1/* IRC extension for IP connection tracking, Version 1.21 2 * (C) 2000-2002 by Harald Welte <laforge@gnumonks.org> 3 * based on RR's ip_conntrack_ftp.c 4 * 5 * This program is free software; you can redistribute it and/or 6 * modify it under the terms of the GNU General Public License 7 * as published by the Free Software Foundation; either version 8 * 2 of the License, or (at your option) any later version. 9 */ 10 11#include <linux/module.h> 12#include <linux/moduleparam.h> 13#include <linux/skbuff.h> 14#include <linux/in.h> 15#include <linux/tcp.h> 16#include <linux/netfilter.h> 17 18#include <net/netfilter/nf_conntrack.h> 19#include <net/netfilter/nf_conntrack_expect.h> 20#include <net/netfilter/nf_conntrack_helper.h> 21#include <linux/netfilter/nf_conntrack_irc.h> 22 23#define MAX_PORTS 8 24static unsigned short ports[MAX_PORTS]; 25static int ports_c; 26static unsigned int max_dcc_channels = 8; 27static unsigned int dcc_timeout __read_mostly = 300; 28/* This is slow, but it's simple. --RR */ 29static char *irc_buffer; 30static DEFINE_SPINLOCK(irc_buffer_lock); 31 32unsigned int (*nf_nat_irc_hook)(struct sk_buff **pskb, 33 enum ip_conntrack_info ctinfo, 34 unsigned int matchoff, 35 unsigned int matchlen, 36 struct nf_conntrack_expect *exp) __read_mostly; 37EXPORT_SYMBOL_GPL(nf_nat_irc_hook); 38 39MODULE_AUTHOR("Harald Welte <laforge@netfilter.org>"); 40MODULE_DESCRIPTION("IRC (DCC) connection tracking helper"); 41MODULE_LICENSE("GPL"); 42MODULE_ALIAS("ip_conntrack_irc"); 43 44module_param_array(ports, ushort, &ports_c, 0400); 45MODULE_PARM_DESC(ports, "port numbers of IRC servers"); 46module_param(max_dcc_channels, uint, 0400); 47MODULE_PARM_DESC(max_dcc_channels, "max number of expected DCC channels per " 48 "IRC session"); 49module_param(dcc_timeout, uint, 0400); 50MODULE_PARM_DESC(dcc_timeout, "timeout on for unestablished DCC channels"); 51 52static const char *dccprotos[] = { 53 "SEND ", "CHAT ", "MOVE ", "TSEND ", "SCHAT " 54}; 55 56#define MINMATCHLEN 5 57 58#define DEBUGP(format, args...) 59 60/* tries to get the ip_addr and port out of a dcc command 61 * return value: -1 on failure, 0 on success 62 * data pointer to first byte of DCC command data 63 * data_end pointer to last byte of dcc command data 64 * ip returns parsed ip of dcc command 65 * port returns parsed port of dcc command 66 * ad_beg_p returns pointer to first byte of addr data 67 * ad_end_p returns pointer to last byte of addr data 68 */ 69static int parse_dcc(char *data, char *data_end, u_int32_t *ip, 70 u_int16_t *port, char **ad_beg_p, char **ad_end_p) 71{ 72 /* at least 12: "AAAAAAAA P\1\n" */ 73 while (*data++ != ' ') 74 if (data > data_end - 12) 75 return -1; 76 77 *ad_beg_p = data; 78 *ip = simple_strtoul(data, &data, 10); 79 80 /* skip blanks between ip and port */ 81 while (*data == ' ') { 82 if (data >= data_end) 83 return -1; 84 data++; 85 } 86 87 *port = simple_strtoul(data, &data, 10); 88 *ad_end_p = data; 89 90 return 0; 91} 92 93static int help(struct sk_buff **pskb, unsigned int protoff, 94 struct nf_conn *ct, enum ip_conntrack_info ctinfo) 95{ 96 unsigned int dataoff; 97 struct tcphdr _tcph, *th; 98 char *data, *data_limit, *ib_ptr; 99 int dir = CTINFO2DIR(ctinfo); 100 struct nf_conntrack_expect *exp; 101 struct nf_conntrack_tuple *tuple; 102 u_int32_t dcc_ip; 103 u_int16_t dcc_port; 104 __be16 port; 105 int i, ret = NF_ACCEPT; 106 char *addr_beg_p, *addr_end_p; 107 typeof(nf_nat_irc_hook) nf_nat_irc; 108 109 /* If packet is coming from IRC server */ 110 if (dir == IP_CT_DIR_REPLY) 111 return NF_ACCEPT; 112 113 /* Until there's been traffic both ways, don't look in packets. */ 114 if (ctinfo != IP_CT_ESTABLISHED && 115 ctinfo != IP_CT_ESTABLISHED + IP_CT_IS_REPLY) 116 return NF_ACCEPT; 117 118 /* Not a full tcp header? */ 119 th = skb_header_pointer(*pskb, protoff, sizeof(_tcph), &_tcph); 120 if (th == NULL) 121 return NF_ACCEPT; 122 123 /* No data? */ 124 dataoff = protoff + th->doff*4; 125 if (dataoff >= (*pskb)->len) 126 return NF_ACCEPT; 127 128 spin_lock_bh(&irc_buffer_lock); 129 ib_ptr = skb_header_pointer(*pskb, dataoff, (*pskb)->len - dataoff, 130 irc_buffer); 131 BUG_ON(ib_ptr == NULL); 132 133 data = ib_ptr; 134 data_limit = ib_ptr + (*pskb)->len - dataoff; 135 136 /* strlen("\1DCC SENT t AAAAAAAA P\1\n")=24 137 * 5+MINMATCHLEN+strlen("t AAAAAAAA P\1\n")=14 */ 138 while (data < data_limit - (19 + MINMATCHLEN)) { 139 if (memcmp(data, "\1DCC ", 5)) { 140 data++; 141 continue; 142 } 143 data += 5; 144 /* we have at least (19+MINMATCHLEN)-5 bytes valid data left */ 145 146 DEBUGP("DCC found in master %u.