/usr/src/xtables-addons-2.6/extensions/pknock/libxt_pknock.c is in xtables-addons-dkms 2.6-1.
This file is owned by root:root, with mode 0o644.
The actual contents of the file can be viewed below.
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* Shared library add-on to iptables to add Port Knocking and SPA matching
* support.
*
* (C) 2006-2009 J. Federico Hernandez <fede.hernandez@gmail.com>
* (C) 2006 Luis Floreani <luis.floreani@gmail.com>
*
* This program is released under the terms of GNU GPL version 2.
*/
#include <getopt.h>
#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#include <xtables.h>
#include <linux/netfilter.h>
#include <linux/netfilter_ipv4/ip_tables.h>
#include "xt_pknock.h"
#include "compat_user.h"
static const struct option pknock_mt_opts[] = {
/* .name, .has_arg, .flag, .val */
{.name = "knockports", .has_arg = true, .val = 'k'},
{.name = "time", .has_arg = true, .val = 't'},
{.name = "autoclose", .has_arg = true, .val = 'a'},
{.name = "name", .has_arg = true, .val = 'n'},
{.name = "opensecret", .has_arg = true, .val = 'o'},
{.name = "closesecret", .has_arg = true, .val = 'z'},
{.name = "strict", .has_arg = false, .val = 'x'},
{.name = "checkip", .has_arg = false, .val = 'c'},
{NULL},
};
static void pknock_mt_help(void)
{
printf("pknock match options:\n"
" --knockports port[,port,port,...] "
"Matches destination port(s).\n"
" --time seconds\n"
"Max allowed time between knocks.\n"
" --autoclose minutes\n"
"Time after which to automatically close opened\n"
"\t\t\t\t\tport(s).\n"
" --strict "
"Knocks sequence must be exact.\n"
" --name rule_name "
"Rule name.\n"
" --checkip "
"Matches if the source ip is in the list.\n"
);
}
static unsigned int
parse_ports(const char *portstring, uint16_t *ports, const char *proto)
{
char *buffer, *cp, *next;
unsigned int i;
buffer = strdup(portstring);
if (buffer == NULL)
xtables_error(OTHER_PROBLEM, "strdup failed");
for (cp = buffer, i = 0; cp != NULL && i < XT_PKNOCK_MAX_PORTS; cp = next, ++i)
{
next=strchr(cp, ',');
if (next != NULL)
*next++ = '\0';
ports[i] = xtables_parse_port(cp, proto);
}
if (cp != NULL)
xtables_error(PARAMETER_PROBLEM, "too many ports specified");
free(buffer);
return i;
}
static char *
proto_to_name(uint8_t proto)
{
switch (proto) {
case IPPROTO_TCP:
return "tcp";
case IPPROTO_UDP:
return "udp";
default:
return NULL;
}
}
static const char *
check_proto(uint16_t pnum, uint8_t invflags)
{
char *proto;
if (invflags & XT_INV_PROTO)
xtables_error(PARAMETER_PROBLEM, PKNOCK "only works with TCP and UDP.");
if ((proto = proto_to_name(pnum)) != NULL)
return proto;
else if (pnum == 0)
xtables_error(PARAMETER_PROBLEM, PKNOCK "needs `-p tcp' or `-p udp'");
else
xtables_error(PARAMETER_PROBLEM, PKNOCK "only works with TCP and UDP.");
}
static int
__pknock_parse(int c, char **argv, int invert, unsigned int *flags,
struct xt_entry_match **match, uint16_t pnum,
uint16_t invflags)
{
const char *proto;
struct xt_pknock_mtinfo *info = (void *)(*match)->data;
unsigned int tmp;
switch (c) {
case 'k': /* --knockports */
if (*flags & XT_PKNOCK_KNOCKPORT)
xtables_error(PARAMETER_PROBLEM, PKNOCK
"cannot use --knockports twice.\n");
proto = check_proto(pnum, invflags);
