net/ipv4/netfilter/ip_conntrack_irc.c

   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  * ip_conntrack_irc.c,v 1.21 2002/02/05 14:49:26 laforge Exp
   6  *
   7  *      This program is free software; you can redistribute it and/or
   8  *      modify it under the terms of the GNU General Public License
   9  *      as published by the Free Software Foundation; either version
  10  *      2 of the License, or (at your option) any later version.
  11  **
  12  *      Module load syntax:
  13  *      insmod ip_conntrack_irc.o ports=port1,port2,...port<MAX_PORTS>
  14  *                          max_dcc_channels=n dcc_timeout=secs
  15  *
  16  *      please give the ports of all IRC servers You wish to connect to.
  17  *      If You don't specify ports, the default will be port 6667.
  18  *      With max_dcc_channels you can define the maximum number of not
  19  *      yet answered DCC channels per IRC session (default 8).
  20  *      With dcc_timeout you can specify how long the system waits for
  21  *      an expected DCC channel (default 300 seconds).
  22  *
  23  */
  24
  25 #include <linux/config.h>
  26 #include <linux/module.h>
  27 #include <linux/netfilter.h>
  28 #include <linux/ip.h>
  29 #include <net/checksum.h>
  30 #include <net/tcp.h>
  31
  32 #include <linux/netfilter_ipv4/lockhelp.h>
  33 #include <linux/netfilter_ipv4/ip_conntrack_helper.h>
  34 #include <linux/netfilter_ipv4/ip_conntrack_irc.h>
  35
  36 #define MAX_PORTS 8
  37 static int ports[MAX_PORTS];
  38 static int ports_c;
  39 static int max_dcc_channels = 8;
  40 static unsigned int dcc_timeout = 300;
  41 /* This is slow, but it's simple. --RR */
  42 static char irc_buffer[65536];
  43
  44 MODULE_AUTHOR("Harald Welte <laforge@netfilter.org>");
  45 MODULE_DESCRIPTION("IRC (DCC) connection tracking helper");
  46 MODULE_LICENSE("GPL");
  47 MODULE_PARM(ports, "1-" __MODULE_STRING(MAX_PORTS) "i");
  48 MODULE_PARM_DESC(ports, "port numbers of IRC servers");
  49 MODULE_PARM(max_dcc_channels, "i");
  50 MODULE_PARM_DESC(max_dcc_channels, "max number of expected DCC channels per IRC session");
  51 MODULE_PARM(dcc_timeout, "i");
  52 MODULE_PARM_DESC(dcc_timeout, "timeout on for unestablished DCC channels");
  53
  54 static char *dccprotos[] = { "SEND ", "CHAT ", "MOVE ", "TSEND ", "SCHAT " };
  55 #define MINMATCHLEN     5
  56
  57 DECLARE_LOCK(ip_irc_lock);
  58 struct module *ip_conntrack_irc = THIS_MODULE;
  59
  60 #if 0
  61 #define DEBUGP(format, args...) printk(KERN_DEBUG "%s:%s:" format, \
  62                                        __FILE__, __FUNCTION__ , ## args)
  63 #else
  64 #define DEBUGP(format, args...)
  65 #endif
  66
  67 int parse_dcc(char *data, char *data_end, u_int32_t * ip, u_int16_t * port,
  68               char **ad_beg_p, char **ad_end_p)
  69 /* tries to get the ip_addr and port out of a dcc command
  70    return value: -1 on failure, 0 on success
  71         data            pointer to first byte of DCC command data
  72         data_end        pointer to last byte of dcc command data
  73         ip              returns parsed ip of dcc command
  74         port            returns parsed port of dcc command
  75         ad_beg_p        returns pointer to first byte of addr data
  76         ad_end_p        returns pointer to last byte of addr data */
  77 {
  78
  79         /* at least 12: "AAAAAAAA P\1\n" */
  80         while (*data++ != ' ')
  81                 if (data > data_end - 12)
  82                         return -1;
  83
  84         *ad_beg_p = data;
  85         *ip = simple_strtoul(data, &data, 10);
  86
  87         /* skip blanks between ip and port */
  88         while (*data == ' ') {
  89                 if (data >= data_end)
  90                         return -1;
  91                 data++;
  92         }
  93
  94         *port = simple_strtoul(data, &data, 10);
  95         *ad_end_p = data;
  96
  97         return 0;
  98 }
  99
 100 static int help(struct sk_buff *skb,
 101                 struct ip_conntrack *ct, enum ip_conntrack_info ctinfo)
 102 {
 103         unsigned int dataoff;
 104         struct tcphdr tcph;
 105         char *data, *data_limit;
 106         int dir = CTINFO2DIR(ctinfo);
 107         struct ip_conntrack_expect *exp;
 108         struct ip_ct_irc_expect *exp_irc_info = NULL;
