netfilter: ip6t_NPT: Ensure to check lower part of prefixes are zero
[~shefty/rdma-dev.git] / net / ipv6 / netfilter / ip6t_NPT.c
1 /*
2  * Copyright (c) 2011, 2012 Patrick McHardy <kaber@trash.net>
3  *
4  * This program is free software; you can redistribute it and/or modify
5  * it under the terms of the GNU General Public License version 2 as
6  * published by the Free Software Foundation.
7  */
8
9 #include <linux/module.h>
10 #include <linux/skbuff.h>
11 #include <linux/ipv6.h>
12 #include <net/ipv6.h>
13 #include <linux/netfilter.h>
14 #include <linux/netfilter_ipv6.h>
15 #include <linux/netfilter_ipv6/ip6t_NPT.h>
16 #include <linux/netfilter/x_tables.h>
17
18 static int ip6t_npt_checkentry(const struct xt_tgchk_param *par)
19 {
20         struct ip6t_npt_tginfo *npt = par->targinfo;
21         __wsum src_sum = 0, dst_sum = 0;
22         struct in6_addr pfx;
23         unsigned int i;
24
25         if (npt->src_pfx_len > 64 || npt->dst_pfx_len > 64)
26                 return -EINVAL;
27
28         /* Ensure that LSB of prefix is zero */
29         ipv6_addr_prefix(&pfx, &npt->src_pfx.in6, npt->src_pfx_len);
30         if (!ipv6_addr_equal(&pfx, &npt->src_pfx.in6))
31                 return -EINVAL;
32         ipv6_addr_prefix(&pfx, &npt->dst_pfx.in6, npt->dst_pfx_len);
33         if (!ipv6_addr_equal(&pfx, &npt->dst_pfx.in6))
34                 return -EINVAL;
35
36         for (i = 0; i < ARRAY_SIZE(npt->src_pfx.in6.s6_addr16); i++) {
37                 src_sum = csum_add(src_sum,
38                                 (__force __wsum)npt->src_pfx.in6.s6_addr16[i]);
39                 dst_sum = csum_add(dst_sum,
40                                 (__force __wsum)npt->dst_pfx.in6.s6_addr16[i]);
41         }
42
43         npt->adjustment = ~csum_fold(csum_sub(src_sum, dst_sum));
44         return 0;
45 }
46
47 static bool ip6t_npt_map_pfx(const struct ip6t_npt_tginfo *npt,
48                              struct in6_addr *addr)
49 {
50         unsigned int pfx_len;
51         unsigned int i, idx;
52         __be32 mask;
53         __sum16 sum;
54
55         pfx_len = max(npt->src_pfx_len, npt->dst_pfx_len);
56         for (i = 0; i < pfx_len; i += 32) {
57                 if (pfx_len - i >= 32)
58                         mask = 0;
59                 else
60                         mask = htonl(~((1 << (pfx_len - i)) - 1));
61
62                 idx = i / 32;
63                 addr->s6_addr32[idx] &= mask;
64                 addr->s6_addr32[idx] |= ~mask & npt->dst_pfx.in6.s6_addr32[idx];
65         }
66
67         if (pfx_len <= 48)
68                 idx = 3;
69         else {
70                 for (idx = 4; idx < ARRAY_SIZE(addr->s6_addr16); idx++) {
71                         if ((__force __sum16)addr->s6_addr16[idx] !=
72                             CSUM_MANGLED_0)
73                                 break;
74                 }
75                 if (idx == ARRAY_SIZE(addr->s6_addr16))
76                         return false;
77         }
78
79         sum = ~csum_fold(csum_add(csum_unfold((__force __sum16)addr->s6_addr16[idx]),
80                                   csum_unfold(npt->adjustment)));
81         if (sum == CSUM_MANGLED_0)
82                 sum = 0;
83         *(__force __sum16 *)&addr->s6_addr16[idx] = sum;
84
85         return true;
86 }
87
88 static unsigned int
89 ip6t_snpt_tg(struct sk_buff *skb, const struct xt_action_param *par)
90 {
91         const struct ip6t_npt_tginfo *npt = par->targinfo;
92
93         if (!ip6t_npt_map_pfx(npt, &ipv6_hdr(skb)->saddr)) {
94                 icmpv6_send(skb, ICMPV6_PARAMPROB, ICMPV6_HDR_FIELD,
95                             offsetof(struct ipv6hdr, saddr));
96                 return NF_DROP;
97         }
98         return XT_CONTINUE;
99 }
100
101 static unsigned int
102 ip6t_dnpt_tg(struct sk_buff *skb, const struct xt_action_param *par)
103 {
104         const struct ip6t_npt_tginfo *npt = par->targinfo;
105
106         if (!ip6t_npt_map_pfx(npt, &ipv6_hdr(skb)->daddr)) {
107                 icmpv6_send(skb, ICMPV6_PARAMPROB, ICMPV6_HDR_FIELD,
108                             offsetof(struct ipv6hdr, daddr));
109                 return NF_DROP;
110         }
111         return XT_CONTINUE;
112 }
113
114 static struct xt_target ip6t_npt_target_reg[] __read_mostly = {
115         {
116                 .name           = "SNPT",
117                 .target         = ip6t_snpt_tg,
118                 .targetsize     = sizeof(struct ip6t_npt_tginfo),
119                 .checkentry     = ip6t_npt_checkentry,
120                 .family         = NFPROTO_IPV6,
121                 .hooks          = (1 << NF_INET_LOCAL_IN) |
122                                   (1 << NF_INET_POST_ROUTING),
123                 .me             = THIS_MODULE,
124         },
125         {
126                 .name           = "DNPT",
127                 .target         = ip6t_dnpt_tg,
128                 .targetsize     = sizeof(struct ip6t_npt_tginfo),
129                 .checkentry     = ip6t_npt_checkentry,
130                 .family         = NFPROTO_IPV6,
131                 .hooks          = (1 << NF_INET_PRE_ROUTING) |
132                                   (1 << NF_INET_LOCAL_OUT),
133                 .me             = THIS_MODULE,
134         },
135 };
136
137 static int __init ip6t_npt_init(void)
138 {
139         return xt_register_targets(ip6t_npt_target_reg,
140                                    ARRAY_SIZE(ip6t_npt_target_reg));
141 }
142
143 static void __exit ip6t_npt_exit(void)
144 {
145         xt_unregister_targets(ip6t_npt_target_reg,
146                               ARRAY_SIZE(ip6t_npt_target_reg));
147 }
148
149 module_init(ip6t_npt_init);
150 module_exit(ip6t_npt_exit);
151
152 MODULE_LICENSE("GPL");
153 MODULE_DESCRIPTION("IPv6-to-IPv6 Network Prefix Translation (RFC 6296)");
154 MODULE_AUTHOR("Patrick McHardy <kaber@trash.net>");
155 MODULE_ALIAS("ip6t_SNPT");
156 MODULE_ALIAS("ip6t_DNPT");