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   1 /*
   2  *  ebt_among
   3  *
   4  *      Authors:
   5  *      Grzegorz Borowiak <grzes@gnu.univ.gda.pl>
   6  *
   7  *  August, 2003
   8  *
   9  */
  10
  11 #include <linux/netfilter_bridge/ebtables.h>
  12 #include <linux/netfilter_bridge/ebt_among.h>
  13 #include <linux/ip.h>
  14 #include <linux/if_arp.h>
  15 #include <linux/module.h>
  16
  17 static bool ebt_mac_wormhash_contains(const struct ebt_mac_wormhash *wh,
  18                                       const char *mac, __be32 ip)
  19 {
  20         /* You may be puzzled as to how this code works.
  21          * Some tricks were used, refer to
  22          *      include/linux/netfilter_bridge/ebt_among.h
  23          * as there you can find a solution of this mystery.
  24          */
  25         const struct ebt_mac_wormhash_tuple *p;
  26         int start, limit, i;
  27         uint32_t cmp[2] = { 0, 0 };
  28         int key = ((const unsigned char *)mac)[5];
  29
  30         memcpy(((char *) cmp) + 2, mac, 6);
  31         start = wh->table[key];
  32         limit = wh->table[key + 1];
  33         if (ip) {
  34                 for (i = start; i < limit; i++) {
  35                         p = &wh->pool[i];
  36                         if (cmp[1] == p->cmp[1] && cmp[0] == p->cmp[0])
  37                                 if (p->ip == 0 || p->ip == ip)
  38                                         return true;
  39                 }
  40         } else {
  41                 for (i = start; i < limit; i++) {
  42                         p = &wh->pool[i];
  43                         if (cmp[1] == p->cmp[1] && cmp[0] == p->cmp[0])
  44                                 if (p->ip == 0)
  45                                         return true;
  46                 }
  47         }
  48         return false;
  49 }
  50
  51 static int ebt_mac_wormhash_check_integrity(const struct ebt_mac_wormhash
  52                                             *wh)
  53 {
  54         int i;
  55
  56         for (i = 0; i < 256; i++) {
  57                 if (wh->table[i] > wh->table[i + 1])
  58                         return -0x100 - i;
  59                 if (wh->table[i] < 0)
  60                         return -0x200 - i;
  61                 if (wh->table[i] > wh->poolsize)
  62                         return -0x300 - i;
  63         }
  64         if (wh->table[256] > wh->poolsize)
  65                 return -0xc00;
  66         return 0;
  67 }
  68
  69 static int get_ip_dst(const struct sk_buff *skb, __be32 *addr)
  70 {
  71         if (eth_hdr(skb)->h_proto == htons(ETH_P_IP)) {
  72                 const struct iphdr *ih;
  73                 struct iphdr _iph;
  74
  75                 ih = skb_header_pointer(skb, 0, sizeof(_iph), &_iph);
  76                 if (ih == NULL)
  77                         return -1;
  78                 *addr = ih->daddr;
  79         } else if (eth_hdr(skb)->h_proto == htons(ETH_P_ARP)) {
  80                 const struct arphdr *ah;
  81                 struct arphdr _arph;
  82                 const __be32 *bp;
  83                 __be32 buf;
  84
  85                 ah = skb_header_pointer(skb, 0, sizeof(_arph), &_arph);
  86                 if (ah == NULL ||
  87                     ah->ar_pln != sizeof(__be32) ||
  88                     ah->ar_hln != ETH_ALEN)
  89                         return -1;
  90                 bp = skb_header_pointer(skb, sizeof(struct arphdr) +
  91                                         2 * ETH_ALEN + sizeof(__be32),
  92                                         sizeof(__be32), &buf);
  93                 if (bp == NULL)
  94                         return -1;
  95                 *addr = *bp;
  96         }
  97         return 0;
  98 }
  99
 100 static int get_ip_src(const struct sk_buff *skb, __be32 *addr)
 101 {
 102         if (eth_hdr(skb)->h_proto == htons(ETH_P_IP)) {
 103                 const struct iphdr *ih;
 104                 struct iphdr _iph;
 105
 106                 ih = skb_header_pointer(skb, 0, sizeof(_iph), &_iph);
 107                 if (ih == NULL)
 108                         return -1;
 109                 *addr = ih->saddr;
 110         } else if (eth_hdr(skb)->h_proto == htons(ETH_P_ARP)) {
 111                 const struct arphdr *ah;
 112                 struct arphdr _arph;
 113                 const __be32 *bp;
 114                 __be32 buf;
 115
 116                 ah = skb_header_pointer(skb, 0, sizeof(_arph), &_arph);
 117                 if (ah == NULL ||
 118                     ah->ar_pln != sizeof(__be32) ||