 109
 110         u_int32_t dcc_ip;
 111         u_int16_t dcc_port;
 112         int i;
 113         char *addr_beg_p, *addr_end_p;
 114
 115         DEBUGP("entered\n");
 116
 117         /* If packet is coming from IRC server */
 118         if (dir == IP_CT_DIR_REPLY)
 119                 return NF_ACCEPT;
 120
 121         /* Until there's been traffic both ways, don't look in packets. */
 122         if (ctinfo != IP_CT_ESTABLISHED
 123             && ctinfo != IP_CT_ESTABLISHED + IP_CT_IS_REPLY) {
 124                 DEBUGP("Conntrackinfo = %u\n", ctinfo);
 125                 return NF_ACCEPT;
 126         }
 127
 128         /* Not a full tcp header? */
 129         if (skb_copy_bits(skb, skb->nh.iph->ihl*4, &tcph, sizeof(tcph)) != 0)
 130                 return NF_ACCEPT;
 131
 132         /* No data? */
 133         dataoff = skb->nh.iph->ihl*4 + tcph.doff*4;
 134         if (dataoff >= skb->len)
 135                 return NF_ACCEPT;
 136
 137         LOCK_BH(&ip_irc_lock);
 138         skb_copy_bits(skb, dataoff, irc_buffer, skb->len - dataoff);
 139
 140         data = irc_buffer;
 141         data_limit = irc_buffer + skb->len - dataoff;
 142
 143         /* strlen("\1DCC SENT t AAAAAAAA P\1\n")=24
 144          * 5+MINMATCHLEN+strlen("t AAAAAAAA P\1\n")=14 */
 145         while (data < (data_limit - (19 + MINMATCHLEN))) {
 146                 if (memcmp(data, "\1DCC ", 5)) {
 147                         data++;
 148                         continue;
 149                 }
 150
 151                 data += 5;
 152                 /* we have at least (19+MINMATCHLEN)-5 bytes valid data left */
 153
 154                 DEBUGP("DCC found in master %u.%u.%u.%u:%u %u.%u.%u.%u:%u...\n",
 155                         NIPQUAD(iph->saddr), ntohs(tcph.source),
 156                         NIPQUAD(iph->daddr), ntohs(tcph.dest));
 157
 158                 for (i = 0; i < ARRAY_SIZE(dccprotos); i++) {
 159                         if (memcmp(data, dccprotos[i], strlen(dccprotos[i]))) {
 160                                 /* no match */
 161                                 continue;
 162                         }
 163
 164                         DEBUGP("DCC %s detected\n", dccprotos[i]);
 165                         data += strlen(dccprotos[i]);
 166                         /* we have at least
 167                          * (19+MINMATCHLEN)-5-dccprotos[i].matchlen bytes valid
 168                          * data left (== 14/13 bytes) */
 169                         if (parse_dcc((char *)data, data_limit, &dcc_ip,
 170                                        &dcc_port, &addr_beg_p, &addr_end_p)) {
 171                                 /* unable to parse */
 172                                 DEBUGP("unable to parse dcc command\n");
 173                                 continue;
 174                         }
 175                         DEBUGP("DCC bound ip/port: %u.%u.%u.%u:%u\n",
 176                                 HIPQUAD(dcc_ip), dcc_port);
 177
 178                         /* dcc_ip can be the internal OR external (NAT'ed) IP
 179                          * Tiago Sousa <mirage@kaotik.org> */
 180                         if (ct->tuplehash[dir].tuple.src.ip != htonl(dcc_ip)
 181                             && ct->tuplehash[IP_CT_DIR_REPLY].tuple.dst.ip != htonl(dcc_ip)) {
 182                                 if (net_ratelimit())
 183                                         printk(KERN_WARNING
 184                                                 "Forged DCC command from "
 185                                                 "%u.%u.%u.%u: %u.%u.%u.%u:%u\n",
 186                                 NIPQUAD(ct->tuplehash[dir].tuple.src.ip),
 187                                                 HIPQUAD(dcc_ip), dcc_port);
 188
 189                                 continue;
 190                         }
 191
 192                         exp = ip_conntrack_expect_alloc();
 193                         if (exp == NULL)
 194                                 goto out;
 195
 196                         exp_irc_info = &exp->help.exp_irc_info;
 197
 198                         /* save position of address in dcc string,
 199                          * necessary for NAT */
 200                         DEBUGP("tcph->seq = %u\n", tcph.seq);
