linux/net/netfilter/nf_conntrack_irc.c
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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
  25static unsigned short ports[MAX_PORTS];
  26static unsigned int ports_c;
  27static unsigned int max_dcc_channels = 8;
  28static unsigned int dcc_timeout __read_mostly = 300;
  29/* This is slow, but it's simple. --RR */
  30static char *irc_buffer;
  31static DEFINE_SPINLOCK(irc_buffer_lock);
  32
  33unsigned 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;
  38EXPORT_SYMBOL_GPL(nf_nat_irc_hook);
  39
  40MODULE_AUTHOR("Harald Welte <laforge@netfilter.org>");
  41MODULE_DESCRIPTION("IRC (DCC) connection tracking helper");
  42MODULE_LICENSE("GPL");
  43MODULE_ALIAS("ip_conntrack_irc");
  44
  45module_param_array(ports, ushort, &ports_c, 0400);
  46MODULE_PARM_DESC(ports, "port numbers of IRC servers");
  47module_param(max_dcc_channels, uint, 0400);
  48MODULE_PARM_DESC(max_dcc_channels, "max number of expected DCC channels per "
  49                                   "IRC session");
  50module_param(dcc_timeout, uint, 0400);
  51MODULE_PARM_DESC(dcc_timeout, "timeout on for unestablished DCC channels");
  52
  53static 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 */
  68static 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
 102static 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
 224static struct nf_conntrack_helper irc[MAX_PORTS] __read_mostly;
 225static char irc_names[MAX_PORTS][sizeof("irc-65535")] __read_mostly;
 226static struct nf_conntrack_expect_policy irc_exp_policy;
 227
 228static void nf_conntrack_irc_fini(void);
 229
 230static 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 */
 280static 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
 289module_init(nf_conntrack_irc_init);
 290module_exit(nf_conntrack_irc_fini);
 291