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   1 /*
   2  *      xt_conntrack - Netfilter module to match connection tracking
   3  *      information. (Superset of Rusty's minimalistic state match.)
   4  *
   5  *      (C) 2001  Marc Boucher (marc@mbsi.ca).
   6  *      Copyright © CC Computer Consultants GmbH, 2007 - 2008
   7  *
   8  *      This program is free software; you can redistribute it and/or modify
   9  *      it under the terms of the GNU General Public License version 2 as
  10  *      published by the Free Software Foundation.
  11  */
  12
  13 #include <linux/module.h>
  14 #include <linux/skbuff.h>
  15 #include <net/ipv6.h>
  16 #include <linux/netfilter/x_tables.h>
  17 #include <linux/netfilter/xt_conntrack.h>
  18 #include <net/netfilter/nf_conntrack.h>
  19
  20 MODULE_LICENSE("GPL");
  21 MODULE_AUTHOR("Marc Boucher <marc@mbsi.ca>");
  22 MODULE_AUTHOR("Jan Engelhardt <jengelh@medozas.de>");
  23 MODULE_DESCRIPTION("Xtables: connection tracking state match");
  24 MODULE_ALIAS("ipt_conntrack");
  25 MODULE_ALIAS("ip6t_conntrack");
  26
  27 static bool
  28 conntrack_addrcmp(const union nf_inet_addr *kaddr,
  29                   const union nf_inet_addr *uaddr,
  30                   const union nf_inet_addr *umask, unsigned int l3proto)
  31 {
  32         if (l3proto == NFPROTO_IPV4)
  33                 return ((kaddr->ip ^ uaddr->ip) & umask->ip) == 0;
  34         else if (l3proto == NFPROTO_IPV6)
  35                 return ipv6_masked_addr_cmp(&kaddr->in6, &umask->in6,
  36                        &uaddr->in6) == 0;
  37         else
  38                 return false;
  39 }
  40
  41 static inline bool
  42 conntrack_mt_origsrc(const struct nf_conn *ct,
  43                      const struct xt_conntrack_mtinfo2 *info,
  44                      u_int8_t family)
  45 {
  46         return conntrack_addrcmp(&ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple.src.u3,
  47                &info->origsrc_addr, &info->origsrc_mask, family);
  48 }
  49
  50 static inline bool
  51 conntrack_mt_origdst(const struct nf_conn *ct,
  52                      const struct xt_conntrack_mtinfo2 *info,
  53                      u_int8_t family)
  54 {
  55         return conntrack_addrcmp(&ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple.dst.u3,
  56                &info->origdst_addr, &info->origdst_mask, family);
  57 }
  58
  59 static inline bool
  60 conntrack_mt_replsrc(const struct nf_conn *ct,
  61                      const struct xt_conntrack_mtinfo2 *info,
  62                      u_int8_t family)
  63 {
  64         return conntrack_addrcmp(&ct->tuplehash[IP_CT_DIR_REPLY].tuple.src.u3,
  65                &info->replsrc_addr, &info->replsrc_mask, family);
  66 }
  67
  68 static inline bool
  69 conntrack_mt_repldst(const struct nf_conn *ct,
  70                      const struct xt_conntrack_mtinfo2 *info,
  71                      u_int8_t family)
  72 {
  73         return conntrack_addrcmp(&ct->tuplehash[IP_CT_DIR_REPLY].tuple.dst.u3,
  74                &info->repldst_addr, &info->repldst_mask, family);
  75 }
  76
  77 static inline bool
  78 ct_proto_port_check(const struct xt_conntrack_mtinfo2 *info,
  79                     const struct nf_conn *ct)
  80 {
  81         const struct nf_conntrack_tuple *tuple;
  82
  83         tuple = &ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple;
  84         if ((info->match_flags & XT_CONNTRACK_PROTO) &&
  85             (nf_ct_protonum(ct) == info->l4proto) ^
  86             !(info->invert_flags & XT_CONNTRACK_PROTO))
  87                 return false;
  88
  89         /* Shortcut to match all recognized protocols by using ->src.all. */
  90         if ((info->match_flags & XT_CONNTRACK_ORIGSRC_PORT) &&
  91             (tuple->src.u.all == info->origsrc_port) ^
