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 matchoff, 37 unsigned int matchlen, 38 struct nf_conntrack_expect *exp) __read_mostly; 39 EXPORT_SYMBOL_GPL(nf_nat_irc_hook); 40 41 MODULE_AUTHOR("Harald Welte <laforge@netfilter.org>"); 42 MODULE_DESCRIPTION("IRC (DCC) connection tracking helper"); 43 MODULE_LICENSE("GPL"); 44 MODULE_ALIAS("ip_conntrack_irc"); 45 MODULE_ALIAS_NFCT_HELPER("irc"); 46 47 module_param_array(ports, ushort, &ports_c, 0400); 48 MODULE_PARM_DESC(ports, "port numbers of IRC servers"); 49 module_param(max_dcc_channels, uint, 0400); 50 MODULE_PARM_DESC(max_dcc_channels, "max number of expected DCC channels per " 51 "IRC session"); 52 module_param(dcc_timeout, uint, 0400); 53 MODULE_PARM_DESC(dcc_timeout, "timeout on for unestablished DCC channels"); 54 55 static const char *const dccprotos[] = { 56 "SEND ", "CHAT ", "MOVE ", "TSEND ", "SCHAT " 57 }; 58 59 #define MINMATCHLEN 5 60 61 /* tries to get the ip_addr and port out of a dcc command 62 * return value: -1 on failure, 0 on success 63 * data pointer to first byte of DCC command data 64 * data_end pointer to last byte of dcc command data 65 * ip returns parsed ip of dcc command 66 * port returns parsed port of dcc command 67 * ad_beg_p returns pointer to first byte of addr data 68 * ad_end_p returns pointer to last byte of addr data 69 */ 70 static int parse_dcc(char *data, const char *data_end, __be32 *ip, 71 u_int16_t *port, char **ad_beg_p, char **ad_end_p) 72 { 73 char *tmp; 74 75 /* at least 12: "AAAAAAAA P\1\n" */ 76 while (*data++ != ' ') 77 if (data > data_end - 12) 78 return -1; 79 80 /* Make sure we have a newline character within the packet boundaries 81 * because simple_strtoul parses until the first invalid character. */ 82 for (tmp = data; tmp <= data_end; tmp++) 83 if (*tmp == '\n') 84 break; 85 if (tmp > data_end || *tmp != '\n') 86 return -1; 87 88 *ad_beg_p = data; 89 *ip = cpu_to_be32(simple_strtoul(data, &data, 10)); 90 91 /* skip blanks between ip and port */ 92 while (*data == ' ') { 93 if (data >= data_end) 94 return -1; 95 data++; 96 } 97 98 *port = simple_strtoul(data, &data, 10); 99 *ad_end_p = data; 100 101 return 0; 102 } 103 104 static int help(struct sk_buff *skb, unsigned int protoff, 105 struct nf_conn *ct, enum ip_conntrack_info ctinfo) 106 { 107 unsigned int dataoff; 108 const struct iphdr *iph; 109 const struct tcphdr *th; 110 struct tcphdr _tcph; 111 const char *data_limit; 112 char *data, *ib_ptr; 113 int dir = CTINFO2DIR(ctinfo); 114 struct nf_conntrack_expect *exp; 115 struct nf_conntrack_tuple *tuple; 116 __be32 dcc_ip; 117 u_int16_t dcc_port; 118 __be16 port; 119 int i, ret = NF_ACCEPT; 120 char *addr_beg_p, *addr_end_p; 121 typeof(nf_nat_irc_hook) nf_nat_irc; 122 123 /* If packet is coming from IRC server */ 124 if (dir == IP_CT_DIR_REPLY) 125 return NF_ACCEPT; 126 127 /* Until there's been traffic both ways, don't look in packets. */ 128 if (ctinfo != IP_CT_ESTABLISHED && 129 ctinfo != IP_CT_ESTABLISHED + IP_CT_IS_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 if (net_ratelimit()) 190 printk(KERN_WARNING 191 "Forged DCC command from %pI4: %pI4:%u\n", 192 &tuple->src.u3.ip, 193 &dcc_ip, dcc_port); 194 continue; 195 } 196 197 exp = nf_ct_expect_alloc(ct); 198 if (exp == NULL) { 199 ret = NF_DROP; 200 goto out; 201 } 202 tuple = &ct->tuplehash[!dir].tuple; 203 port = htons(dcc_port); 204 nf_ct_expect_init(exp, NF_CT_EXPECT_CLASS_DEFAULT, 205 tuple->src.l3num, 206 NULL, &tuple->dst.u3, 207 IPPROTO_TCP, NULL, &port); 208 209 nf_nat_irc = rcu_dereference(nf_nat_irc_hook); 210 if (nf_nat_irc && ct->status & IPS_NAT_MASK) 211 ret = nf_nat_irc(skb, ctinfo, 212 addr_beg_p - ib_ptr, 213 addr_end_p - addr_beg_p, 214 exp); 215 else if (nf_ct_expect_related(exp) != 0) 216 ret = NF_DROP; 217 nf_ct_expect_put(exp); 218 goto out; 219 } 220 } 221 out: 222 spin_unlock_bh(&irc_buffer_lock); 223 return ret; 224 } 225 226 static struct nf_conntrack_helper irc[MAX_PORTS] __read_mostly; 227 static char irc_names[MAX_PORTS][sizeof("irc-65535")] __read_mostly; 228 static struct nf_conntrack_expect_policy irc_exp_policy; 229 230 static void nf_conntrack_irc_fini(void); 231 232 static int __init nf_conntrack_irc_init(void) 233 { 234 int i, ret; 235 char *tmpname; 236 237 if (max_dcc_channels < 1) { 238 printk("nf_ct_irc: max_dcc_channels must not be zero\n"); 239 return -EINVAL; 240 } 241 242 irc_exp_policy.max_expected = max_dcc_channels; 243 irc_exp_policy.timeout = dcc_timeout; 244 245 irc_buffer = kmalloc(65536, GFP_KERNEL); 246 if (!irc_buffer) 247 return -ENOMEM; 248 249 /* If no port given, default to standard irc port */ 250 if (ports_c == 0) 251 ports[ports_c++] = IRC_PORT; 252 253 for (i = 0; i < ports_c; i++) { 254 irc[i].tuple.src.l3num = AF_INET; 255 irc[i].tuple.src.u.tcp.port = htons(ports[i]); 256 irc[i].tuple.dst.protonum = IPPROTO_TCP; 257 irc[i].expect_policy = &irc_exp_policy; 258 irc[i].me = THIS_MODULE; 259 irc[i].help = help; 260 261 tmpname = &irc_names[i][0]; 262 if (ports[i] == IRC_PORT) 263 sprintf(tmpname, "irc"); 264 else 265 sprintf(tmpname, "irc-%u", i); 266 irc[i].name = tmpname; 267 268 ret = nf_conntrack_helper_register(&irc[i]); 269 if (ret) { 270 printk("nf_ct_irc: failed to register helper " 271 "for pf: %u port: %u\n", 272 irc[i].tuple.src.l3num, ports[i]); 273 nf_conntrack_irc_fini(); 274 return ret; 275 } 276 } 277 return 0; 278 } 279 280 /* This function is intentionally _NOT_ defined as __exit, because 281 * it is needed by the init function */ 282 static void nf_conntrack_irc_fini(void) 283 { 284 int i; 285 286 for (i = 0; i < ports_c; i++) 287 nf_conntrack_helper_unregister(&irc[i]); 288 kfree(irc_buffer); 289 } 290 291 module_init(nf_conntrack_irc_init); 292 module_exit(nf_conntrack_irc_fini); 293