net/netfilter/xt_conntrack.c

   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 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
  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 inline bool
 116 port_match(u16 min, u16 max, u16 port, bool invert)
 117 {
 118         return (port >= min && port <= max) ^ invert;
 119 }
 120
 121 static inline bool
 122 ct_proto_port_check_v3(const struct xt_conntrack_mtinfo3 *info,
 123                        const struct nf_conn *ct)
 124 {
 125         const struct nf_conntrack_tuple *tuple;
 126
 127         tuple = &ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple;
 128         if ((info->match_flags & XT_CONNTRACK_PROTO) &&
 129             (nf_ct_protonum(ct) == info->l4proto) ^
 130             !(info->invert_flags & XT_CONNTRACK_PROTO))
 131                 return false;
 132
 133         /* Shortcut to match all recognized protocols by using ->src.all. */
 134         if ((info->match_flags & XT_CONNTRACK_ORIGSRC_PORT) &&
 135             !port_match(info->origsrc_port, info->origsrc_port_high,
 136                         ntohs(tuple->src.u.all),
 137                         info->invert_flags & XT_CONNTRACK_ORIGSRC_PORT))
 138                 return false;
 139
 140         if ((info->match_flags & XT_CONNTRACK_ORIGDST_PORT) &&
 141             !port_match(info->origdst_port, info->origdst_port_high,
 142                         ntohs(tuple->dst.u.all),
 143                         info->invert_flags & XT_CONNTRACK_ORIGDST_PORT))
 144                 return false;
 145
 146         tuple = &ct->tuplehash[IP_CT_DIR_REPLY].tuple;
 147
 148         if ((info->match_flags & XT_CONNTRACK_REPLSRC_PORT) &&
 149             !port_match(info->replsrc_port, info->replsrc_port_high,
 150                         ntohs(tuple->src.u.all),
 151                         info->invert_flags & XT_CONNTRACK_REPLSRC_PORT))
 152                 return false;
 153
 154         if ((info->match_flags & XT_CONNTRACK_REPLDST_PORT) &&
 155             !port_match(info->repldst_port, info->repldst_port_high,
 156                         ntohs(tuple->dst.u.all),
 157                         info->invert_flags & XT_CONNTRACK_REPLDST_PORT))
 158                 return false;
 159
 160         return true;
 161 }
 162
 163 static bool
 164 conntrack_mt(const struct sk_buff *skb, struct xt_action_param *par,
 165              u16 state_mask, u16 status_mask)
 166 {
 167         const struct xt_conntrack_mtinfo2 *info = par->matchinfo;
 168         enum ip_conntrack_info ctinfo;
 169         const struct nf_conn *ct;
 170         unsigned int statebit;
 171
 172         ct = nf_ct_get(skb, &ctinfo);
 173
 174         if (ct) {
 175                 if (nf_ct_is_untracked(ct))
 176                         statebit = XT_CONNTRACK_STATE_UNTRACKED;
 177                 else
 178                         statebit = XT_CONNTRACK_STATE_BIT(ctinfo);
 179         } else
 180                 statebit = XT_CONNTRACK_STATE_INVALID;
 181
 182         if (info->match_flags & XT_CONNTRACK_STATE) {
 183                 if (ct != NULL) {
 184                         if (test_bit(IPS_SRC_NAT_BIT, &ct->status))
 185                                 statebit |= XT_CONNTRACK_STATE_SNAT;
 186                         if (test_bit(IPS_DST_NAT_BIT, &ct->status))
 187                                 statebit |= XT_CONNTRACK_STATE_DNAT;
 188                 }
 189                 if (!!(state_mask & statebit) ^
 190                     !(info->invert_flags & XT_CONNTRACK_STATE))
 191                         return false;
 192         }
 193
 194         if (ct == NULL)
 195                 return info->match_flags & XT_CONNTRACK_STATE;
 196         if ((info->match_flags & XT_CONNTRACK_DIRECTION) &&
 197             (CTINFO2DIR(ctinfo) == IP_CT_DIR_ORIGINAL) ^
 198             !(info->invert_flags & XT_CONNTRACK_DIRECTION))
 199                 return false;
 200
 201         if (info->match_flags & XT_CONNTRACK_ORIGSRC)
 202                 if (conntrack_mt_origsrc(ct, info, par->family) ^
 203                     !(info->invert_flags & XT_CONNTRACK_ORIGSRC))
 204                         return false;
 205
 206         if (info->match_flags & XT_CONNTRACK_ORIGDST)
 207                 if (conntrack_mt_origdst(ct, info, par->family) ^
 208                     !(info->invert_flags & XT_CONNTRACK_ORIGDST))
 209                         return false;
 210
 211         if (info->match_flags & XT_CONNTRACK_REPLSRC)
 212                 if (conntrack_mt_replsrc(ct, info, par->family) ^
