netfilter: ebtables: do centralized size checking
[linux-2.6.git] / net / bridge / netfilter / ebt_arp.c
1 /*
2  *  ebt_arp
3  *
4  *      Authors:
5  *      Bart De Schuymer <bdschuym@pandora.be>
6  *      Tim Gardner <timg@tpi.com>
7  *
8  *  April, 2002
9  *
10  */
11 #include <linux/if_arp.h>
12 #include <linux/if_ether.h>
13 #include <linux/module.h>
14 #include <linux/netfilter/x_tables.h>
15 #include <linux/netfilter_bridge/ebtables.h>
16 #include <linux/netfilter_bridge/ebt_arp.h>
17
18 static int ebt_filter_arp(const struct sk_buff *skb, const struct net_device *in,
19    const struct net_device *out, const void *data, unsigned int datalen)
20 {
21         const struct ebt_arp_info *info = data;
22         const struct arphdr *ah;
23         struct arphdr _arph;
24
25         ah = skb_header_pointer(skb, 0, sizeof(_arph), &_arph);
26         if (ah == NULL)
27                 return EBT_NOMATCH;
28         if (info->bitmask & EBT_ARP_OPCODE && FWINV(info->opcode !=
29            ah->ar_op, EBT_ARP_OPCODE))
30                 return EBT_NOMATCH;
31         if (info->bitmask & EBT_ARP_HTYPE && FWINV(info->htype !=
32            ah->ar_hrd, EBT_ARP_HTYPE))
33                 return EBT_NOMATCH;
34         if (info->bitmask & EBT_ARP_PTYPE && FWINV(info->ptype !=
35            ah->ar_pro, EBT_ARP_PTYPE))
36                 return EBT_NOMATCH;
37
38         if (info->bitmask & (EBT_ARP_SRC_IP | EBT_ARP_DST_IP | EBT_ARP_GRAT)) {
39                 const __be32 *sap, *dap;
40                 __be32 saddr, daddr;
41
42                 if (ah->ar_pln != sizeof(__be32) || ah->ar_pro != htons(ETH_P_IP))
43                         return EBT_NOMATCH;
44                 sap = skb_header_pointer(skb, sizeof(struct arphdr) +
45                                         ah->ar_hln, sizeof(saddr),
46                                         &saddr);
47                 if (sap == NULL)
48                         return EBT_NOMATCH;
49                 dap = skb_header_pointer(skb, sizeof(struct arphdr) +
50                                         2*ah->ar_hln+sizeof(saddr),
51                                         sizeof(daddr), &daddr);
52                 if (dap == NULL)
53                         return EBT_NOMATCH;
54                 if (info->bitmask & EBT_ARP_SRC_IP &&
55                     FWINV(info->saddr != (*sap & info->smsk), EBT_ARP_SRC_IP))
56                         return EBT_NOMATCH;
57                 if (info->bitmask & EBT_ARP_DST_IP &&
58                     FWINV(info->daddr != (*dap & info->dmsk), EBT_ARP_DST_IP))
59                         return EBT_NOMATCH;
60                 if (info->bitmask & EBT_ARP_GRAT &&
61                     FWINV(*dap != *sap, EBT_ARP_GRAT))
62                         return EBT_NOMATCH;
63         }
64
65         if (info->bitmask & (EBT_ARP_SRC_MAC | EBT_ARP_DST_MAC)) {
66                 const unsigned char *mp;
67                 unsigned char _mac[ETH_ALEN];
68                 uint8_t verdict, i;
69
70                 if (ah->ar_hln != ETH_ALEN || ah->ar_hrd != htons(ARPHRD_ETHER))
71                         return EBT_NOMATCH;
72                 if (info->bitmask & EBT_ARP_SRC_MAC) {
73                         mp = skb_header_pointer(skb, sizeof(struct arphdr),
74                                                 sizeof(_mac), &_mac);
75                         if (mp == NULL)
76                                 return EBT_NOMATCH;
77                         verdict = 0;
78                         for (i = 0; i < 6; i++)
79                                 verdict |= (mp[i] ^ info->smaddr[i]) &
80                                        info->smmsk[i];
81                         if (FWINV(verdict != 0, EBT_ARP_SRC_MAC))
82                                 return EBT_NOMATCH;
83                 }
84
85                 if (info->bitmask & EBT_ARP_DST_MAC) {
86                         mp = skb_header_pointer(skb, sizeof(struct arphdr) +
87                                                 ah->ar_hln + ah->ar_pln,
88                                                 sizeof(_mac), &_mac);
89                         if (mp == NULL)
90                                 return EBT_NOMATCH;
91                         verdict = 0;
92                         for (i = 0; i < 6; i++)
93                                 verdict |= (mp[i] ^ info->dmaddr[i]) &
94                                         info->dmmsk[i];
95                         if (FWINV(verdict != 0, EBT_ARP_DST_MAC))
96                                 return EBT_NOMATCH;
97                 }
98         }
99
100         return EBT_MATCH;
101 }
102
103 static int ebt_arp_check(const char *tablename, unsigned int hookmask,
104    const struct ebt_entry *e, void *data, unsigned int datalen)
105 {
106         const struct ebt_arp_info *info = data;
107
108         if ((e->ethproto != htons(ETH_P_ARP) &&
109            e->ethproto != htons(ETH_P_RARP)) ||
110            e->invflags & EBT_IPROTO)
111                 return -EINVAL;
112         if (info->bitmask & ~EBT_ARP_MASK || info->invflags & ~EBT_ARP_MASK)
113                 return -EINVAL;
114         return 0;
115 }
116
117 static struct ebt_match filter_arp __read_mostly = {
118         .name           = EBT_ARP_MATCH,
119         .match          = ebt_filter_arp,
120         .check          = ebt_arp_check,
121         .matchsize      = XT_ALIGN(sizeof(struct ebt_arp_info)),
122         .me             = THIS_MODULE,
123 };
124
125 static int __init ebt_arp_init(void)
126 {
127         return ebt_register_match(&filter_arp);
128 }
129
130 static void __exit ebt_arp_fini(void)
131 {
132         ebt_unregister_match(&filter_arp);
133 }
134
135 module_init(ebt_arp_init);
136 module_exit(ebt_arp_fini);
137 MODULE_DESCRIPTION("Ebtables: ARP protocol packet match");
138 MODULE_LICENSE("GPL");