r4sas/ts3init_linux_netfilter_module
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Added new target: TS3INIT_MORPH_TO_GET_COOKIE. Its rewrites an incomming packet into a TS3INIT_GET_COOKIE.

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*/
This commit is contained in:
Maximilian Münchow 2016-10-13 16:17:49 +02:00
parent 52cc424be2
commit 716f509066
3 changed files with 184 additions and 3 deletions
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3
src/Makefile.xtables
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@ -1,6 +1,5 @@
CFLAGS = -O2 -Wall
LIBS = libxt_ts3init_get_cookie.so libxt_ts3init_get_puzzle.so libxt_TS3INIT_RESET.so libxt_TS3INIT_SET_COOKIE.so
LIBS = libxt_ts3init_get_cookie.so libxt_ts3init_get_puzzle.so libxt_TS3INIT_RESET.so libxt_TS3INIT_SET_COOKIE.so libxt_TS3INIT_MORPH_TO_GET_COOKIE.so
all: $(LIBS)
clean:

53
src/libxt_TS3INIT_MORPH_TO_GET_COOKIE.c Normal file
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@ -0,0 +1,53 @@
/*
* "libxt_ts3init_reset" target 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_cookie_seed.h"
#include "ts3init_target.h"
static void ts3init_morph_to_get_cookie_help(void)
{
printf("TS3INIT_MORPH_TO_GET_COOKIE takes no options\n\n");
}
static int ts3init_morph_to_get_cookie_parse(int c, char **argv, int invert, unsigned int *flags,
const void *entry, struct xt_entry_target **target)
{
return false;
}
static void ts3init_morph_to_get_cookie_check(unsigned int flags)
{
}
/* register and init */
static struct xtables_target ts3init_morph_to_get_cookie_tg_reg =
{
.name = "TS3INIT_MORPH_TO_GET_COOKIE",
.revision = 0,
.family = NFPROTO_UNSPEC,
.version = XTABLES_VERSION,
.help = ts3init_morph_to_get_cookie_help,
.parse = ts3init_morph_to_get_cookie_parse,
.final_check = ts3init_morph_to_get_cookie_check,
};
static __attribute__((constructor)) void ts3init_morph_to_get_cookie_tg_ldr(void)
{
xtables_register_target(&ts3init_morph_to_get_cookie_tg_reg);
}

