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
  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@computergmbh.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_mt_v0(const struct sk_buff *skb, const struct xt_match_param *par)
  29 {
  30         const struct xt_conntrack_info *sinfo = par->matchinfo;
  31         const struct nf_conn *ct;
  32         enum ip_conntrack_info ctinfo;
  33         unsigned int statebit;
  34
  35         ct = nf_ct_get(skb, &ctinfo);
  36
  37 #define FWINV(bool, invflg) ((bool) ^ !!(sinfo->invflags & (invflg)))
  38
  39         if (ct == &nf_conntrack_untracked)
  40                 statebit = XT_CONNTRACK_STATE_UNTRACKED;
  41         else if (ct)
  42                 statebit = XT_CONNTRACK_STATE_BIT(ctinfo);
  43         else
  44                 statebit = XT_CONNTRACK_STATE_INVALID;
  45
  46         if (sinfo->flags & XT_CONNTRACK_STATE) {
  47                 if (ct) {
  48                         if (test_bit(IPS_SRC_NAT_BIT, &ct->status))
  49                                 statebit |= XT_CONNTRACK_STATE_SNAT;
  50                         if (test_bit(IPS_DST_NAT_BIT, &ct->status))
  51                                 statebit |= XT_CONNTRACK_STATE_DNAT;
  52                 }
  53                 if (FWINV((statebit & sinfo->statemask) == 0,
  54                           XT_CONNTRACK_STATE))
  55                         return false;
  56         }
  57
  58         if (ct == NULL) {
  59                 if (sinfo->flags & ~XT_CONNTRACK_STATE)
  60                         return false;
  61                 return true;
  62         }
  63
  64         if (sinfo->flags & XT_CONNTRACK_PROTO &&
  65             FWINV(nf_ct_protonum(ct) !=
  66                   sinfo->tuple[IP_CT_DIR_ORIGINAL].dst.protonum,
  67                   XT_CONNTRACK_PROTO))
  68                 return false;
  69
  70         if (sinfo->flags & XT_CONNTRACK_ORIGSRC &&
  71             FWINV((ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple.src.u3.ip &
  72                    sinfo->sipmsk[IP_CT_DIR_ORIGINAL].s_addr) !=
  73                   sinfo->tuple[IP_CT_DIR_ORIGINAL].src.ip,
  74                   XT_CONNTRACK_ORIGSRC))
  75                 return false;
  76
  77         if (sinfo->flags & XT_CONNTRACK_ORIGDST &&
  78             FWINV((ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple.dst.u3.ip &
  79                    sinfo->dipmsk[IP_CT_DIR_ORIGINAL].s_addr) !=
  80                   sinfo->tuple[IP_CT_DIR_ORIGINAL].dst.ip,
  81                   XT_CONNTRACK_ORIGDST))
  82                 return false;
  83
  84         if (sinfo->flags & XT_CONNTRACK_REPLSRC &&
  85             FWINV((ct->tuplehash[IP_CT_DIR_REPLY].tuple.src.u3.ip &
  86                    sinfo->sipmsk[IP_CT_DIR_REPLY].s_addr) !=
  87                   sinfo->tuple[IP_CT_DIR_REPLY].src.ip,
  88                   XT_CONNTRACK_REPLSRC))
  89                 return false;
  90
  91         if (sinfo->flags & XT_CONNTRACK_REPLDST &&
  92             FWINV((ct->tuplehash[IP_CT_DIR_REPLY].tuple.dst.u3.ip &
  93                    sinfo->dipmsk[IP_CT_DIR_REPLY].s_addr) !=
  94                   sinfo->tuple[IP_CT_DIR_REPLY].dst.ip,
  95                   XT_CONNTRACK_REPLDST))
  96                 return false;
  97
  98         if (sinfo->flags & XT_CONNTRACK_STATUS &&
  99             FWINV((ct->status & sinfo->statusmask) == 0,
 100                   XT_CONNTRACK_STATUS))
 101                 return false;
 102
 103         if(sinfo->flags & XT_CONNTRACK_EXPIRES) {
 104                 unsigned long expires = timer_pending(&ct->timeout) ?