 119                     ah->ar_hln != ETH_ALEN)
 120                         return -1;
 121                 bp = skb_header_pointer(skb, sizeof(struct arphdr) +
 122                                         ETH_ALEN, sizeof(__be32), &buf);
 123                 if (bp == NULL)
 124                         return -1;
 125                 *addr = *bp;
 126         }
 127         return 0;
 128 }
 129
 130 static bool ebt_filter_among(const struct sk_buff *skb,
 131                              const struct net_device *in,
 132                              const struct net_device *out, const void *data,
 133                              unsigned int datalen)
 134 {
 135         const struct ebt_among_info *info = data;
 136         const char *dmac, *smac;
 137         const struct ebt_mac_wormhash *wh_dst, *wh_src;
 138         __be32 dip = 0, sip = 0;
 139
 140         wh_dst = ebt_among_wh_dst(info);
 141         wh_src = ebt_among_wh_src(info);
 142
 143         if (wh_src) {
 144                 smac = eth_hdr(skb)->h_source;
 145                 if (get_ip_src(skb, &sip))
 146                         return false;
 147                 if (!(info->bitmask & EBT_AMONG_SRC_NEG)) {
 148                         /* we match only if it contains */
 149                         if (!ebt_mac_wormhash_contains(wh_src, smac, sip))
 150                                 return false;
 151                 } else {
 152                         /* we match only if it DOES NOT contain */
 153                         if (ebt_mac_wormhash_contains(wh_src, smac, sip))
 154                                 return false;
 155                 }
 156         }
 157
 158         if (wh_dst) {
 159                 dmac = eth_hdr(skb)->h_dest;
 160                 if (get_ip_dst(skb, &dip))
 161                         return false;
 162                 if (!(info->bitmask & EBT_AMONG_DST_NEG)) {
 163                         /* we match only if it contains */
 164                         if (!ebt_mac_wormhash_contains(wh_dst, dmac, dip))
 165                                 return false;
 166                 } else {
 167                         /* we match only if it DOES NOT contain */
 168                         if (ebt_mac_wormhash_contains(wh_dst, dmac, dip))
 169                                 return false;
 170                 }
 171         }
 172
 173         return true;
 174 }
 175
 176 static bool
 177 ebt_among_check(const char *tablename, unsigned int hookmask,
 178                 const struct ebt_entry *e, void *data,
 179                 unsigned int datalen)
 180 {
 181         const struct ebt_among_info *info = data;
 182         int expected_length = sizeof(struct ebt_among_info);
 183         const struct ebt_mac_wormhash *wh_dst, *wh_src;
 184         int err;
 185
 186         wh_dst = ebt_among_wh_dst(info);
 187         wh_src = ebt_among_wh_src(info);
 188         expected_length += ebt_mac_wormhash_size(wh_dst);
 189         expected_length += ebt_mac_wormhash_size(wh_src);
 190
 191         if (datalen != EBT_ALIGN(expected_length)) {
 192                 printk(KERN_WARNING
 193                        "ebtables: among: wrong size: %d "
 194                        "against expected %d, rounded to %Zd\n",
 195                        datalen, expected_length,
 196                        EBT_ALIGN(expected_length));
 197                 return false;
 198         }
 199         if (wh_dst && (err = ebt_mac_wormhash_check_integrity(wh_dst))) {
 200                 printk(KERN_WARNING
 201                        "ebtables: among: dst integrity fail: %x\n", -err);
 202                 return false;
 203         }
 204         if (wh_src && (err = ebt_mac_wormhash_check_integrity(wh_src))) {
 205                 printk(KERN_WARNING
 206                        "ebtables: among: src integrity fail: %x\n", -err);
 207                 return false;
 208         }
 209         return true;
 210 }
 211
 212 static struct ebt_match filter_among __read_mostly = {
 213         .name           = EBT_AMONG_MATCH,
 214         .match          = ebt_filter_among,
 215         .check          = ebt_among_check,
 216         .matchsize      = -1, /* special case */
 217         .me             = THIS_MODULE,
 218 };
 219
 220 static int __init ebt_among_init(void)
 221 {
 222         return ebt_register_match(&filter_among);
 223 }
 224
 225 static void __exit ebt_among_fini(void)
 226 {
 227         ebt_unregister_match(&filter_among);
 228 }
 229
 230 module_init(ebt_among_init);
 231 module_exit(ebt_among_fini);
 232 MODULE_DESCRIPTION("Ebtables: Combined MAC/IP address list matching");
 233 MODULE_LICENSE("GPL");