131
src/ts3init_target.c
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@ -20,6 +20,7 @@
#ifdef CONFIG_BRIDGE_NETFILTER
# include <linux/netfilter_bridge.h>
#endif
#include <linux/random.h>
#include <net/ip.h>
#include <net/ip6_checksum.h>
#include <net/ip6_route.h>
@ -378,7 +379,119 @@ static int ts3init_set_cookie_tg_check(const struct xt_tgchk_param *par)
}
return 0;
}
}
static inline void
ts3init_fill_get_cookie_payload(u8 *payload)
{
time_t current_unix_time = ts3init_get_cached_unix_time();
payload[TS3INIT_HEADER_CLIENT_LENGTH - 1] = COMMAND_GET_COOKIE;
payload[TS3INIT_HEADER_CLIENT_LENGTH + 0] = current_unix_time << 24;
payload[TS3INIT_HEADER_CLIENT_LENGTH + 1] = current_unix_time << 16;
payload[TS3INIT_HEADER_CLIENT_LENGTH + 2] = current_unix_time << 8;
payload[TS3INIT_HEADER_CLIENT_LENGTH + 3] = current_unix_time;
get_random_bytes(&payload[TS3INIT_HEADER_CLIENT_LENGTH + 4], 4);
memset(&payload[TS3INIT_HEADER_CLIENT_LENGTH + 8], 0, 8);
}
/*
* The 'TS3INIT_MORPH_TO_GET_COOKIE' target handler.
* Morphes the incomming packet into a TS3INIT_GET_COOKIE
*/
static unsigned int
ts3init_morph_to_get_cookie_ipv4_tg(struct sk_buff *skb, const struct xt_action_param *par)
{
struct iphdr *ip;
struct udphdr *udp, udp_buf;
u8 *payload, payload_buf[TS3INIT_HEADER_CLIENT_LENGTH + 16];
unsigned int data_len;
int length_difference;
if (!skb_make_writable(skb, 0))
return NF_DROP;
ip = ip_hdr(skb);
udp = skb_header_pointer(skb, par->thoff, sizeof(udp_buf), &udp_buf);
if (udp == NULL)
return NF_DROP;
if (ip->frag_off & htons(IP_OFFSET))
return NF_DROP;
data_len = ntohs(udp->len) - sizeof(*udp);
if (data_len < 1 || data_len > 512)
return NF_DROP;
length_difference = sizeof(payload_buf) - data_len;
if (length_difference > 0)
skb_put(skb, length_difference);
else if (length_difference < 0)
skb_trim(skb, skb->len + length_difference);
payload = skb_header_pointer(skb, par->thoff + sizeof(udp), sizeof(payload_buf), payload_buf);
ts3init_fill_get_cookie_payload(payload);
udp->len = htons(sizeof(*udp) + sizeof(payload_buf));
udp->check = 0;
udp->check = csum_tcpudp_magic(ip->saddr, ip->daddr,
ntohs(udp->len), IPPROTO_UDP,
csum_partial(udp, ntohs(udp->len), 0));
ip->tot_len = htons(skb->len);
skb->ip_summed = CHECKSUM_NONE;
if (skb->len > dst_mtu(skb_dst(skb)))
return NF_DROP;
return NF_ACCEPT;
}
/*
* The 'TS3INIT_MORPH_TO_GET_COOKIE' target handler.
* Morphes the incomming packet into a TS3INIT_GET_COOKIE
*/
static unsigned int
ts3init_morph_to_get_cookie_ipv6_tg(struct sk_buff *skb, const struct xt_action_param *par)
{
struct ipv6hdr *ip;
struct udphdr *udp, udp_buf;
u8 *payload, payload_buf[TS3INIT_HEADER_CLIENT_LENGTH + 16];
unsigned int data_len;
int length_difference;
if (!skb_make_writable(skb, 0))
return NF_DROP;
ip = ipv6_hdr(skb);
udp = skb_header_pointer(skb, par->thoff, sizeof(udp_buf), &udp_buf);
if (udp == NULL)
return NF_DROP;
data_len = ntohs(udp->len) - sizeof(*udp);
if (data_len < 1 || data_len > 512)
return NF_DROP;
length_difference = sizeof(payload_buf) - data_len;
if (length_difference > 0)
skb_put(skb, length_difference);
else if (length_difference < 0)
skb_trim(skb, skb->len + length_difference);
payload = skb_header_pointer(skb, par->thoff + sizeof(udp), sizeof(payload_buf), payload_buf);
ts3init_fill_get_cookie_payload(payload);
udp->len = htons(sizeof(*udp) + sizeof(payload_buf));
udp->check = 0;
udp->check = csum_ipv6_magic(&ip->saddr, &ip->daddr,
ntohs(udp->len), IPPROTO_UDP,
csum_partial(udp, ntohs(udp->len), 0));
ip->payload_len = htons(skb->len);
skb->ip_summed = CHECKSUM_NONE;
if (skb->len > dst_mtu(skb_dst(skb)))
return NF_DROP;
return NF_ACCEPT;
}
static struct xt_target ts3init_tg_reg[] __read_mostly = {
{
@ -417,6 +530,22 @@ static struct xt_target ts3init_tg_reg[] __read_mostly = {
.checkentry = ts3init_set_cookie_tg_check,
.me = THIS_MODULE,
},
{
.name = "TS3INIT_MORPH_TO_GET_COOKIE",
.revision = 0,
.family = NFPROTO_IPV4,
.proto = IPPROTO_UDP,
.target = ts3init_morph_to_get_cookie_ipv4_tg,
.me = THIS_MODULE,
},
{
.name = "TS3INIT_MORPH_TO_GET_COOKIE",
.revision = 0,
.family = NFPROTO_IPV6,
.proto = IPPROTO_UDP,
.target = ts3init_morph_to_get_cookie_ipv6_tg,
.me = THIS_MODULE,
},
};
int ts3init_target_init(void)