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 * (C) 2006-2012 Patrick McHardy <kaber@trash.net> 5 * 6 * This program is free software; you can redistribute it and/or 7 * modify it under the terms of the GNU General Public License 8 * as published by the Free Software Foundation; either version 9 * 2 of the License, or (at your option) any later version. 10 */ 11 12 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt 13 14 #include <linux/module.h> 15 #include <linux/moduleparam.h> 16 #include <linux/skbuff.h> 17 #include <linux/in.h> 18 #include <linux/ip.h> 19 #include <linux/tcp.h> 20 #include <linux/netfilter.h> 21 #include <linux/slab.h> 22 23 #include <net/netfilter/nf_conntrack.h> 24 #include <net/netfilter/nf_conntrack_expect.h> 25 #include <net/netfilter/nf_conntrack_helper.h> 26 #include <linux/netfilter/nf_conntrack_irc.h> 27 28 #define MAX_PORTS 8 29 static unsigned short ports[MAX_PORTS]; 30 static unsigned int ports_c; 31 static unsigned int max_dcc_channels = 8; 32 static unsigned int dcc_timeout __read_mostly = 300; 33 /* This is slow, but it's simple. --RR */ 34 static char *irc_buffer; 35 static DEFINE_SPINLOCK(irc_buffer_lock); 36 37 unsigned int (*nf_nat_irc_hook)(struct sk_buff *skb, 38 enum ip_conntrack_info ctinfo, 39 unsigned int protoff, 40 unsigned int matchoff, 41 unsigned int matchlen, 42 struct nf_conntrack_expect *exp) __read_mostly; 43 EXPORT_SYMBOL_GPL(nf_nat_irc_hook); 44 45 MODULE_AUTHOR("Harald Welte <laforge@netfilter.org>"); 46 MODULE_DESCRIPTION("IRC (DCC) connection tracking helper"); 47 MODULE_LICENSE("GPL"); 48 MODULE_ALIAS("ip_conntrack_irc"); 49 MODULE_ALIAS_NFCT_HELPER("irc"); 50 51 module_param_array(ports, ushort, &ports_c, 0400); 52 MODULE_PARM_DESC(ports, "port numbers of IRC servers"); 53 module_param(max_dcc_channels, uint, 0400); 54 MODULE_PARM_DESC(max_dcc_channels, "max number of expected DCC channels per " 55 "IRC session"); 56 module_param(dcc_timeout, uint, 0400); 57 MODULE_PARM_DESC(dcc_timeout, "timeout on for unestablished DCC channels"); 58 59 static const char *const dccprotos[] = { 60 "SEND ", "CHAT ", "MOVE ", "TSEND ", "SCHAT " 61 }; 62 63 #define MINMATCHLEN 5 64 65 /* tries to get the ip_addr and port out of a dcc command 66 * return value: -1 on failure, 0 on success 67 * data pointer to first byte of DCC command data 68 * data_end pointer to last byte of dcc command data 69 * ip returns parsed ip of dcc command 70 * port returns parsed port of dcc command 71 * ad_beg_p returns pointer to first byte of addr data 72 * ad_end_p returns pointer to last byte of addr data 73 */ 74 static int parse_dcc(char *data, const char *data_end, __be32 *ip, 75 u_int16_t *port, char **ad_beg_p, char **ad_end_p) 76 { 77 char *tmp; 78 79 /* at least 12: "AAAAAAAA P\1\n" */ 80 while (*data++ != ' ') 81 if (data > data_end - 12) 82 return -1; 83 84 /* Make sure we have a newline character within the packet boundaries 85 * because simple_strtoul parses until the first invalid character. */ 86 for (tmp = data; tmp <= data_end; tmp++) 87 if (*tmp == '\n') 88 break; 89 if (tmp > data_end || *tmp != '\n') 90 return -1; 91 92 *ad_beg_p = data; 93 *ip = cpu_to_be32(simple_strtoul(data, &data, 10)); 94 95 /* skip blanks between ip and port */ 96 while (*data == ' ') { 97 if (data >= data_end) 98 return -1; 99 data++; 100 } 101 102 *port = simple_strtoul(data, &data, 10); 103 *ad_end_p = data; 104 105 return 0; 106 } 107 108 static int help(struct sk_buff *skb, unsigned int protoff, 109 struct nf_conn *ct, enum ip_conntrack_info ctinfo) 110 { 111 unsigned int dataoff; 112 const struct iphdr *iph; 113 const struct tcphdr *th; 114 struct tcphdr _tcph; 115 const char *data_limit; 116 char *data, *ib_ptr; 117 int dir = CTINFO2DIR(ctinfo); 118 struct nf_conntrack_expect *exp; 119 struct nf_conntrack_tuple *tuple; 120 __be32 dcc_ip; 121 u_int16_t dcc_port; 122 __be16 port; 123 int i, ret = NF_ACCEPT; 124 char *addr_beg_p, *addr_end_p; 125 typeof(nf_nat_irc_hook) nf_nat_irc; 126 127 /* If packet is coming from IRC server */ 128 if (dir == IP_CT_DIR_REPLY) 129 return NF_ACCEPT; 130 131 /* Until there's been traffic both ways, don't look in