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