/*
 * Copyright 2026, Vincent Douillet <vincent@vdouillet.fr>
 *
 * 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.
 *
 * 3. Neither the name of the copyright holder nor the names of its contributors
 * may be used to endorse or promote products derived from this software without
 * specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS 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 COPYRIGHT HOLDER 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 <linux/landlock.h>
#include <sys/prctl.h>
#include <sys/syscall.h>

#include <fcntl.h>
#include <stddef.h>

#include "vll_sandbox.h"

/*
 * TODO add missing accesses to deny them by default.
 * Also move inside vll_create_ruleset
 */
static struct landlock_ruleset_attr ruleset_attr = {
    .handled_access_fs =
        LANDLOCK_ACCESS_FS_WRITE_FILE |
        LANDLOCK_ACCESS_FS_READ_FILE |
        LANDLOCK_ACCESS_FS_READ_DIR |
        LANDLOCK_ACCESS_FS_REMOVE_DIR |
        LANDLOCK_ACCESS_FS_REMOVE_FILE |
        LANDLOCK_ACCESS_FS_MAKE_DIR |
        LANDLOCK_ACCESS_FS_MAKE_REG,
};

int
vll_create_ruleset()
{
    int abi;

    abi = syscall(SYS_landlock_create_ruleset, NULL, 0,
            LANDLOCK_CREATE_RULESET_VERSION);
    if (abi < 0)
        return -1;

    return syscall(SYS_landlock_create_ruleset, &ruleset_attr,
            sizeof(ruleset_attr), 0);
}

int
vll_add_rule(int ruleset_fd, const char *path, const char perm)
{
    int err;
    struct landlock_path_beneath_attr path_beneath;

    path_beneath.allowed_access = 0;
    if (perm & VLL_READ)
        path_beneath.allowed_access |= LANDLOCK_ACCESS_FS_READ_FILE |
            LANDLOCK_ACCESS_FS_READ_DIR;
    if (perm & VLL_WRITE)
        path_beneath.allowed_access |= LANDLOCK_ACCESS_FS_WRITE_FILE |
            LANDLOCK_ACCESS_FS_REMOVE_DIR | LANDLOCK_ACCESS_FS_REMOVE_FILE |
            LANDLOCK_ACCESS_FS_MAKE_DIR | LANDLOCK_ACCESS_FS_MAKE_REG;

    if (!path_beneath.allowed_access)
        return -1;

    path_beneath.parent_fd = open(path, O_CLOEXEC);
    if (path_beneath.parent_fd < 0)
        return -1;

    err = syscall(SYS_landlock_add_rule, ruleset_fd,
            LANDLOCK_RULE_PATH_BENEATH, &path_beneath, 0);
    close(path_beneath.parent_fd);
    if (err)
        return -1;

    return 0;
}

int
vll_restrict_self(int ruleset_fd)
{
    int ret;

    ret = 0;
    if (prctl(PR_SET_NO_NEW_PRIVS, 1, 0, 0, 0)) {
        ret = -1;
        goto end;
    }
    if (syscall(SYS_landlock_restrict_self, ruleset_fd, 0)) {
        ret = -1;
        goto end;
    }

    end:
    close(ruleset_fd);
    return ret;
}