 105                                         (ct->timeout.expires - jiffies)/HZ : 0;
 106
 107                 if (FWINV(!(expires >= sinfo->expires_min &&
 108                             expires <= sinfo->expires_max),
 109                           XT_CONNTRACK_EXPIRES))
 110                         return false;
 111         }
 112         return true;
 113 #undef FWINV
 114 }
 115
 116 static bool
 117 conntrack_addrcmp(const union nf_inet_addr *kaddr,
 118                   const union nf_inet_addr *uaddr,
 119                   const union nf_inet_addr *umask, unsigned int l3proto)
 120 {
 121         if (l3proto == NFPROTO_IPV4)
 122                 return ((kaddr->ip ^ uaddr->ip) & umask->ip) == 0;
 123         else if (l3proto == NFPROTO_IPV6)
 124                 return ipv6_masked_addr_cmp(&kaddr->in6, &umask->in6,
 125                        &uaddr->in6) == 0;
 126         else
 127                 return false;
 128 }
 129
 130 static inline bool
 131 conntrack_mt_origsrc(const struct nf_conn *ct,
 132                      const struct xt_conntrack_mtinfo2 *info,
 133                      u_int8_t family)
 134 {
 135         return conntrack_addrcmp(&ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple.src.u3,
 136                &info->origsrc_addr, &info->origsrc_mask, family);
 137 }
 138
 139 static inline bool
 140 conntrack_mt_origdst(const struct nf_conn *ct,
 141                      const struct xt_conntrack_mtinfo2 *info,
 142                      u_int8_t family)
 143 {
 144         return conntrack_addrcmp(&ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple.dst.u3,
 145                &info->origdst_addr, &info->origdst_mask, family);
 146 }
 147
 148 static inline bool
 149 conntrack_mt_replsrc(const struct nf_conn *ct,
 150                      const struct xt_conntrack_mtinfo2 *info,
 151                      u_int8_t family)
 152 {
 153         return conntrack_addrcmp(&ct->tuplehash[IP_CT_DIR_REPLY].tuple.src.u3,
 154                &info->replsrc_addr, &info->replsrc_mask, family);
 155 }
 156
 157 static inline bool
 158 conntrack_mt_repldst(const struct nf_conn *ct,
 159                      const struct xt_conntrack_mtinfo2 *info,
 160                      u_int8_t family)
 161 {
 162         return conntrack_addrcmp(&ct->tuplehash[IP_CT_DIR_REPLY].tuple.dst.u3,
 163                &info->repldst_addr, &info->repldst_mask, family);
 164 }
 165
 166 static inline bool
 167 ct_proto_port_check(const struct xt_conntrack_mtinfo2 *info,
 168                     const struct nf_conn *ct)
 169 {
 170         const struct nf_conntrack_tuple *tuple;
 171
 172         tuple = &ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple;
 173         if ((info->match_flags & XT_CONNTRACK_PROTO) &&
 174             (nf_ct_protonum(ct) == info->l4proto) ^
 175             !(info->invert_flags & XT_CONNTRACK_PROTO))
 176                 return false;
 177
 178         /* Shortcut to match all recognized protocols by using ->src.all. */
 179         if ((info->match_flags & XT_CONNTRACK_ORIGSRC_PORT) &&
 180             (tuple->src.u.all == info->origsrc_port) ^
 181             !(info->invert_flags & XT_CONNTRACK_ORIGSRC_PORT))
 182                 return false;
 183
 184         if ((info->match_flags & XT_CONNTRACK_ORIGDST_PORT) &&
 185             (tuple->dst.u.all == info->origdst_port) ^
 186             !(info->invert_flags & XT_CONNTRACK_ORIGDST_PORT))
 187                 return false;
 188
 189         tuple = &ct->tuplehash[IP_CT_DIR_REPLY].tuple;
 190
 191         if ((info->match_flags & XT_CONNTRACK_REPLSRC_PORT) &&
 192             (tuple->src.u.all == info->replsrc_port) ^
 193             !(info->invert_flags & XT_CONNTRACK_REPLSRC_PORT))
 194                 return false;
 195
 196         if ((info->match_flags & XT_CONNTRACK_REPLDST_PORT) &&
 197             (tuple->dst.u.all == info->repldst_port) ^
 198             !(info->invert_flags & XT_CONNTRACK_REPLDST_PORT))
 199                 return false;
 200
 201         return true;
 202 }
 203
 204 static bool
 205 conntrack_mt(const struct sk_buff *skb, const struct xt_match_param *par)
 206 {
 207         const struct xt_conntrack_mtinfo2 *info = par->matchinfo;
 208         enum ip_conntrack_info ctinfo;
 209         const struct nf_conn *ct;
 210         unsigned int statebit;
 211
 212         ct = nf_ct_get(skb, &ctinfo);
 213
 214         if (ct == &nf_conntrack_untracked)
