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 net_device *in,
  29                 const struct net_device *out, const struct xt_match *match,
  30                 const void *matchinfo, int offset, unsigned int protoff,
  31                 bool *hotdrop)
  32 {
  33         const struct xt_conntrack_info *sinfo = matchinfo;
  34         const struct nf_conn *ct;
  35         enum ip_conntrack_info ctinfo;
  36         unsigned int statebit;
  37
  38         ct = nf_ct_get(skb, &ctinfo);
  39
  40 #define FWINV(bool, invflg) ((bool) ^ !!(sinfo->invflags & (invflg)))
  41
  42         if (ct == &nf_conntrack_untracked)
  43                 statebit = XT_CONNTRACK_STATE_UNTRACKED;
  44         else if (ct)
  45                 statebit = XT_CONNTRACK_STATE_BIT(ctinfo);
  46         else
  47                 statebit = XT_CONNTRACK_STATE_INVALID;
  48
  49         if (sinfo->flags & XT_CONNTRACK_STATE) {
  50                 if (ct) {
  51                         if (test_bit(IPS_SRC_NAT_BIT, &ct->status))
  52                                 statebit |= XT_CONNTRACK_STATE_SNAT;
  53                         if (test_bit(IPS_DST_NAT_BIT, &ct->status))
  54                                 statebit |= XT_CONNTRACK_STATE_DNAT;
  55                 }
  56                 if (FWINV((statebit & sinfo->statemask) == 0,
  57                           XT_CONNTRACK_STATE))
  58                         return false;
  59         }
  60
  61         if (ct == NULL) {
  62                 if (sinfo->flags & ~XT_CONNTRACK_STATE)
  63                         return false;
  64                 return true;
  65         }
  66
  67         if (sinfo->flags & XT_CONNTRACK_PROTO &&
  68             FWINV(nf_ct_protonum(ct) !=
  69                   sinfo->tuple[IP_CT_DIR_ORIGINAL].dst.protonum,
  70                   XT_CONNTRACK_PROTO))
  71                 return false;
  72
  73         if (sinfo->flags & XT_CONNTRACK_ORIGSRC &&
  74             FWINV((ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple.src.u3.ip &
  75                    sinfo->sipmsk[IP_CT_DIR_ORIGINAL].s_addr) !=
  76                   sinfo->tuple[IP_CT_DIR_ORIGINAL].src.ip,
  77                   XT_CONNTRACK_ORIGSRC))
  78                 return false;
  79
  80         if (sinfo->flags & XT_CONNTRACK_ORIGDST &&
  81             FWINV((ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple.dst.u3.ip &
  82                    sinfo->dipmsk[IP_CT_DIR_ORIGINAL].s_addr) !=
  83                   sinfo->tuple[IP_CT_DIR_ORIGINAL].dst.ip,
  84                   XT_CONNTRACK_ORIGDST))
  85                 return false;
  86
  87         if (sinfo->flags & XT_CONNTRACK_REPLSRC &&
  88             FWINV((ct->tuplehash[IP_CT_DIR_REPLY].tuple.src.u3.ip &
  89                    sinfo->sipmsk[IP_CT_DIR_REPLY].s_addr) !=
  90                   sinfo->tuple[IP_CT_DIR_REPLY].src.ip,
  91                   XT_CONNTRACK_REPLSRC))
  92                 return false;
  93
  94         if (sinfo->flags & XT_CONNTRACK_REPLDST &&
  95             FWINV((ct->tuplehash[IP_CT_DIR_REPLY].tuple.dst.u3.ip &
  96                    sinfo->dipmsk[IP_CT_DIR_REPLY].s_addr) !=
  97                   sinfo->tuple[IP_CT_DIR_REPLY].dst.ip,
  98                   XT_CONNTRACK_REPLDST))
  99                 return false;
 100
 101         if (sinfo->flags & XT_CONNTRACK_STATUS &&
 102             FWINV((ct->status & sinfo->statusmask) == 0,
 103                   XT_CONNTRACK_STATUS))
 104                 return false;
 105
 106         if(sinfo->flags & XT_CONNTRACK_EXPIRES) {
 107                 unsigned long expires = timer_pending(&ct->timeout) ?
