net/netfilter/nf_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  * 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 #include <linux/slab.h>
  19
  20 #include <net/netfilter/nf_conntrack.h>
  21 #include <net/netfilter/nf_conntrack_expect.h>
  22 #include <net/netfilter/nf_conntrack_helper.h>
  23 #include <linux/netfilter/nf_conntrack_irc.h>
  24
  25 #define MAX_PORTS 8
  26 static unsigned short ports[MAX_PORTS];
  27 static unsigned int ports_c;
  28 static unsigned int max_dcc_channels = 8;
  29 static unsigned int dcc_timeout __read_mostly = 300;
  30 /* This is slow, but it's simple. --RR */
  31 static char *irc_buffer;
  32 static DEFINE_SPINLOCK(irc_buffer_lock);
  33
  34 unsigned int (*nf_nat_irc_hook)(struct sk_buff *skb,
  35                                 enum ip_conntrack_info ctinfo,
  36                                 unsigned int matchoff,
  37                                 unsigned int matchlen,
  38                                 struct nf_conntrack_expect *exp) __read_mostly;
  39 EXPORT_SYMBOL_GPL(nf_nat_irc_hook);
  40
  41 MODULE_AUTHOR("Harald Welte <laforge@netfilter.org>");
  42 MODULE_DESCRIPTION("IRC (DCC) connection tracking helper");
  43 MODULE_LICENSE("GPL");
  44 MODULE_ALIAS("ip_conntrack_irc");
  45 MODULE_ALIAS_NFCT_HELPER("irc");
  46
  47 module_param_array(ports, ushort, &ports_c, 0400);
  48 MODULE_PARM_DESC(ports, "port numbers of IRC servers");
  49 module_param(max_dcc_channels, uint, 0400);
  50 MODULE_PARM_DESC(max_dcc_channels, "max number of expected DCC channels per "
  51                                    "IRC session");
  52 module_param(dcc_timeout, uint, 0400);
  53 MODULE_PARM_DESC(dcc_timeout, "timeout on for unestablished DCC channels");
  54
  55 static const char *const dccprotos[] = {
  56         "SEND ", "CHAT ", "MOVE ", "TSEND ", "SCHAT "
  57 };
  58
  59 #define MINMATCHLEN     5
  60
  61 /* tries to get the ip_addr and port out of a dcc command
  62  * return value: -1 on failure, 0 on success
  63  *      data            pointer to first byte of DCC command data
  64  *      data_end        pointer to last byte of dcc command data
  65  *      ip              returns parsed ip of dcc command
  66  *      port            returns parsed port of dcc command
  67  *      ad_beg_p        returns pointer to first byte of addr data
  68  *      ad_end_p        returns pointer to last byte of addr data
  69  */
  70 static int parse_dcc(char *data, const char *data_end, __be32 *ip,
  71                      u_int16_t *port, char **ad_beg_p, char **ad_end_p)
  72 {
  73         char *tmp;
  74
  75         /* at least 12: "AAAAAAAA P\1\n" */
  76         while (*data++ != ' ')
  77                 if (data > data_end - 12)
  78                         return -1;
  79
  80         /* Make sure we have a newline character within the packet boundaries
  81          * because simple_strtoul parses until the first invalid character. */
  82         for (tmp = data; tmp <= data_end; tmp++)
  83                 if (*tmp == '\n')
  84                         break;
  85         if (tmp > data_end || *tmp != '\n')
  86                 return -1;
  87
  88         *ad_beg_p = data;
  89         *ip = cpu_to_be32(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 *skb, unsigned int protoff,
 105                 struct nf_conn *ct, enum ip_conntrack_info ctinfo)
 106 {
 107         unsigned int dataoff;
 108         const struct iphdr *iph;
 109         const struct tcphdr *th;
 110         struct tcphdr _tcph;
 111         const char *data_limit;
 112         char *data, *ib_ptr;
 113         int dir = CTINFO2DIR(ctinfo);
 114         struct nf_conntrack_expect *exp;
 115         struct nf_conntrack_tuple *tuple;
 116         __be32 dcc_ip;
 117         u_int16_t dcc_port;