 215                 statebit = XT_CONNTRACK_STATE_UNTRACKED;
 216         else if (ct != NULL)
 217                 statebit = XT_CONNTRACK_STATE_BIT(ctinfo);
 218         else
 219                 statebit = XT_CONNTRACK_STATE_INVALID;
 220
 221         if (info->match_flags & XT_CONNTRACK_STATE) {
 222                 if (ct != NULL) {
 223                         if (test_bit(IPS_SRC_NAT_BIT, &ct->status))
 224                                 statebit |= XT_CONNTRACK_STATE_SNAT;
 225                         if (test_bit(IPS_DST_NAT_BIT, &ct->status))
 226                                 statebit |= XT_CONNTRACK_STATE_DNAT;
 227                 }
 228                 if (!!(info->state_mask & statebit) ^
 229                     !(info->invert_flags & XT_CONNTRACK_STATE))
 230                         return false;
 231         }
 232
 233         if (ct == NULL)
 234                 return info->match_flags & XT_CONNTRACK_STATE;
 235         if ((info->match_flags & XT_CONNTRACK_DIRECTION) &&
 236             (CTINFO2DIR(ctinfo) == IP_CT_DIR_ORIGINAL) ^
 237             !!(info->invert_flags & XT_CONNTRACK_DIRECTION))
 238                 return false;
 239
 240         if (info->match_flags & XT_CONNTRACK_ORIGSRC)
 241                 if (conntrack_mt_origsrc(ct, info, par->family) ^
 242                     !(info->invert_flags & XT_CONNTRACK_ORIGSRC))
 243                         return false;
 244
 245         if (info->match_flags & XT_CONNTRACK_ORIGDST)
 246                 if (conntrack_mt_origdst(ct, info, par->family) ^
 247                     !(info->invert_flags & XT_CONNTRACK_ORIGDST))
 248                         return false;
 249
 250         if (info->match_flags & XT_CONNTRACK_REPLSRC)
 251                 if (conntrack_mt_replsrc(ct, info, par->family) ^
 252                     !(info->invert_flags & XT_CONNTRACK_REPLSRC))
 253                         return false;
 254
 255         if (info->match_flags & XT_CONNTRACK_REPLDST)
 256                 if (conntrack_mt_repldst(ct, info, par->family) ^
 257                     !(info->invert_flags & XT_CONNTRACK_REPLDST))
 258                         return false;
 259
 260         if (!ct_proto_port_check(info, ct))
 261                 return false;
 262
 263         if ((info->match_flags & XT_CONNTRACK_STATUS) &&
 264             (!!(info->status_mask & ct->status) ^
 265             !(info->invert_flags & XT_CONNTRACK_STATUS)))
 266                 return false;
 267
 268         if (info->match_flags & XT_CONNTRACK_EXPIRES) {
 269                 unsigned long expires = 0;
 270
 271                 if (timer_pending(&ct->timeout))
 272                         expires = (ct->timeout.expires - jiffies) / HZ;
 273                 if ((expires >= info->expires_min &&
 274                     expires <= info->expires_max) ^
 275                     !(info->invert_flags & XT_CONNTRACK_EXPIRES))
 276                         return false;
 277         }
 278         return true;
 279 }
 280
 281 static bool
 282 conntrack_mt_v1(const struct sk_buff *skb, const struct xt_match_param *par)
 283 {
 284         const struct xt_conntrack_mtinfo2 *const *info = par->matchinfo;
 285         struct xt_match_param newpar = *par;
 286
 287         newpar.matchinfo = *info;
 288         return conntrack_mt(skb, &newpar);
 289 }
 290
 291 static bool conntrack_mt_check(const struct xt_mtchk_param *par)
 292 {
 293         if (nf_ct_l3proto_try_module_get(par->family) < 0) {
 294                 printk(KERN_WARNING "can't load conntrack support for "
 295                                     "proto=%u\n", par->family);
 296                 return false;
 297         }
 298         return true;
 299 }
 300
 301 static bool conntrack_mt_check_v1(const struct xt_mtchk_param *par)
 302 {
 303         struct xt_conntrack_mtinfo1 *info = par->matchinfo;
 304         struct xt_conntrack_mtinfo2 *up;
 305         int ret = conntrack_mt_check(par);
 306
 307         if (ret < 0)
 308                 return ret;
 309
 310         up = kmalloc(sizeof(*up), GFP_KERNEL);
 311         if (up == NULL) {
 312                 nf_ct_l3proto_module_put(par->family);
 313                 return -ENOMEM;
 314         }
 315
 316         /*
 317          * The strategy here is to minimize the overhead of v1 matching,
 318          * by prebuilding a v2 struct and putting the pointer into the
 319          * v1 dataspace.
