ladybird/Userland/utmpupdate.cpp

/*
 * Copyright (c) 2020, Andreas Kling <kling@serenityos.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 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 <AK/JsonObject.h>
#include <AK/JsonValue.h>
#include <LibCore/ArgsParser.h>
#include <LibCore/DateTime.h>
#include <LibCore/File.h>

int main(int argc, char** argv)
{
    if (pledge("stdio wpath cpath", nullptr) < 0) {
        perror("pledge");
        return 1;
    }

    if (unveil("/var/run/utmp", "rwc") < 0) {
        perror("unveil");
        return 1;
    }

    unveil(nullptr, nullptr);

    pid_t pid = 0;
    bool flag_create = false;
    bool flag_delete = false;
    const char* tty_name = nullptr;
    const char* from = nullptr;

    Core::ArgsParser args_parser;
    args_parser.add_option(flag_create, "Create entry", "create", 'c');
    args_parser.add_option(flag_delete, "Delete entry", "delete", 'd');
    args_parser.add_option(pid, "PID", "PID", 'p', "PID");
    args_parser.add_option(from, "From", "from", 'f', "From");
    args_parser.add_positional_argument(tty_name, "TTY name", "tty");

    args_parser.parse(argc, argv);

    if (flag_create && flag_delete) {
        warn() << "-c and -d are mutually exclusive";
        return 1;
    }

    dbg() << "Updating utmp from UID=" << getuid() << " GID=" << getgid() << " EGID=" << getegid() << " PID=" << pid;

    auto file_or_error = Core::File::open("/var/run/utmp", Core::IODevice::ReadWrite);
    if (file_or_error.is_error()) {
        dbg() << "Error: " << file_or_error.error();
        return 1;
    }

    auto& file = *file_or_error.value();

    auto file_contents = file.read_all();
    auto previous_json = JsonValue::from_string(file_contents);

    JsonObject json;

    if (!previous_json.has_value() || !previous_json.value().is_object()) {
        dbg() << "Error: Could not parse JSON";
    } else {
        json = previous_json.value().as_object();
    }

    if (flag_create) {
        JsonObject entry;
        entry.set("pid", pid);
        entry.set("uid", getuid());
        entry.set("from", from);
        entry.set("login_at", time(nullptr));
        json.set(tty_name, move(entry));
    } else {
        ASSERT(flag_delete);
        dbg() << "Removing " << tty_name << " from utmp";
        json.remove(tty_name);
    }

    if (!file.seek(0)) {
        dbg() << "Seek failed";
        return 1;
    }

    if (!file.truncate(0)) {
        dbg() << "Truncation failed";
        return 1;
    }

    if (!file.write(json.to_string())) {
        dbg() << "Write failed";
        return 1;
    }

    return 0;
}