 108                                         (ct->timeout.expires - jiffies)/HZ : 0;
 109
 110                 if (FWINV(!(expires >= sinfo->expires_min &&
 111                             expires <= sinfo->expires_max),
 112                           XT_CONNTRACK_EXPIRES))
 113                         return false;
 114         }
 115         return true;
 116 #undef FWINV
 117 }
 118
 119 static bool
 120 conntrack_addrcmp(const union nf_inet_addr *kaddr,
 121                   const union nf_inet_addr *uaddr,
 122                   const union nf_inet_addr *umask, unsigned int l3proto)
 123 {
 124         if (l3proto == AF_INET)
 125                 return ((kaddr->ip ^ uaddr->ip) & umask->ip) == 0;
 126         else if (l3proto == AF_INET6)
 127                 return ipv6_masked_addr_cmp(&kaddr->in6, &umask->in6,
 128                        &uaddr->in6) == 0;
 129         else
 130                 return false;
 131 }
 132
 133 static inline bool
 134 conntrack_mt_origsrc(const struct nf_conn *ct,
 135                      const struct xt_conntrack_mtinfo1 *info,
 136                      unsigned int family)
 137 {
 138         return conntrack_addrcmp(&ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple.src.u3,
 139                &info->origsrc_addr, &info->origsrc_mask, family);
 140 }
 141
 142 static inline bool
 143 conntrack_mt_origdst(const struct nf_conn *ct,
 144                      const struct xt_conntrack_mtinfo1 *info,
 145                      unsigned int family)
 146 {
 147         return conntrack_addrcmp(&ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple.dst.u3,
 148                &info->origdst_addr, &info->origdst_mask, family);
 149 }
 150
 151 static inline bool
 152 conntrack_mt_replsrc(const struct nf_conn *ct,
 153                      const struct xt_conntrack_mtinfo1 *info,
 154                      unsigned int family)
 155 {
 156         return conntrack_addrcmp(&ct->tuplehash[IP_CT_DIR_REPLY].tuple.src.u3,
 157                &info->replsrc_addr, &info->replsrc_mask, family);
 158 }
 159
 160 static inline bool
 161 conntrack_mt_repldst(const struct nf_conn *ct,
 162                      const struct xt_conntrack_mtinfo1 *info,
 163                      unsigned int family)
 164 {
 165         return conntrack_addrcmp(&ct->tuplehash[IP_CT_DIR_REPLY].tuple.dst.u3,
 166                &info->repldst_addr, &info->repldst_mask, family);
 167 }
 168
 169 static inline bool
 170 ct_proto_port_check(const struct xt_conntrack_mtinfo1 *info,
 171                     const struct nf_conn *ct)
 172 {
 173         const struct nf_conntrack_tuple *tuple;
 174
 175         tuple = &ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple;
 176         if ((info->match_flags & XT_CONNTRACK_PROTO) &&
 177             (nf_ct_protonum(ct) == info->l4proto) ^
 178             !(info->invert_flags & XT_CONNTRACK_PROTO))
 179                 return false;
 180
 181         /* Shortcut to match all recognized protocols by using ->src.all. */
 182         if ((info->match_flags & XT_CONNTRACK_ORIGSRC_PORT) &&
 183             (tuple->src.u.all == info->origsrc_port) ^
 184             !(info->invert_flags & XT_CONNTRACK_ORIGSRC_PORT))
 185                 return false;
 186
 187         if ((info->match_flags & XT_CONNTRACK_ORIGDST_PORT) &&
 188             (tuple->dst.u.all == info->origdst_port) ^
 189             !(info->invert_flags & XT_CONNTRACK_ORIGDST_PORT))
 190                 return false;
 191
 192         tuple = &ct->tuplehash[IP_CT_DIR_REPLY].tuple;
 193
 194         if ((info->match_flags & XT_CONNTRACK_REPLSRC_PORT) &&
 195             (tuple->src.u.all == info->replsrc_port) ^
 196             !(info->invert_flags & XT_CONNTRACK_REPLSRC_PORT))
 197                 return false;
 198
 199         if ((info->match_flags & XT_CONNTRACK_REPLDST_PORT) &&
 200             (tuple->dst.u.all == info->repldst_port) ^
 201             !(info->invert_flags & XT_CONNTRACK_REPLDST_PORT))
 202                 return false;
 203
 204         return true;
 205 }
 206
 207 static bool
 208 conntrack_mt(const struct sk_buff *skb, const struct net_device *in,
