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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         /* at least 12: "AAAAAAAA P\1\n" */
  72         while (*data++ != ' ')
  73                 if (data > data_end - 12)
  74                         return -1;
  75
  76         *ad_beg_p = data;
  77         *ip = simple_strtoul(data, &data, 10);
  78
  79         /* skip blanks between ip and port */
  80         while (*data == ' ') {
  81                 if (data >= data_end)
  82                         return -1;
  83                 data++;
  84         }
  85
  86         *port = simple_strtoul(data, &data, 10);
  87         *ad_end_p = data;
  88
  89         return 0;
  90 }
  91
  92 static int help(struct sk_buff *skb, unsigned int protoff,
  93                 struct nf_conn *ct, enum ip_conntrack_info ctinfo)
  94 {
  95         unsigned int dataoff;
  96         const struct iphdr *iph;
  97         const struct tcphdr *th;
  98         struct tcphdr _tcph;
  99         const char *data_limit;
 100         char *data, *ib_ptr;
 101         int dir = CTINFO2DIR(ctinfo);
 102         struct nf_conntrack_expect *exp;
 103         struct nf_conntrack_tuple *tuple;
 104         u_int32_t dcc_ip;
 105         u_int16_t dcc_port;
 106         __be16 port;
 107         int i, ret = NF_ACCEPT;
 108         char *addr_beg_p, *addr_end_p;
 109         typeof(nf_nat_irc_hook) nf_nat_irc;
 110
 111         /* If packet is coming from IRC server */
 112         if (dir == IP_CT_DIR_REPLY)
 113                 return NF_ACCEPT;
 114
 115         /* Until there's been traffic both ways, don't look in packets. */
 116         if (ctinfo != IP_CT_ESTABLISHED &&
 117             ctinfo != IP_CT_ESTABLISHED + IP_CT_IS_REPLY)
 118                 return NF_ACCEPT;
 119
 120         /* Not a full tcp header? */
 121         th = skb_header_pointer(skb, protoff, sizeof(_tcph), &_tcph);
 122         if (th == NULL)
 123                 return NF_ACCEPT;
 124
 125         /* No data? */
 126         dataoff = protoff + th->doff*4;
 127         if (dataoff >= skb->len)
 128                 return NF_ACCEPT;
 129
 130         spin_lock_bh(&irc_buffer_lock);
 131         ib_ptr = skb_header_pointer(skb, dataoff, skb->len - dataoff,
 132                                     irc_buffer);
 133         BUG_ON(ib_ptr == NULL);
 134
 135         data = ib_ptr;
 136         data_limit = ib_ptr + skb->len - dataoff;
 137
 138         /* strlen("\1DCC SENT t AAAAAAAA P\1\n")=24
 139          * 5+MINMATCHLEN+strlen("t AAAAAAAA P\1\n")=14 */
 140         while (data < data_limit - (19 + MINMATCHLEN)) {
 141                 if (memcmp(data, "\1DCC ", 5)) {
 142                         data++;
 143                         continue;
 144                 }
 145                 data += 5;
 146                 /* we have at least (19+MINMATCHLEN)-5 bytes valid data left */
 147
 148                 iph = ip_hdr(skb);
 149                 pr_debug("DCC found in master %u.%u.%u.%u:%u %u.%u.%u.%u:%u\n",
 150                          NIPQUAD(iph->saddr), ntohs(th->source),
 151                          NIPQUAD(iph->daddr), ntohs(th->dest));
 152
 153                 for (i = 0; i < ARRAY_SIZE(dccprotos); i++) {
 154                         if (memcmp(data, dccprotos[i], strlen(dccprotos[i]))) {
 155                                 /* no match */
 156                                 continue;
 157                         }
 158                         data += strlen(dccprotos[i]);
 159                         pr_debug("DCC %s detected\n", dccprotos[i]);
 160
 161                         /* we have at least
 162                          * (19+MINMATCHLEN)-5-dccprotos[i].matchlen bytes valid
 163                          * data left (== 14/13 bytes) */
 164                         if (parse_dcc(data, data_limit, &dcc_ip,
 165                                        &dcc_port, &addr_beg_p, &addr_end_p)) {
 166                                 pr_debug("unable to parse dcc command\n");
 167                                 continue;
 168                         }
 169                         pr_debug("DCC bound ip/port: %u.%u.%u.%u:%u\n",
 170                                  HIPQUAD(dcc_ip), dcc_port);
 171
 172                         /* dcc_ip can be the internal OR external (NAT'ed) IP */
 173                         tuple = &ct->tuplehash[dir].tuple;
 174                         if (tuple->src.u3.ip != htonl(dcc_ip) &&
