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 && ctinfo != IP_CT_ESTABLISHED_REPLY) 129 return NF_ACCEPT; 130 131 /* Not a full tcp header? */ 132 th = skb_header_pointer(skb, protoff, sizeof(_tcph), &_tcph); 133 if (th == NULL) 134 return NF_ACCEPT; 135 136 /* No data? */ 137 dataoff = protoff + th->doff*4; 138 if (dataoff >= skb->len) 139 return NF_ACCEPT; 140 141 spin_lock_bh(&irc_buffer_lock); 142 ib_ptr = skb_header_pointer(skb, dataoff, skb->len - dataoff, 143 irc_buffer); 144 BUG_ON(ib_ptr == NULL); 145 146 data = ib_ptr; 147 data_limit = ib_ptr + skb->len - dataoff; 148 149 /* strlen("\1DCC SENT t AAAAAAAA P\1\n")=24 150 * 5+MINMATCHLEN+strlen("t AAAAAAAA P\1\n")=14 */ 151 while (data < data_limit - (19 + MINMATCHLEN)) { 152 if (memcmp(data, "\1DCC ", 5)) { 153 data++; 154 continue; 155 } 156 data += 5; 157 /* we have at least (19+MINMATCHLEN)-5 bytes valid data left */ 158 159 iph = ip_hdr(skb); 160 pr_debug("DCC found in master %pI4:%u %pI4:%u\n", 161 &iph->saddr, ntohs(th->source), 162 &iph->daddr, ntohs(th->dest)); 163 164 for (i = 0; i < ARRAY_SIZE(dccprotos); i++) { 165 if (memcmp(data, dccprotos[i], strlen(dccprotos[i]))) { 166 /* no match */ 167 continue; 168 } 169 data += strlen(dccprotos[i]); 170 pr_debug("DCC %s detected\n", dccprotos[i]); 171 172 /* we have at least 173 * (19+MINMATCHLEN)-5-dccprotos[i].matchlen bytes valid 174 * data left (== 14/13 bytes) */ 175 if (parse_dcc(data, data_limit, &dcc_ip, 176 &dcc_port, &addr_beg_p, &addr_end_p)) { 177 pr_debug("unable to parse dcc command\n"); 178 continue; 179 } 180 181 pr_debug("DCC bound ip/port: %pI4:%u\n", 182 &dcc_ip, dcc_port); 183 184 /* dcc_ip can be the internal OR external (NAT'ed) IP */ 185 tuple = &ct->tuplehash[dir].tuple; 186 if (tuple->src.u3.ip != dcc_ip && 187 tuple->dst.u3.ip != dcc_ip) { 188 if (net_ratelimit()) 189 printk(KERN_WARNING 190 "Forged DCC command from %pI4: %pI4:%u\n", 191 &tuple->src.u3.ip, 192 &dcc_ip, dcc_port); 193 continue; 194 } 195 196 exp = nf_ct_expect_alloc(ct); 197 if (exp == NULL) { 198 ret = NF_DROP; 199 goto out; 200 } 201 tuple = &ct->tuplehash[!dir].tuple; 202 port = htons(dcc_port); 203 nf_ct_expect_init(exp, NF_CT_EXPECT_CLASS_DEFAULT, 204 tuple->src.l3num, 205 NULL, &tuple->dst.u3, 206 IPPROTO_TCP, NULL, &port); 207 208 nf_nat_irc = rcu_dereference(nf_nat_irc_hook); 209 if (nf_nat_irc && ct->status & IPS_NAT_MASK) 210 ret = nf_nat_irc(skb, ctinfo, 211 addr_beg_p - ib_ptr, 212 addr_end_p - addr_beg_p, 213 exp); 214 else if (nf_ct_expect_related(exp) != 0) 215 ret = NF_DROP; 216 nf_ct_expect_put(exp); 217 goto out; 218 } 219 } 220 out: 221 spin_unlock_bh(&irc_buffer_lock); 222 return ret; 223 } 224 225 static struct nf_conntrack_helper irc[MAX_PORTS] __read_mostly; 226 static char irc_names[MAX_PORTS][sizeof("irc-65535")] __read_mostly; 227 static struct nf_conntrack_expect_policy irc_exp_policy; 228 229 static void nf_conntrack_irc_fini(void); 230 231 static int __init nf_conntrack_irc_init(void) 232 { 233 int i, ret; 234 char *tmpname; 235 236 if (max_dcc_channels < 1) { 237 printk(KERN_ERR "nf_ct_irc: max_dcc_channels must not be zero\n"); 238 return -EINVAL; 239 } 240 241 irc_exp_policy.max_expected = max_dcc_channels; 242 irc_exp_policy.timeout = dcc_timeout; 243 244 irc_buffer = kmalloc(65536, GFP_KERNEL); 245 if (!irc_buffer) 246 return -ENOMEM; 247 248 /* If no port given, default to standard irc port */ 249 if (ports_c == 0) 250 ports[ports_c++] = IRC_PORT; 251 252 for (i = 0; i < ports_c; i++) { 253 irc[i].tuple.src.l3num = AF_INET; 254 irc[i].tuple.src.u.tcp.port = htons(ports[i]); 255 irc[i].tuple.dst.protonum = IPPROTO_TCP; 256 irc[i].expect_policy = &irc_exp_policy; 257 irc[i].me = THIS_MODULE; 258 irc[i].help = help; 259 260 tmpname = &irc_names[i][0]; 261 if (ports[i] == IRC_PORT) 262 sprintf(tmpname, "irc"); 263 else 264 sprintf(tmpname, "irc-%u", i); 265 irc[i].name = tmpname; 266 267 ret = nf_conntrack_helper_register(&irc[i]); 268 if (ret) { 269 printk(KERN_ERR "nf_ct_irc: failed to register helper " 270 "for pf: %u port: %u\n", 271 irc[i].tuple.src.l3num, ports[i]); 272 nf_conntrack_irc_fini(); 273 return ret; 274 } 275 } 276 return 0; 277 } 278 279 /* This function is intentionally _NOT_ defined as __exit, because 280 * it is needed by the init function */ 281 static void nf_conntrack_irc_fini(void) 282 { 283 int i; 284 285 for (i = 0; i < ports_c; i++) 286 nf_conntrack_helper_unregister(&irc[i]); 287 kfree(irc_buffer); 288 } 289 290 module_init(nf_conntrack_irc_init); 291 module_exit(nf_conntrack_irc_fini); 292