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 #ifdef MODULE_PARM
  48 MODULE_PARM(ports, "1-" __MODULE_STRING(MAX_PORTS) "i");
  49 MODULE_PARM_DESC(ports, "port numbers of IRC servers");
  50 MODULE_PARM(max_dcc_channels, "i");
  51 MODULE_PARM_DESC(max_dcc_channels, "max number of expected DCC channels per IRC session");
  52 MODULE_PARM(dcc_timeout, "i");
  53 MODULE_PARM_DESC(dcc_timeout, "timeout on for unestablished DCC channels");
  54 #endif
  55
  56 static char *dccprotos[] = { "SEND ", "CHAT ", "MOVE ", "TSEND ", "SCHAT " };
  57 #define MINMATCHLEN     5
  58
  59 DECLARE_LOCK(ip_irc_lock);
  60 struct module *ip_conntrack_irc = THIS_MODULE;
  61
  62 #if 0
  63 #define DEBUGP(format, args...) printk(KERN_DEBUG "%s:%s:" format, \
  64                                        __FILE__, __FUNCTION__ , ## args)
  65 #else
  66 #define DEBUGP(format, args...)
  67 #endif
  68
  69 int parse_dcc(char *data, char *data_end, u_int32_t * ip, u_int16_t * port,
  70               char **ad_beg_p, char **ad_end_p)
  71 /* tries to get the ip_addr and port out of a dcc command
  72    return value: -1 on failure, 0 on success
  73         data            pointer to first byte of DCC command data
  74         data_end        pointer to last byte of dcc command data
  75         ip              returns parsed ip of dcc command
  76         port            returns parsed port of dcc command
  77         ad_beg_p        returns pointer to first byte of addr data
  78         ad_end_p        returns pointer to last byte of addr data */
  79 {
  80
  81         /* at least 12: "AAAAAAAA P\1\n" */
  82         while (*data++ != ' ')
  83                 if (data > data_end - 12)
  84                         return -1;
  85
  86         *ad_beg_p = data;
  87         *ip = 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,
 103                 struct ip_conntrack *ct, enum ip_conntrack_info ctinfo)
 104 {
 105         unsigned int dataoff;
 106         struct tcphdr tcph;
 107         char *data, *data_limit;
 108         int dir = CTINFO2DIR(ctinfo);
 109         struct ip_conntrack_expect *exp;
 110         struct ip_ct_irc_expect *exp_irc_info = NULL;
 111
 112         u_int32_t dcc_ip;
 113         u_int16_t dcc_port;
 114         int i;
 115         char *addr_beg_p, *addr_end_p;
 116
 117         DEBUGP("entered\n");
 118
 119         /* If packet is coming from IRC server */
 120         if (dir == IP_CT_DIR_REPLY)
 121                 return NF_ACCEPT;
 122
 123         /* Until there's been traffic both ways, don't look in packets. */
 124         if (ctinfo != IP_CT_ESTABLISHED
 125             && ctinfo != IP_CT_ESTABLISHED + IP_CT_IS_REPLY) {
 126                 DEBUGP("Conntrackinfo = %u\n", ctinfo);
 127                 return NF_ACCEPT;
 128         }
 129
 130         /* Not a full tcp header? */
 131         if (skb_copy_bits(skb, skb->nh.iph->ihl*4, &tcph, sizeof(tcph)) != 0)
 132                 return NF_ACCEPT;
 133
 134         /* No data? */
 135         dataoff = skb->nh.iph->ihl*4 + tcph.doff*4;
 136         if (dataoff >= skb->len)
 137                 return NF_ACCEPT;
 138
 139         LOCK_BH(&ip_irc_lock);
 140         skb_copy_bits(skb, dataoff, irc_buffer, skb->len - dataoff);
 141
 142         data = irc_buffer;
 143         data_limit = irc_buffer + skb->len - dataoff;
 144
 145         /* strlen("\1DCC SENT t AAAAAAAA P\1\n")=24
 146          * 5+MINMATCHLEN+strlen("t AAAAAAAA P\1\n")=14 */
 147         while (data < (data_limit - (19 + MINMATCHLEN))) {
 148                 if (memcmp(data, "\1DCC ", 5)) {
 149                         data++;
 150                         continue;
 151                 }
 152
 153                 data += 5;
 154                 /* we have at least (19+MINMATCHLEN)-5 bytes valid data left */
 155
 156                 DEBUGP("DCC found in master %u.%u.%u.%u:%u %u.%u.%u.%u:%u...\n",
 157                         NIPQUAD(iph->saddr), ntohs(tcph.source),
 158                         NIPQUAD(iph->daddr), ntohs(tcph.dest));
 159
 160                 for (i = 0; i < ARRAY_SIZE(dccprotos); i++) {
 161                         if (memcmp(data, dccprotos[i], strlen(dccprotos[i]))) {
 162                                 /* no match */
 163                                 continue;
 164                         }
 165
 166                         DEBUGP("DCC %s detected\n", dccprotos[i]);
 167                         data += strlen(dccprotos[i]);
 168                         /* we have at least
 169                          * (19+MINMATCHLEN)-5-dccprotos[i].matchlen bytes valid
 170                          * data left (== 14/13 bytes) */
 171                         if (parse_dcc((char *)data, data_limit, &dcc_ip,
 172                                        &dcc_port, &addr_beg_p, &addr_end_p)) {
 173                                 /* unable to parse */
 174                                 DEBUGP("unable to parse dcc command\n");
 175                                 continue;
 176                         }
 177                         DEBUGP("DCC bound ip/port: %u.%u.%u.%u:%u\n",
 178                                 HIPQUAD(dcc_ip), dcc_port);
 179
 180                         /* dcc_ip can be the internal OR external (NAT'ed) IP
 181                          * Tiago Sousa <mirage@kaotik.org> */
 182                         if (ct->tuplehash[dir].tuple.src.ip != htonl(dcc_ip)