  92             !(info->invert_flags & XT_CONNTRACK_ORIGSRC_PORT))
  93                 return false;
  94
  95         if ((info->match_flags & XT_CONNTRACK_ORIGDST_PORT) &&
  96             (tuple->dst.u.all == info->origdst_port) ^
  97             !(info->invert_flags & XT_CONNTRACK_ORIGDST_PORT))
  98                 return false;
  99
 100         tuple = &ct->tuplehash[IP_CT_DIR_REPLY].tuple;
 101
 102         if ((info->match_flags & XT_CONNTRACK_REPLSRC_PORT) &&
 103             (tuple->src.u.all == info->replsrc_port) ^
 104             !(info->invert_flags & XT_CONNTRACK_REPLSRC_PORT))
 105                 return false;
 106
 107         if ((info->match_flags & XT_CONNTRACK_REPLDST_PORT) &&
 108             (tuple->dst.u.all == info->repldst_port) ^
 109             !(info->invert_flags & XT_CONNTRACK_REPLDST_PORT))
 110                 return false;
 111
 112         return true;
 113 }
 114
 115 static bool
 116 conntrack_mt(const struct sk_buff *skb, const struct xt_match_param *par)
 117 {
 118         const struct xt_conntrack_mtinfo2 *info = par->matchinfo;
 119         enum ip_conntrack_info ctinfo;
 120         const struct nf_conn *ct;
 121         unsigned int statebit;
 122
 123         ct = nf_ct_get(skb, &ctinfo);
 124
 125         if (ct == &nf_conntrack_untracked)
 126                 statebit = XT_CONNTRACK_STATE_UNTRACKED;
 127         else if (ct != NULL)
 128                 statebit = XT_CONNTRACK_STATE_BIT(ctinfo);
 129         else
 130                 statebit = XT_CONNTRACK_STATE_INVALID;
 131
 132         if (info->match_flags & XT_CONNTRACK_STATE) {
 133                 if (ct != NULL) {
 134                         if (test_bit(IPS_SRC_NAT_BIT, &ct->status))
 135                                 statebit |= XT_CONNTRACK_STATE_SNAT;
 136                         if (test_bit(IPS_DST_NAT_BIT, &ct->status))
 137                                 statebit |= XT_CONNTRACK_STATE_DNAT;
 138                 }
 139                 if (!!(info->state_mask & statebit) ^
 140                     !(info->invert_flags & XT_CONNTRACK_STATE))
 141                         return false;
 142         }
 143
 144         if (ct == NULL)
 145                 return info->match_flags & XT_CONNTRACK_STATE;
 146         if ((info->match_flags & XT_CONNTRACK_DIRECTION) &&
 147             (CTINFO2DIR(ctinfo) == IP_CT_DIR_ORIGINAL) ^
 148             !!(info->invert_flags & XT_CONNTRACK_DIRECTION))
 149                 return false;
 150
 151         if (info->match_flags & XT_CONNTRACK_ORIGSRC)
 152                 if (conntrack_mt_origsrc(ct, info, par->family) ^
 153                     !(info->invert_flags & XT_CONNTRACK_ORIGSRC))
 154                         return false;
 155
 156         if (info->match_flags & XT_CONNTRACK_ORIGDST)
 157                 if (conntrack_mt_origdst(ct, info, par->family) ^
 158                     !(info->invert_flags & XT_CONNTRACK_ORIGDST))
 159                         return false;
 160
 161         if (info->match_flags & XT_CONNTRACK_REPLSRC)
 162                 if (conntrack_mt_replsrc(ct, info, par->family) ^
 163                     !(info->invert_flags & XT_CONNTRACK_REPLSRC))
 164                         return false;
 165
 166         if (info->match_flags & XT_CONNTRACK_REPLDST)
 167                 if (conntrack_mt_repldst(ct, info, par->family) ^
 168                     !(info->invert_flags & XT_CONNTRACK_REPLDST))
 169                         return false;
 170
 171         if (!ct_proto_port_check(info, ct))
 172                 return false;
 173
 174         if ((info->match_flags & XT_CONNTRACK_STATUS) &&
 175             (!!(info->status_mask & ct->status) ^
 176             !(info->invert_flags & XT_CONNTRACK_STATUS)))
 177                 return false;
 178
 179         if (info->match_flags & XT_CONNTRACK_EXPIRES) {
 180                 unsigned long expires = 0;