 118         __be16 port;
 119         int i, ret = NF_ACCEPT;
 120         char *addr_beg_p, *addr_end_p;
 121         typeof(nf_nat_irc_hook) nf_nat_irc;
 122
 123         /* If packet is coming from IRC server */
 124         if (dir == IP_CT_DIR_REPLY)
 125                 return NF_ACCEPT;
 126
 127         /* Until there's been traffic both ways, don't look in packets. */
 128         if (ctinfo != IP_CT_ESTABLISHED && ctinfo != IP_CT_ESTABLISHED_REPLY)
 129                 return NF_ACCEPT;
 130
 131         /* Not a full tcp header? */
 132         th = skb_header_pointer(skb, protoff, sizeof(_tcph), &_tcph);
 133         if (th == NULL)
 134                 return NF_ACCEPT;
 135
 136         /* No data? */
 137         dataoff = protoff + th->doff*4;
 138         if (dataoff >= skb->len)
 139                 return NF_ACCEPT;
 140
 141         spin_lock_bh(&irc_buffer_lock);
 142         ib_ptr = skb_header_pointer(skb, dataoff, skb->len - dataoff,
 143                                     irc_buffer);
 144         BUG_ON(ib_ptr == NULL);
 145
 146         data = ib_ptr;
 147         data_limit = ib_ptr + skb->len - dataoff;
 148
 149         /* strlen("\1DCC SENT t AAAAAAAA P\1\n")=24
 150          * 5+MINMATCHLEN+strlen("t AAAAAAAA P\1\n")=14 */
 151         while (data < data_limit - (19 + MINMATCHLEN)) {
 152                 if (memcmp(data, "\1DCC ", 5)) {
 153                         data++;
 154                         continue;
 155                 }
 156                 data += 5;
 157                 /* we have at least (19+MINMATCHLEN)-5 bytes valid data left */
 158
 159                 iph = ip_hdr(skb);
 160                 pr_debug("DCC found in master %pI4:%u %pI4:%u\n",
 161                          &iph->saddr, ntohs(th->source),
 162                          &iph->daddr, ntohs(th->dest));
 163
 164                 for (i = 0; i < ARRAY_SIZE(dccprotos); i++) {
 165                         if (memcmp(data, dccprotos[i], strlen(dccprotos[i]))) {
 166                                 /* no match */
 167                                 continue;
 168                         }
 169                         data += strlen(dccprotos[i]);
 170                         pr_debug("DCC %s detected\n", dccprotos[i]);
 171
 172                         /* we have at least
 173                          * (19+MINMATCHLEN)-5-dccprotos[i].matchlen bytes valid
 174                          * data left (== 14/13 bytes) */
 175                         if (parse_dcc(data, data_limit, &dcc_ip,
 176                                        &dcc_port, &addr_beg_p, &addr_end_p)) {
 177                                 pr_debug("unable to parse dcc command\n");
 178                                 continue;
 179                         }
 180
 181                         pr_debug("DCC bound ip/port: %pI4:%u\n",
 182                                  &dcc_ip, dcc_port);
 183
 184                         /* dcc_ip can be the internal OR external (NAT'ed) IP */
 185                         tuple = &ct->tuplehash[dir].tuple;
 186                         if (tuple->src.u3.ip != dcc_ip &&
 187                             tuple->dst.u3.ip != dcc_ip) {
 188                                 if (net_ratelimit())
 189                                         printk(KERN_WARNING
 190                                                 "Forged DCC command from %pI4: %pI4:%u\n",
 191                                                 &tuple->src.u3.ip,
 192                                                 &dcc_ip, dcc_port);
 193                                 continue;
 194                         }
 195
 196                         exp = nf_ct_expect_alloc(ct);
 197                         if (exp == NULL) {
 198                                 ret = NF_DROP;
