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 unsigned int (*ip_nat_irc_hook)(struct sk_buff **pskb,
  47                                 enum ip_conntrack_info ctinfo,
  48                                 unsigned int matchoff,
  49                                 unsigned int matchlen,
  50                                 struct ip_conntrack_expect *exp);
  51 EXPORT_SYMBOL_GPL(ip_nat_irc_hook);
  52
  53 MODULE_AUTHOR("Harald Welte <laforge@netfilter.org>");
  54 MODULE_DESCRIPTION("IRC (DCC) connection tracking helper");
  55 MODULE_LICENSE("GPL");
  56 module_param_array(ports, int, &ports_c, 0400);
  57 MODULE_PARM_DESC(ports, "port numbers of IRC servers");
  58 module_param(max_dcc_channels, int, 0400);
  59 MODULE_PARM_DESC(max_dcc_channels, "max number of expected DCC channels per IRC session");
  60 module_param(dcc_timeout, int, 0400);
  61 MODULE_PARM_DESC(dcc_timeout, "timeout on for unestablished DCC channels");
  62
  63 static char *dccprotos[] = { "SEND ", "CHAT ", "MOVE ", "TSEND ", "SCHAT " };
  64 #define MINMATCHLEN     5
  65
  66 #if 0
  67 #define DEBUGP(format, args...) printk(KERN_DEBUG "%s:%s:" format, \
  68                                        __FILE__, __FUNCTION__ , ## args)
  69 #else
  70 #define DEBUGP(format, args...)
  71 #endif
  72
  73 static int parse_dcc(char *data, char *data_end, u_int32_t *ip,
  74                      u_int16_t *port, char **ad_beg_p, char **ad_end_p)
  75 /* tries to get the ip_addr and port out of a dcc command
  76    return value: -1 on failure, 0 on success
  77         data            pointer to first byte of DCC command data
  78         data_end        pointer to last byte of dcc command data
  79         ip              returns parsed ip of dcc command
  80         port            returns parsed port of dcc command
  81         ad_beg_p        returns pointer to first byte of addr data
  82         ad_end_p        returns pointer to last byte of addr data */
  83 {
  84
  85         /* at least 12: "AAAAAAAA P\1\n" */
  86         while (*data++ != ' ')
  87                 if (data > data_end - 12)
  88                         return -1;
  89
  90         *ad_beg_p = data;
  91         *ip = 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 **pskb,
 107                 struct ip_conntrack *ct, enum ip_conntrack_info ctinfo)
 108 {
 109         unsigned int dataoff;
 110         struct tcphdr _tcph, *th;
 111         char *data, *data_limit, *ib_ptr;
 112         int dir = CTINFO2DIR(ctinfo);
 113         struct ip_conntrack_expect *exp;
 114         u32 seq;
 115         u_int32_t dcc_ip;
 116         u_int16_t dcc_port;
 117         int i, ret = NF_ACCEPT;
 118         char *addr_beg_p, *addr_end_p;
 119
 120         DEBUGP("entered\n");
 121
 122         /* If packet is coming from IRC server */
 123         if (dir == IP_CT_DIR_REPLY)
 124                 return NF_ACCEPT;
 125
 126         /* Until there's been traffic both ways, don't look in packets. */
 127         if (ctinfo != IP_CT_ESTABLISHED
 128             && ctinfo != IP_CT_ESTABLISHED + IP_CT_IS_REPLY) {
 129                 DEBUGP("Conntrackinfo = %u\n", ctinfo);
 130                 return NF_ACCEPT;
 131         }
 132
 133         /* Not a full tcp header? */
 134         th = skb_header_pointer(*pskb, (*pskb)->nh.iph->ihl*4,
 135                                 sizeof(_tcph), &_tcph);
 136         if (th == NULL)
 137                 return NF_ACCEPT;
 138
 139         /* No data? */
 140         dataoff = (*pskb)->nh.iph->ihl*4 + th->doff*4;
 141         if (dataoff >= (*pskb)->len)
 142                 return NF_ACCEPT;
 143
 144         LOCK_BH(&irc_buffer_lock);
 145         ib_ptr = skb_header_pointer(*pskb, dataoff,
 146                                     (*pskb)->len - dataoff, irc_buffer);
 147         BUG_ON(ib_ptr == NULL);
 148
 149         data = ib_ptr;
 150         data_limit = ib_ptr + (*pskb)->len - dataoff;
 151
 152         /* strlen("\1DCC SENT t AAAAAAAA P\1\n")=24
 153          * 5+MINMATCHLEN+strlen("t AAAAAAAA P\1\n")=14 */
 154         while (data < (data_limit - (19 + MINMATCHLEN))) {
 155                 if (memcmp(data, "\1DCC ", 5)) {
 156                         data++;
 157                         continue;
 158                 }
 159
 160                 data += 5;
 161                 /* we have at least (19+MINMATCHLEN)-5 bytes valid data left */
 162
 163                 DEBUGP("DCC found in master %u.%u.%u.%u:%u %u.%u.%u.%u:%u...\n",
 164                         NIPQUAD(iph->saddr), ntohs(th->source),
 165                         NIPQUAD(iph->daddr), ntohs(th->dest));
 166
 167                 for (i = 0; i < ARRAY_SIZE(dccprotos); i++) {
 168                         if (memcmp(data, dccprotos[i], strlen(dccprotos[i]))) {
 169                                 /* no match */
 170                                 continue;
 171                         }
 172
 173                         DEBUGP("DCC %s detected\n", dccprotos[i]);
 174                         data += strlen(dccprotos[i]);
 175                         /* we have at least
 176                          * (19+MINMATCHLEN)-5-dccprotos[i].matchlen bytes valid
 177                          * data left (== 14/13 bytes) */
 178                         if (parse_dcc((char *)data, data_limit, &dcc_ip,
 179                                        &dcc_port, &addr_beg_p, &addr_end_p)) {
 180                                 /* unable to parse */
 181                                 DEBUGP("unable to parse dcc command\n");
 182                                 continue;
 183                         }
 184                         DEBUGP("DCC bound ip/port: %u.%u.%u.%u:%u\n",
