1 // SPDX-License-Identifier: GPL-2.0-or-later 2 /* IRC extension for IP connection tracking, Version 1.21 3 * (C) 2000-2002 by Harald Welte <laforge@gnumonks.org> 4 * based on RR's ip_conntrack_ftp.c 5 * (C) 2006-2012 Patrick McHardy <kaber@trash.net> 6 */ 7 8 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt 9 10 #include <linux/module.h> 11 #include <linux/moduleparam.h> 12 #include <linux/skbuff.h> 13 #include <linux/in.h> 14 #include <linux/ip.h> 15 #include <linux/tcp.h> 16 #include <linux/netfilter.h> 17 #include <linux/slab.h> 18 19 #include <net/netfilter/nf_conntrack.h> 20 #include <net/netfilter/nf_conntrack_expect.h> 21 #include <net/netfilter/nf_conntrack_helper.h> 22 #include <linux/netfilter/nf_conntrack_irc.h> 23 24 #define MAX_PORTS 8 25 static unsigned short ports[MAX_PORTS]; 26 static unsigned int ports_c; 27 static unsigned int max_dcc_channels = 8; 28 static unsigned int dcc_timeout __read_mostly = 300; 29 /* This is slow, but it's simple. --RR */ 30 static char *irc_buffer; 31 static DEFINE_SPINLOCK(irc_buffer_lock); 32 33 unsigned int (*nf_nat_irc_hook)(struct sk_buff *skb, 34 enum ip_conntrack_info ctinfo, 35 unsigned int protoff, 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 #define HELPER_NAME "irc" 42 #define MAX_SEARCH_SIZE 4095 43 44 MODULE_AUTHOR("Harald Welte <laforge@netfilter.org>"); 45 MODULE_DESCRIPTION("IRC (DCC) connection tracking helper"); 46 MODULE_LICENSE("GPL"); 47 MODULE_ALIAS("ip_conntrack_irc"); 48 MODULE_ALIAS_NFCT_HELPER(HELPER_NAME); 49 50 module_param_array(ports, ushort, &ports_c, 0400); 51 MODULE_PARM_DESC(ports, "port numbers of IRC servers"); 52 module_param(max_dcc_channels, uint, 0400); 53 MODULE_PARM_DESC(max_dcc_channels, "max number of expected DCC channels per " 54 "IRC session"); 55 module_param(dcc_timeout, uint, 0400); 56 MODULE_PARM_DESC(dcc_timeout, "timeout on for unestablished DCC channels"); 57 58 static const char *const dccprotos[] = { 59 "SEND ", "CHAT ", "MOVE ", "TSEND ", "SCHAT " 60 }; 61 62 #define MINMATCHLEN 5 63 64 /* tries to get the ip_addr and port out of a dcc command 65 * return value: -1 on failure, 0 on success 66 * data pointer to first byte of DCC command data 67 * data_end pointer to last byte of dcc command data 68 * ip returns parsed ip of dcc command 69 * port returns parsed port of dcc command 70 * ad_beg_p returns pointer to first byte of addr data 71 * ad_end_p returns pointer to last byte of addr data 72 */ 73 static int parse_dcc(char *data, const char *data_end, __be32 *ip, 74 u_int16_t *port, char **ad_beg_p, char **ad_end_p) 75 { 76 char *tmp; 77 78 /* at least 12: "AAAAAAAA P\1\n" */ 79 while (*data++ != ' ') 80 if (data > data_end - 12) 81 return -1; 82 83 /* Make sure we have a newline character within the packet boundaries 84 * because simple_strtoul parses until the first invalid character. */ 85 for (tmp = data; tmp <= data_end; tmp++) 86 if (*tmp == '\n') 87 break; 88 if (tmp > data_end || *tmp != '\n') 89 return -1; 90 91 *ad_beg_p = data; 92 *ip = cpu_to_be32(simple_strtoul(data, &data, 10)); 93 94 /* skip blanks between ip and port */ 95 while (*data == ' ') { 96 if (data >= data_end) 97 return -1; 98 data++; 99 } 100 101 *port = simple_strtoul(data, &data, 10); 102 *ad_end_p = data; 103 104 return 0; 105 } 106 107 static int help(struct sk_buff *skb, unsigned int protoff, 108 struct nf_conn *ct, enum ip_conntrack_info ctinfo) 109 { 110 unsigned int dataoff; 111 const struct iphdr *iph; 112 const struct tcphdr *th; 113 struct tcphdr _tcph; 114 const char *data_limit; 115 char *data, *ib_ptr; 116 int dir = CTINFO2DIR(ctinfo); 117 struct nf_conntrack_expect *exp; 118 struct nf_conntrack_tuple *tuple; 119 __be32 dcc_ip; 120 u_int16_t dcc_port; 121 __be16 port; 122 int i, ret = NF_ACCEPT; 123 char *addr_beg_p, *addr_end_p; 124 typeof(nf_nat_irc_hook) nf_nat_irc; 125 unsigned int datalen; 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 datalen = skb->len - dataoff; 146 if (datalen > MAX_SEARCH_SIZE) 147 datalen = MAX_SEARCH_SIZE; 148 149 spin_lock_bh(&irc_buffer_lock); 150 ib_ptr = skb_header_pointer(skb, dataoff, datalen, 151 irc_buffer); 152 if (!ib_ptr) { 153 spin_unlock_bh(&irc_buffer_lock); 154 return NF_ACCEPT; 