 183                             && ct->tuplehash[IP_CT_DIR_REPLY].tuple.dst.ip != htonl(dcc_ip)) {
 184                                 if (net_ratelimit())
 185                                         printk(KERN_WARNING
 186                                                 "Forged DCC command from "
 187                                                 "%u.%u.%u.%u: %u.%u.%u.%u:%u\n",
 188                                 NIPQUAD(ct->tuplehash[dir].tuple.src.ip),
 189                                                 HIPQUAD(dcc_ip), dcc_port);
 190
 191                                 continue;
 192                         }
 193
 194                         exp = ip_conntrack_expect_alloc();
 195                         if (exp == NULL)
 196                                 goto out;
 197
 198                         exp_irc_info = &exp->help.exp_irc_info;
 199
 200                         /* save position of address in dcc string,
 201                          * necessary for NAT */
 202                         DEBUGP("tcph->seq = %u\n", tcph.seq);
 203                         exp->seq = ntohl(tcph.seq) + (addr_beg_p - irc_buffer);
 204                         exp_irc_info->len = (addr_end_p - addr_beg_p);
 205                         exp_irc_info->port = dcc_port;
 206                         DEBUGP("wrote info seq=%u (ofs=%u), len=%d\n",
 207                                 exp->seq, (addr_end_p - _data), exp_irc_info->len);
 208
 209                         exp->tuple = ((struct ip_conntrack_tuple)
 210                                 { { 0, { 0 } },
 211                                   { ct->tuplehash[dir].tuple.src.ip, { .tcp = { htons(dcc_port) } },
 212                                     IPPROTO_TCP }});
 213                         exp->mask = ((struct ip_conntrack_tuple)
 214                                 { { 0, { 0 } },
 215                                   { 0xFFFFFFFF, { .tcp = { 0xFFFF } }, 0xFFFF }});
 216
 217                         exp->expectfn = NULL;
 218
 219                         DEBUGP("expect_related %u.%u.%u.%u:%u-%u.%u.%u.%u:%u\n",
 220                                 NIPQUAD(exp->tuple.src.ip),
 221                                 ntohs(exp->tuple.src.u.tcp.port),
 222                                 NIPQUAD(exp->tuple.dst.ip),
 223                                 ntohs(exp->tuple.dst.u.tcp.port));
 224
 225                         ip_conntrack_expect_related(exp, ct);
 226
 227                         goto out;
 228                 } /* for .. NUM_DCCPROTO */
 229         } /* while data < ... */
 230
 231  out:
 232         UNLOCK_BH(&ip_irc_lock);
 233         return NF_ACCEPT;
 234 }
 235
 236 static struct ip_conntrack_helper irc_helpers[MAX_PORTS];
 237 static char irc_names[MAX_PORTS][10];
 238
 239 static void fini(void);
 240
 241 static int __init init(void)
 242 {
 243         int i, ret;
 244         struct ip_conntrack_helper *hlpr;
 245         char *tmpname;
 246
 247         if (max_dcc_channels < 1) {
 248                 printk("ip_conntrack_irc: max_dcc_channels must be a positive integer\n");
 249                 return -EBUSY;
 250         }
 251         if (dcc_timeout < 0) {
 252                 printk("ip_conntrack_irc: dcc_timeout must be a positive integer\n");
 253                 return -EBUSY;
 254         }
 255
 256         /* If no port given, default to standard irc port */
 257         if (ports[0] == 0)
 258                 ports[0] = IRC_PORT;
 259
 260         for (i = 0; (i < MAX_PORTS) && ports[i]; i++) {
 261                 hlpr = &irc_helpers[i];
 262                 hlpr->tuple.src.u.tcp.port = htons(ports[i]);
 263                 hlpr->tuple.dst.protonum = IPPROTO_TCP;
 264                 hlpr->mask.src.u.tcp.port = 0xFFFF;
 265                 hlpr->mask.dst.protonum = 0xFFFF;
 266                 hlpr->max_expected = max_dcc_channels;
 267                 hlpr->timeout = dcc_timeout;
 268                 hlpr->flags = IP_CT_HELPER_F_REUSE_EXPECT;
 269                 hlpr->me = ip_conntrack_irc;
 270                 hlpr->help = help;
 271
 272                 tmpname = &irc_names[i][0];
 273                 if (ports[i] == IRC_PORT)
 274                         sprintf(tmpname, "irc");
 275                 else
 276                         sprintf(tmpname, "irc-%d", i);
 277                 hlpr->name = tmpname;
 278
 279                 DEBUGP("port #%d: %d\n", i, ports[i]);
 280
 281                 ret = ip_conntrack_helper_register(hlpr);
 282
 283                 if (ret) {
 284                         printk("ip_conntrack_irc: ERROR registering port %d\n",
 285                                 ports[i]);
 286                         fini();
 287                         return -EBUSY;
 288                 }
 289                 ports_c++;
 290         }
 291         return 0;
 292 }
 293
 294 /* This function is intentionally _NOT_ defined as __exit, because
 295  * it is needed by the init function */
 296 static void fini(void)
 297 {
 298         int i;
 299         for (i = 0; i < ports_c; i++) {
 300                 DEBUGP("unregistering port %d\n",
 301                        ports[i]);
 302                 ip_conntrack_helper_unregister(&irc_helpers[i]);
 303         }
 304 }
 305
 306 PROVIDES_CONNTRACK(irc);
 307 EXPORT_SYMBOL(ip_irc_lock);
 308
 309 module_init(init);
 310 module_exit(fini);