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