/*-
 * SPDX-License-Identifier: BSD-2-Clause
 *
 * Copyright (c) 2010 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 "namespace.h"
#include <sys/endian.h>
#include <sys/stat.h>
#include <sys/uio.h>
#include <errno.h>
#include <fcntl.h>
#include <stdio.h>
#include <string.h>
#include <unistd.h>
#include <utmpx.h>
#include "utxdb.h"
#include "un-namespace.h"

static FILE *
futx_open(const char *file)
{
        FILE *fp;
        struct stat sb;
        int fd;

        fd = _open(file, O_CREAT|O_RDWR|O_EXLOCK|O_CLOEXEC, 0644);
        if (fd < 0)
                return (NULL);

        /* Safety check: never use broken files. */
        if (_fstat(fd, &sb) != -1 && sb.st_size % sizeof(struct futx) != 0) {
                _close(fd);
                errno = EFTYPE;
                return (NULL);
        }

        fp = fdopen(fd, "r+");
        if (fp == NULL) {
                _close(fd);
                return (NULL);
        }
        return (fp);
}

static int
utx_active_add(const struct futx *fu)
{
        FILE *fp;
        struct futx fe;
        off_t partial;
        int error, ret;

        partial = -1;
        ret = 0;

        /*
         * Register user login sessions.  Overwrite entries of sessions
         * that have already been terminated.
         */
        fp = futx_open(_PATH_UTX_ACTIVE);
        if (fp == NULL)
                return (-1);
        while (fread(&fe, sizeof(fe), 1, fp) == 1) {
                switch (fe.fu_type) {
                case BOOT_TIME:
                        /* Leave these intact. */
                        break;
                case USER_PROCESS:
                case INIT_PROCESS:
                case LOGIN_PROCESS:
                case DEAD_PROCESS:
                        /* Overwrite when ut_id matches. */
                        if (memcmp(fu->fu_id, fe.fu_id, sizeof(fe.fu_id)) ==
                            0) {
                                ret = fseeko(fp, -(off_t)sizeof(fe), SEEK_CUR);
                                goto exact;
                        }
                        if (fe.fu_type != DEAD_PROCESS)
                                break;
                        /* FALLTHROUGH */
                default:
                        /* Allow us to overwrite unused records. */
                        if (partial == -1) {
                                partial = ftello(fp);
                                /*
                                 * Distinguish errors from valid values so we
                                 * don't overwrite good data by accident.
                                 */
                                if (partial != -1)
                                        partial -= (off_t)sizeof(fe);
                        }
                        break;
                }
        }

        /*
         * No exact match found.  Use the partial match.  If no partial
         * match was found, just append a new record.
         */
        if (partial != -1)
                ret = fseeko(fp, partial, SEEK_SET);
exact:
        if (ret == -1)
                error = errno;
        else if (fwrite(fu, sizeof(*fu), 1, fp) < 1)
                error = errno;
        else
                error = 0;
        fclose(fp);
        if (error != 0)
                errno = error;
        return (error == 0 ? 0 : 1);
}

static int
utx_active_remove(struct futx *fu)
{
        FILE *fp;
        struct futx fe;
        int error, ret;

        /*
         * Remove user login sessions, having the same ut_id.
         */
        fp = futx_open(_PATH_UTX_ACTIVE);
        if (fp == NULL)
                return (-1);
        error = ESRCH;
        ret = -1;
        while (fread(&fe, sizeof(fe), 1, fp) == 1 && ret != 0)
                switch (fe.fu_type) {
                case USER_PROCESS:
                case INIT_PROCESS:
                case LOGIN_PROCESS:
                        if (memcmp(fu->fu_id, fe.fu_id, sizeof(fe.fu_id)) != 0)
                                continue;

                        /* Terminate session. */
                        if (fseeko(fp, -(off_t)sizeof(fe), SEEK_CUR) == -1)
                                error = errno;
                        else if (fwrite(fu, sizeof(*fu), 1, fp) < 1)
                                error = errno;
                        else
                                ret = 0;

                }

        fclose(fp);
        if (ret != 0)
                errno = error;
        return (ret);
}

static void
utx_active_init(const struct futx *fu)
{
        int fd;