 185                                 HIPQUAD(dcc_ip), dcc_port);
 186
 187                         /* dcc_ip can be the internal OR external (NAT'ed) IP
 188                          * Tiago Sousa <mirage@kaotik.org> */
 189                         if (ct->tuplehash[dir].tuple.src.ip != htonl(dcc_ip)
 190                             && ct->tuplehash[IP_CT_DIR_REPLY].tuple.dst.ip != htonl(dcc_ip)) {
 191                                 if (net_ratelimit())
 192                                         printk(KERN_WARNING
 193                                                 "Forged DCC command from "
 194                                                 "%u.%u.%u.%u: %u.%u.%u.%u:%u\n",
 195                                 NIPQUAD(ct->tuplehash[dir].tuple.src.ip),
 196                                                 HIPQUAD(dcc_ip), dcc_port);
 197
 198                                 continue;
 199                         }
 200
 201                         exp = ip_conntrack_expect_alloc();
 202                         if (exp == NULL) {
 203                                 ret = NF_DROP;
 204                                 goto out;
 205                         }
 206
 207                         /* save position of address in dcc string,
 208                          * necessary for NAT */
 209                         DEBUGP("tcph->seq = %u\n", th->seq);
 210                         seq = ntohl(th->seq) + (addr_beg_p - ib_ptr);
 211
 212                         /* We refer to the reverse direction ("!dir")
 213                          * tuples here, because we're expecting
 214                          * something in the other * direction.
 215                          * Doesn't matter unless NAT is happening.  */
 216                         exp->tuple = ((struct ip_conntrack_tuple)
 217                                 { { 0, { 0 } },
 218                                   { ct->tuplehash[!dir].tuple.dst.ip,
 219                                     { .tcp = { htons(dcc_port) } },
 220                                     IPPROTO_TCP }});
 221                         exp->mask = ((struct ip_conntrack_tuple)
 222                                 { { 0, { 0 } },
 223                                   { 0xFFFFFFFF, { .tcp = { 0xFFFF } }, 0xFF }});
 224                         exp->expectfn = NULL;
 225                         exp->master = ct;
 226                         if (ip_nat_irc_hook)
 227                                 ret = ip_nat_irc_hook(pskb, ctinfo,
 228                                                       addr_beg_p - ib_ptr,
 229                                                       addr_end_p - addr_beg_p,
 230                                                       exp);
 231                         else if (ip_conntrack_expect_related(exp) != 0) {
 232                                 ip_conntrack_expect_free(exp);
 233                                 ret = NF_DROP;
 234                         }
 235                         goto out;
 236                 } /* for .. NUM_DCCPROTO */
 237         } /* while data < ... */
 238
 239  out:
 240         UNLOCK_BH(&irc_buffer_lock);
 241         return ret;
 242 }
 243
 244 static struct ip_conntrack_helper irc_helpers[MAX_PORTS];
 245 static char irc_names[MAX_PORTS][10];
 246
 247 static void fini(void);
 248
 249 static int __init init(void)
 250 {
 251         int i, ret;
 252         struct ip_conntrack_helper *hlpr;
 253         char *tmpname;
 254
 255         if (max_dcc_channels < 1) {
 256                 printk("ip_conntrack_irc: max_dcc_channels must be a positive integer\n");
 257                 return -EBUSY;
 258         }
 259         if (dcc_timeout < 0) {
 260                 printk("ip_conntrack_irc: dcc_timeout must be a positive integer\n");
 261                 return -EBUSY;
 262         }
 263
 264         /* If no port given, default to standard irc port */
 265         if (ports_c == 0)
 266                 ports[ports_c++] = IRC_PORT;
 267
 268         for (i = 0; i < ports_c; i++) {
 269                 hlpr = &irc_helpers[i];
 270                 hlpr->tuple.src.u.tcp.port = htons(ports[i]);
 271                 hlpr->tuple.dst.protonum = IPPROTO_TCP;
 272                 hlpr->mask.src.u.tcp.port = 0xFFFF;
 273                 hlpr->mask.dst.protonum = 0xFF;
 274                 hlpr->max_expected = max_dcc_channels;
 275                 hlpr->timeout = dcc_timeout;
 276                 hlpr->me = THIS_MODULE;
 277                 hlpr->help = help;
 278
 279                 tmpname = &irc_names[i][0];
 280                 if (ports[i] == IRC_PORT)
 281                         sprintf(tmpname, "irc");
 282                 else
 283                         sprintf(tmpname, "irc-%d", i);
 284                 hlpr->name = tmpname;
 285
 286                 DEBUGP("port #%d: %d\n", i, ports[i]);
 287
 288                 ret = ip_conntrack_helper_register(hlpr);
 289
 290                 if (ret) {
 291                         printk("ip_conntrack_irc: ERROR registering port %d\n",
 292                                 ports[i]);
 293                         fini();
 294                         return -EBUSY;
 295                 }
 296         }
 297         return 0;
 298 }
 299
 300 /* This function is intentionally _NOT_ defined as __exit, because
 301  * it is needed by the init function */
 302 static void fini(void)
 303 {
 304         int i;
 305         for (i = 0; i < ports_c; i++) {
 306                 DEBUGP("unregistering port %d\n",
 307                        ports[i]);
 308                 ip_conntrack_helper_unregister(&irc_helpers[i]);
 309         }
 310 }
 311
 312 module_init(init);
 313 module_exit(fini);