ts3init_linux_netfilter_module/src/libxt_ts3init_get_puzzle.c

/*
 *    "ts3init_get_cookie and ts3init_get_puzzle" match extension for iptables
 *    Niels Werensteijn <niels werensteijn [at] teamspeak com>, 2016-10-03
 *
 *    This program is free software; you can redistribute it and/or modify it
 *    under the terms of the GNU General Public License; either version 2
 *    or 3 of the License, as published by the Free Software Foundation.
 */

#include <stdbool.h>
#include <stddef.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <getopt.h>
#include <xtables.h>
#include <fcntl.h>
#include <errno.h>
#include <unistd.h>
#include "ts3init_random_seed.h"
#include "ts3init_match.h"

#define param_act(t, s, f) xtables_param_act((t), "ts3init_get_puzzle", (s), (f))
#define ARRAY_SIZE(x) (sizeof(x) / sizeof(*(x)))

static void ts3init_get_puzzle_help(void)
{
    printf(
        "ts3init_get_puzzle match options:\n"
        "  --min-client n               The client needs to be at least version n.\n"
        "  --check-cookie               Check that the cookie was generated by same seed.\n"
        "  --random-seed <seed>         Seed is a %i byte hex number.\n"
        "                               A source could be /dev/random.\n"
        "  --random-seed-file <file>    Read the seed from a file.\n",
        RANDOM_SEED_LEN
);
}

static const struct option ts3init_get_puzzle_opts[] = {
    {.name = "min-client",        .has_arg = true,  .val = '1'},
    {.name = "check-cookie",      .has_arg = false, .val = '2'},
    {.name = "random-seed",       .has_arg = true,  .val = '3'},
    {.name = "random-seed-file",  .has_arg = true,  .val = '4'},
    {NULL},
};

static int ts3init_get_puzzle_parse(int c, char **argv, int invert, unsigned int *flags,
                           const void *entry, struct xt_entry_match **match)
{
    struct xt_ts3init_get_puzzle_mtinfo *info = (void *)(*match)->data;
    int client_version;

    switch (c) {
    case '1':
        param_act(XTF_ONLY_ONCE, "--min-client", info->common_options & CHK_COMMON_CLIENT_VERSION);
        param_act(XTF_NO_INVERT, "--min-client", invert);
        client_version = atoi(optarg);
        if (client_version <= 0)
            xtables_error(PARAMETER_PROBLEM,
                "ts3init_get_cookie: invalid min-client version");
        info->common_options |= CHK_COMMON_CLIENT_VERSION;
        info->min_client_version = client_version - CLIENT_VERSION_OFFSET;
        return true;

    case '2':
        param_act(XTF_ONLY_ONCE, "--check-cookie", info->specific_options & CHK_GET_PUZZLE_CHECK_COOKIE);
        param_act(XTF_NO_INVERT, "--check-cookie", invert);
        info->specific_options |= CHK_GET_PUZZLE_CHECK_COOKIE;
        *flags |= CHK_GET_PUZZLE_CHECK_COOKIE;
        return true;

    case '3':
        param_act(XTF_ONLY_ONCE, "--random-seed", info->specific_options & CHK_GET_PUZZLE_RANDOM_SEED_FROM_ARGUMENT);
        param_act(XTF_NO_INVERT, "--random-seed", invert);
        if (strlen(optarg) != (RANDOM_SEED_LEN * 2))
            xtables_error(PARAMETER_PROBLEM,
                "ts3init_get_puzzle: invalid random seed length");
        if (!parse_random_seed(optarg, info->random_seed))
            xtables_error(PARAMETER_PROBLEM,
                "ts3init_get_puzzle: invalid random seed. (not lowercase hex)");
        info->specific_options |= CHK_GET_PUZZLE_RANDOM_SEED_FROM_ARGUMENT;
        *flags |= CHK_GET_PUZZLE_RANDOM_SEED_FROM_ARGUMENT;
        return true;

    case '4':
        param_act(XTF_ONLY_ONCE, "--random-seed-file", info->specific_options & CHK_GET_PUZZLE_RANDOM_SEED_FROM_FILE);
        param_act(XTF_NO_INVERT, "--random-seed-file", invert);

