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 #include <linux/moduleparam.h>
  36
  37 #define MAX_PORTS 8
  38 static int ports[MAX_PORTS];
  39 static int ports_c;
  40 static int max_dcc_channels = 8;
  41 static unsigned int dcc_timeout = 300;
  42 /* This is slow, but it's simple. --RR */
  43 static char irc_buffer[65536];
  44 static DECLARE_LOCK(irc_buffer_lock);
  45
  46 MODULE_AUTHOR("Harald Welte <laforge@netfilter.org>");
  47 MODULE_DESCRIPTION("IRC (DCC) connection tracking helper");
  48 MODULE_LICENSE("GPL");
  49 module_param_array(ports, int, ports_c, 0400);
  50 MODULE_PARM_DESC(ports, "port numbers of IRC servers");
  51 module_param(max_dcc_channels, int, 0400);
  52 MODULE_PARM_DESC(max_dcc_channels, "max number of expected DCC channels per IRC session");
  53 module_param(dcc_timeout, int, 0400);
  54 MODULE_PARM_DESC(dcc_timeout, "timeout on for unestablished DCC channels");
  55
  56 static char *dccprotos[] = { "SEND ", "CHAT ", "MOVE ", "TSEND ", "SCHAT " };
  57 #define MINMATCHLEN     5
  58
  59 struct module *ip_conntrack_irc = THIS_MODULE;
  60
  61 #if 0
  62 #define DEBUGP(format, args...) printk(KERN_DEBUG "%s:%s:" format, \
  63                                        __FILE__, __FUNCTION__ , ## args)
  64 #else
  65 #define DEBUGP(format, args...)
  66 #endif
  67
  68 int parse_dcc(char *data, char *data_end, u_int32_t * ip, u_int16_t * port,
  69               char **ad_beg_p, char **ad_end_p)
  70 /* tries to get the ip_addr and port out of a dcc command
  71    return value: -1 on failure, 0 on success
  72         data            pointer to first byte of DCC command data
  73         data_end        pointer to last byte of dcc command data
  74         ip              returns parsed ip of dcc command
  75         port            returns parsed port of dcc command
  76         ad_beg_p        returns pointer to first byte of addr data
  77         ad_end_p        returns pointer to last byte of addr data */
  78 {
  79
  80         /* at least 12: "AAAAAAAA P\1\n" */
  81         while (*data++ != ' ')
  82                 if (data > data_end - 12)
  83                         return -1;
  84
  85         *ad_beg_p = data;
  86         *ip = simple_strtoul(data, &data, 10);
  87
  88         /* skip blanks between ip and port */
  89         while (*data == ' ') {
  90                 if (data >= data_end)
  91                         return -1;
  92                 data++;
  93         }
  94
  95         *port = simple_strtoul(data, &data, 10);
  96         *ad_end_p = data;
  97
  98         return 0;
  99 }
 100
 101 static int help(struct sk_buff *skb,
 102                 struct ip_conntrack *ct, enum ip_conntrack_info ctinfo)
 103 {
 104         unsigned int dataoff;
 105         struct tcphdr _tcph, *th;
 106         char *data, *data_limit, *ib_ptr;
 107         int dir = CTINFO2DIR(ctinfo);
 108         struct ip_conntrack_expect *exp;
 109         struct ip_ct_irc_expect *exp_irc_info = NULL;
 110
 111         u_int32_t dcc_ip;
 112         u_int16_t dcc_port;
 113         int i;
 114         char *addr_beg_p, *addr_end_p;
 115
 116         DEBUGP("entered\n");
 117
 118         /* If packet is coming from IRC server */
 119         if (dir == IP_CT_DIR_REPLY)
 120                 return NF_ACCEPT;
 121
 122         /* Until there's been traffic both ways, don't look in packets. */
 123         if (ctinfo != IP_CT_ESTABLISHED
 124             && ctinfo != IP_CT_ESTABLISHED + IP_CT_IS_REPLY) {
 125                 DEBUGP("Conntrackinfo = %u\n", ctinfo);
 126                 return NF_ACCEPT;
 127         }
 128
 129         /* Not a full tcp header? */
 130         th = skb_header_pointer(skb, skb->nh.iph->ihl*4,
 131                                 sizeof(_tcph), &_tcph);
 132         if (th == NULL)
 133                 return NF_ACCEPT;
 134
 135         /* No data? */