info->ports_count = parse_ports(optarg, info->port, proto);
info->option |= XT_PKNOCK_KNOCKPORT;
*flags |= XT_PKNOCK_KNOCKPORT;
#if DEBUG
printf("ports_count: %d\n", info->ports_count);
#endif
break;
case 't': /* --time */
if (*flags & XT_PKNOCK_TIME)
xtables_error(PARAMETER_PROBLEM, PKNOCK
"cannot use --time twice.\n");
info->max_time = atoi(optarg);
if (info->max_time == 0)
xtables_error(PARAMETER_PROBLEM, PKNOCK
"--time number must be > 0.\n");
info->option |= XT_PKNOCK_TIME;
*flags |= XT_PKNOCK_TIME;
break;
case 'a': /* --autoclose */
if (*flags & XT_PKNOCK_AUTOCLOSE)
xtables_error(PARAMETER_PROBLEM, PKNOCK
"cannot use --autoclose twice.\n");
if (!xtables_strtoui(optarg, NULL, &tmp, 0, ~0U))
xtables_param_act(XTF_BAD_VALUE, PKNOCK,
"--autoclose", optarg);
info->autoclose_time = tmp;
info->option |= XT_PKNOCK_AUTOCLOSE;
*flags |= XT_PKNOCK_AUTOCLOSE;
break;
case 'n': /* --name */
if (*flags & XT_PKNOCK_NAME)
xtables_error(PARAMETER_PROBLEM, PKNOCK
"cannot use --name twice.\n");
memset(info->rule_name, 0, sizeof(info->rule_name));
strncpy(info->rule_name, optarg, sizeof(info->rule_name) - 1);
info->rule_name_len = strlen(info->rule_name);
info->option |= XT_PKNOCK_NAME;
*flags |= XT_PKNOCK_NAME;
#if DEBUG
printf("info->rule_name: %s\n", info->rule_name);
#endif
break;
case 'o': /* --opensecret */
if (*flags & XT_PKNOCK_OPENSECRET)
xtables_error(PARAMETER_PROBLEM, PKNOCK
"cannot use --opensecret twice.\n");
memset(info->open_secret, 0, sizeof(info->open_secret));
strncpy(info->open_secret, optarg, sizeof(info->open_secret) - 1);
info->open_secret_len = strlen(info->open_secret);
info->option |= XT_PKNOCK_OPENSECRET;
*flags |= XT_PKNOCK_OPENSECRET;
break;
case 'z': /* --closesecret */
if (*flags & XT_PKNOCK_CLOSESECRET)
xtables_error(PARAMETER_PROBLEM, PKNOCK
"cannot use --closesecret twice.\n");
memset(info->close_secret, 0, sizeof(info->close_secret));
strncpy(info->close_secret, optarg, sizeof(info->close_secret) - 1);
info->close_secret_len = strlen(info->close_secret);
info->option |= XT_PKNOCK_CLOSESECRET;
*flags |= XT_PKNOCK_CLOSESECRET;
break;
case 'c': /* --checkip */
if (*flags & XT_PKNOCK_CHECKIP)
xtables_error(PARAMETER_PROBLEM, PKNOCK
"cannot use --checkip twice.\n");
info->option |= XT_PKNOCK_CHECKIP;
*flags |= XT_PKNOCK_CHECKIP;
break;
case 'x': /* --strict */
if (*flags & XT_PKNOCK_STRICT)
xtables_error(PARAMETER_PROBLEM, PKNOCK
"cannot use --strict twice.\n");
info->option |= XT_PKNOCK_STRICT;
*flags |= XT_PKNOCK_STRICT;
break;
default:
return 0;
}
if (invert)
xtables_error(PARAMETER_PROBLEM, PKNOCK "does not support invert.");
return 1;
}
static int pknock_mt_parse(int c, char **argv, int invert, unsigned int *flags,
const void *e, struct xt_entry_match **match)
{
const struct ipt_entry *entry = e;
return __pknock_parse(c, argv, invert, flags, match,
entry->ip.proto, entry->ip.invflags);
}
static void pknock_mt_check(unsigned int flags)
{
if (!(flags & XT_PKNOCK_NAME))
xtables_error(PARAMETER_PROBLEM, PKNOCK
"--name option is required.\n");
if (flags & XT_PKNOCK_KNOCKPORT) {
if (flags & XT_PKNOCK_CHECKIP)
xtables_error(PARAMETER_PROBLEM, PKNOCK
"cannot specify --knockports with --checkip.\n");
if ((flags & XT_PKNOCK_OPENSECRET)
&& !(flags & XT_PKNOCK_CLOSESECRET))