        if (read_random_seed_from_file("ts3init_get_puzzle", optarg, info->random_seed))
            memcpy(info->random_seed_path, optarg, strlen(optarg) + 1);
        info->specific_options |= CHK_GET_PUZZLE_RANDOM_SEED_FROM_FILE;
        *flags |= CHK_GET_PUZZLE_RANDOM_SEED_FROM_FILE;
        return true;

    default:
        return false;
    }
}

static void ts3init_get_puzzle_save(const void *ip, const struct xt_entry_match *match)
{
    int i;
    const struct xt_ts3init_get_puzzle_mtinfo *info = (const void *)match->data;
    if (info->common_options & CHK_COMMON_CLIENT_VERSION)
    {
        printf(" --min-client %u", info->min_client_version + CLIENT_VERSION_OFFSET);
    }
    if (info->specific_options & CHK_GET_PUZZLE_CHECK_COOKIE)
    {
        printf(" --check-cookie");
    }
    if (info->specific_options & CHK_GET_PUZZLE_RANDOM_SEED_FROM_ARGUMENT)
    {
        printf(" --random-seed ");
        for (i = 0; i < RANDOM_SEED_LEN; i++)
        {
                printf("%02X", info->random_seed[i]);
        }
    }
    if (info->specific_options & CHK_GET_PUZZLE_RANDOM_SEED_FROM_FILE)
    {
        printf(" --random-seed-file \"%s\"", info->random_seed_path);
    }
}

static void ts3init_get_puzzle_print(const void *ip, const struct xt_entry_match *match,
                            int numeric)
{
    printf(" -m ts3init_get_puzzle");
    ts3init_get_puzzle_save(ip, match);
}

static void ts3init_get_puzzle_check(unsigned int flags)
{
    bool seed_from_argument = flags & CHK_GET_PUZZLE_RANDOM_SEED_FROM_ARGUMENT;
    bool seed_from_file = flags & CHK_GET_PUZZLE_RANDOM_SEED_FROM_FILE;
    if (seed_from_argument && seed_from_file)
    {
        xtables_error(PARAMETER_PROBLEM,
            "ts3init_get_puzzle: --random-seed and --random-seed-file "
            "can not be specified at the same time");
    }
    if (flags & CHK_GET_PUZZLE_CHECK_COOKIE)
    {
        if (!seed_from_argument && !seed_from_file)
        {
            xtables_error(PARAMETER_PROBLEM,
                "ts3init_get_puzzle: --check-cookie requires either "
                "--random-seed or --random-seed-file");
        }
    }
}

/* register and init */
static struct xtables_match ts3init_mt_reg[] =
{
    {
        .name          = "ts3init_get_puzzle",
        .revision      = 0,
        .family        = NFPROTO_IPV4,
        .version       = XTABLES_VERSION,
        .size          = XT_ALIGN(sizeof(struct xt_ts3init_get_puzzle_mtinfo)),
        .userspacesize = XT_ALIGN(sizeof(struct xt_ts3init_get_puzzle_mtinfo)),
        .help          = ts3init_get_puzzle_help,
        .parse         = ts3init_get_puzzle_parse,
        .print         = ts3init_get_puzzle_print,
        .save          = ts3init_get_puzzle_save,
        .extra_opts    = ts3init_get_puzzle_opts,
        .final_check   = ts3init_get_puzzle_check,
    },
    {
        .name          = "ts3init_get_puzzle",
        .revision      = 0,
        .family        = NFPROTO_IPV6,
        .version       = XTABLES_VERSION,
        .size          = XT_ALIGN(sizeof(struct xt_ts3init_get_puzzle_mtinfo)),
        .userspacesize = XT_ALIGN(sizeof(struct xt_ts3init_get_puzzle_mtinfo)),
        .help          = ts3init_get_puzzle_help,
        .parse         = ts3init_get_puzzle_parse,
        .print         = ts3init_get_puzzle_print,
        .save          = ts3init_get_puzzle_save,
        .extra_opts    = ts3init_get_puzzle_opts,
        .final_check   = ts3init_get_puzzle_check,
    }
};

static __attribute__((constructor)) void ts3init_mt_ldr(void)
{
    xtables_register_matches(ts3init_mt_reg, ARRAY_SIZE(ts3init_mt_reg));
}