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/ip.h> 16 #include <linux/tcp.h> 17 #include <linux/netfilter.h> 18 #include <linux/slab.h> 19 20 #include <net/netfilter/nf_conntrack.h> 21 #include <net/netfilter/nf_conntrack_expect.h> 22 #include <net/netfilter/nf_conntrack_helper.h> 23 #include <linux/netfilter/nf_conntrack_irc.h> 24 25 #define MAX_PORTS 8 26 static unsigned short ports[MAX_PORTS]; 27 static unsigned int ports_c; 28 static unsigned int max_dcc_channels = 8; 29 static unsigned int dcc_timeout __read_mostly = 300; 30 /* This is slow, but it's simple. --RR */ 31 static char *irc_buffer; 32 static DEFINE_SPINLOCK(irc_buffer_lock); 33 34 unsigned int (*nf_nat_irc_hook)(struct sk_buff *skb, 35 enum ip_conntrack_info ctinfo, 36 unsigned int protoff, 37 unsigned int matchoff, 38 unsigned int matchlen, 39 struct nf_conntrack_expect *exp) __read_mostly; 40 EXPORT_SYMBOL_GPL(nf_nat_irc_hook); 41 42 MODULE_AUTHOR("Harald Welte <laforge@netfilter.org>"); 43 MODULE_DESCRIPTION("IRC (DCC) connection tracking helper"); 44 MODULE_LICENSE("GPL"); 45 MODULE_ALIAS("ip_conntrack_irc"); 46 MODULE_ALIAS_NFCT_HELPER("irc"); 47 48 module_param_array(ports, ushort, &ports_c, 0400); 49 MODULE_PARM_DESC(ports, "port numbers of IRC servers"); 50 module_param(max_dcc_channels, uint, 0400); 51 MODULE_PARM_DESC(max_dcc_channels, "max number of expected DCC channels per " 52 "IRC session"); 53 module_param(dcc_timeout, uint, 0400); 54 MODULE_PARM_DESC(dcc_timeout, "timeout on for unestablished DCC channels"); 55 56 static const char *const dccprotos[] = { 57 "SEND ", "CHAT ", "MOVE ", "TSEND ", "SCHAT " 58 }; 59 60 #define MINMATCHLEN 5 61 62 /* tries to get the ip_addr and port out of a dcc command 63 * return value: -1 on failure, 0 on success 64 * data pointer to first byte of DCC command data 65 * data_end pointer to last byte of dcc command data 66 * ip returns parsed ip of dcc command 67 * port returns parsed port of dcc command 68 * ad_beg_p returns pointer to first byte of addr data 69 * ad_end_p returns pointer to last byte of addr data 70 */ 71 static int parse_dcc(char *data, const char *data_end, __be32 *ip, 72 u_int16_t *port, char **ad_beg_p, char **ad_end_p) 73 { 74 char *tmp; 75 76 /* at least 12: "AAAAAAAA P\1\n" */ 77 while (*data++ != ' ') 78 if (data > data_end - 12) 79 return -1; 80 81 /* Make sure we have a newline character within the packet boundaries 82 * because simple_strtoul parses until the first invalid character. */ 83 for (tmp = data; tmp <= data_end; tmp++) 84 if (*tmp == '\n') 85 break; 86 if (tmp > data_end || *tmp != '\n') 87 return -1; 88 89 *ad_beg_p = data; 90 *ip = cpu_to_be32(simple_strtoul(data, &data, 10)); 91 92 /* skip blanks between ip and port */ 93 while (*data == ' ') { 94 if (data >= data_end) 95 return -1; 96 data++; 97 } 98 99 *port = simple_strtoul(data, &data, 10); 100 *ad_end_p = data; 101 102 return 0; 103 } 104 105 static int help(struct sk_buff *skb, unsigned int protoff, 106 struct nf_conn *ct, enum ip_conntrack_info ctinfo) 107 { 108 unsigned int dataoff; 109 const struct iphdr *iph; 110 const struct tcphdr *th; 111 struct tcphdr _tcph; 112 const char *data_limit; 113 char *data, *ib_ptr; 114 int dir = CTINFO2DIR(ctinfo); 115 struct nf_conntrack_expect *exp; 116 struct nf_conntrack_tuple *tuple; 117 __be32 dcc_ip; 118 u_int16_t dcc_port; 119 __be16 port; 120 int i, ret = NF_ACCEPT; 121 char *addr_beg_p, *addr_end_p; 122 typeof(nf_nat_irc_hook) nf_nat_irc; 123 124 /* If packet is coming from IRC server */ 125 if (dir == IP_CT_DIR_REPLY) 126 return NF_ACCEPT; 127 128 /* Until there's been traffic both ways, don't look in packets. */ 129 if (ctinfo != IP_CT_ESTABLISHED && ctinfo != IP_CT_ESTABLISHED_REPLY) 130 return NF_ACCEPT; 131 132 /* Not a full tcp header? */ 133 th = skb_header_pointer(skb, protoff, sizeof(_tcph), &_tcph); 134 if (th == NULL) 135 return NF_ACCEPT; 136 137 /* No data? */ 138 dataoff = protoff + th->doff*4; 139 if (dataoff >= skb->len) 140 return NF_ACCEPT; 141 142 