packets. */ 132 if (ctinfo != IP_CT_ESTABLISHED && ctinfo != IP_CT_ESTABLISHED_REPLY) 133 return NF_ACCEPT; 134 135 /* Not a full tcp header? */ 136 th = skb_header_pointer(skb, protoff, sizeof(_tcph), &_tcph); 137 if (th == NULL) 138 return NF_ACCEPT; 139 140 /* No data? */ 141 dataoff = protoff + th->doff*4; 142 if (dataoff >= skb->len) 143 return NF_ACCEPT; 144 145 spin_lock_bh(&irc_buffer_lock); 146 ib_ptr = skb_header_pointer(skb, dataoff, skb->len - dataoff, 147 irc_buffer); 148 BUG_ON(ib_ptr == NULL); 149 150 data = ib_ptr; 151 data_limit = ib_ptr + skb->len - dataoff; 152 153 /* strlen("\1DCC SENT t AAAAAAAA P\1\n")=24 154 * 5+MINMATCHLEN+strlen("t AAAAAAAA P\1\n")=14 */ 155 while (data < data_limit - (19 + MINMATCHLEN)) { 156 if (memcmp(data, "\1DCC ", 5)) { 157 data++; 158 continue; 159 } 160 data += 5; 161 /* we have at least (19+MINMATCHLEN)-5 bytes valid data left */ 162 163 iph = ip_hdr(skb); 164 pr_debug("DCC found in master %pI4:%u %pI4:%u\n", 165 &iph->saddr, ntohs(th->source), 166 &iph->daddr, ntohs(th->dest)); 167 168 for (i = 0; i < ARRAY_SIZE(dccprotos); i++) { 169 if (memcmp(data, dccprotos[i], strlen(dccprotos[i]))) { 170 /* no match */ 171 continue; 172 } 173 data += strlen(dccprotos[i]); 174 pr_debug("DCC %s detected\n", dccprotos[i]); 175 176 /* we have at least 177 * (19+MINMATCHLEN)-5-dccprotos[i].matchlen bytes valid 178 * data left (== 14/13 bytes) */ 179 if (parse_dcc(data, data_limit, &dcc_ip, 180 &dcc_port, &addr_beg_p, &addr_end_p)) { 181 pr_debug("unable to parse dcc command\n"); 182 continue; 183 } 184 185 pr_debug("DCC bound ip/port: %pI4:%u\n", 186 &dcc_ip, dcc_port); 187 188 /* dcc_ip can be the internal OR external (NAT'ed) IP */ 189 tuple = &ct->tuplehash[dir].tuple; 190 if (tuple->src.u3.ip != dcc_ip && 191 tuple->dst.u3.ip != dcc_ip) { 192 net_warn_ratelimited("Forged DCC command from %pI4: %pI4:%u\n", 193 &tuple->src.u3.ip, 194 &dcc_ip, dcc_port); 195 continue; 196 } 197 198 exp = nf_ct_expect_alloc(ct); 199 if (exp == NULL) { 200 nf_ct_helper_log(skb, ct, 201 "cannot alloc expectation"); 202 ret = NF_DROP; 203 goto out; 204 } 205 tuple = &ct->tuplehash[!dir].tuple; 206 port = htons(dcc_port); 207 nf_ct_expect_init(exp, NF_CT_EXPECT_CLASS_DEFAULT, 208 tuple->src.l3num, 209 NULL, &tuple->dst.u3, 210 IPPROTO_TCP, NULL, &port); 211 212 nf_nat_irc = rcu_dereference(nf_nat_irc_hook); 213 if (nf_nat_irc && ct->status & IPS_NAT_MASK) 214 ret = nf_nat_irc(skb, ctinfo, protoff, 215 addr_beg_p - ib_ptr, 216 addr_end_p - addr_beg_p, 217 exp); 218 else if (nf_ct_expect_related(exp) != 0) { 219 nf_ct_helper_log(skb, ct, 220 "cannot add expectation"); 221 ret = NF_DROP; 222 } 223 nf_ct_expect_put(exp); 224 goto out; 225 } 226 } 227 out: 228 spin_unlock_bh(&irc_buffer_lock); 229 return ret; 230 } 231 232 static struct nf_conntrack_helper irc[MAX_PORTS] __read_mostly; 233 static struct nf_conntrack_expect_policy irc_exp_policy; 234 235 static void nf_conntrack_irc_fini(void); 236 237 static int __init nf_conntrack_irc_init(void) 238 { 239 int i, ret; 240 241 if (max_dcc_channels < 1) { 242 pr_err("max_dcc_channels must not be zero\n"); 243 return -EINVAL; 244 } 245 246 irc_exp_policy.max_expected = max_dcc_channels; 247 irc_exp_policy.timeout = dcc_timeout; 248 249 irc_buffer = kmalloc(65536, GFP_KERNEL); 250 if (!irc_buffer) 251 return -ENOMEM; 252 253 /* If no port given, default to standard irc port */ 254 if (ports_c == 0) 255 ports[ports_c++] = IRC_PORT; 256 257 for (i = 0; i < ports_c; i++) { 258 nf_ct_helper_init(&irc[i], AF_INET, IPPROTO_TCP, "irc", 259 IRC_PORT, ports[i], i, &irc_exp_policy, 260 0, 0, help, NULL, THIS_MODULE); 261 } 262 263 ret = nf_conntrack_helpers_register(&irc[0], ports_c); 264 if (ret) { 265 pr_err("failed to register helpers\n"); 266 kfree(irc_buffer); 267 return ret; 268 } 269 270 return 0; 271 } 272 273 /* This function is intentionally _NOT_ defined as __exit, because 274 * it is needed by the init function */ 275 static void nf_conntrack_irc_fini(void) 276 { 277 nf_conntrack_helpers_unregister(irc, ports_c); 278 kfree(irc_buffer); 279 } 280 281 module_init(nf_conntrack_irc_init); 282 module_exit(nf_conntrack_irc_fini); 283