_close(sconn->sc_chan);
        free(sconn);
}

int
service_connection_clone(struct service *service,
    struct service_connection *sconn)
{
        struct service_connection *newsconn;
        int serrno, sock[2];

        if (socketpair(PF_UNIX, SOCK_STREAM | SOCK_NONBLOCK, 0, sock) < 0)
                return (-1);

        newsconn = service_connection_add(service, sock[0],
            service_connection_get_limits(sconn));
        if (newsconn == NULL) {
                serrno = errno;
                close(sock[0]);
                close(sock[1]);
                errno = serrno;
                return (-1);
        }

        return (sock[1]);
}

struct service_connection *
service_connection_first(struct service *service)
{
        struct service_connection *sconn;

        assert(service->s_magic == SERVICE_MAGIC);

        sconn = TAILQ_FIRST(&service->s_connections);
        assert(sconn == NULL ||
            sconn->sc_magic == SERVICE_CONNECTION_MAGIC);
        return (sconn);
}

struct service_connection *
service_connection_next(struct service_connection *sconn)
{

        assert(sconn->sc_magic == SERVICE_CONNECTION_MAGIC);

        sconn = TAILQ_NEXT(sconn, sc_next);
        assert(sconn == NULL ||
            sconn->sc_magic == SERVICE_CONNECTION_MAGIC);
        return (sconn);
}

cap_channel_t *
service_connection_get_chan(const struct service_connection *sconn)
{

        assert(sconn->sc_magic == SERVICE_CONNECTION_MAGIC);

        return (sconn->sc_chan);
}

int
service_connection_get_sock(const struct service_connection *sconn)
{

        assert(sconn->sc_magic == SERVICE_CONNECTION_MAGIC);

        return (cap_sock(sconn->sc_chan));
}

const nvlist_t *
service_connection_get_limits(const struct service_connection *sconn)
{

        assert(sconn->sc_magic == SERVICE_CONNECTION_MAGIC);

        return (sconn->sc_limits);
}

void
service_connection_set_limits(struct service_connection *sconn,
    nvlist_t *limits)
{

        assert(sconn->sc_magic == SERVICE_CONNECTION_MAGIC);

        nvlist_destroy(sconn->sc_limits);
        sconn->sc_limits = limits;
}

void
service_message(struct service *service, struct service_connection *sconn)
{
        nvlist_t *nvlin, *nvlout;
        const char *cmd;
        int error, flags;

        flags = 0;
        if ((service->s_flags & CASPER_SERVICE_NO_UNIQ_LIMITS) != 0)
                flags = NV_FLAG_NO_UNIQUE;

        nvlin = cap_recv_nvlist(service_connection_get_chan(sconn));
        if (nvlin == NULL) {
                service_connection_remove(service, sconn);
                return;
        }

        error = EDOOFUS;
        nvlout = nvlist_create(flags);

        cmd = nvlist_get_string(nvlin, "cmd");
        if (strcmp(cmd, "limit_set") == 0) {
                nvlist_t *nvllim;

                nvllim = nvlist_take_nvlist(nvlin, "limits");
                if (service->s_limit == NULL) {
                        error = EOPNOTSUPP;
                } else {
                        error = service->s_limit(
                            service_connection_get_limits(sconn), nvllim);
                }
                if (error == 0) {
                        service_connection_set_limits(sconn, nvllim);
                        /* Function consumes nvllim. */
                } else {
                        nvlist_destroy(nvllim);
                }
        } else if (strcmp(cmd, "limit_get") == 0) {
                const nvlist_t *nvllim;

                nvllim = service_connection_get_limits(sconn);
                if (nvllim != NULL)
                        nvlist_add_nvlist(nvlout, "limits", nvllim);
                else
                        nvlist_add_null(nvlout, "limits");
                error = 0;
        } else if (strcmp(cmd, "clone") == 0) {
                int sock;

                sock = service_connection_clone(service, sconn);
                if (sock == -1) {
                        error = errno;
                } else {
                        nvlist_move_descriptor(nvlout, "sock", sock);
                        error = 0;
                }
        } else {
                error = service->s_command(cmd,
                    service_connection_get_limits(sconn), nvlin, nvlout);
        }

