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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  *      Jan Engelhardt <jengelh@computergmbh.de>
   8  *
   9  *      This program is free software; you can redistribute it and/or modify
  10  *      it under the terms of the GNU General Public License version 2 as
  11  *      published by the Free Software Foundation.
  12  */
  13
  14 #include <linux/module.h>
  15 #include <linux/skbuff.h>
  16 #include <net/ipv6.h>
  17 #include <linux/netfilter/x_tables.h>
  18 #include <linux/netfilter/xt_conntrack.h>
  19 #include <net/netfilter/nf_conntrack.h>
  20
  21 MODULE_LICENSE("GPL");
  22 MODULE_AUTHOR("Marc Boucher <marc@mbsi.ca>");
  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(ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple.dst.protonum !=
  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 & umask->ip) == uaddr->ip;
 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 bool
 170 conntrack_mt(const struct sk_buff *skb, const struct net_device *in,
 171              const struct net_device *out, const struct xt_match *match,
 172              const void *matchinfo, int offset, unsigned int protoff,
 173              bool *hotdrop)
 174 {
 175         const struct xt_conntrack_mtinfo1 *info = matchinfo;
 176         enum ip_conntrack_info ctinfo;
 177         const struct nf_conn *ct;
 178         unsigned int statebit;
 179
 180         ct = nf_ct_get(skb, &ctinfo);
 181
 182         if (ct == &nf_conntrack_untracked)
 183                 statebit = XT_CONNTRACK_STATE_UNTRACKED;
 184         else if (ct != NULL)
 185                 statebit = XT_CONNTRACK_STATE_BIT(ctinfo);
 186         else
 187                 statebit = XT_CONNTRACK_STATE_INVALID;
 188
 189         if (info->match_flags & XT_CONNTRACK_STATE) {
 190                 if (ct != NULL) {
 191                         if (test_bit(IPS_SRC_NAT_BIT, &ct->status))
 192                                 statebit |= XT_CONNTRACK_STATE_SNAT;
 193                         if (test_bit(IPS_DST_NAT_BIT, &ct->status))
 194                                 statebit |= XT_CONNTRACK_STATE_DNAT;
 195                 }
 196                 if ((info->state_mask & statebit) ^
 197                     !(info->invert_flags & XT_CONNTRACK_STATE))
 198                         return false;
 199         }
 200
 201         if (ct == NULL)
 202                 return info->match_flags & XT_CONNTRACK_STATE;
 203
 204         if ((info->match_flags & XT_CONNTRACK_PROTO) &&
 205             ((ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple.dst.protonum ==
 206             info->l4proto) ^ !(info->invert_flags & XT_CONNTRACK_PROTO)))
 207                 return false;
 208
 209         if (info->match_flags & XT_CONNTRACK_ORIGSRC)
 210                 if (conntrack_mt_origsrc(ct, info, match->family) ^
 211                     !(info->invert_flags & XT_CONNTRACK_ORIGSRC))
 212                         return false;
 213
 214         if (info->match_flags & XT_CONNTRACK_ORIGDST)
 215                 if (conntrack_mt_origdst(ct, info, match->family) ^
 216                     !(info->invert_flags & XT_CONNTRACK_ORIGDST))
 217                         return false;
 218
 219         if (info->match_flags & XT_CONNTRACK_REPLSRC)
 220                 if (conntrack_mt_replsrc(ct, info, match->family) ^
 221                     !(info->invert_flags & XT_CONNTRACK_REPLSRC))
 222                         return false;
 223
 224         if (info->match_flags & XT_CONNTRACK_REPLDST)
 225                 if (conntrack_mt_repldst(ct, info, match->family) ^
 226                     !(info->invert_flags & XT_CONNTRACK_REPLDST))
 227                         return false;
 228
 229         if ((info->match_flags & XT_CONNTRACK_STATUS) &&
 230             (!!(info->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_check(const char *tablename, const void *ip,
 249                    const struct xt_match *match, void *matchinfo,
 250                    unsigned int hook_mask)
 251 {
 252         if (nf_ct_l3proto_try_module_get(match->family) < 0) {
 253                 printk(KERN_WARNING "can't load conntrack support for "
 254                                     "proto=%u\n", match->family);
 255                 return false;
 256         }
 257         return true;
 258 }
 259
 260 static void