xtables_error(PARAMETER_PROBLEM, PKNOCK
"--opensecret must go with --closesecret.\n");
if ((flags & XT_PKNOCK_CLOSESECRET)
&& !(flags & XT_PKNOCK_OPENSECRET))
xtables_error(PARAMETER_PROBLEM, PKNOCK
"--closesecret must go with --opensecret.\n");
}
if (flags & XT_PKNOCK_CHECKIP) {
if (flags & XT_PKNOCK_KNOCKPORT)
xtables_error(PARAMETER_PROBLEM, PKNOCK
"cannot specify --checkip with --knockports.\n");
if ((flags & XT_PKNOCK_OPENSECRET)
|| (flags & XT_PKNOCK_CLOSESECRET))
xtables_error(PARAMETER_PROBLEM, PKNOCK
"cannot specify --opensecret and"
" --closesecret with --checkip.\n");
if (flags & XT_PKNOCK_TIME)
xtables_error(PARAMETER_PROBLEM, PKNOCK
"cannot specify --time with --checkip.\n");
if (flags & XT_PKNOCK_AUTOCLOSE)
xtables_error(PARAMETER_PROBLEM, PKNOCK
"cannot specify --autoclose with --checkip.\n");
} else if (!(flags & (XT_PKNOCK_OPENSECRET | XT_PKNOCK_TIME))) {
xtables_error(PARAMETER_PROBLEM, PKNOCK
"you must specify --time.\n");
}
}
static void pknock_mt_print(const void *ip,
const struct xt_entry_match *match, int numeric)
{
const struct xt_pknock_mtinfo *info = (void *)match->data;
int i;
printf(" pknock ");
if (info->option & XT_PKNOCK_KNOCKPORT) {
printf("knockports ");
for (i = 0; i < info->ports_count; ++i)
printf("%s%d", i ? "," : "", info->port[i]);
printf(" ");
}
if (info->option & XT_PKNOCK_TIME)
printf("time %ld ", (long)info->max_time);
if (info->option & XT_PKNOCK_AUTOCLOSE)
printf("autoclose %lu ", (unsigned long)info->autoclose_time);
if (info->option & XT_PKNOCK_NAME)
printf("name %s ", info->rule_name);
if (info->option & XT_PKNOCK_OPENSECRET)
printf("opensecret ");
if (info->option & XT_PKNOCK_CLOSESECRET)
printf("closesecret ");
if (info->option & XT_PKNOCK_STRICT)
printf("strict ");
if (info->option & XT_PKNOCK_CHECKIP)
printf("checkip ");
}
static void pknock_mt_save(const void *ip, const struct xt_entry_match *match)
{
int i;
const struct xt_pknock_mtinfo *info = (void *)match->data;
if (info->option & XT_PKNOCK_KNOCKPORT) {
printf(" --knockports ");
for (i = 0; i < info->ports_count; ++i)
printf("%s%d", i ? "," : "", info->port[i]);
printf(" ");
}
if (info->option & XT_PKNOCK_TIME)
printf(" --time %ld ", (long)info->max_time);
if (info->option & XT_PKNOCK_AUTOCLOSE)
printf(" --autoclose %lu ",
(unsigned long)info->autoclose_time);
if (info->option & XT_PKNOCK_NAME)
printf(" --name %s ", info->rule_name);
if (info->option & XT_PKNOCK_OPENSECRET)
printf(" --opensecret ");
if (info->option & XT_PKNOCK_CLOSESECRET)
printf(" --closesecret ");
if (info->option & XT_PKNOCK_STRICT)
printf(" --strict ");
if (info->option & XT_PKNOCK_CHECKIP)
printf(" --checkip ");
}
static struct xtables_match pknock_mt_reg = {
.name = "pknock",
.version = XTABLES_VERSION,
.revision = 1,
.family = NFPROTO_IPV4,
.size = XT_ALIGN(sizeof(struct xt_pknock_mtinfo)),
.userspacesize = XT_ALIGN(sizeof(struct xt_pknock_mtinfo)),
.help = pknock_mt_help,
.parse = pknock_mt_parse,
.final_check = pknock_mt_check,
.print = pknock_mt_print,
.save = pknock_mt_save,
.extra_opts = pknock_mt_opts,
};
static __attribute__((constructor)) void pknock_mt_ldr(void)
{
xtables_register_match(&pknock_mt_reg);
}
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