        nvlist_destroy(nvlin);
        nvlist_add_number(nvlout, "error", (uint64_t)error);

        if (cap_send_nvlist(service_connection_get_chan(sconn), nvlout) == -1)
                service_connection_remove(service, sconn);

        nvlist_destroy(nvlout);
}

static int
fd_add(fd_set *fdsp, int maxfd, int fd)
{

        FD_SET(fd, fdsp);
        return (fd > maxfd ? fd : maxfd);
}

const char *
service_name(struct service *service)
{

        assert(service->s_magic == SERVICE_MAGIC);
        return (service->s_name);
}

int
service_get_channel_flags(struct service *service)
{
        int flags;

        assert(service->s_magic == SERVICE_MAGIC);
        flags = 0;

        if ((service->s_flags & CASPER_SERVICE_NO_UNIQ_LIMITS) != 0)
                flags |= CASPER_NO_UNIQ;

        return (flags);
}

static void
stdnull(void)
{
        int fd;

        fd = open(_PATH_DEVNULL, O_RDWR);
        if (fd == -1)
                errx(1, "Unable to open %s", _PATH_DEVNULL);

        if (setsid() == -1)
                errx(1, "Unable to detach from session");

        if (dup2(fd, STDIN_FILENO) == -1)
                errx(1, "Unable to cover stdin");
        if (dup2(fd, STDOUT_FILENO) == -1)
                errx(1, "Unable to cover stdout");
        if (dup2(fd, STDERR_FILENO) == -1)
                errx(1, "Unable to cover stderr");

        if (fd > STDERR_FILENO)
                close(fd);
}

static void
service_clean(int *sockp, int *procfdp, uint64_t flags)
{
        int fd, maxfd, minfd;

        fd_fix_environment(sockp);
        fd_fix_environment(procfdp);

        assert(*sockp > STDERR_FILENO);
        assert(*procfdp > STDERR_FILENO);
        assert(*sockp != *procfdp);

        if ((flags & CASPER_SERVICE_STDIO) == 0)
                stdnull();

        if ((flags & CASPER_SERVICE_FD) == 0) {
                if (*procfdp > *sockp) {
                        maxfd = *procfdp;
                        minfd = *sockp;
                } else {
                        maxfd = *sockp;
                        minfd = *procfdp;
                }

                for (fd = STDERR_FILENO + 1; fd < maxfd; fd++) {
                        if (fd != minfd)
                                close(fd);
                }
                closefrom(maxfd + 1);
        }
}

void
service_start(struct service *service, int sock, int procfd)
{
        struct service_connection *sconn, *sconntmp;
        fd_set fds;
        int maxfd, nfds;

        assert(service != NULL);
        assert(service->s_magic == SERVICE_MAGIC);
        setproctitle("%s", service->s_name);
        service_clean(&sock, &procfd, service->s_flags);

        if (service_connection_add(service, sock, NULL) == NULL)
                _exit(1);

        for (;;) {
                FD_ZERO(&fds);
                maxfd = -1;
                for (sconn = service_connection_first(service); sconn != NULL;
                    sconn = service_connection_next(sconn)) {
                        maxfd = fd_add(&fds, maxfd,
                            service_connection_get_sock(sconn));
                }

                assert(maxfd >= 0);
                assert(maxfd + 1 <= (int)FD_SETSIZE);
                nfds = select(maxfd + 1, &fds, NULL, NULL, NULL);
                if (nfds < 0) {
                        if (errno != EINTR)
                                _exit(1);
                        continue;
                } else if (nfds == 0) {
                        /* Timeout. */
                        abort();
                }

                for (sconn = service_connection_first(service); sconn != NULL;
                    sconn = sconntmp) {
                        /*
                         * Prepare for connection to be removed from the list
                         * on failure.
                         */
                        sconntmp = service_connection_next(sconn);
                        if (FD_ISSET(service_connection_get_sock(sconn), &fds))
                                service_message(service, sconn);
                }
                if (service_connection_first(service) == NULL) {
                        /*
                         * No connections left, exiting.
                         */
                        break;
                }
        }

        _exit(0);
}