 181
 182                 if (timer_pending(&ct->timeout))
 183                         expires = (ct->timeout.expires - jiffies) / HZ;
 184                 if ((expires >= info->expires_min &&
 185                     expires <= info->expires_max) ^
 186                     !(info->invert_flags & XT_CONNTRACK_EXPIRES))
 187                         return false;
 188         }
 189         return true;
 190 }
 191
 192 static bool
 193 conntrack_mt_v1(const struct sk_buff *skb, const struct xt_match_param *par)
 194 {
 195         const struct xt_conntrack_mtinfo2 *const *info = par->matchinfo;
 196         struct xt_match_param newpar = *par;
 197
 198         newpar.matchinfo = *info;
 199         return conntrack_mt(skb, &newpar);
 200 }
 201
 202 static bool conntrack_mt_check(const struct xt_mtchk_param *par)
 203 {
 204         if (nf_ct_l3proto_try_module_get(par->family) < 0) {
 205                 printk(KERN_WARNING "can't load conntrack support for "
 206                                     "proto=%u\n", par->family);
 207                 return false;
 208         }
 209         return true;
 210 }
 211
 212 static bool conntrack_mt_check_v1(const struct xt_mtchk_param *par)
 213 {
 214         struct xt_conntrack_mtinfo1 *info = par->matchinfo;
 215         struct xt_conntrack_mtinfo2 *up;
 216         int ret = conntrack_mt_check(par);
 217
 218         if (ret < 0)
 219                 return ret;
 220
 221         up = kmalloc(sizeof(*up), GFP_KERNEL);
 222         if (up == NULL) {
 223                 nf_ct_l3proto_module_put(par->family);
 224                 return -ENOMEM;
 225         }
 226
 227         /*
 228          * The strategy here is to minimize the overhead of v1 matching,
 229          * by prebuilding a v2 struct and putting the pointer into the
 230          * v1 dataspace.
 231          */
 232         memcpy(up, info, offsetof(typeof(*info), state_mask));
 233         up->state_mask  = info->state_mask;
 234         up->status_mask = info->status_mask;
 235         *(void **)info  = up;
 236         return true;
 237 }
 238
 239 static void conntrack_mt_destroy(const struct xt_mtdtor_param *par)
 240 {
 241         nf_ct_l3proto_module_put(par->family);
 242 }
 243
 244 static void conntrack_mt_destroy_v1(const struct xt_mtdtor_param *par)
 245 {
 246         struct xt_conntrack_mtinfo2 **info = par->matchinfo;
 247         kfree(*info);
 248         conntrack_mt_destroy(par);
 249 }
 250
 251 static struct xt_match conntrack_mt_reg[] __read_mostly = {
 252         {
 253                 .name       = "conntrack",
 254                 .revision   = 1,
 255                 .family     = NFPROTO_UNSPEC,
 256                 .matchsize  = sizeof(struct xt_conntrack_mtinfo1),
 257                 .match      = conntrack_mt_v1,
 258                 .checkentry = conntrack_mt_check_v1,
 259                 .destroy    = conntrack_mt_destroy_v1,
 260                 .me         = THIS_MODULE,
 261         },
 262         {
 263                 .name       = "conntrack",
 264                 .revision   = 2,
 265                 .family     = NFPROTO_UNSPEC,
 266                 .matchsize  = sizeof(struct xt_conntrack_mtinfo2),
 267                 .match      = conntrack_mt,
 268                 .checkentry = conntrack_mt_check,
 269                 .destroy    = conntrack_mt_destroy,
 270                 .me         = THIS_MODULE,
 271         },
 272 };
 273
 274 static int __init conntrack_mt_init(void)
 275 {
 276         return xt_register_matches(conntrack_mt_reg,
 277                ARRAY_SIZE(conntrack_mt_reg));
 278 }
 279
 280 static void __exit conntrack_mt_exit(void)
 281 {
 282         xt_unregister_matches(conntrack_mt_reg, ARRAY_SIZE(conntrack_mt_reg));
 283 }
 284
 285 module_init(conntrack_mt_init);
 286 module_exit(conntrack_mt_exit);