 209              const struct net_device *out, const struct xt_match *match,
 210              const void *matchinfo, int offset, unsigned int protoff,
 211              bool *hotdrop)
 212 {
 213         const struct xt_conntrack_mtinfo1 *info = matchinfo;
 214         enum ip_conntrack_info ctinfo;
 215         const struct nf_conn *ct;
 216         unsigned int statebit;
 217
 218         ct = nf_ct_get(skb, &ctinfo);
 219
 220         if (ct == &nf_conntrack_untracked)
 221                 statebit = XT_CONNTRACK_STATE_UNTRACKED;
 222         else if (ct != NULL)
 223                 statebit = XT_CONNTRACK_STATE_BIT(ctinfo);
 224         else
 225                 statebit = XT_CONNTRACK_STATE_INVALID;
 226
 227         if (info->match_flags & XT_CONNTRACK_STATE) {
 228                 if (ct != NULL) {
 229                         if (test_bit(IPS_SRC_NAT_BIT, &ct->status))
 230                                 statebit |= XT_CONNTRACK_STATE_SNAT;
 231                         if (test_bit(IPS_DST_NAT_BIT, &ct->status))
 232                                 statebit |= XT_CONNTRACK_STATE_DNAT;
 233                 }
 234                 if (!!(info->state_mask & statebit) ^
 235                     !(info->invert_flags & XT_CONNTRACK_STATE))
 236                         return false;
 237         }
 238
 239         if (ct == NULL)
 240                 return info->match_flags & XT_CONNTRACK_STATE;
 241         if ((info->match_flags & XT_CONNTRACK_DIRECTION) &&
 242             (CTINFO2DIR(ctinfo) == IP_CT_DIR_ORIGINAL) ^
 243             !!(info->invert_flags & XT_CONNTRACK_DIRECTION))
 244                 return false;
 245
 246         if (info->match_flags & XT_CONNTRACK_ORIGSRC)
 247                 if (conntrack_mt_origsrc(ct, info, match->family) ^
 248                     !(info->invert_flags & XT_CONNTRACK_ORIGSRC))
 249                         return false;
 250
 251         if (info->match_flags & XT_CONNTRACK_ORIGDST)
 252                 if (conntrack_mt_origdst(ct, info, match->family) ^
 253                     !(info->invert_flags & XT_CONNTRACK_ORIGDST))
 254                         return false;
 255
 256         if (info->match_flags & XT_CONNTRACK_REPLSRC)
 257                 if (conntrack_mt_replsrc(ct, info, match->family) ^
 258                     !(info->invert_flags & XT_CONNTRACK_REPLSRC))
 259                         return false;
 260
 261         if (info->match_flags & XT_CONNTRACK_REPLDST)
 262                 if (conntrack_mt_repldst(ct, info, match->family) ^
 263                     !(info->invert_flags & XT_CONNTRACK_REPLDST))
 264                         return false;
 265
 266         if (!ct_proto_port_check(info, ct))
 267                 return false;
 268
 269         if ((info->match_flags & XT_CONNTRACK_STATUS) &&
 270             (!!(info->status_mask & ct->status) ^
 271             !(info->invert_flags & XT_CONNTRACK_STATUS)))
 272                 return false;
 273
 274         if (info->match_flags & XT_CONNTRACK_EXPIRES) {
 275                 unsigned long expires = 0;
 276
 277                 if (timer_pending(&ct->timeout))
 278                         expires = (ct->timeout.expires - jiffies) / HZ;
 279                 if ((expires >= info->expires_min &&
 280                     expires <= info->expires_max) ^
 281                     !(info->invert_flags & XT_CONNTRACK_EXPIRES))
 282                         return false;
 283         }
 284         return true;
 285 }
 286
 287 static bool
 288 conntrack_mt_check(const char *tablename, const void *ip,
 289                    const struct xt_match *match, void *matchinfo,
 290                    unsigned int hook_mask)
 291 {
 292         if (nf_ct_l3proto_try_module_get(match->family) < 0) {
 293                 printk(KERN_WARNING "can't load conntrack support for "
 294                                     "proto=%u\n", match->family);
 295                 return false;
 296         }
 297         return true;
 298 }
 299
 300 static void
 301 conntrack_mt_destroy(const struct xt_match *match, void *matchinfo)
 302 {
 303         nf_ct_l3proto_module_put(match->family);
 304 }
 305
 306 #ifdef CONFIG_COMPAT
 307 struct compat_xt_conntrack_info