 136         dataoff = skb->nh.iph->ihl*4 + th->doff*4;
 137         if (dataoff >= skb->len)
 138                 return NF_ACCEPT;
 139
 140         LOCK_BH(&irc_buffer_lock);
 141         ib_ptr = skb_header_pointer(skb, dataoff,
 142                                     skb->len - dataoff, irc_buffer);
 143         BUG_ON(ib_ptr == NULL);
 144
 145         data = ib_ptr;
 146         data_limit = ib_ptr + skb->len - dataoff;
 147
 148         /* strlen("\1DCC SENT t AAAAAAAA P\1\n")=24
 149          * 5+MINMATCHLEN+strlen("t AAAAAAAA P\1\n")=14 */
 150         while (data < (data_limit - (19 + MINMATCHLEN))) {
 151                 if (memcmp(data, "\1DCC ", 5)) {
 152                         data++;
 153                         continue;
 154                 }
 155
 156                 data += 5;
 157                 /* we have at least (19+MINMATCHLEN)-5 bytes valid data left */
 158
 159                 DEBUGP("DCC found in master %u.%u.%u.%u:%u %u.%u.%u.%u:%u...\n",
 160                         NIPQUAD(iph->saddr), ntohs(th->source),
 161                         NIPQUAD(iph->daddr), ntohs(th->dest));
 162
 163                 for (i = 0; i < ARRAY_SIZE(dccprotos); i++) {
 164                         if (memcmp(data, dccprotos[i], strlen(dccprotos[i]))) {
 165                                 /* no match */
 166                                 continue;
 167                         }
 168
 169                         DEBUGP("DCC %s detected\n", dccprotos[i]);
 170                         data += strlen(dccprotos[i]);
 171                         /* we have at least
 172                          * (19+MINMATCHLEN)-5-dccprotos[i].matchlen bytes valid
 173                          * data left (== 14/13 bytes) */
 174                         if (parse_dcc((char *)data, data_limit, &dcc_ip,
 175                                        &dcc_port, &addr_beg_p, &addr_end_p)) {
 176                                 /* unable to parse */
 177                                 DEBUGP("unable to parse dcc command\n");
 178                                 continue;
 179                         }
 180                         DEBUGP("DCC bound ip/port: %u.%u.%u.%u:%u\n",
 181                                 HIPQUAD(dcc_ip), dcc_port);
 182
 183                         /* dcc_ip can be the internal OR external (NAT'ed) IP
 184                          * Tiago Sousa <mirage@kaotik.org> */
 185                         if (ct->tuplehash[dir].tuple.src.ip != htonl(dcc_ip)
 186                             && ct->tuplehash[IP_CT_DIR_REPLY].tuple.dst.ip != htonl(dcc_ip)) {
 187                                 if (net_ratelimit())
 188                                         printk(KERN_WARNING
 189                                                 "Forged DCC command from "
 190                                                 "%u.%u.%u.%u: %u.%u.%u.%u:%u\n",
 191                                 NIPQUAD(ct->tuplehash[dir].tuple.src.ip),
 192                                                 HIPQUAD(dcc_ip), dcc_port);
 193
 194                                 continue;
 195                         }
 196
 197                         exp = ip_conntrack_expect_alloc();
 198                         if (exp == NULL)
 199                                 goto out;
 200
 201                         exp_irc_info = &exp->help.exp_irc_info;
 202
 203                         /* save position of address in dcc string,
 204                          * necessary for NAT */
 205                         DEBUGP("tcph->seq = %u\n", th->seq);
 206                         exp->seq = ntohl(th->seq) + (addr_beg_p - ib_ptr);
 207                         exp_irc_info->len = (addr_end_p - addr_beg_p);
 208                         exp_irc_info->port = dcc_port;
 209                         DEBUGP("wrote info seq=%u (ofs=%u), len=%d\n",
 210                                 exp->seq, (addr_end_p - _data), exp_irc_info->len);
