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/module.h>
  26 #include <linux/netfilter.h>
  27 #include <linux/ip.h>
  28 #include <net/checksum.h>
  29 #include <net/tcp.h>
  30
  31 #include <linux/netfilter_ipv4/ip_conntrack_helper.h>
  32 #include <linux/netfilter_ipv4/ip_conntrack_irc.h>
  33 #include <linux/moduleparam.h>
  34
  35 #define MAX_PORTS 8
  36 static unsigned short ports[MAX_PORTS];
  37 static int ports_c;
  38 static unsigned int max_dcc_channels = 8;
  39 static unsigned int dcc_timeout = 300;
  40 /* This is slow, but it's simple. --RR */
  41 static char *irc_buffer;
  42 static DEFINE_SPINLOCK(irc_buffer_lock);
  43
  44 unsigned int (*ip_nat_irc_hook)(struct sk_buff **pskb,
  45                                 enum ip_conntrack_info ctinfo,
  46                                 unsigned int matchoff,
  47                                 unsigned int matchlen,
  48                                 struct ip_conntrack_expect *exp);
  49 EXPORT_SYMBOL_GPL(ip_nat_irc_hook);
  50
  51 MODULE_AUTHOR("Harald Welte <laforge@netfilter.org>");
  52 MODULE_DESCRIPTION("IRC (DCC) connection tracking helper");
  53 MODULE_LICENSE("GPL");
  54 module_param_array(ports, ushort, &ports_c, 0400);
  55 MODULE_PARM_DESC(ports, "port numbers of IRC servers");
  56 module_param(max_dcc_channels, uint, 0400);
  57 MODULE_PARM_DESC(max_dcc_channels, "max number of expected DCC channels per IRC session");
  58 module_param(dcc_timeout, uint, 0400);
  59 MODULE_PARM_DESC(dcc_timeout, "timeout on for unestablished DCC channels");
  60
  61 static const char *dccprotos[] = { "SEND ", "CHAT ", "MOVE ", "TSEND ", "SCHAT " };
  62 #define MINMATCHLEN     5
  63
  64 #if 0
  65 #define DEBUGP(format, args...) printk(KERN_DEBUG "%s:%s:" format, \
  66                                        __FILE__, __FUNCTION__ , ## args)
  67 #else
  68 #define DEBUGP(format, args...)
  69 #endif
  70
  71 static int parse_dcc(char *data, char *data_end, u_int32_t *ip,
  72                      u_int16_t *port, char **ad_beg_p, char **ad_end_p)
  73 /* tries to get the ip_addr and port out of a dcc command
  74    return value: -1 on failure, 0 on success
  75         data            pointer to first byte of DCC command data
  76         data_end        pointer to last byte of dcc command data
  77         ip              returns parsed ip of dcc command
  78         port            returns parsed port of dcc command
  79         ad_beg_p        returns pointer to first byte of addr data
  80         ad_end_p        returns pointer to last byte of addr data */
  81 {
  82
  83         /* at least 12: "AAAAAAAA P\1\n" */
  84         while (*data++ != ' ')
  85                 if (data > data_end - 12)
  86                         return -1;
  87
  88         *ad_beg_p = data;
  89         *ip = simple_strtoul(data, &data, 10);
  90
  91         /* skip blanks between ip and port */
  92         while (*data == ' ') {
  93                 if (data >= data_end)
  94                         return -1;
  95                 data++;
  96         }
  97
  98         *port = simple_strtoul(data, &data, 10);
  99         *ad_end_p = data;
 100
 101         return 0;
 102 }
 103
 104 static int help(struct sk_buff **pskb,
 105                 struct ip_conntrack *ct, enum ip_conntrack_info ctinfo)
 106 {
 107         unsigned int dataoff;
 108         struct tcphdr _tcph, *th;
 109         char *data, *data_limit, *ib_ptr;
 110         int dir = CTINFO2DIR(ctinfo);
 111         struct ip_conntrack_expect *exp;
 112         u32 seq;
 113         u_int32_t dcc_ip;
 114         u_int16_t dcc_port;
 115         int i, ret = NF_ACCEPT;
 116         char *addr_beg_p, *addr_end_p;
 117
 118         DEBUGP("entered\n");
 119
 120         /* If packet is coming from IRC server */
 121         if (dir == IP_CT_DIR_REPLY)
 122                 return NF_ACCEPT;
 123
 124         /* Until there's been traffic both ways, don't look in packets. */
 125         if (ctinfo != IP_CT_ESTABLISHED
 126             && ctinfo != IP_CT_ESTABLISHED + IP_CT_IS_REPLY) {
 127                 DEBUGP("Conntrackinfo = %u\n", ctinfo);
 128                 return NF_ACCEPT;
