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   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/tcp.h>
  16 #include <linux/netfilter.h>
  17
  18 #include <net/netfilter/nf_conntrack.h>
  19 #include <net/netfilter/nf_conntrack_expect.h>
  20 #include <net/netfilter/nf_conntrack_helper.h>
  21 #include <linux/netfilter/nf_conntrack_irc.h>
  22
  23 #define MAX_PORTS 8
  24 static unsigned short ports[MAX_PORTS];
  25 static int ports_c;
  26 static unsigned int max_dcc_channels = 8;
  27 static unsigned int dcc_timeout __read_mostly = 300;
  28 /* This is slow, but it's simple. --RR */
  29 static char *irc_buffer;
  30 static DEFINE_SPINLOCK(irc_buffer_lock);
  31
  32 unsigned int (*nf_nat_irc_hook)(struct sk_buff **pskb,
  33                                 enum ip_conntrack_info ctinfo,
  34                                 unsigned int matchoff,
  35                                 unsigned int matchlen,
  36                                 struct nf_conntrack_expect *exp) __read_mostly;
  37 EXPORT_SYMBOL_GPL(nf_nat_irc_hook);
  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
  44 module_param_array(ports, ushort, &ports_c, 0400);
  45 MODULE_PARM_DESC(ports, "port numbers of IRC servers");
  46 module_param(max_dcc_channels, uint, 0400);
  47 MODULE_PARM_DESC(max_dcc_channels, "max number of expected DCC channels per "
  48                                    "IRC session");
  49 module_param(dcc_timeout, uint, 0400);
  50 MODULE_PARM_DESC(dcc_timeout, "timeout on for unestablished DCC channels");
  51
  52 static const char *dccprotos[] = {
  53         "SEND ", "CHAT ", "MOVE ", "TSEND ", "SCHAT "
  54 };
  55
  56 #define MINMATCHLEN     5
  57
  58 #if 0
  59 #define DEBUGP(format, args...) printk(KERN_DEBUG "%s:%s:" format, \
  60                                        __FILE__, __FUNCTION__ , ## args)
  61 #else
  62 #define DEBUGP(format, args...)
  63 #endif
  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, char *data_end, u_int32_t *ip,
  75                      u_int16_t *port, char **ad_beg_p, char **ad_end_p)
  76 {
  77         /* at least 12: "AAAAAAAA P\1\n" */
  78         while (*data++ != ' ')
  79                 if (data > data_end - 12)
  80                         return -1;
  81
  82         *ad_beg_p = data;
  83         *ip = simple_strtoul(data, &data, 10);
  84
  85         /* skip blanks between ip and port */
  86         while (*data == ' ') {
  87                 if (data >= data_end)
  88                         return -1;
  89                 data++;
  90         }
  91
  92         *port = simple_strtoul(data, &data, 10);
  93         *ad_end_p = data;
  94
  95         return 0;
  96 }
  97
  98 static int help(struct sk_buff **pskb, unsigned int protoff,
  99                 struct nf_conn *ct, enum ip_conntrack_info ctinfo)
 100 {
 101         unsigned int dataoff;
 102         struct tcphdr _tcph, *th;
 103         char *data, *data_limit, *ib_ptr;
 104         int dir = CTINFO2DIR(ctinfo);
 105         struct nf_conntrack_expect *exp;
 106         struct nf_conntrack_tuple *tuple;
 107         u_int32_t dcc_ip;
 108         u_int16_t dcc_port;
 109         __be16 port;
 110         int i, ret = NF_ACCEPT;
 111         char *addr_beg_p, *addr_end_p;
 112         typeof(nf_nat_irc_hook) nf_nat_irc;
 113
 114         /* If packet is coming from IRC server */
 115         if (dir == IP_CT_DIR_REPLY)
 116                 return NF_ACCEPT;
 117
 118         /* Until there's been traffic both ways, don't look in packets. */
 119         if (ctinfo != IP_CT_ESTABLISHED &&
 120             ctinfo != IP_CT_ESTABLISHED + IP_CT_IS_REPLY)
 121                 return NF_ACCEPT;
 122
 123         /* Not a full tcp header? */
 124         th = skb_header_pointer(*pskb, protoff, sizeof(_tcph), &_tcph);
 125         if (th == NULL)
 126                 return NF_ACCEPT;
 127
 128         /* No data? */
 129         dataoff = protoff + th->doff*4;
 130         if (dataoff >= (*pskb)->len)
 131                 return NF_ACCEPT;
 132
 133         spin_lock_bh(&irc_buffer_lock);
 134         ib_ptr = skb_header_pointer(*pskb, dataoff, (*pskb)->len - dataoff,
 135                                     irc_buffer);
 136         BUG_ON(ib_ptr == NULL);
 137
 138         data = ib_ptr;
 139         data_limit = ib_ptr + (*pskb)->len - dataoff;
 140
 141         /* strlen("\1DCC SENT t AAAAAAAA P\1\n")=24
 142          * 5+MINMATCHLEN+strlen("t AAAAAAAA P\1\n")=14 */
 143         while (data < data_limit - (19 + MINMATCHLEN)) {
 144                 if (memcmp(data, "\1DCC ", 5)) {
 145                         data++;
 146                         continue;
 147                 }
 148                 data += 5;
 149                 /* we have at least (19+MINMATCHLEN)-5 bytes valid data left */
 150
 151                 DEBUGP("DCC found in master %u.%u.%u.%u:%u %u.%u.%u.%u:%u...\n",
 152                         NIPQUAD(iph->saddr), ntohs(th->source),
 153                         NIPQUAD(iph->daddr), ntohs(th->dest));
 154
 155                 for (i = 0; i < ARRAY_SIZE(dccprotos); i++) {
 156                         if (memcmp(data, dccprotos[i], strlen(dccprotos[i]))) {
 157                                 /* no match */
 158                                 continue;
 159                         }
 160                         data += strlen(dccprotos[i]);
 161                         DEBUGP("DCC %s detected\n", dccprotos[i]);
