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   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  * This program is free software; you can redistribute it and/or
   6  * modify it under the terms of the GNU General Public License
   7  * as published by the Free Software Foundation; either version
   8  * 2 of the License, or (at your option) any later version.
   9  */
  10
  11 #include <linux/module.h>
  12 #include <linux/moduleparam.h>
  13 #include <linux/skbuff.h>
  14 #include <linux/in.h>
  15 #include <linux/ip.h>
  16 #include <linux/tcp.h>
  17 #include <linux/netfilter.h>
  18
  19 #include <net/netfilter/nf_conntrack.h>
  20 #include <net/netfilter/nf_conntrack_expect.h>
  21 #include <net/netfilter/nf_conntrack_helper.h>
  22 #include <linux/netfilter/nf_conntrack_irc.h>
  23
  24 #define MAX_PORTS 8
  25 static unsigned short ports[MAX_PORTS];
  26 static unsigned int ports_c;
  27 static unsigned int max_dcc_channels = 8;
  28 static unsigned int dcc_timeout __read_mostly = 300;
  29 /* This is slow, but it's simple. --RR */
  30 static char *irc_buffer;
  31 static DEFINE_SPINLOCK(irc_buffer_lock);
  32
  33 unsigned int (*nf_nat_irc_hook)(struct sk_buff *skb,
  34                                 enum ip_conntrack_info ctinfo,
  35                                 unsigned int matchoff,
  36                                 unsigned int matchlen,
  37                                 struct nf_conntrack_expect *exp) __read_mostly;
  38 EXPORT_SYMBOL_GPL(nf_nat_irc_hook);
  39
  40 MODULE_AUTHOR("Harald Welte <laforge@netfilter.org>");
  41 MODULE_DESCRIPTION("IRC (DCC) connection tracking helper");
  42 MODULE_LICENSE("GPL");
  43 MODULE_ALIAS("ip_conntrack_irc");
  44
  45 module_param_array(ports, ushort, &ports_c, 0400);
  46 MODULE_PARM_DESC(ports, "port numbers of IRC servers");
  47 module_param(max_dcc_channels, uint, 0400);
  48 MODULE_PARM_DESC(max_dcc_channels, "max number of expected DCC channels per "
  49                                    "IRC session");
  50 module_param(dcc_timeout, uint, 0400);
  51 MODULE_PARM_DESC(dcc_timeout, "timeout on for unestablished DCC channels");
  52
  53 static const char *const dccprotos[] = {
  54         "SEND ", "CHAT ", "MOVE ", "TSEND ", "SCHAT "
  55 };
  56
  57 #define MINMATCHLEN     5
  58
  59 /* tries to get the ip_addr and port out of a dcc command
  60  * return value: -1 on failure, 0 on success
  61  *      data            pointer to first byte of DCC command data
  62  *      data_end        pointer to last byte of dcc command data
  63  *      ip              returns parsed ip of dcc command
  64  *      port            returns parsed port of dcc command
  65  *      ad_beg_p        returns pointer to first byte of addr data
  66  *      ad_end_p        returns pointer to last byte of addr data
  67  */
  68 static int parse_dcc(char *data, const char *data_end, u_int32_t *ip,
  69                      u_int16_t *port, char **ad_beg_p, char **ad_end_p)
  70 {
  71         char *tmp;
  72
  73         /* at least 12: "AAAAAAAA P\1\n" */
  74         while (*data++ != ' ')
  75                 if (data > data_end - 12)
  76                         return -1;
  77
  78         /* Make sure we have a newline character within the packet boundaries
  79          * because simple_strtoul parses until the first invalid character. */
  80         for (tmp = data; tmp <= data_end; tmp++)
  81                 if (*tmp == '\n')
  82                         break;
  83         if (tmp > data_end || *tmp != '\n')
  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, unsigned int protoff,
 103                 struct nf_conn *ct, enum ip_conntrack_info ctinfo)
 104 {
 105         unsigned int dataoff;
 106         const struct iphdr *iph;
 107         const struct tcphdr *th;
 108         struct tcphdr _tcph;
 109         const char *data_limit;
 110         char *data, *ib_ptr;
 111         int dir = CTINFO2DIR(ctinfo);
 112         struct nf_conntrack_expect *exp;
 113         struct nf_conntrack_tuple *tuple;
 114         u_int32_t dcc_ip;
 115         u_int16_t dcc_port;
 116         __be16 port;
 117         int i, ret = NF_ACCEPT;
 118         char *addr_beg_p, *addr_end_p;
 119         typeof(nf_nat_irc_hook) nf_nat_irc;
 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                 return NF_ACCEPT;
 129
 130         /* Not a full tcp header? */
 131         th = skb_header_pointer(skb, protoff, sizeof(_tcph), &_tcph);
 132         if (th == NULL)
 133                 return NF_ACCEPT;
 134
 135         /* No data? */
 136         dataoff = protoff + th->doff*4;
 137         if (dataoff >= skb->len)
 138                 return NF_ACCEPT;
 139
 140         spin_lock_bh(&irc_buffer_lock);
 141         ib_ptr = skb_header_pointer(skb, dataoff, skb->len - dataoff,
 142                                     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                 data += 5;
 156                 /* we have at least (19+MINMATCHLEN)-5 bytes valid data left */
 157
 158                 iph = ip_hdr(skb);
 159                 pr_debug("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                         data += strlen(dccprotos[i]);
 169                         pr_debug("DCC %s detected\n", dccprotos[i]);
 170
 171                         /* we have at least