 129         }
 130
 131         /* Not a full tcp header? */
 132         th = skb_header_pointer(*pskb, (*pskb)->nh.iph->ihl*4,
 133                                 sizeof(_tcph), &_tcph);
 134         if (th == NULL)
 135                 return NF_ACCEPT;
 136
 137         /* No data? */
 138         dataoff = (*pskb)->nh.iph->ihl*4 + th->doff*4;
 139         if (dataoff >= (*pskb)->len)
 140                 return NF_ACCEPT;
 141
 142         spin_lock_bh(&irc_buffer_lock);
 143         ib_ptr = skb_header_pointer(*pskb, dataoff,
 144                                     (*pskb)->len - dataoff, irc_buffer);
 145         BUG_ON(ib_ptr == NULL);
 146
 147         data = ib_ptr;
 148         data_limit = ib_ptr + (*pskb)->len - dataoff;
 149
 150         /* strlen("\1DCC SENT t AAAAAAAA P\1\n")=24
 151          * 5+MINMATCHLEN+strlen("t AAAAAAAA P\1\n")=14 */
 152         while (data < (data_limit - (19 + MINMATCHLEN))) {
 153                 if (memcmp(data, "\1DCC ", 5)) {
 154                         data++;
 155                         continue;
 156                 }
 157
 158                 data += 5;
 159                 /* we have at least (19+MINMATCHLEN)-5 bytes valid data left */
 160
 161                 DEBUGP("DCC found in master %u.%u.%u.%u:%u %u.%u.%u.%u:%u...\n",
 162                         NIPQUAD(iph->saddr), ntohs(th->source),
 163                         NIPQUAD(iph->daddr), ntohs(th->dest));
 164
 165                 for (i = 0; i < ARRAY_SIZE(dccprotos); i++) {
 166                         if (memcmp(data, dccprotos[i], strlen(dccprotos[i]))) {
 167                                 /* no match */
 168                                 continue;
 169                         }
 170
 171                         DEBUGP("DCC %s detected\n", dccprotos[i]);
 172                         data += strlen(dccprotos[i]);
 173                         /* we have at least
 174                          * (19+MINMATCHLEN)-5-dccprotos[i].matchlen bytes valid
 175                          * data left (== 14/13 bytes) */
 176                         if (parse_dcc((char *)data, data_limit, &dcc_ip,
 177                                        &dcc_port, &addr_beg_p, &addr_end_p)) {
 178                                 /* unable to parse */
 179                                 DEBUGP("unable to parse dcc command\n");
 180                                 continue;
 181                         }
 182                         DEBUGP("DCC bound ip/port: %u.%u.%u.%u:%u\n",
 183                                 HIPQUAD(dcc_ip), dcc_port);
 184
 185                         /* dcc_ip can be the internal OR external (NAT'ed) IP
 186                          * Tiago Sousa <mirage@kaotik.org> */
 187                         if (ct->tuplehash[dir].tuple.src.ip != htonl(dcc_ip)
 188                             && ct->tuplehash[IP_CT_DIR_REPLY].tuple.dst.ip != htonl(dcc_ip)) {
 189                                 if (net_ratelimit())
 190                                         printk(KERN_WARNING
 191                                                 "Forged DCC command from "
 192                                                 "%u.%u.%u.%u: %u.%u.%u.%u:%u\n",
 193                                 NIPQUAD(ct->tuplehash[dir].tuple.src.ip),
 194                                                 HIPQUAD(dcc_ip), dcc_port);
 195
 196                                 continue;
 197                         }
 198
 199                         exp = ip_conntrack_expect_alloc(ct);
 200                         if (exp == NULL) {
 201                                 ret = NF_DROP;
 202                                 goto out;
 203                         }
 204
 205                         /* save position of address in dcc string,
 206                          * necessary for NAT */
 207                         DEBUGP("tcph->seq = %u\n", th->seq);
 208                         seq = ntohl(th->seq) + (addr_beg_p - ib_ptr);
 209
 210                         /* We refer to the reverse direction ("!dir")
 211                          * tuples here, because we're expecting
 212                          * something in the other * direction.
