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1 | /* |
2 | * iptables module for DCCP protocol header matching |
3 | * |
4 | * (C) 2005 by Harald Welte <laforge@netfilter.org> |
5 | * |
6 | * This program is free software; you can redistribute it and/or modify |
7 | * it under the terms of the GNU General Public License version 2 as |
8 | * published by the Free Software Foundation. |
9 | */ |
10 | |
11 | #include <linux/module.h> |
12 | #include <linux/skbuff.h> |
13 | #include <linux/slab.h> |
14 | #include <linux/spinlock.h> |
15 | #include <net/ip.h> |
16 | #include <linux/dccp.h> |
17 | |
18 | #include <linux/netfilter/x_tables.h> |
19 | #include <linux/netfilter/xt_dccp.h> |
20 | |
21 | #include <linux/netfilter_ipv4/ip_tables.h> |
22 | #include <linux/netfilter_ipv6/ip6_tables.h> |
23 | |
24 | MODULE_LICENSE("GPL"); |
25 | MODULE_AUTHOR("Harald Welte <laforge@netfilter.org>"); |
26 | MODULE_DESCRIPTION("Xtables: DCCP protocol packet match"); |
27 | MODULE_ALIAS("ipt_dccp"); |
28 | MODULE_ALIAS("ip6t_dccp"); |
29 | |
30 | #define DCCHECK(cond, option, flag, invflag) (!((flag) & (option)) \ |
31 | || (!!((invflag) & (option)) ^ (cond))) |
32 | |
33 | static unsigned char *dccp_optbuf; |
34 | static DEFINE_SPINLOCK(dccp_buflock); |
35 | |
36 | static inline bool |
37 | dccp_find_option(u_int8_t option, |
38 | const struct sk_buff *skb, |
39 | unsigned int protoff, |
40 | const struct dccp_hdr *dh, |
41 | bool *hotdrop) |
42 | { |
43 | /* tcp.doff is only 4 bits, ie. max 15 * 4 bytes */ |
44 | const unsigned char *op; |
45 | unsigned int optoff = __dccp_hdr_len(dh); |
46 | unsigned int optlen = dh->dccph_doff*4 - __dccp_hdr_len(dh); |
47 | unsigned int i; |
48 | |
49 | if (dh->dccph_doff * 4 < __dccp_hdr_len(dh)) |
50 | goto invalid; |
51 | |
52 | if (!optlen) |
53 | return false; |
54 | |
55 | spin_lock_bh(&dccp_buflock); |
56 | op = skb_header_pointer(skb, protoff + optoff, optlen, dccp_optbuf); |
57 | if (op == NULL) { |
58 | /* If we don't have the whole header, drop packet. */ |
59 | goto partial; |
60 | } |
61 | |
62 | for (i = 0; i < optlen; ) { |
63 | if (op[i] == option) { |
64 | spin_unlock_bh(&dccp_buflock); |
65 | return true; |
66 | } |
67 | |
68 | if (op[i] < 2) |
69 | i++; |
70 | else |
71 | i += op[i+1]?:1; |
72 | } |
73 | |
74 | spin_unlock_bh(&dccp_buflock); |
75 | return false; |
76 | |
77 | partial: |
78 | spin_unlock_bh(&dccp_buflock); |
79 | invalid: |
80 | *hotdrop = true; |
81 | return false; |
82 | } |
83 | |
84 | |
85 | static inline bool |
86 | match_types(const struct dccp_hdr *dh, u_int16_t typemask) |
87 | { |
88 | return typemask & (1 << dh->dccph_type); |
89 | } |
90 | |
91 | static inline bool |
92 | match_option(u_int8_t option, const struct sk_buff *skb, unsigned int protoff, |
93 | const struct dccp_hdr *dh, bool *hotdrop) |
94 | { |
95 | return dccp_find_option(option, skb, protoff, dh, hotdrop); |