spin_lock_bh(&irc_buffer_lock); 143 ib_ptr = skb_header_pointer(skb, dataoff, skb->len - dataoff, 144 irc_buffer); 145 BUG_ON(ib_ptr == NULL); 146 147 data = ib_ptr; 148 data_limit = ib_ptr + skb->len - dataoff; 149 150 /* strlen("\1DCC SENT t AAAAAAAA P\1\n")=24 151 * 5+MINMATCHLEN+strlen("t AAAAAAAA P\1\n")=14 */ 152 while (data < data_limit - (19 + MINMATCHLEN)) { 153 if (memcmp(data, "\1DCC ", 5)) { 154 data++; 155 continue; 156 } 157 data += 5; 158 /* we have at least (19+MINMATCHLEN)-5 bytes valid data left */ 159 160 iph = ip_hdr(skb); 161 pr_debug("DCC found in master %pI4:%u %pI4:%u\n", 162 &iph->saddr, ntohs(th->source), 163 &iph->daddr, ntohs(th->dest)); 164 165 for (i = 0; i < ARRAY_SIZE(dccprotos); i++) { 166 if (memcmp(data, dccprotos[i], strlen(dccprotos[i]))) { 167 /* no match */ 168 continue; 169 } 170 data += strlen(dccprotos[i]); 171 pr_debug("DCC %s detected\n", dccprotos[i]); 172 173 /* we have at least 174 * (19+MINMATCHLEN)-5-dccprotos[i].matchlen bytes valid 175 * data left (== 14/13 bytes) */ 176 if (parse_dcc(data, data_limit, &dcc_ip, 177 &dcc_port, &addr_beg_p, &addr_end_p)) { 178 pr_debug("unable to parse dcc command\n"); 179 continue; 180 } 181 182 pr_debug("DCC bound ip/port: %pI4:%u\n", 183 &dcc_ip, dcc_port); 184 185 /* dcc_ip can be the internal OR external (NAT'ed) IP */ 186 tuple = &ct->tuplehash[dir].tuple; 187 if (tuple->src.u3.ip != dcc_ip && 188 tuple->dst.u3.ip != dcc_ip) { 189 net_warn_ratelimited("Forged DCC command from %pI4: %pI4:%u\n", 190 &tuple->src.u3.ip, 191 &dcc_ip, dcc_port); 192 continue; 193 } 194 195 exp = nf_ct_expect_alloc(ct); 196 if (exp == NULL) { 197 ret = NF_DROP; 198 goto out; 199 } 200 tuple = &ct->tuplehash[!dir].tuple; 201 port = htons(dcc_port); 202 nf_ct_expect_init(exp, NF_CT_EXPECT_CLASS_DEFAULT, 203 tuple->src.l3num, 204 NULL, &tuple->dst.u3, 205 IPPROTO_TCP, NULL, &port); 206 207 nf_nat_irc = rcu_dereference(nf_nat_irc_hook); 208 if (nf_nat_irc && ct->status & IPS_NAT_MASK) 209 ret = nf_nat_irc(skb, ctinfo, protoff, 210 addr_beg_p - ib_ptr, 211 addr_end_p - addr_beg_p, 212 exp); 213 else if (nf_ct_expect_related(exp) != 0) 214 ret = NF_DROP; 215 nf_ct_expect_put(exp); 216 goto out; 217 } 218 } 219 out: 220 spin_unlock_bh(&irc_buffer_lock); 221 return ret; 222 } 223 224 static struct nf_conntrack_helper irc[MAX_PORTS] __read_mostly; 225 static struct nf_conntrack_expect_policy irc_exp_policy; 226 227 static void nf_conntrack_irc_fini(void); 228 229 static int __init nf_conntrack_irc_init(void) 230 { 231 int i, ret; 232 233 if (max_dcc_channels < 1) { 234 printk(KERN_ERR "nf_ct_irc: max_dcc_channels must not be zero\n"); 235 return -EINVAL; 236 } 237 238 irc_exp_policy.max_expected = max_dcc_channels; 239 irc_exp_policy.timeout = dcc_timeout; 240 241 irc_buffer = kmalloc(65536, GFP_KERNEL); 242 if (!irc_buffer) 243 return -ENOMEM; 244 245 /* If no port given, default to standard irc port */ 246 if (ports_c == 0) 247 ports[ports_c++] = IRC_PORT; 248 249 for (i = 0; i < ports_c; i++) { 250 irc[i].tuple.src.l3num = AF_INET; 251 irc[i].tuple.src.u.tcp.port = htons(ports[i]); 252 irc[i].tuple.dst.protonum = IPPROTO_TCP; 253 irc[i].expect_policy = &irc_exp_policy; 254 irc[i].me = THIS_MODULE; 255 irc[i].help = help; 256 257 if (ports[i] == IRC_PORT) 258 sprintf(irc[i].name, "irc"); 259 else 260 sprintf(irc[i].name, "irc-%u", i); 261 262 ret = nf_conntrack_helper_register(&irc[i]); 263 if (ret) { 264 printk(KERN_ERR "nf_ct_irc: failed to register helper " 265 "for pf: %u port: %u\n", 266 irc[i].tuple.src.l3num, ports[i]); 267 nf_conntrack_irc_fini(); 268 return ret; 269 } 270 } 271 return 0; 272 } 273 274 /* This function is intentionally _NOT_ defined as __exit, because 275 * it is needed by the init function */ 276 static void nf_conntrack_irc_fini(void) 277 { 278 int i; 279 280 for (i = 0; i < ports_c; i++) 281 nf_conntrack_helper_unregister(&irc[i]); 282 kfree(irc_buffer); 283 } 284 285 module_init(nf_conntrack_irc_init); 286 module_exit(nf_conntrack_irc_fini); 287