        /* Initialize utx.active with a single BOOT_TIME record. */
        fd = _open(_PATH_UTX_ACTIVE, O_CREAT|O_RDWR|O_TRUNC, 0644);
        if (fd < 0)
                return;
        _write(fd, fu, sizeof(*fu));
        _close(fd);
}

static void
utx_active_purge(void)
{

        truncate(_PATH_UTX_ACTIVE, 0);
}

static int
utx_lastlogin_add(const struct futx *fu)
{
        struct futx fe;
        FILE *fp;
        int error, ret;

        ret = 0;

        /*
         * Write an entry to lastlogin.  Overwrite the entry if the
         * current user already has an entry.  If not, append a new
         * entry.
         */
        fp = futx_open(_PATH_UTX_LASTLOGIN);
        if (fp == NULL)
                return (-1);
        while (fread(&fe, sizeof fe, 1, fp) == 1) {
                if (strncmp(fu->fu_user, fe.fu_user, sizeof fe.fu_user) != 0)
                        continue;

                /* Found a previous lastlogin entry for this user. */
                ret = fseeko(fp, -(off_t)sizeof fe, SEEK_CUR);
                break;
        }
        if (ret == -1)
                error = errno;
        else if (fwrite(fu, sizeof *fu, 1, fp) < 1) {
                error = errno;
                ret = -1;
        }
        fclose(fp);
        if (ret == -1)
                errno = error;
        return (ret);
}

static void
utx_lastlogin_upgrade(void)
{
        struct stat sb;
        int fd;

        fd = _open(_PATH_UTX_LASTLOGIN, O_RDWR|O_CLOEXEC, 0644);
        if (fd < 0)
                return;

        /*
         * Truncate broken lastlogin files.  In the future we should
         * check for older versions of the file format here and try to
         * upgrade it.
         */
        if (_fstat(fd, &sb) != -1 && sb.st_size % sizeof(struct futx) != 0)
                ftruncate(fd, 0);
        _close(fd);
}

static int
utx_log_add(const struct futx *fu)
{
        struct iovec vec[2];
        int error, fd;
        uint16_t l;

        /*
         * Append an entry to the log file.  We only need to append
         * records to this file, so to conserve space, trim any trailing
         * zero-bytes.  Prepend a length field, indicating the length of
         * the record, excluding the length field itself.
         */
        for (l = sizeof(*fu); l > 0 && ((const char *)fu)[l - 1] == '\0'; l--) ;
        vec[0].iov_base = &l;
        vec[0].iov_len = sizeof(l);
        vec[1].iov_base = __DECONST(void *, fu);
        vec[1].iov_len = l;
        l = htobe16(l);

        fd = _open(_PATH_UTX_LOG, O_CREAT|O_WRONLY|O_APPEND|O_CLOEXEC, 0644);
        if (fd < 0)
                return (-1);
        if (_writev(fd, vec, 2) == -1)
                error = errno;
        else
                error = 0;
        _close(fd);
        if (error != 0)
                errno = error;
        return (error == 0 ? 0 : 1);
}

struct utmpx *
pututxline(const struct utmpx *utmpx)
{
        struct futx fu;
        int bad;

        bad = 0;

        utx_to_futx(utmpx, &fu);

        switch (fu.fu_type) {
        case BOOT_TIME:
                utx_active_init(&fu);
                utx_lastlogin_upgrade();
                break;
        case SHUTDOWN_TIME:
                utx_active_purge();
                break;
        case OLD_TIME:
        case NEW_TIME:
                break;
        case USER_PROCESS:
                bad |= utx_active_add(&fu);
                bad |= utx_lastlogin_add(&fu);
                break;
#if 0 /* XXX: Are these records of any use to us? */
        case INIT_PROCESS:
        case LOGIN_PROCESS:
                bad |= utx_active_add(&fu);
                break;
#endif
        case DEAD_PROCESS:
                /*
                 * In case writing a logout entry fails, never attempt
                 * to write it to utx.log.  The logout entry's ut_id
                 * might be invalid.
                 */
                if (utx_active_remove(&fu) != 0)
                        return (NULL);
                break;
        default:
                errno = EINVAL;
                return (NULL);
        }

        bad |= utx_log_add(&fu);
        return (bad ? NULL : futx_to_utx(&fu));
}