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 nf_nat_irc_hook_fn __rcu *nf_nat_irc_hook __read_mostly; 34 EXPORT_SYMBOL_GPL(nf_nat_irc_hook); 35 36 #define HELPER_NAME "irc" 37 #define MAX_SEARCH_SIZE 4095 38 39 MODULE_AUTHOR("Harald Welte <laforge@netfilter.org>"); 40 MODULE_DESCRIPTION("IRC (DCC) connection tracking helper"); 41 MODULE_LICENSE("GPL"); 42 MODULE_ALIAS("ip_conntrack_irc"); 43 MODULE_ALIAS_NFCT_HELPER(HELPER_NAME); 44 45 module_param_array(ports, ushort, &ports_c, 0400); 46 MODULE_PARM_DESC(ports, "port numbers of IRC servers"); 47 module_param(max_dcc_channels, uint, 0400); 48 MODULE_PARM_DESC(max_dcc_channels, "max number of expected DCC channels per " 49 "IRC session"); 50 module_param(dcc_timeout, uint, 0400); 51 MODULE_PARM_DESC(dcc_timeout, "timeout on for unestablished DCC channels"); 52 53 static const char *const dccprotos[] = { 54 "SEND ", "CHAT ", "MOVE ", "TSEND ", "SCHAT " 55 }; 56 57 #define MINMATCHLEN 5 58 59 /* tries to get the ip_addr and port out of a dcc command 60 * return value: -1 on failure, 0 on success 61 * data pointer to first byte of DCC command data 62 * data_end one past end of data 63 * ip returns parsed ip of dcc command 64 * port returns parsed port of dcc command 65 * ad_beg_p returns pointer to first byte of addr data 66 * ad_end_p returns pointer to last byte of addr data 67 */ 68 static int parse_dcc(char *data, const char *data_end, __be32 *ip, 69 u_int16_t *port, char **ad_beg_p, char **ad_end_p) 70 { 71 char *tmp; 72 73 /* at least 12: "AAAAAAAA P\1\n" */ 74 while (*data++ != ' ') 75 if (data > data_end - 12) 76 return -1; 77 78 /* Make sure we have a newline character within the packet boundaries 79 * because simple_strtoul parses until the first invalid character. */ 80 for (tmp = data; tmp < data_end; tmp++) 81 if (*tmp == '\n') 82 break; 83 if (tmp >= data_end || *tmp != '\n') 84 return -1; 85 86 *ad_beg_p = data; 87 *ip = cpu_to_be32(simple_strtoul(data, &data, 10)); 88 89 /* skip blanks between ip and port */ 90 while (*data == ' ') { 91 if (data >= data_end) 92 return -1; 93 data++; 94 } 95 96 *port = simple_strtoul(data, &data, 10); 97 *ad_end_p = data; 98 99 return 0; 100 } 101 102 static int help(struct sk_buff *skb, unsigned int protoff, 103 struct nf_conn *ct, enum ip_conntrack_info ctinfo) 104 { 105 unsigned int dataoff; 106 const struct iphdr *iph; 107 const struct tcphdr *th; 108 struct tcphdr _tcph; 109 const char *data_limit; 110 char *data, *ib_ptr; 111 int dir = CTINFO2DIR(ctinfo); 112 struct nf_conntrack_expect *exp; 113 struct nf_conntrack_tuple *tuple; 114 __be32 dcc_ip; 115 u_int16_t dcc_port; 116 __be16 port; 117 int i, ret = NF_ACCEPT; 118 char *addr_beg_p, *addr_end_p; 119 nf_nat_irc_hook_fn *nf_nat_irc; 120 unsigned int datalen; 121 122 /* If packet is coming from IRC server */ 123 if (dir == IP_CT_DIR_REPLY) 124 return NF_ACCEPT; 125 126 /* Until there's been traffic both ways, don't look in packets. */ 127 if (ctinfo != IP_CT_ESTABLISHED && ctinfo != IP_CT_ESTABLISHED_REPLY) 128 return NF_ACCEPT; 129 130 /* Not a full tcp header? */ 131 th = skb_header_pointer(skb, protoff, sizeof(_tcph), &_tcph); 132 if (th == NULL) 133 return NF_ACCEPT; 134 135 /* No data? */ 136 dataoff = protoff + th->doff*4; 137 if (dataoff >= skb->len) 138 return NF_ACCEPT; 139 140 datalen = skb->len - dataoff; 141 if (datalen > MAX_SEARCH_SIZE) 142 datalen = MAX_SEARCH_SIZE; 143 144 spin_lock_bh(&irc_buffer_lock); 145 ib_ptr = skb_header_pointer(skb, dataoff, datalen, 146 irc_buffer); 147 if (!ib_ptr) { 148 spin_unlock_bh(&irc_buffer_lock); 149 return NF_ACCEPT; 150 } 151 152 data = ib_ptr; 153 data_limit = ib_ptr + datalen; 154 155 /* Skip any whitespace */ 156 while (data < data_limit - 10) { 157 if (*data == ' ' || *data == '\r' || *data == '\n') 158 data++; 159 else 160 break; 161 } 162 163 /* strlen("PRIVMSG x ")=10 */ 164 if (data < data_limit - 10) { 165 if (strncasecmp("PRIVMSG ", data, 8)) 166 goto out; 167 data += 8; 168 } 169 170 /* strlen(" :\1DCC SENT t AAAAAAAA P\1\n")=26 171 * 7+MINMATCHLEN+strlen("t AAAAAAAA P\1\n")=26 172 */ 173 while (data < data_limit - (21 + MINMATCHLEN)) { 174 /* Find first " :", the start of message */ 175 if (memcmp(data, " :", 2)) { 176 data++; 177 continue; 178 } 179 data += 2; 180 181 /* then check that place only for the DCC command */ 182 if (memcmp(data, "\1DCC ", 5)) 183 goto out; 184 data += 5; 185 /* we have at least (21+MINMATCHLEN)-(2+5) bytes valid data left */ 186 187 iph = ip_hdr(skb); 188 pr_debug("DCC found in master %pI4:%u %pI4:%u\n", 189 &iph->saddr, ntohs(th->source), 190 &iph->daddr, ntohs(th->dest)); 191 192 for (i = 0; i < ARRAY_SIZE(dccprotos); i++) { 193 if (memcmp(data, dccprotos[i], strlen(dccprotos[i]))) { 194 /* no match */ 195 continue; 196 } 197 data += strlen(dccprotos[i]); 198 pr_debug("DCC %s detected\n", dccprotos[i]); 199 200 /* we have at least 201 * (21+MINMATCHLEN)-7-dccprotos[i].matchlen bytes valid 202 * data left (== 14/13 bytes) */ 203 if (parse_dcc(data, data_limit, &dcc_ip, 204 &dcc_port, &addr_beg_p, &addr_end_p)) { 205 pr_debug("unable to parse dcc command\n"); 206 goto out; 207 } 208 209 pr_debug("DCC bound ip/port: %pI4:%u\n", 210 &dcc_ip, dcc_port); 211 212 /* dcc_ip can be the internal OR external (NAT'ed) IP */ 213 tuple = &ct->tuplehash[dir].tuple; 214 if ((tuple->src.u3.ip != dcc_ip && 215 ct->tuplehash[!dir].tuple.dst.u3.ip != dcc_ip) || 216 dcc_port == 0) { 217 net_warn_ratelimited("Forged DCC command from %pI4: %pI4:%u\n", 218 &tuple->src.u3.ip, 219 &dcc_ip, dcc_port); 220 goto out; 221 } 222 223 exp = nf_ct_expect_alloc(ct); 224 if (exp == NULL) { 225 nf_ct_helper_log(skb, ct, 226 "cannot alloc expectation"); 227 ret = NF_DROP; 228 goto out; 229 } 230 tuple = &ct->tuplehash[!dir].tuple; 231 port = htons(dcc_port); 232 nf_ct_expect_init(exp, NF_CT_EXPECT_CLASS_DEFAULT, 233 tuple->src.l3num, 234 NULL, &tuple->dst.u3, 235 IPPROTO_TCP, NULL, &port); 236 237 nf_nat_irc = rcu_dereference(nf_nat_irc_hook); 238 if (nf_nat_irc && ct->status & IPS_NAT_MASK) 239 ret = nf_nat_irc(skb, ctinfo, protoff, 240 addr_beg_p - ib_ptr, 241 addr_end_p - addr_beg_p, 242 exp); 243 else if (nf_ct_expect_related(exp, 0) != 0) { 244 nf_ct_helper_log(skb, ct, 245 "cannot add expectation"); 246 ret = NF_DROP; 247 } 248 nf_ct_expect_put(exp); 249 goto out; 250 } 251 } 252 out: 253 spin_unlock_bh(&irc_buffer_lock); 254 return ret; 255 } 256 257 static struct nf_conntrack_helper irc[MAX_PORTS] __read_mostly; 258 static struct nf_conntrack_helper *irc_ptr[MAX_PORTS] __read_mostly; 259 static struct nf_conntrack_expect_policy irc_exp_policy; 260 261 static int __init nf_conntrack_irc_init(void) 262 { 263 int i, ret; 264 265 nf_conntrack_helper_deprecated(HELPER_NAME); 266 267 if (max_dcc_channels < 1) { 268 pr_err("max_dcc_channels must not be zero\n"); 269 return -EINVAL; 270 } 271 272 if (max_dcc_channels > NF_CT_EXPECT_MAX_CNT) { 273 pr_err("max_dcc_channels must not be more than %u\n", 274 NF_CT_EXPECT_MAX_CNT); 275 return -EINVAL; 276 } 277 278 irc_exp_policy.max_expected = max_dcc_channels; 279 irc_exp_policy.timeout = dcc_timeout; 280 281 irc_buffer = kmalloc(MAX_SEARCH_SIZE + 1, GFP_KERNEL); 282 if (!irc_buffer) 283 return -ENOMEM; 284 285 /* If no port given, default to standard irc port */ 286 if (ports_c == 0) 287 ports[ports_c++] = IRC_PORT; 288 289 for (i = 0; i < ports_c; i++) { 290 nf_ct_helper_init(&irc[i], AF_INET, IPPROTO_TCP, HELPER_NAME, 291 IRC_PORT, ports[i], i, &irc_exp_policy, 292 0, help, NULL, THIS_MODULE); 293 } 294 295 ret = nf_conntrack_helpers_register(&irc[0], ports_c, irc_ptr); 296 if (ret) { 297 pr_err("failed to register helpers\n"); 298 kfree(irc_buffer); 299 return ret; 300 } 301 302 return 0; 303 } 304 305 static void __exit nf_conntrack_irc_fini(void) 306 { 307 nf_conntrack_helpers_unregister(irc_ptr, ports_c); 308 kfree(irc_buffer); 309 } 310 311 module_init(nf_conntrack_irc_init); 312 module_exit(nf_conntrack_irc_fini); 313