 175                             tuple->dst.u3.ip != htonl(dcc_ip)) {
 176                                 if (net_ratelimit())
 177                                         printk(KERN_WARNING
 178                                                 "Forged DCC command from "
 179                                                 "%u.%u.%u.%u: %u.%u.%u.%u:%u\n",
 180                                                 NIPQUAD(tuple->src.u3.ip),
 181                                                 HIPQUAD(dcc_ip), dcc_port);
 182                                 continue;
 183                         }
 184
 185                         exp = nf_ct_expect_alloc(ct);
 186                         if (exp == NULL) {
 187                                 ret = NF_DROP;
 188                                 goto out;
 189                         }
 190                         tuple = &ct->tuplehash[!dir].tuple;
 191                         port = htons(dcc_port);
 192                         nf_ct_expect_init(exp, NF_CT_EXPECT_CLASS_DEFAULT,
 193                                           tuple->src.l3num,
 194                                           NULL, &tuple->dst.u3,
 195                                           IPPROTO_TCP, NULL, &port);
 196
 197                         nf_nat_irc = rcu_dereference(nf_nat_irc_hook);
 198                         if (nf_nat_irc && ct->status & IPS_NAT_MASK)
 199                                 ret = nf_nat_irc(skb, ctinfo,
 200                                                  addr_beg_p - ib_ptr,
 201                                                  addr_end_p - addr_beg_p,
 202                                                  exp);
 203                         else if (nf_ct_expect_related(exp) != 0)
 204                                 ret = NF_DROP;
 205                         nf_ct_expect_put(exp);
 206                         goto out;
 207                 }
 208         }
 209  out:
 210         spin_unlock_bh(&irc_buffer_lock);
 211         return ret;
 212 }
 213
 214 static struct nf_conntrack_helper irc[MAX_PORTS] __read_mostly;
 215 static char irc_names[MAX_PORTS][sizeof("irc-65535")] __read_mostly;
 216 static struct nf_conntrack_expect_policy irc_exp_policy;
 217
 218 static void nf_conntrack_irc_fini(void);
 219
 220 static int __init nf_conntrack_irc_init(void)
 221 {
 222         int i, ret;
 223         char *tmpname;
 224
 225         if (max_dcc_channels < 1) {
 226                 printk("nf_ct_irc: max_dcc_channels must not be zero\n");
 227                 return -EINVAL;
 228         }
 229
 230         irc_exp_policy.max_expected = max_dcc_channels;
 231         irc_exp_policy.timeout = dcc_timeout;
 232
 233         irc_buffer = kmalloc(65536, GFP_KERNEL);
 234         if (!irc_buffer)
 235                 return -ENOMEM;
 236
 237         /* If no port given, default to standard irc port */
 238         if (ports_c == 0)
 239                 ports[ports_c++] = IRC_PORT;
 240
 241         for (i = 0; i < ports_c; i++) {
 242                 irc[i].tuple.src.l3num = AF_INET;
 243                 irc[i].tuple.src.u.tcp.port = htons(ports[i]);
 244                 irc[i].tuple.dst.protonum = IPPROTO_TCP;
 245                 irc[i].expect_policy = &irc_exp_policy;
 246                 irc[i].me = THIS_MODULE;
 247                 irc[i].help = help;
 248
 249                 tmpname = &irc_names[i][0];
 250                 if (ports[i] == IRC_PORT)
 251                         sprintf(tmpname, "irc");
 252                 else
 253                         sprintf(tmpname, "irc-%u", i);
 254                 irc[i].name = tmpname;
 255
 256                 ret = nf_conntrack_helper_register(&irc[i]);
 257                 if (ret) {
 258                         printk("nf_ct_irc: failed to register helper "
 259                                "for pf: %u port: %u\n",
 260                                irc[i].tuple.src.l3num, ports[i]);
 261                         nf_conntrack_irc_fini();
 262                         return ret;
 263                 }
 264         }
 265         return 0;
 266 }
 267
 268 /* This function is intentionally _NOT_ defined as __exit, because
 269  * it is needed by the init function */
 270 static void nf_conntrack_irc_fini(void)
 271 {
 272         int i;
 273
 274         for (i = 0; i < ports_c; i++)
 275                 nf_conntrack_helper_unregister(&irc[i]);
 276         kfree(irc_buffer);
 277 }
 278
 279 module_init(nf_conntrack_irc_init);
 280 module_exit(nf_conntrack_irc_fini);