 211
 212                         exp->tuple = ((struct ip_conntrack_tuple)
 213                                 { { 0, { 0 } },
 214                                   { ct->tuplehash[dir].tuple.src.ip, { .tcp = { htons(dcc_port) } },
 215                                     IPPROTO_TCP }});
 216                         exp->mask = ((struct ip_conntrack_tuple)
 217                                 { { 0, { 0 } },
 218                                   { 0xFFFFFFFF, { .tcp = { 0xFFFF } }, 0xFFFF }});
 219
 220                         exp->expectfn = NULL;
 221
 222                         DEBUGP("expect_related %u.%u.%u.%u:%u-%u.%u.%u.%u:%u\n",
 223                                 NIPQUAD(exp->tuple.src.ip),
 224                                 ntohs(exp->tuple.src.u.tcp.port),
 225                                 NIPQUAD(exp->tuple.dst.ip),
 226                                 ntohs(exp->tuple.dst.u.tcp.port));
 227
 228                         ip_conntrack_expect_related(exp, ct);
 229
 230                         goto out;
 231                 } /* for .. NUM_DCCPROTO */
 232         } /* while data < ... */
 233
 234  out:
 235         UNLOCK_BH(&irc_buffer_lock);
 236         return NF_ACCEPT;
 237 }
 238
 239 static struct ip_conntrack_helper irc_helpers[MAX_PORTS];
 240 static char irc_names[MAX_PORTS][10];
 241
 242 static void fini(void);
 243
 244 static int __init init(void)
 245 {
 246         int i, ret;
 247         struct ip_conntrack_helper *hlpr;
 248         char *tmpname;
 249
 250         if (max_dcc_channels < 1) {
 251                 printk("ip_conntrack_irc: max_dcc_channels must be a positive integer\n");
 252                 return -EBUSY;
 253         }
 254         if (dcc_timeout < 0) {
 255                 printk("ip_conntrack_irc: dcc_timeout must be a positive integer\n");
 256                 return -EBUSY;
 257         }
 258
 259         /* If no port given, default to standard irc port */
 260         if (ports_c == 0)
 261                 ports[ports_c++] = IRC_PORT;
 262
 263         for (i = 0; i < ports_c; i++) {
 264                 hlpr = &irc_helpers[i];
 265                 hlpr->tuple.src.u.tcp.port = htons(ports[i]);
 266                 hlpr->tuple.dst.protonum = IPPROTO_TCP;
 267                 hlpr->mask.src.u.tcp.port = 0xFFFF;
 268                 hlpr->mask.dst.protonum = 0xFFFF;
 269                 hlpr->max_expected = max_dcc_channels;
 270                 hlpr->timeout = dcc_timeout;
 271                 hlpr->flags = IP_CT_HELPER_F_REUSE_EXPECT;
 272                 hlpr->me = ip_conntrack_irc;
 273                 hlpr->help = help;
 274
 275                 tmpname = &irc_names[i][0];
 276                 if (ports[i] == IRC_PORT)
 277                         sprintf(tmpname, "irc");
 278                 else
 279                         sprintf(tmpname, "irc-%d", i);
 280                 hlpr->name = tmpname;
 281
 282                 DEBUGP("port #%d: %d\n", i, ports[i]);
 283
 284                 ret = ip_conntrack_helper_register(hlpr);
 285
 286                 if (ret) {
 287                         printk("ip_conntrack_irc: ERROR registering port %d\n",
 288                                 ports[i]);
 289                         fini();
 290                         return -EBUSY;
 291                 }
 292         }
 293         return 0;
 294 }
 295
 296 /* This function is intentionally _NOT_ defined as __exit, because
 297  * it is needed by the init function */
 298 static void fini(void)
 299 {
 300         int i;
 301         for (i = 0; i < ports_c; i++) {
 302                 DEBUGP("unregistering port %d\n",
 303                        ports[i]);
 304                 ip_conntrack_helper_unregister(&irc_helpers[i]);
 305         }
 306 }
 307
 308 PROVIDES_CONNTRACK(irc);
 309
 310 module_init(init);
 311 module_exit(fini);