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Add a reworked IPv4 options match - xt_ipv4options
This revision 1 of ipv4options makes it possible to match the presence or absence of any of the 32 possible IP options, either all or any of the options the user specified.
This commit is contained in:
Jan Engelhardt
177
extensions/libxt_ipv4options.c
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177
extensions/libxt_ipv4options.c
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/*
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* "ipv4options" match extension for iptables
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* Coprygith © Jan Engelhardt, 2009
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*
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* This program is free software; you can redistribute it and/or
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* modify it under the terms of the GNU General Public License; either
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* version 2 of the License, or any later version, as published by the
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* Free Software Foundation.
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*/
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#include <getopt.h>
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#include <stdbool.h>
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#include <stdint.h>
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#include <stdio.h>
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#include <string.h>
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#include <xtables.h>
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#include "xt_ipv4options.h"
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/*
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* Overview from http://www.networksorcery.com/enp/protocol/ip.htm
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* Not providing strings for options that seem to be most distant in the past.
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*/
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static const char *const v4opt_names[32] = {
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[ 1] = "nop",
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[ 2] = "security", /* RFC 1108 */
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[ 3] = "lsrr", /* RFC 791 */
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[ 4] = "timestamp", /* RFC 781, 791 */
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[ 7] = "record-route", /* RFC 791 */
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[ 9] = "ssrr", /* RFC 791 */
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[11] = "mtu-probe", /* RFC 1063 */
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[12] = "mtu-reply", /* RFC 1063 */
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[18] = "traceroute", /* RFC 1393 */
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[20] = "router-alert", /* RFC 2113 */
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};
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static void ipv4options_mt_help(void)
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{
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printf(
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"ipv4options match options:\n"
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"--flags [!]symbol[,...] Match presence/absence (!) of option\n"
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" (either by name or number)\n"
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"--any Interpret --flags as OR-combined\n\n");
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}
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static const struct option ipv4options_mt_opts[] = {
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{.name = "flags", .has_arg = true, .val = 'f'},
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{.name = "any", .has_arg = false, .val = 'a'},
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{NULL},
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};
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static void ipv4options_parse_flagspec(struct xt_ipv4options_mtinfo1 *info,
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char *arg)
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{
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unsigned int i, opt;
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bool inv;
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char *p;
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while (true) {
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p = strchr(arg, ',');
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if (p != NULL)
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*p = '\0';
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inv = false;
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opt = 0;
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if (*arg == '!') {
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inv = true;
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++arg;
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}
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for (i = 1; i < 32;++i)
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if (v4opt_names[i] != NULL &&
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strcmp(v4opt_names[i], arg) == 0) {
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opt = i;
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break;
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}
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if (opt == 0 &&
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!strtonum(arg, NULL, &opt, 0, UINT8_MAX))
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exit_error(PARAMETER_PROBLEM,
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"ipv4options: Bad option value \"%s\"", arg);
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if (opt == 0)
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exit_error(PARAMETER_PROBLEM,
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"ipv4options: Option value may not be zero");
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info->map |= (1 << opt);
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if (inv)
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info->invert |= (1 << opt);
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if (p == NULL)
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break;
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arg = p + 1;
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}
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}
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static int ipv4options_mt_parse(int c, char **argv, int invert,
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unsigned int *flags, const void *entry, struct xt_entry_match **match)
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{
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struct xt_ipv4options_mtinfo1 *info = (void *)(*match)->data;
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switch (c) {
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case 'a': /* --any */
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param_act(P_NO_INVERT, "ipv4options", "--any", invert);
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info->flags |= XT_V4OPTS_ANY;
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return true;
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case 'f': /* --flags */
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param_act(P_NO_INVERT, "ipv4options", "--flags", invert);
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ipv4options_parse_flagspec(info, optarg);
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return true;
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}
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return false;
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}
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/* no checking of *flags - no IPv4 options is also valid */
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static void ipv4options_print_flags(const struct xt_ipv4options_mtinfo1 *info,
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bool numeric)
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{
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uint32_t tmp = info->map;
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unsigned int i;
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for (i = 1; i < 32; ++i)
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if (tmp & (1 << i)) {
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if (info->invert & (1 << i))
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printf("!");
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if (!numeric && v4opt_names[i] != NULL)
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printf("%s", v4opt_names[i]);
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else
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printf("%u", i);
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tmp &= ~(1 << i);
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if (tmp)
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printf(",");
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}
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}
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static void ipv4options_mt_print(const void *ip,
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const struct xt_entry_match *match, int numeric)
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{
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const struct xt_ipv4options_mtinfo1 *info = (void *)match->data;
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printf("ipv4options %s ",
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(info->flags & XT_V4OPTS_ANY) ? "any-of" : "all-of");
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ipv4options_print_flags(info, numeric);
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printf(" ");
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}
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static void ipv4options_mt_save(const void *ip,
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const struct xt_entry_match *match)
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{
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const struct xt_ipv4options_mtinfo1 *info = (void *)match->data;
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if (info->map != 0) {
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printf("--flags ");
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ipv4options_print_flags(info, true);
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}
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if (info->flags & XT_V4OPTS_ANY)
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printf(" --any");
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printf(" ");
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}
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static struct xtables_match ipv4options_mt_reg = {
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.version = XTABLES_VERSION,
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.name = "ipv4options",
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.revision = 1,
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.family = PF_INET,
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.size = XT_ALIGN(sizeof(struct xt_ipv4options_mtinfo1)),
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.userspacesize = XT_ALIGN(sizeof(struct xt_ipv4options_mtinfo1)),
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.help = ipv4options_mt_help,
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.parse = ipv4options_mt_parse,
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.print = ipv4options_mt_print,
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.save = ipv4options_mt_save,
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.extra_opts = ipv4options_mt_opts,
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};
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static __attribute__((constructor)) void ipv4options_mt_ldr(void)
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{
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xtables_register_match(&ipv4options_mt_reg);
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}
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