 201                         exp->seq = ntohl(tcph.seq) + (addr_beg_p - irc_buffer);
 202                         exp_irc_info->len = (addr_end_p - addr_beg_p);
 203                         exp_irc_info->port = dcc_port;
 204                         DEBUGP("wrote info seq=%u (ofs=%u), len=%d\n",
 205                                 exp->seq, (addr_end_p - _data), exp_irc_info->len);
 206
 207                         exp->tuple = ((struct ip_conntrack_tuple)
 208                                 { { 0, { 0 } },
 209                                   { ct->tuplehash[dir].tuple.src.ip, { .tcp = { htons(dcc_port) } },
 210                                     IPPROTO_TCP }});
 211                         exp->mask = ((struct ip_conntrack_tuple)
 212                                 { { 0, { 0 } },
 213                                   { 0xFFFFFFFF, { .tcp = { 0xFFFF } }, 0xFFFF }});
 214
 215                         exp->expectfn = NULL;
 216
 217                         DEBUGP("expect_related %u.%u.%u.%u:%u-%u.%u.%u.%u:%u\n",
 218                                 NIPQUAD(exp->tuple.src.ip),
 219                                 ntohs(exp->tuple.src.u.tcp.port),
 220                                 NIPQUAD(exp->tuple.dst.ip),
 221                                 ntohs(exp->tuple.dst.u.tcp.port));
 222
 223                         ip_conntrack_expect_related(exp, ct);
 224
 225                         goto out;
 226                 } /* for .. NUM_DCCPROTO */
 227         } /* while data < ... */
 228
 229  out:
 230         UNLOCK_BH(&ip_irc_lock);
 231         return NF_ACCEPT;
 232 }
 233
 234 static struct ip_conntrack_helper irc_helpers[MAX_PORTS];
 235 static char irc_names[MAX_PORTS][10];
 236
 237 static void fini(void);
 238
 239 static int __init init(void)
 240 {
 241         int i, ret;
 242         struct ip_conntrack_helper *hlpr;
 243         char *tmpname;
 244
 245         if (max_dcc_channels < 1) {
 246                 printk("ip_conntrack_irc: max_dcc_channels must be a positive integer\n");
 247                 return -EBUSY;
 248         }
 249         if (dcc_timeout < 0) {
 250                 printk("ip_conntrack_irc: dcc_timeout must be a positive integer\n");
 251                 return -EBUSY;
 252         }
 253
 254         /* If no port given, default to standard irc port */
 255         if (ports[0] == 0)
 256                 ports[0] = IRC_PORT;
 257
 258         for (i = 0; (i < MAX_PORTS) && ports[i]; i++) {
 259                 hlpr = &irc_helpers[i];
 260                 hlpr->tuple.src.u.tcp.port = htons(ports[i]);
 261                 hlpr->tuple.dst.protonum = IPPROTO_TCP;
 262                 hlpr->mask.src.u.tcp.port = 0xFFFF;
 263                 hlpr->mask.dst.protonum = 0xFFFF;
 264                 hlpr->max_expected = max_dcc_channels;
 265                 hlpr->timeout = dcc_timeout;
 266                 hlpr->flags = IP_CT_HELPER_F_REUSE_EXPECT;
 267                 hlpr->me = ip_conntrack_irc;
 268                 hlpr->help = help;
 269
 270                 tmpname = &irc_names[i][0];
 271                 if (ports[i] == IRC_PORT)
 272                         sprintf(tmpname, "irc");
 273                 else
 274                         sprintf(tmpname, "irc-%d", i);
 275                 hlpr->name = tmpname;
 276
 277                 DEBUGP("port #%d: %d\n", i, ports[i]);
 278
 279                 ret = ip_conntrack_helper_register(hlpr);
 280
 281                 if (ret) {
 282                         printk("ip_conntrack_irc: ERROR registering port %d\n",
 283                                 ports[i]);
 284                         fini();
 285                         return -EBUSY;
 286                 }
 287                 ports_c++;
 288         }
 289         return 0;
 290 }
 291
 292 /* This function is intentionally _NOT_ defined as __exit, because
 293  * it is needed by the init function */
 294 static void fini(void)
 295 {
 296         int i;
 297         for (i = 0; i < ports_c; i++) {
 298                 DEBUGP("unregistering port %d\n",
 299                        ports[i]);
 300                 ip_conntrack_helper_unregister(&irc_helpers[i]);
 301         }
 302 }
 303
 304 PROVIDES_CONNTRACK(irc);
 305 EXPORT_SYMBOL(ip_irc_lock);
 306
 307 module_init(init);
 308 module_exit(fini);