155 } 156 157 data = ib_ptr; 158 data_limit = ib_ptr + datalen; 159 160 /* Skip any whitespace */ 161 while (data < data_limit - 10) { 162 if (*data == ' ' || *data == '\r' || *data == '\n') 163 data++; 164 else 165 break; 166 } 167 168 /* strlen("PRIVMSG x ")=10 */ 169 if (data < data_limit - 10) { 170 if (strncasecmp("PRIVMSG ", data, 8)) 171 goto out; 172 data += 8; 173 } 174 175 /* strlen(" :\1DCC SENT t AAAAAAAA P\1\n")=26 176 * 7+MINMATCHLEN+strlen("t AAAAAAAA P\1\n")=26 177 */ 178 while (data < data_limit - (21 + MINMATCHLEN)) { 179 /* Find first " :", the start of message */ 180 if (memcmp(data, " :", 2)) { 181 data++; 182 continue; 183 } 184 data += 2; 185 186 /* then check that place only for the DCC command */ 187 if (memcmp(data, "\1DCC ", 5)) 188 goto out; 189 data += 5; 190 /* we have at least (21+MINMATCHLEN)-(2+5) bytes valid data left */ 191 192 iph = ip_hdr(skb); 193 pr_debug("DCC found in master %pI4:%u %pI4:%u\n", 194 &iph->saddr, ntohs(th->source), 195 &iph->daddr, ntohs(th->dest)); 196 197 for (i = 0; i < ARRAY_SIZE(dccprotos); i++) { 198 if (memcmp(data, dccprotos[i], strlen(dccprotos[i]))) { 199 /* no match */ 200 continue; 201 } 202 data += strlen(dccprotos[i]); 203 pr_debug("DCC %s detected\n", dccprotos[i]); 204 205 /* we have at least 206 * (21+MINMATCHLEN)-7-dccprotos[i].matchlen bytes valid 207 * data left (== 14/13 bytes) */ 208 if (parse_dcc(data, data_limit, &dcc_ip, 209 &dcc_port, &addr_beg_p, &addr_end_p)) { 210 pr_debug("unable to parse dcc command\n"); 211 continue; 212 } 213 214 pr_debug("DCC bound ip/port: %pI4:%u\n", 215 &dcc_ip, dcc_port); 216 217 /* dcc_ip can be the internal OR external (NAT'ed) IP */ 218 tuple = &ct->tuplehash[dir].tuple; 219 if ((tuple->src.u3.ip != dcc_ip && 220 ct->tuplehash[!dir].tuple.dst.u3.ip != dcc_ip) || 221 dcc_port == 0) { 222 net_warn_ratelimited("Forged DCC command from %pI4: %pI4:%u\n", 223 &tuple->src.u3.ip, 224 &dcc_ip, dcc_port); 225 continue; 226 } 227 228 exp = nf_ct_expect_alloc(ct); 229 if (exp == NULL) { 230 nf_ct_helper_log(skb, ct, 231 "cannot alloc expectation"); 232 ret = NF_DROP; 233 goto out; 234 } 235 tuple = &ct->tuplehash[!dir].tuple; 236 port = htons(dcc_port); 237 nf_ct_expect_init(exp, NF_CT_EXPECT_CLASS_DEFAULT, 238 tuple->src.l3num, 239 NULL, &tuple->dst.u3, 240 IPPROTO_TCP, NULL, &port); 241 242 nf_nat_irc = rcu_dereference(nf_nat_irc_hook); 243 if (nf_nat_irc && ct->status & IPS_NAT_MASK) 244 ret = nf_nat_irc(skb, ctinfo, protoff, 245 addr_beg_p - ib_ptr, 246 addr_end_p - addr_beg_p, 247 exp); 248 else if (nf_ct_expect_related(exp, 0) != 0) { 249 nf_ct_helper_log(skb, ct, 250 "cannot add expectation"); 251 ret = NF_DROP; 252 } 253 nf_ct_expect_put(exp); 254 goto out; 255 } 256 } 257 out: 258 spin_unlock_bh(&irc_buffer_lock); 259 return ret; 260 } 261 262 static struct nf_conntrack_helper irc[MAX_PORTS] __read_mostly; 263 static struct nf_conntrack_expect_policy irc_exp_policy; 264 265 static int __init nf_conntrack_irc_init(void) 266 { 267 int i, ret; 268 269 if (max_dcc_channels < 1) { 270 pr_err("max_dcc_channels must not be zero\n"); 271 return -EINVAL; 272 } 273 274 if (max_dcc_channels > NF_CT_EXPECT_MAX_CNT) { 275 pr_err("max_dcc_channels must not be more than %u\n", 276 NF_CT_EXPECT_MAX_CNT); 277 return -EINVAL; 278 } 279 280 irc_exp_policy.max_expected = max_dcc_channels; 281 irc_exp_policy.timeout = dcc_timeout; 282 283 irc_buffer = kmalloc(MAX_SEARCH_SIZE + 1, GFP_KERNEL); 284 if (!irc_buffer) 285 return -ENOMEM; 286 287 /* If no port given, default to standard irc port */ 288 if (ports_c == 0) 289 ports[ports_c++] = IRC_PORT; 290 291 for (i = 0; i < ports_c; i++) { 292 nf_ct_helper_init(&irc[i], AF_INET, IPPROTO_TCP, HELPER_NAME, 293 IRC_PORT, ports[i], i, &irc_exp_policy, 294 0, help, NULL, THIS_MODULE); 295 } 296 297 ret = nf_conntrack_helpers_register(&irc[0], ports_c); 298 if (ret) { 299 pr_err("failed to register helpers\n"); 300 kfree(irc_buffer); 301 return ret; 302 } 303 304 return 0; 305 } 306 307 static void __exit nf_conntrack_irc_fini(void) 308 { 309 nf_conntrack_helpers_unregister(irc, ports_c); 310 kfree(irc_buffer); 311 } 312 313 module_init(nf_conntrack_irc_init); 314 module_exit(nf_conntrack_irc_fini); 315