 162
 163                         /* we have at least
 164                          * (19+MINMATCHLEN)-5-dccprotos[i].matchlen bytes valid
 165                          * data left (== 14/13 bytes) */
 166                         if (parse_dcc((char *)data, data_limit, &dcc_ip,
 167                                        &dcc_port, &addr_beg_p, &addr_end_p)) {
 168                                 DEBUGP("unable to parse dcc command\n");
 169                                 continue;
 170                         }
 171                         DEBUGP("DCC bound ip/port: %u.%u.%u.%u:%u\n",
 172                                 HIPQUAD(dcc_ip), dcc_port);
 173
 174                         /* dcc_ip can be the internal OR external (NAT'ed) IP */
 175                         tuple = &ct->tuplehash[dir].tuple;
 176                         if (tuple->src.u3.ip != htonl(dcc_ip) &&
 177                             tuple->dst.u3.ip != htonl(dcc_ip)) {
 178                                 if (net_ratelimit())
 179                                         printk(KERN_WARNING
 180                                                 "Forged DCC command from "
 181                                                 "%u.%u.%u.%u: %u.%u.%u.%u:%u\n",
 182                                                 NIPQUAD(tuple->src.u3.ip),
 183                                                 HIPQUAD(dcc_ip), dcc_port);
 184                                 continue;
 185                         }
 186
 187                         exp = nf_conntrack_expect_alloc(ct);
 188                         if (exp == NULL) {
 189                                 ret = NF_DROP;
 190                                 goto out;
 191                         }
 192                         tuple = &ct->tuplehash[!dir].tuple;
 193                         port = htons(dcc_port);
 194                         nf_conntrack_expect_init(exp, tuple->src.l3num,
 195                                                  NULL, &tuple->dst.u3,
 196                                                  IPPROTO_TCP, NULL, &port);
 197
 198                         nf_nat_irc = rcu_dereference(nf_nat_irc_hook);
 199                         if (nf_nat_irc && ct->status & IPS_NAT_MASK)
 200                                 ret = nf_nat_irc(pskb, ctinfo,
 201                                                  addr_beg_p - ib_ptr,
 202                                                  addr_end_p - addr_beg_p,
 203                                                  exp);
 204                         else if (nf_conntrack_expect_related(exp) != 0)
 205                                 ret = NF_DROP;
 206                         nf_conntrack_expect_put(exp);
 207                         goto out;
 208                 }
 209         }
 210  out:
 211         spin_unlock_bh(&irc_buffer_lock);
 212         return ret;
 213 }
 214
 215 static struct nf_conntrack_helper irc[MAX_PORTS] __read_mostly;
 216 static char irc_names[MAX_PORTS][sizeof("irc-65535")] __read_mostly;
 217
 218 static void nf_conntrack_irc_fini(void);
 219
 220 static int __init nf_conntrack_irc_init(void)
 221 {
 222         int i, ret;
 223         char *tmpname;
 224
 225         if (max_dcc_channels < 1) {
 226                 printk("nf_ct_irc: max_dcc_channels must not be zero\n");
 227                 return -EINVAL;
 228         }
 229
 230         irc_buffer = kmalloc(65536, GFP_KERNEL);
 231         if (!irc_buffer)
 232                 return -ENOMEM;
 233
 234         /* If no port given, default to standard irc port */
 235         if (ports_c == 0)
 236                 ports[ports_c++] = IRC_PORT;
 237
 238         for (i = 0; i < ports_c; i++) {
 239                 irc[i].tuple.src.l3num = AF_INET;
 240                 irc[i].tuple.src.u.tcp.port = htons(ports[i]);
 241                 irc[i].tuple.dst.protonum = IPPROTO_TCP;
 242                 irc[i].mask.src.l3num = 0xFFFF;
 243                 irc[i].mask.src.u.tcp.port = htons(0xFFFF);
 244                 irc[i].mask.dst.protonum = 0xFF;
 245                 irc[i].max_expected = max_dcc_channels;
 246                 irc[i].timeout = dcc_timeout;
 247                 irc[i].me = THIS_MODULE;
 248                 irc[i].help = help;
 249
 250                 tmpname = &irc_names[i][0];
 251                 if (ports[i] == IRC_PORT)
 252                         sprintf(tmpname, "irc");
 253                 else
 254                         sprintf(tmpname, "irc-%u", i);
 255                 irc[i].name = tmpname;
 256
 257                 ret = nf_conntrack_helper_register(&irc[i]);
 258                 if (ret) {
 259                         printk("nf_ct_irc: failed to register helper "
 260                                "for pf: %u port: %u\n",
 261                                irc[i].tuple.src.l3num, ports[i]);
 262                         nf_conntrack_irc_fini();
 263                         return ret;
 264                 }
 265         }
 266         return 0;
 267 }
 268
 269 /* This function is intentionally _NOT_ defined as __exit, because
 270  * it is needed by the init function */
 271 static void nf_conntrack_irc_fini(void)
 272 {
 273         int i;
 274
 275         for (i = 0; i < ports_c; i++)
 276                 nf_conntrack_helper_unregister(&irc[i]);
 277         kfree(irc_buffer);
 278 }
 279
 280 module_init(nf_conntrack_irc_init);
 281 module_exit(nf_conntrack_irc_fini);