// SPDX-License-Identifier: GPL-2.0-or-later
/* IRC extension for IP connection tracking, Version 1.21
* (C) 2000-2002 by Harald Welte <[email protected]>
* based on RR's ip_conntrack_ftp.c
* (C) 2006-2012 Patrick McHardy <[email protected]>
*/
#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
#include <linux/module.h>
#include <linux/moduleparam.h>
#include <linux/skbuff.h>
#include <linux/in.h>
#include <linux/ip.h>
#include <linux/tcp.h>
#include <linux/netfilter.h>
#include <linux/slab.h>
#include <net/netfilter/nf_conntrack.h>
#include <net/netfilter/nf_conntrack_expect.h>
#include <net/netfilter/nf_conntrack_helper.h>
#include <linux/netfilter/nf_conntrack_irc.h>
#define MAX_PORTS 8
static unsigned short ports[MAX_PORTS];
static unsigned int ports_c;
static unsigned int max_dcc_channels = 8;
static unsigned int dcc_timeout __read_mostly = 300;
/* This is slow, but it's simple. --RR */
static char *irc_buffer;
static DEFINE_SPINLOCK(irc_buffer_lock);
unsigned int (*nf_nat_irc_hook)(struct sk_buff *skb,
enum ip_conntrack_info ctinfo,
unsigned int protoff,
unsigned int matchoff,
unsigned int matchlen,
struct nf_conntrack_expect *exp) __read_mostly;
EXPORT_SYMBOL_GPL(nf_nat_irc_hook);
#define HELPER_NAME "irc"
#define MAX_SEARCH_SIZE 4095
MODULE_AUTHOR("Harald Welte <[email protected]>");
MODULE_DESCRIPTION("IRC (DCC) connection tracking helper");
MODULE_LICENSE("GPL");
MODULE_ALIAS("ip_conntrack_irc");
MODULE_ALIAS_NFCT_HELPER(HELPER_NAME);
module_param_array(ports, ushort, &ports_c, 0400);
MODULE_PARM_DESC(ports, "port numbers of IRC servers");
module_param(max_dcc_channels, uint, 0400);
MODULE_PARM_DESC(max_dcc_channels, "max number of expected DCC channels per "
"IRC session");
module_param(dcc_timeout, uint, 0400);
MODULE_PARM_DESC(dcc_timeout, "timeout on for unestablished DCC channels");
static const char *const dccprotos[] = {
"SEND ", "CHAT ", "MOVE ", "TSEND ", "SCHAT "
};
#define MINMATCHLEN 5
/* tries to get the ip_addr and port out of a dcc command
* return value: -1 on failure, 0 on success
* data pointer to first byte of DCC command data
* data_end pointer to last byte of dcc command data
* ip returns parsed ip of dcc command
* port returns parsed port of dcc command
* ad_beg_p returns pointer to first byte of addr data
* ad_end_p returns pointer to last byte of addr data
*/
static int parse_dcc(char *data, const char *data_end, __be32 *ip,
u_int16_t *port, char **ad_beg_p, char **ad_end_p)
{
char *tmp;
/* at least 12: "AAAAAAAA P\1\n" */
while (*data++ != ' ')
if (data > data_end - 12)
return -1;
/* Make sure we have a newline character within the packet boundaries
* because simple_strtoul parses until the first invalid character. */
for (tmp = data; tmp <= data_end; tmp++)
if (*tmp == '\n')
break;
if (tmp > data_end || *tmp != '\n')
return -1;
*ad_beg_p = data;
*ip = cpu_to_be32(simple_strtoul(data, &data, 10));
/* skip blanks between ip and port */
while (*data == ' ') {
if (data >= data_end)
return -1;
data++;
}
*port = simple_strtoul(data, &data, 10);
*ad_end_p = data;
return 0;
}
static int help(struct sk_buff *skb, unsigned int protoff,
struct nf_conn *ct, enum ip_conntrack_info ctinfo)
{
unsigned int dataoff;
const struct iphdr *iph;
const struct tcphdr *th;
struct tcphdr _tcph;
const char *data_limit;
char *data, *ib_ptr;
int dir = CTINFO2DIR(ctinfo);
struct nf_conntrack_expect *exp;
struct nf_conntrack_tuple *tuple;
__be32 dcc_ip;
u_int16_t dcc_port;
__be16 port;
int i, ret = NF_ACCEPT;
char *addr_beg_p, *addr_end_p;
typeof(nf_nat_irc_hook) nf_nat_irc;
unsigned int datalen;
/* If packet is coming from IRC server */
if (dir == IP_CT_DIR_REPLY)
return NF_ACCEPT;
/* Until there's been traffic both ways, don't look in packets. */
if (ctinfo != IP_CT_ESTABLISHED && ctinfo != IP_CT_ESTABLISHED_REPLY)
return NF_ACCEPT;
/* Not a full tcp header? */
th = skb_header_pointer(skb, protoff, sizeof(_tcph), &_tcph);
if (th == NULL)
return NF_ACCEPT;
/* No data? */