 308 {
 309         compat_uint_t                   statemask;
 310         compat_uint_t                   statusmask;
 311         struct ip_conntrack_old_tuple   tuple[IP_CT_DIR_MAX];
 312         struct in_addr                  sipmsk[IP_CT_DIR_MAX];
 313         struct in_addr                  dipmsk[IP_CT_DIR_MAX];
 314         compat_ulong_t                  expires_min;
 315         compat_ulong_t                  expires_max;
 316         u_int8_t                        flags;
 317         u_int8_t                        invflags;
 318 };
 319
 320 static void conntrack_mt_compat_from_user_v0(void *dst, void *src)
 321 {
 322         const struct compat_xt_conntrack_info *cm = src;
 323         struct xt_conntrack_info m = {
 324                 .statemask      = cm->statemask,
 325                 .statusmask     = cm->statusmask,
 326                 .expires_min    = cm->expires_min,
 327                 .expires_max    = cm->expires_max,
 328                 .flags          = cm->flags,
 329                 .invflags       = cm->invflags,
 330         };
 331         memcpy(m.tuple, cm->tuple, sizeof(m.tuple));
 332         memcpy(m.sipmsk, cm->sipmsk, sizeof(m.sipmsk));
 333         memcpy(m.dipmsk, cm->dipmsk, sizeof(m.dipmsk));
 334         memcpy(dst, &m, sizeof(m));
 335 }
 336
 337 static int conntrack_mt_compat_to_user_v0(void __user *dst, void *src)
 338 {
 339         const struct xt_conntrack_info *m = src;
 340         struct compat_xt_conntrack_info cm = {
 341                 .statemask      = m->statemask,
 342                 .statusmask     = m->statusmask,
 343                 .expires_min    = m->expires_min,
 344                 .expires_max    = m->expires_max,
 345                 .flags          = m->flags,
 346                 .invflags       = m->invflags,
 347         };
 348         memcpy(cm.tuple, m->tuple, sizeof(cm.tuple));
 349         memcpy(cm.sipmsk, m->sipmsk, sizeof(cm.sipmsk));
 350         memcpy(cm.dipmsk, m->dipmsk, sizeof(cm.dipmsk));
 351         return copy_to_user(dst, &cm, sizeof(cm)) ? -EFAULT : 0;
 352 }
 353 #endif
 354
 355 static struct xt_match conntrack_mt_reg[] __read_mostly = {
 356         {
 357                 .name       = "conntrack",
 358                 .revision   = 0,
 359                 .family     = AF_INET,
 360                 .match      = conntrack_mt_v0,
 361                 .checkentry = conntrack_mt_check,
 362                 .destroy    = conntrack_mt_destroy,
 363                 .matchsize  = sizeof(struct xt_conntrack_info),
 364                 .me         = THIS_MODULE,
 365 #ifdef CONFIG_COMPAT
 366                 .compatsize       = sizeof(struct compat_xt_conntrack_info),
 367                 .compat_from_user = conntrack_mt_compat_from_user_v0,
 368                 .compat_to_user   = conntrack_mt_compat_to_user_v0,
 369 #endif
 370         },
 371         {
 372                 .name       = "conntrack",
 373                 .revision   = 1,
 374                 .family     = AF_INET,
 375                 .matchsize  = sizeof(struct xt_conntrack_mtinfo1),
 376                 .match      = conntrack_mt,
 377                 .checkentry = conntrack_mt_check,
 378                 .destroy    = conntrack_mt_destroy,
 379                 .me         = THIS_MODULE,
 380         },
 381         {
 382                 .name       = "conntrack",
 383                 .revision   = 1,
 384                 .family     = AF_INET6,
 385                 .matchsize  = sizeof(struct xt_conntrack_mtinfo1),
 386                 .match      = conntrack_mt,
 387                 .checkentry = conntrack_mt_check,
 388                 .destroy    = conntrack_mt_destroy,
 389                 .me         = THIS_MODULE,
 390         },
 391 };
 392
 393 static int __init conntrack_mt_init(void)
 394 {
 395         return xt_register_matches(conntrack_mt_reg,
 396                ARRAY_SIZE(conntrack_mt_reg));
 397 }
 398
 399 static void __exit conntrack_mt_exit(void)
 400 {
 401         xt_unregister_matches(conntrack_mt_reg, ARRAY_SIZE(conntrack_mt_reg));
 402 }
 403
 404 module_init(conntrack_mt_init);
 405 module_exit(conntrack_mt_exit);