 213                     !(info->invert_flags & XT_CONNTRACK_REPLSRC))
 214                         return false;
 215
 216         if (info->match_flags & XT_CONNTRACK_REPLDST)
 217                 if (conntrack_mt_repldst(ct, info, par->family) ^
 218                     !(info->invert_flags & XT_CONNTRACK_REPLDST))
 219                         return false;
 220
 221         if (par->match->revision != 3) {
 222                 if (!ct_proto_port_check(info, ct))
 223                         return false;
 224         } else {
 225                 if (!ct_proto_port_check_v3(par->matchinfo, ct))
 226                         return false;
 227         }
 228
 229         if ((info->match_flags & XT_CONNTRACK_STATUS) &&
 230             (!!(status_mask & ct->status) ^
 231             !(info->invert_flags & XT_CONNTRACK_STATUS)))
 232                 return false;
 233
 234         if (info->match_flags & XT_CONNTRACK_EXPIRES) {
 235                 unsigned long expires = 0;
 236
 237                 if (timer_pending(&ct->timeout))
 238                         expires = (ct->timeout.expires - jiffies) / HZ;
 239                 if ((expires >= info->expires_min &&
 240                     expires <= info->expires_max) ^
 241                     !(info->invert_flags & XT_CONNTRACK_EXPIRES))
 242                         return false;
 243         }
 244         return true;
 245 }
 246
 247 static bool
 248 conntrack_mt_v1(const struct sk_buff *skb, struct xt_action_param *par)
 249 {
 250         const struct xt_conntrack_mtinfo1 *info = par->matchinfo;
 251
 252         return conntrack_mt(skb, par, info->state_mask, info->status_mask);
 253 }
 254
 255 static bool
 256 conntrack_mt_v2(const struct sk_buff *skb, struct xt_action_param *par)
 257 {
 258         const struct xt_conntrack_mtinfo2 *info = par->matchinfo;
 259
 260         return conntrack_mt(skb, par, info->state_mask, info->status_mask);
 261 }
 262
 263 static bool
 264 conntrack_mt_v3(const struct sk_buff *skb, struct xt_action_param *par)
 265 {
 266         const struct xt_conntrack_mtinfo3 *info = par->matchinfo;
 267
 268         return conntrack_mt(skb, par, info->state_mask, info->status_mask);
 269 }
 270
 271 static int conntrack_mt_check(const struct xt_mtchk_param *par)
 272 {
 273         int ret;
 274
 275         ret = nf_ct_l3proto_try_module_get(par->family);
 276         if (ret < 0)
 277                 pr_info("cannot load conntrack support for proto=%u\n",
 278                         par->family);
 279         return ret;
 280 }
 281
 282 static void conntrack_mt_destroy(const struct xt_mtdtor_param *par)
 283 {
 284         nf_ct_l3proto_module_put(par->family);
 285 }
 286
 287 static struct xt_match conntrack_mt_reg[] __read_mostly = {
 288         {
 289                 .name       = "conntrack",
 290                 .revision   = 1,
 291                 .family     = NFPROTO_UNSPEC,
 292                 .matchsize  = sizeof(struct xt_conntrack_mtinfo1),
 293                 .match      = conntrack_mt_v1,
 294                 .checkentry = conntrack_mt_check,
 295                 .destroy    = conntrack_mt_destroy,
 296                 .me         = THIS_MODULE,
 297         },
 298         {
 299                 .name       = "conntrack",
 300                 .revision   = 2,
 301                 .family     = NFPROTO_UNSPEC,
 302                 .matchsize  = sizeof(struct xt_conntrack_mtinfo2),
 303                 .match      = conntrack_mt_v2,
 304                 .checkentry = conntrack_mt_check,
 305                 .destroy    = conntrack_mt_destroy,
 306                 .me         = THIS_MODULE,
 307         },
 308         {
 309                 .name       = "conntrack",
 310                 .revision   = 3,
 311                 .family     = NFPROTO_UNSPEC,
 312                 .matchsize  = sizeof(struct xt_conntrack_mtinfo3),
 313                 .match      = conntrack_mt_v3,
 314                 .checkentry = conntrack_mt_check,
 315                 .destroy    = conntrack_mt_destroy,
 316                 .me         = THIS_MODULE,
 317         },
 318 };
 319
 320 static int __init conntrack_mt_init(void)
 321 {
 322         return xt_register_matches(conntrack_mt_reg,
 323                ARRAY_SIZE(conntrack_mt_reg));
 324 }
 325
 326 static void __exit conntrack_mt_exit(void)
 327 {
 328         xt_unregister_matches(conntrack_mt_reg, ARRAY_SIZE(conntrack_mt_reg));
 329 }
 330
 331 module_init(conntrack_mt_init);
 332 module_exit(conntrack_mt_exit);