%u.%u.%u:%u %u.%u.%u.%u:%u...\n", 147 NIPQUAD(iph->saddr), ntohs(th->source), 148 NIPQUAD(iph->daddr), ntohs(th->dest)); 149 150 for (i = 0; i < ARRAY_SIZE(dccprotos); i++) { 151 if (memcmp(data, dccprotos[i], strlen(dccprotos[i]))) { 152 /* no match */ 153 continue; 154 } 155 data += strlen(dccprotos[i]); 156 DEBUGP("DCC %s detected\n", dccprotos[i]); 157 158 /* we have at least 159 * (19+MINMATCHLEN)-5-dccprotos[i].matchlen bytes valid 160 * data left (== 14/13 bytes) */ 161 if (parse_dcc((char *)data, data_limit, &dcc_ip, 162 &dcc_port, &addr_beg_p, &addr_end_p)) { 163 DEBUGP("unable to parse dcc command\n"); 164 continue; 165 } 166 DEBUGP("DCC bound ip/port: %u.%u.%u.%u:%u\n", 167 HIPQUAD(dcc_ip), dcc_port); 168 169 /* dcc_ip can be the internal OR external (NAT'ed) IP */ 170 tuple = &ct->tuplehash[dir].tuple; 171 if (tuple->src.u3.ip != htonl(dcc_ip) && 172 tuple->dst.u3.ip != htonl(dcc_ip)) { 173 if (net_ratelimit()) 174 printk(KERN_WARNING 175 "Forged DCC command from " 176 "%u.%u.%u.%u: %u.%u.%u.%u:%u\n", 177 NIPQUAD(tuple->src.u3.ip), 178 HIPQUAD(dcc_ip), dcc_port); 179 continue; 180 } 181 182 exp = nf_conntrack_expect_alloc(ct); 183 if (exp == NULL) { 184 ret = NF_DROP; 185 goto out; 186 } 187 tuple = &ct->tuplehash[!dir].tuple; 188 port = htons(dcc_port); 189 nf_conntrack_expect_init(exp, tuple->src.l3num, 190 NULL, &tuple->dst.u3, 191 IPPROTO_TCP, NULL, &port); 192 193 nf_nat_irc = rcu_dereference(nf_nat_irc_hook); 194 if (nf_nat_irc && ct->status & IPS_NAT_MASK) 195 ret = nf_nat_irc(pskb, ctinfo, 196 addr_beg_p - ib_ptr, 197 addr_end_p - addr_beg_p, 198 exp); 199 else if (nf_conntrack_expect_related(exp) != 0) 200 ret = NF_DROP; 201 nf_conntrack_expect_put(exp); 202 goto out; 203 } 204 } 205 out: 206 spin_unlock_bh(&irc_buffer_lock); 207 return ret; 208} 209 210static struct nf_conntrack_helper irc[MAX_PORTS] __read_mostly; 211static char irc_names[MAX_PORTS][sizeof("irc-65535")] __read_mostly; 212 213static void nf_conntrack_irc_fini(void); 214 215static int __init nf_conntrack_irc_init(void) 216{ 217 int i, ret; 218 char *tmpname; 219 220 if (max_dcc_channels < 1) { 221 printk("nf_ct_irc: max_dcc_channels must not be zero\n"); 222 return -EINVAL; 223 } 224 225 irc_buffer = kmalloc(65536, GFP_KERNEL); 226 if (!irc_buffer) 227 return -ENOMEM; 228 229 /* If no port given, default to standard irc port */ 230 if (ports_c == 0) 231 ports[ports_c++] = IRC_PORT; 232 233 for (i = 0; i < ports_c; i++) { 234 irc[i].tuple.src.l3num = AF_INET; 235 irc[i].tuple.src.u.tcp.port = htons(ports[i]); 236 irc[i].tuple.dst.protonum = IPPROTO_TCP; 237 irc[i].mask.src.l3num = 0xFFFF; 238 irc[i].mask.src.u.tcp.port = htons(0xFFFF); 239 irc[i].mask.dst.protonum = 0xFF; 240 irc[i].max_expected = max_dcc_channels; 241 irc[i].timeout = dcc_timeout; 242 irc[i].me = THIS_MODULE; 243 irc[i].help = help; 244 245 tmpname = &irc_names[i][0]; 246 if (ports[i] == IRC_PORT) 247 sprintf(tmpname, "irc"); 248 else 249 sprintf(tmpname, "irc-%u", i); 250 irc[i].name = tmpname; 251 252 ret = nf_conntrack_helper_register(&irc[i]); 253 if (ret) { 254 printk("nf_ct_irc: failed to register helper " 255 "for pf: %u port: %u\n", 256 irc[i].tuple.src.l3num, ports[i]); 257 nf_conntrack_irc_fini(); 258 return ret; 259 } 260 } 261 return 0; 262} 263 264/* This function is intentionally _NOT_ defined as __exit, because 265 * it is needed by the init function */ 266static void nf_conntrack_irc_fini(void) 267{ 268 int i; 269 270 for (i = 0; i < ports_c; i++) 271 nf_conntrack_helper_unregister(&irc[i]); 272 kfree(irc_buffer); 273} 274 275module_init(nf_conntrack_irc_init); 276module_exit(nf_conntrack_irc_fini); 277