96 | } |
97 | |
98 | static bool |
99 | dccp_mt(const struct sk_buff *skb, const struct xt_match_param *par) |
100 | { |
101 | const struct xt_dccp_info *info = par->matchinfo; |
102 | const struct dccp_hdr *dh; |
103 | struct dccp_hdr _dh; |
104 | |
105 | if (par->fragoff != 0) |
106 | return false; |
107 | |
108 | dh = skb_header_pointer(skb, par->thoff, sizeof(_dh), &_dh); |
109 | if (dh == NULL) { |
110 | *par->hotdrop = true; |
111 | return false; |
112 | } |
113 | |
114 | return DCCHECK(ntohs(dh->dccph_sport) >= info->spts[0] |
115 | && ntohs(dh->dccph_sport) <= info->spts[1], |
116 | XT_DCCP_SRC_PORTS, info->flags, info->invflags) |
117 | && DCCHECK(ntohs(dh->dccph_dport) >= info->dpts[0] |
118 | && ntohs(dh->dccph_dport) <= info->dpts[1], |
119 | XT_DCCP_DEST_PORTS, info->flags, info->invflags) |
120 | && DCCHECK(match_types(dh, info->typemask), |
121 | XT_DCCP_TYPE, info->flags, info->invflags) |
122 | && DCCHECK(match_option(info->option, skb, par->thoff, dh, |
123 | par->hotdrop), |
124 | XT_DCCP_OPTION, info->flags, info->invflags); |
125 | } |
126 | |
127 | static bool dccp_mt_check(const struct xt_mtchk_param *par) |
128 | { |
129 | const struct xt_dccp_info *info = par->matchinfo; |
130 | |
131 | return !(info->flags & ~XT_DCCP_VALID_FLAGS) |
132 | && !(info->invflags & ~XT_DCCP_VALID_FLAGS) |
133 | && !(info->invflags & ~info->flags); |
134 | } |
135 | |
136 | static struct xt_match dccp_mt_reg[] __read_mostly = { |
137 | { |
138 | .name = "dccp", |
139 | .family = NFPROTO_IPV4, |
140 | .checkentry = dccp_mt_check, |
141 | .match = dccp_mt, |
142 | .matchsize = sizeof(struct xt_dccp_info), |
143 | .proto = IPPROTO_DCCP, |
144 | .me = THIS_MODULE, |
145 | }, |
146 | { |
147 | .name = "dccp", |
148 | .family = NFPROTO_IPV6, |
149 | .checkentry = dccp_mt_check, |
150 | .match = dccp_mt, |
151 | .matchsize = sizeof(struct xt_dccp_info), |
152 | .proto = IPPROTO_DCCP, |
153 | .me = THIS_MODULE, |
154 | }, |
155 | }; |
156 | |
157 | static int __init dccp_mt_init(void) |
158 | { |
159 | int ret; |
160 | |
161 | /* doff is 8 bits, so the maximum option size is (4*256). Don't put |
162 | * this in BSS since DaveM is worried about locked TLB's for kernel |
163 | * BSS. */ |
164 | dccp_optbuf = kmalloc(256 * 4, GFP_KERNEL); |
165 | if (!dccp_optbuf) |
166 | return -ENOMEM; |
167 | ret = xt_register_matches(dccp_mt_reg, ARRAY_SIZE(dccp_mt_reg)); |
168 | if (ret) |
169 | goto out_kfree; |
170 | return ret; |
171 | |
172 | out_kfree: |
173 | kfree(dccp_optbuf); |
174 | return ret; |
175 | } |
176 | |
177 | static void __exit dccp_mt_exit(void) |
178 | { |
179 | xt_unregister_matches(dccp_mt_reg, ARRAY_SIZE(dccp_mt_reg)); |
180 | kfree(dccp_optbuf); |
181 | } |
182 | |
183 | module_init(dccp_mt_init); |
184 | module_exit(dccp_mt_exit); |
185 |
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