 320          */
 321         memcpy(up, info, offsetof(typeof(*info), state_mask));
 322         up->state_mask  = info->state_mask;
 323         up->status_mask = info->status_mask;
 324         *(void **)info  = up;
 325         return true;
 326 }
 327
 328 static void conntrack_mt_destroy(const struct xt_mtdtor_param *par)
 329 {
 330         nf_ct_l3proto_module_put(par->family);
 331 }
 332
 333 static void conntrack_mt_destroy_v1(const struct xt_mtdtor_param *par)
 334 {
 335         struct xt_conntrack_mtinfo2 **info = par->matchinfo;
 336         kfree(*info);
 337         conntrack_mt_destroy(par);
 338 }
 339
 340 #ifdef CONFIG_COMPAT
 341 struct compat_xt_conntrack_info
 342 {
 343         compat_uint_t                   statemask;
 344         compat_uint_t                   statusmask;
 345         struct ip_conntrack_old_tuple   tuple[IP_CT_DIR_MAX];
 346         struct in_addr                  sipmsk[IP_CT_DIR_MAX];
 347         struct in_addr                  dipmsk[IP_CT_DIR_MAX];
 348         compat_ulong_t                  expires_min;
 349         compat_ulong_t                  expires_max;
 350         u_int8_t                        flags;
 351         u_int8_t                        invflags;
 352 };
 353
 354 static void conntrack_mt_compat_from_user_v0(void *dst, void *src)
 355 {
 356         const struct compat_xt_conntrack_info *cm = src;
 357         struct xt_conntrack_info m = {
 358                 .statemask      = cm->statemask,
 359                 .statusmask     = cm->statusmask,
 360                 .expires_min    = cm->expires_min,
 361                 .expires_max    = cm->expires_max,
 362                 .flags          = cm->flags,
 363                 .invflags       = cm->invflags,
 364         };
 365         memcpy(m.tuple, cm->tuple, sizeof(m.tuple));
 366         memcpy(m.sipmsk, cm->sipmsk, sizeof(m.sipmsk));
 367         memcpy(m.dipmsk, cm->dipmsk, sizeof(m.dipmsk));
 368         memcpy(dst, &m, sizeof(m));
 369 }
 370
 371 static int conntrack_mt_compat_to_user_v0(void __user *dst, void *src)
 372 {
 373         const struct xt_conntrack_info *m = src;
 374         struct compat_xt_conntrack_info cm = {
 375                 .statemask      = m->statemask,
 376                 .statusmask     = m->statusmask,
 377                 .expires_min    = m->expires_min,
 378                 .expires_max    = m->expires_max,
 379                 .flags          = m->flags,
 380                 .invflags       = m->invflags,
 381         };
 382         memcpy(cm.tuple, m->tuple, sizeof(cm.tuple));
 383         memcpy(cm.sipmsk, m->sipmsk, sizeof(cm.sipmsk));
 384         memcpy(cm.dipmsk, m->dipmsk, sizeof(cm.dipmsk));
 385         return copy_to_user(dst, &cm, sizeof(cm)) ? -EFAULT : 0;
 386 }
 387 #endif
 388
 389 static struct xt_match conntrack_mt_reg[] __read_mostly = {
 390         {
 391                 .name       = "conntrack",
 392                 .revision   = 0,
 393                 .family     = NFPROTO_IPV4,
 394                 .match      = conntrack_mt_v0,
 395                 .checkentry = conntrack_mt_check,
 396                 .destroy    = conntrack_mt_destroy,
 397                 .matchsize  = sizeof(struct xt_conntrack_info),
 398                 .me         = THIS_MODULE,
 399 #ifdef CONFIG_COMPAT
 400                 .compatsize       = sizeof(struct compat_xt_conntrack_info),
 401                 .compat_from_user = conntrack_mt_compat_from_user_v0,
 402                 .compat_to_user   = conntrack_mt_compat_to_user_v0,
 403 #endif
 404         },
 405         {
 406                 .name       = "conntrack",
 407                 .revision   = 1,
 408                 .family     = NFPROTO_UNSPEC,
 409                 .matchsize  = sizeof(struct xt_conntrack_mtinfo1),
 410                 .match      = conntrack_mt_v1,
 411                 .checkentry = conntrack_mt_check_v1,
 412                 .destroy    = conntrack_mt_destroy_v1,
 413                 .me         = THIS_MODULE,
 414         },
 415         {
 416                 .name       = "conntrack",
 417                 .revision   = 2,
 418                 .family     = NFPROTO_UNSPEC,
 419                 .matchsize  = sizeof(struct xt_conntrack_mtinfo2),
 420                 .match      = conntrack_mt,
 421                 .checkentry = conntrack_mt_check,
 422                 .destroy    = conntrack_mt_destroy,
 423                 .me         = THIS_MODULE,
 424         },
 425 };
 426
 427 static int __init conntrack_mt_init(void)
 428 {
 429         return xt_register_matches(conntrack_mt_reg,
 430                ARRAY_SIZE(conntrack_mt_reg));
 431 }
 432
 433 static void __exit conntrack_mt_exit(void)
 434 {
 435         xt_unregister_matches(conntrack_mt_reg, ARRAY_SIZE(conntrack_mt_reg));
 436 }
 437
 438 module_init(conntrack_mt_init);
 439 module_exit(conntrack_mt_exit);