 213                          * Doesn't matter unless NAT is happening.  */
 214                         exp->tuple = ((struct ip_conntrack_tuple)
 215                                 { { 0, { 0 } },
 216                                   { ct->tuplehash[!dir].tuple.dst.ip,
 217                                     { .tcp = { htons(dcc_port) } },
 218                                     IPPROTO_TCP }});
 219                         exp->mask = ((struct ip_conntrack_tuple)
 220                                 { { 0, { 0 } },
 221                                   { 0xFFFFFFFF, { .tcp = { 0xFFFF } }, 0xFF }});
 222                         exp->expectfn = NULL;
 223                         exp->flags = 0;
 224                         if (ip_nat_irc_hook)
 225                                 ret = ip_nat_irc_hook(pskb, ctinfo,
 226                                                       addr_beg_p - ib_ptr,
 227                                                       addr_end_p - addr_beg_p,
 228                                                       exp);
 229                         else if (ip_conntrack_expect_related(exp) != 0)
 230                                 ret = NF_DROP;
 231                         ip_conntrack_expect_put(exp);
 232                         goto out;
 233                 } /* for .. NUM_DCCPROTO */
 234         } /* while data < ... */
 235
 236  out:
 237         spin_unlock_bh(&irc_buffer_lock);
 238         return ret;
 239 }
 240
 241 static struct ip_conntrack_helper irc_helpers[MAX_PORTS];
 242 static char irc_names[MAX_PORTS][sizeof("irc-65535")];
 243
 244 static void ip_conntrack_irc_fini(void);
 245
 246 static int __init ip_conntrack_irc_init(void)
 247 {
 248         int i, ret;
 249         struct ip_conntrack_helper *hlpr;
 250         char *tmpname;
 251
 252         if (max_dcc_channels < 1) {
 253                 printk("ip_conntrack_irc: max_dcc_channels must be a positive integer\n");
 254                 return -EBUSY;
 255         }
 256
 257         irc_buffer = kmalloc(65536, GFP_KERNEL);
 258         if (!irc_buffer)
 259                 return -ENOMEM;
 260
 261         /* If no port given, default to standard irc port */
 262         if (ports_c == 0)
 263                 ports[ports_c++] = IRC_PORT;
 264
 265         for (i = 0; i < ports_c; i++) {
 266                 hlpr = &irc_helpers[i];
 267                 hlpr->tuple.src.u.tcp.port = htons(ports[i]);
 268                 hlpr->tuple.dst.protonum = IPPROTO_TCP;
 269                 hlpr->mask.src.u.tcp.port = 0xFFFF;
 270                 hlpr->mask.dst.protonum = 0xFF;
 271                 hlpr->max_expected = max_dcc_channels;
 272                 hlpr->timeout = dcc_timeout;
 273                 hlpr->me = THIS_MODULE;
 274                 hlpr->help = help;
 275
 276                 tmpname = &irc_names[i][0];
 277                 if (ports[i] == IRC_PORT)
 278                         sprintf(tmpname, "irc");
 279                 else
 280                         sprintf(tmpname, "irc-%d", i);
 281                 hlpr->name = tmpname;
 282
 283                 DEBUGP("port #%d: %d\n", i, ports[i]);
 284
 285                 ret = ip_conntrack_helper_register(hlpr);
 286
 287                 if (ret) {
 288                         printk("ip_conntrack_irc: ERROR registering port %d\n",
 289                                 ports[i]);
 290                         ip_conntrack_irc_fini();
 291                         return -EBUSY;
 292                 }
 293         }
 294         return 0;
 295 }
 296
 297 /* This function is intentionally _NOT_ defined as __exit, because
 298  * it is needed by the init function */
 299 static void ip_conntrack_irc_fini(void)
 300 {
 301         int i;
 302         for (i = 0; i < ports_c; i++) {
 303                 DEBUGP("unregistering port %d\n",
 304                        ports[i]);
 305                 ip_conntrack_helper_unregister(&irc_helpers[i]);
 306         }
 307         kfree(irc_buffer);
 308 }
 309
 310 module_init(ip_conntrack_irc_init);
 311 module_exit(ip_conntrack_irc_fini);