 172                          * (19+MINMATCHLEN)-5-dccprotos[i].matchlen bytes valid
 173                          * data left (== 14/13 bytes) */
 174                         if (parse_dcc(data, data_limit, &dcc_ip,
 175                                        &dcc_port, &addr_beg_p, &addr_end_p)) {
 176                                 pr_debug("unable to parse dcc command\n");
 177                                 continue;
 178                         }
 179                         pr_debug("DCC bound ip/port: %u.%u.%u.%u:%u\n",
 180                                  HIPQUAD(dcc_ip), dcc_port);
 181
 182                         /* dcc_ip can be the internal OR external (NAT'ed) IP */
 183                         tuple = &ct->tuplehash[dir].tuple;
 184                         if (tuple->src.u3.ip != htonl(dcc_ip) &&
 185                             tuple->dst.u3.ip != htonl(dcc_ip)) {
 186                                 if (net_ratelimit())
 187                                         printk(KERN_WARNING
 188                                                 "Forged DCC command from "
 189                                                 "%u.%u.%u.%u: %u.%u.%u.%u:%u\n",
 190                                                 NIPQUAD(tuple->src.u3.ip),
 191                                                 HIPQUAD(dcc_ip), dcc_port);
 192                                 continue;
 193                         }
 194
 195                         exp = nf_ct_expect_alloc(ct);
 196                         if (exp == NULL) {
 197                                 ret = NF_DROP;
 198                                 goto out;
 199                         }
 200                         tuple = &ct->tuplehash[!dir].tuple;
 201                         port = htons(dcc_port);
 202                         nf_ct_expect_init(exp, NF_CT_EXPECT_CLASS_DEFAULT,
 203                                           tuple->src.l3num,
 204                                           NULL, &tuple->dst.u3,
 205                                           IPPROTO_TCP, NULL, &port);
 206
 207                         nf_nat_irc = rcu_dereference(nf_nat_irc_hook);
 208                         if (nf_nat_irc && ct->status & IPS_NAT_MASK)
 209                                 ret = nf_nat_irc(skb, ctinfo,
 210                                                  addr_beg_p - ib_ptr,
 211                                                  addr_end_p - addr_beg_p,
 212                                                  exp);
 213                         else if (nf_ct_expect_related(exp) != 0)
 214                                 ret = NF_DROP;
 215                         nf_ct_expect_put(exp);
 216                         goto out;
 217                 }
 218         }
 219  out:
 220         spin_unlock_bh(&irc_buffer_lock);
 221         return ret;
 222 }
 223
 224 static struct nf_conntrack_helper irc[MAX_PORTS] __read_mostly;
 225 static char irc_names[MAX_PORTS][sizeof("irc-65535")] __read_mostly;
 226 static struct nf_conntrack_expect_policy irc_exp_policy;
 227
 228 static void nf_conntrack_irc_fini(void);
 229
 230 static int __init nf_conntrack_irc_init(void)
 231 {
 232         int i, ret;
 233         char *tmpname;
 234
 235         if (max_dcc_channels < 1) {
 236                 printk("nf_ct_irc: max_dcc_channels must not be zero\n");
 237                 return -EINVAL;
 238         }
 239
 240         irc_exp_policy.max_expected = max_dcc_channels;
 241         irc_exp_policy.timeout = dcc_timeout;
 242
 243         irc_buffer = kmalloc(65536, GFP_KERNEL);
 244         if (!irc_buffer)
 245                 return -ENOMEM;
 246
 247         /* If no port given, default to standard irc port */
 248         if (ports_c == 0)
 249                 ports[ports_c++] = IRC_PORT;
 250
 251         for (i = 0; i < ports_c; i++) {
 252                 irc[i].tuple.src.l3num = AF_INET;
 253                 irc[i].tuple.src.u.tcp.port = htons(ports[i]);
 254                 irc[i].tuple.dst.protonum = IPPROTO_TCP;
 255                 irc[i].expect_policy = &irc_exp_policy;
 256                 irc[i].me = THIS_MODULE;
 257                 irc[i].help = help;
 258
 259                 tmpname = &irc_names[i][0];
 260                 if (ports[i] == IRC_PORT)
 261                         sprintf(tmpname, "irc");
 262                 else
 263                         sprintf(tmpname, "irc-%u", i);
 264                 irc[i].name = tmpname;
 265
 266                 ret = nf_conntrack_helper_register(&irc[i]);
 267                 if (ret) {
 268                         printk("nf_ct_irc: failed to register helper "
 269                                "for pf: %u port: %u\n",
 270                                irc[i].tuple.src.l3num, ports[i]);
 271                         nf_conntrack_irc_fini();
 272                         return ret;
 273                 }
 274         }
 275         return 0;
 276 }
 277
 278 /* This function is intentionally _NOT_ defined as __exit, because
 279  * it is needed by the init function */
 280 static void nf_conntrack_irc_fini(void)
 281 {
 282         int i;
 283
 284         for (i = 0; i < ports_c; i++)
 285                 nf_conntrack_helper_unregister(&irc[i]);
 286         kfree(irc_buffer);
 287 }
 288
 289 module_init(nf_conntrack_irc_init);
 290 module_exit(nf_conntrack_irc_fini);