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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@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_mtinfo1 *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_mtinfo1 *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_mtinfo1 *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_mtinfo1 *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_mtinfo1 *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_mtinfo1 *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->match->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->match->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->match->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->match->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_check(const char *tablename, const void *ip,
 283                    const struct xt_match *match, void *matchinfo,
 284                    unsigned int hook_mask)
 285 {
 286         if (nf_ct_l3proto_try_module_get(match->family) < 0) {
 287                 printk(KERN_WARNING "can't load conntrack support for "
 288                                     "proto=%u\n", match->family);
 289                 return false;
 290         }
 291         return true;
 292 }
 293
 294 static void
 295 conntrack_mt_destroy(const struct xt_match *match, void *matchinfo)
 296 {
 297         nf_ct_l3proto_module_put(match->family);
 298 }
 299
 300 #ifdef CONFIG_COMPAT
 301 struct compat_xt_conntrack_info
 302 {
 303         compat_uint_t                   statemask;
 304         compat_uint_t                   statusmask;
 305         struct ip_conntrack_old_tuple   tuple[IP_CT_DIR_MAX];
 306         struct in_addr                  sipmsk[IP_CT_DIR_MAX];
 307         struct in_addr                  dipmsk[IP_CT_DIR_MAX];
 308         compat_ulong_t                  expires_min;
 309         compat_ulong_t                  expires_max;
 310         u_int8_t                        flags;
 311         u_int8_t                        invflags;
 312 };
 313
 314 static void conntrack_mt_compat_from_user_v0(void *dst, void *src)
 315 {
 316         const struct compat_xt_conntrack_info *cm = src;
 317         struct xt_conntrack_info m = {
 318                 .statemask      = cm->statemask,
 319                 .statusmask     = cm->statusmask,
 320                 .expires_min    = cm->expires_min,
 321                 .expires_max    = cm->expires_max,
 322                 .flags          = cm->flags,
 323                 .invflags       = cm->invflags,
 324         };
 325         memcpy(m.tuple, cm->tuple, sizeof(m.tuple));
 326         memcpy(m.sipmsk, cm->sipmsk, sizeof(m.sipmsk));
 327         memcpy(m.dipmsk, cm->dipmsk, sizeof(m.dipmsk));
 328         memcpy(dst, &m, sizeof(m));
 329 }
 330
 331 static int conntrack_mt_compat_to_user_v0(void __user *dst, void *src)
 332 {
 333         const struct xt_conntrack_info *m = src;
 334         struct compat_xt_conntrack_info cm = {
 335                 .statemask      = m->statemask,
 336                 .statusmask     = m->statusmask,
 337                 .expires_min    = m->expires_min,
 338                 .expires_max    = m->expires_max,
 339                 .flags          = m->flags,
 340                 .invflags       = m->invflags,
 341         };
 342         memcpy(cm.tuple, m->tuple, sizeof(cm.tuple));
 343         memcpy(cm.sipmsk, m->sipmsk, sizeof(cm.sipmsk));
 344         memcpy(cm.dipmsk, m->dipmsk, sizeof(cm.dipmsk));
 345         return copy_to_user(dst, &cm, sizeof(cm)) ? -EFAULT : 0;
 346 }
 347 #endif
 348
 349 static struct xt_match conntrack_mt_reg[] __read_mostly = {
 350         {
 351                 .name       = "conntrack",
 352                 .revision   = 0,
 353                 .family     = NFPROTO_IPV4,
 354                 .match      = conntrack_mt_v0,
 355                 .checkentry = conntrack_mt_check,
 356                 .destroy    = conntrack_mt_destroy,
 357                 .matchsize  = sizeof(struct xt_conntrack_info),
 358                 .me         = THIS_MODULE,
 359 #ifdef CONFIG_COMPAT
 360                 .compatsize       = sizeof(struct compat_xt_conntrack_info),
 361                 .compat_from_user = conntrack_mt_compat_from_user_v0,
 362                 .compat_to_user   = conntrack_mt_compat_to_user_v0,
 363 #endif
 364         },
 365         {
 366                 .name       = "conntrack",
 367                 .revision   = 1,
 368                 .family     = NFPROTO_IPV4,
 369                 .matchsize  = sizeof(struct xt_conntrack_mtinfo1),
 370                 .match      = conntrack_mt,
 371                 .checkentry = conntrack_mt_check,
 372                 .destroy    = conntrack_mt_destroy,
 373                 .me         = THIS_MODULE,
 374         },
 375         {
 376                 .name       = "conntrack",
 377                 .revision   = 1,
 378                 .family     = NFPROTO_IPV6,
 379                 .matchsize  = sizeof(struct xt_conntrack_mtinfo1),
 380                 .match      = conntrack_mt,
 381                 .checkentry = conntrack_mt_check,
 382                 .destroy    = conntrack_mt_destroy,
 383                 .me         = THIS_MODULE,
 384         },
 385 };
 386
 387 static int __init conntrack_mt_init(void)
 388 {
 389         return xt_register_matches(conntrack_mt_reg,
 390                ARRAY_SIZE(conntrack_mt_reg));
 391 }
 392
 393 static void __exit conntrack_mt_exit(void)
 394 {
 395         xt_unregister_matches(conntrack_mt_reg, ARRAY_SIZE(conntrack_mt_reg));
 396 }
 397
 398 module_init(conntrack_mt_init);
 399 module_exit(conntrack_mt_exit);