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