 261 conntrack_mt_destroy(const struct xt_match *match, void *matchinfo)
 262 {
 263         nf_ct_l3proto_module_put(match->family);
 264 }
 265
 266 #ifdef CONFIG_COMPAT
 267 struct compat_xt_conntrack_info
 268 {
 269         compat_uint_t                   statemask;
 270         compat_uint_t                   statusmask;
 271         struct ip_conntrack_old_tuple   tuple[IP_CT_DIR_MAX];
 272         struct in_addr                  sipmsk[IP_CT_DIR_MAX];
 273         struct in_addr                  dipmsk[IP_CT_DIR_MAX];
 274         compat_ulong_t                  expires_min;
 275         compat_ulong_t                  expires_max;
 276         u_int8_t                        flags;
 277         u_int8_t                        invflags;
 278 };
 279
 280 static void conntrack_mt_compat_from_user_v0(void *dst, void *src)
 281 {
 282         const struct compat_xt_conntrack_info *cm = src;
 283         struct xt_conntrack_info m = {
 284                 .statemask      = cm->statemask,
 285                 .statusmask     = cm->statusmask,
 286                 .expires_min    = cm->expires_min,
 287                 .expires_max    = cm->expires_max,
 288                 .flags          = cm->flags,
 289                 .invflags       = cm->invflags,
 290         };
 291         memcpy(m.tuple, cm->tuple, sizeof(m.tuple));
 292         memcpy(m.sipmsk, cm->sipmsk, sizeof(m.sipmsk));
 293         memcpy(m.dipmsk, cm->dipmsk, sizeof(m.dipmsk));
 294         memcpy(dst, &m, sizeof(m));
 295 }
 296
 297 static int conntrack_mt_compat_to_user_v0(void __user *dst, void *src)
 298 {
 299         const struct xt_conntrack_info *m = src;
 300         struct compat_xt_conntrack_info cm = {
 301                 .statemask      = m->statemask,
 302                 .statusmask     = m->statusmask,
 303                 .expires_min    = m->expires_min,
 304                 .expires_max    = m->expires_max,
 305                 .flags          = m->flags,
 306                 .invflags       = m->invflags,
 307         };
 308         memcpy(cm.tuple, m->tuple, sizeof(cm.tuple));
 309         memcpy(cm.sipmsk, m->sipmsk, sizeof(cm.sipmsk));
 310         memcpy(cm.dipmsk, m->dipmsk, sizeof(cm.dipmsk));
 311         return copy_to_user(dst, &cm, sizeof(cm)) ? -EFAULT : 0;
 312 }
 313 #endif
 314
 315 static struct xt_match conntrack_mt_reg[] __read_mostly = {
 316         {
 317                 .name       = "conntrack",
 318                 .revision   = 0,
 319                 .family     = AF_INET,
 320                 .match      = conntrack_mt_v0,
 321                 .checkentry = conntrack_mt_check,
 322                 .destroy    = conntrack_mt_destroy,
 323                 .matchsize  = sizeof(struct xt_conntrack_info),
 324                 .me         = THIS_MODULE,
 325 #ifdef CONFIG_COMPAT
 326                 .compatsize       = sizeof(struct compat_xt_conntrack_info),
 327                 .compat_from_user = conntrack_mt_compat_from_user_v0,
 328                 .compat_to_user   = conntrack_mt_compat_to_user_v0,
 329 #endif
 330         },
 331         {
 332                 .name       = "conntrack",
 333                 .revision   = 1,
 334                 .family     = AF_INET,
 335                 .matchsize  = sizeof(struct xt_conntrack_mtinfo1),
 336                 .match      = conntrack_mt,
 337                 .checkentry = conntrack_mt_check,
 338                 .destroy    = conntrack_mt_destroy,
 339                 .me         = THIS_MODULE,
 340         },
 341         {
 342                 .name       = "conntrack",
 343                 .revision   = 1,
 344                 .family     = AF_INET6,
 345                 .matchsize  = sizeof(struct xt_conntrack_mtinfo1),
 346                 .match      = conntrack_mt,
 347                 .checkentry = conntrack_mt_check,
 348                 .destroy    = conntrack_mt_destroy,
 349                 .me         = THIS_MODULE,
 350         },
 351 };
 352
 353 static int __init conntrack_mt_init(void)
 354 {
 355         return xt_register_matches(conntrack_mt_reg,
 356                ARRAY_SIZE(conntrack_mt_reg));
 357 }
 358
 359 static void __exit conntrack_mt_exit(void)
 360 {
 361         xt_unregister_matches(conntrack_mt_reg, ARRAY_SIZE(conntrack_mt_reg));
 362 }
 363
 364 module_init(conntrack_mt_init);
 365 module_exit(conntrack_mt_exit);