 199                                 goto out;
 200                         }
 201                         tuple = &ct->tuplehash[!dir].tuple;
 202                         port = htons(dcc_port);
 203                         nf_ct_expect_init(exp, NF_CT_EXPECT_CLASS_DEFAULT,
 204                                           tuple->src.l3num,
 205                                           NULL, &tuple->dst.u3,
 206                                           IPPROTO_TCP, NULL, &port);
 207
 208                         nf_nat_irc = rcu_dereference(nf_nat_irc_hook);
 209                         if (nf_nat_irc && ct->status & IPS_NAT_MASK)
 210                                 ret = nf_nat_irc(skb, ctinfo,
 211                                                  addr_beg_p - ib_ptr,
 212                                                  addr_end_p - addr_beg_p,
 213                                                  exp);
 214                         else if (nf_ct_expect_related(exp) != 0)
 215                                 ret = NF_DROP;
 216                         nf_ct_expect_put(exp);
 217                         goto out;
 218                 }
 219         }
 220  out:
 221         spin_unlock_bh(&irc_buffer_lock);
 222         return ret;
 223 }
 224
 225 static struct nf_conntrack_helper irc[MAX_PORTS] __read_mostly;
 226 static char irc_names[MAX_PORTS][sizeof("irc-65535")] __read_mostly;
 227 static struct nf_conntrack_expect_policy irc_exp_policy;
 228
 229 static void nf_conntrack_irc_fini(void);
 230
 231 static int __init nf_conntrack_irc_init(void)
 232 {
 233         int i, ret;
 234         char *tmpname;
 235
 236         if (max_dcc_channels < 1) {
 237                 printk(KERN_ERR "nf_ct_irc: max_dcc_channels must not be zero\n");
 238                 return -EINVAL;
 239         }
 240
 241         irc_exp_policy.max_expected = max_dcc_channels;
 242         irc_exp_policy.timeout = dcc_timeout;
 243
 244         irc_buffer = kmalloc(65536, GFP_KERNEL);
 245         if (!irc_buffer)
 246                 return -ENOMEM;
 247
 248         /* If no port given, default to standard irc port */
 249         if (ports_c == 0)
 250                 ports[ports_c++] = IRC_PORT;
 251
 252         for (i = 0; i < ports_c; i++) {
 253                 irc[i].tuple.src.l3num = AF_INET;
 254                 irc[i].tuple.src.u.tcp.port = htons(ports[i]);
 255                 irc[i].tuple.dst.protonum = IPPROTO_TCP;
 256                 irc[i].expect_policy = &irc_exp_policy;
 257                 irc[i].me = THIS_MODULE;
 258                 irc[i].help = help;
 259
 260                 tmpname = &irc_names[i][0];
 261                 if (ports[i] == IRC_PORT)
 262                         sprintf(tmpname, "irc");
 263                 else
 264                         sprintf(tmpname, "irc-%u", i);
 265                 irc[i].name = tmpname;
 266
 267                 ret = nf_conntrack_helper_register(&irc[i]);
 268                 if (ret) {
 269                         printk(KERN_ERR "nf_ct_irc: failed to register helper "
 270                                "for pf: %u port: %u\n",
 271                                irc[i].tuple.src.l3num, ports[i]);
 272                         nf_conntrack_irc_fini();
 273                         return ret;
 274                 }
 275         }
 276         return 0;
 277 }
 278
 279 /* This function is intentionally _NOT_ defined as __exit, because
 280  * it is needed by the init function */
 281 static void nf_conntrack_irc_fini(void)
 282 {
 283         int i;
 284
 285         for (i = 0; i < ports_c; i++)
 286                 nf_conntrack_helper_unregister(&irc[i]);
 287         kfree(irc_buffer);
 288 }
 289
 290 module_init(nf_conntrack_irc_init);
 291 module_exit(nf_conntrack_irc_fini);