dataoff = protoff + th->doff*4;
if (dataoff >= skb->len)
return NF_ACCEPT;
datalen = skb->len - dataoff;
if (datalen > MAX_SEARCH_SIZE)
datalen = MAX_SEARCH_SIZE;
spin_lock_bh(&irc_buffer_lock);
ib_ptr = skb_header_pointer(skb, dataoff, datalen,
irc_buffer);
if (!ib_ptr) {
spin_unlock_bh(&irc_buffer_lock);
return NF_ACCEPT;
}
data = ib_ptr;
data_limit = ib_ptr + datalen;
/* Skip any whitespace */
while (data < data_limit - 10) {
if (*data == ' ' || *data == '\r' || *data == '\n')
data++;
else
break;
}
/* strlen("PRIVMSG x ")=10 */
if (data < data_limit - 10) {
if (strncasecmp("PRIVMSG ", data, 8))
goto out;
data += 8;
}
/* strlen(" :\1DCC SENT t AAAAAAAA P\1\n")=26
* 7+MINMATCHLEN+strlen("t AAAAAAAA P\1\n")=26
*/
while (data < data_limit - (21 + MINMATCHLEN)) {
/* Find first " :", the start of message */
if (memcmp(data, " :", 2)) {
data++;
continue;
}
data += 2;
/* then check that place only for the DCC command */
if (memcmp(data, "\1DCC ", 5))
goto out;
data += 5;
/* we have at least (21+MINMATCHLEN)-(2+5) bytes valid data left */
iph = ip_hdr(skb);
pr_debug("DCC found in master %pI4:%u %pI4:%u\n",
&iph->saddr, ntohs(th->source),
&iph->daddr, ntohs(th->dest));
for (i = 0; i < ARRAY_SIZE(dccprotos); i++) {
if (memcmp(data, dccprotos[i], strlen(dccprotos[i]))) {
/* no match */
continue;
}
data += strlen(dccprotos[i]);
pr_debug("DCC %s detected\n", dccprotos[i]);
/* we have at least
* (21+MINMATCHLEN)-7-dccprotos[i].matchlen bytes valid
* data left (== 14/13 bytes) */
if (parse_dcc(data, data_limit, &dcc_ip,
&dcc_port, &addr_beg_p, &addr_end_p)) {
pr_debug("unable to parse dcc command\n");
continue;
}
pr_debug("DCC bound ip/port: %pI4:%u\n",
&dcc_ip, dcc_port);
/* dcc_ip can be the internal OR external (NAT'ed) IP */
tuple = &ct->tuplehash[dir].tuple;
if ((tuple->src.u3.ip != dcc_ip &&
ct->tuplehash[!dir].tuple.dst.u3.ip != dcc_ip) ||
dcc_port == 0) {
net_warn_ratelimited("Forged DCC command from %pI4: %pI4:%u\n",
&tuple->src.u3.ip,
&dcc_ip, dcc_port);
continue;
}
exp = nf_ct_expect_alloc(ct);
if (exp == NULL) {
nf_ct_helper_log(skb, ct,
"cannot alloc expectation");
ret = NF_DROP;
goto out;
}
tuple = &ct->tuplehash[!dir].tuple;
port = htons(dcc_port);
nf_ct_expect_init(exp, NF_CT_EXPECT_CLASS_DEFAULT,
tuple->src.l3num,
NULL, &tuple->dst.u3,
IPPROTO_TCP, NULL, &port);
nf_nat_irc = rcu_dereference(nf_nat_irc_hook);
if (nf_nat_irc && ct->status & IPS_NAT_MASK)
ret = nf_nat_irc(skb, ctinfo, protoff,
addr_beg_p - ib_ptr,
addr_end_p - addr_beg_p,
exp);
else if (nf_ct_expect_related(exp, 0) != 0) {
nf_ct_helper_log(skb, ct,
"cannot add expectation");
ret = NF_DROP;
}
nf_ct_expect_put(exp);
goto out;
}
}
out:
spin_unlock_bh(&irc_buffer_lock);
return ret;
}
static struct nf_conntrack_helper irc[MAX_PORTS] __read_mostly;
static struct nf_conntrack_expect_policy irc_exp_policy;
static int __init nf_conntrack_irc_init(void)
{
int i, ret;
if (max_dcc_channels < 1) {
pr_err("max_dcc_channels must not be zero\n");
return -EINVAL;
}
if (max_dcc_channels > NF_CT_EXPECT_MAX_CNT) {
pr_err("max_dcc_channels must not be more than %u\n",
NF_CT_EXPECT_MAX_CNT);
return -EINVAL;
}
irc_exp_policy.max_expected = max_dcc_channels;
irc_exp_policy.timeout = dcc_timeout;
irc_buffer = kmalloc(MAX_SEARCH_SIZE + 1, GFP_KERNEL);
if (!irc_buffer)
return -ENOMEM;
/* If no port given, default to standard irc port */
if (ports_c == 0)
ports[ports_c++] = IRC_PORT;
for (i = 0; i < ports_c; i++) {
nf_ct_helper_init(&irc[i], AF_INET, IPPROTO_TCP, HELPER_NAME,
IRC_PORT, ports[i], i, &irc_exp_policy,
0, help, NULL, THIS_MODULE);
}
ret = nf_conntrack_helpers_register(&irc[0], ports_c);
if (ret) {
pr_err("failed to register helpers\n");
kfree(irc_buffer);
return ret;
}
return 0;
}
static void __exit nf_conntrack_irc_fini(void)
{
nf_conntrack_helpers_unregister(irc, ports_c);
kfree(irc_buffer);
}
module_init(nf_conntrack_irc_init);
module_exit(nf_conntrack_irc_fini);
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