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1 | // SPDX-License-Identifier: GPL-2.0-only | |
2 | /* | |
3 | * iptables module for DCCP protocol header matching | |
4 | * | |
5 | * (C) 2005 by Harald Welte <laforge@netfilter.org> | |
6 | */ | |
7 | ||
8 | #include <linux/module.h> | |
9 | #include <linux/skbuff.h> | |
10 | #include <linux/slab.h> | |
11 | #include <linux/spinlock.h> | |
12 | #include <net/ip.h> | |
13 | #include <linux/dccp.h> | |
14 | ||
15 | #include <linux/netfilter/x_tables.h> | |
16 | #include <linux/netfilter/xt_dccp.h> | |
17 | ||
18 | #include <linux/netfilter_ipv4/ip_tables.h> | |
19 | #include <linux/netfilter_ipv6/ip6_tables.h> | |
20 | ||
21 | MODULE_LICENSE("GPL"); | |
22 | MODULE_AUTHOR("Harald Welte <laforge@netfilter.org>"); | |
23 | MODULE_DESCRIPTION("Xtables: DCCP protocol packet match"); | |
24 | MODULE_ALIAS("ipt_dccp"); | |
25 | MODULE_ALIAS("ip6t_dccp"); | |
26 | ||
27 | #define DCCHECK(cond, option, flag, invflag) (!((flag) & (option)) \ | |
28 | || (!!((invflag) & (option)) ^ (cond))) | |
29 | ||
30 | static unsigned char *dccp_optbuf; | |
31 | static DEFINE_SPINLOCK(dccp_buflock); | |
32 | ||
33 | static inline bool | |
34 | dccp_find_option(u_int8_t option, | |
35 | const struct sk_buff *skb, | |
36 | unsigned int protoff, | |
37 | const struct dccp_hdr *dh, | |
38 | bool *hotdrop) | |
39 | { | |
40 | /* tcp.doff is only 4 bits, ie. max 15 * 4 bytes */ | |
41 | const unsigned char *op; | |
42 | unsigned int optoff = __dccp_hdr_len(dh); | |
43 | unsigned int optlen = dh->dccph_doff*4 - __dccp_hdr_len(dh); | |
44 | unsigned int i; | |
45 | ||
46 | if (dh->dccph_doff * 4 < __dccp_hdr_len(dh)) | |
47 | goto invalid; | |
48 | ||
49 | if (!optlen) | |
50 | return false; | |
51 | ||
52 | spin_lock_bh(&dccp_buflock); | |
53 | op = skb_header_pointer(skb, protoff + optoff, optlen, dccp_optbuf); | |
54 | if (op == NULL) { | |
55 | /* If we don't have the whole header, drop packet. */ | |
56 | goto partial; | |
57 | } | |
58 | ||
59 | for (i = 0; i < optlen; ) { | |
60 | if (op[i] == option) { | |
61 | spin_unlock_bh(&dccp_buflock); | |
62 | return true; | |
63 | } | |
64 | ||
65 | if (op[i] < 2) | |
66 | i++; | |
67 | else | |
68 | i += op[i+1]?:1; | |
69 | } | |
70 | ||
71 | spin_unlock_bh(&dccp_buflock); | |
72 | return false; | |
73 | ||
74 | partial: | |
75 | spin_unlock_bh(&dccp_buflock); | |
76 | invalid: | |
77 | *hotdrop = true; | |
78 | return false; | |
79 | } | |
80 | ||
81 | ||
82 | static inline bool | |
83 | match_types(const struct dccp_hdr *dh, u_int16_t typemask) | |
84 | { | |
85 | return typemask & (1 << dh->dccph_type); | |
86 | } | |
87 | ||
88 | static inline bool | |
89 | match_option(u_int8_t option, const struct sk_buff *skb, unsigned int protoff, | |
90 | const struct dccp_hdr *dh, bool *hotdrop) | |
91 | { | |
92 | return dccp_find_option(option, skb, protoff, dh, hotdrop); | |
93 | } | |
94 | ||
95 | static bool | |
96 | dccp_mt(const struct sk_buff *skb, struct xt_action_param *par) | |
97 | { | |
98 | const struct xt_dccp_info *info = par->matchinfo; | |
99 | const struct dccp_hdr *dh; | |
100 | struct dccp_hdr _dh; | |
101 | ||
102 | if (par->fragoff != 0) | |
103 | return false; | |
104 | ||
105 | dh = skb_header_pointer(skb, par->thoff, sizeof(_dh), &_dh); | |
106 | if (dh == NULL) { | |
107 | par->hotdrop = true; | |
108 | return false; | |
109 | } | |
110 | ||
111 | return DCCHECK(ntohs(dh->dccph_sport) >= info->spts[0] | |
112 | && ntohs(dh->dccph_sport) <= info->spts[1], | |
113 | XT_DCCP_SRC_PORTS, info->flags, info->invflags) | |
114 | && DCCHECK(ntohs(dh->dccph_dport) >= info->dpts[0] | |
115 | && ntohs(dh->dccph_dport) <= info->dpts[1], | |
116 | XT_DCCP_DEST_PORTS, info->flags, info->invflags) | |
117 | && DCCHECK(match_types(dh, info->typemask), | |
118 | XT_DCCP_TYPE, info->flags, info->invflags) | |
119 | && DCCHECK(match_option(info->option, skb, par->thoff, dh, | |
120 | &par->hotdrop), | |
121 | XT_DCCP_OPTION, info->flags, info->invflags); | |
122 | } | |
123 | ||
124 | static int dccp_mt_check(const struct xt_mtchk_param *par) | |
125 | { | |
126 | const struct xt_dccp_info *info = par->matchinfo; | |
127 | ||
128 | if (info->flags & ~XT_DCCP_VALID_FLAGS) | |
129 | return -EINVAL; | |
130 | if (info->invflags & ~XT_DCCP_VALID_FLAGS) | |
131 | return -EINVAL; | |
132 | if (info->invflags & ~info->flags) | |
133 | return -EINVAL; | |
134 | return 0; | |
135 | } | |
136 | ||
137 | static struct xt_match dccp_mt_reg[] __read_mostly = { | |
138 | { | |
139 | .name = "dccp", | |
140 | .family = NFPROTO_IPV4, | |
141 | .checkentry = dccp_mt_check, | |
142 | .match = dccp_mt, | |
143 | .matchsize = sizeof(struct xt_dccp_info), | |
144 | .proto = IPPROTO_DCCP, | |
145 | .me = THIS_MODULE, | |
146 | }, | |
147 | { | |
148 | .name = "dccp", | |
149 | .family = NFPROTO_IPV6, | |
150 | .checkentry = dccp_mt_check, | |
151 | .match = dccp_mt, | |
152 | .matchsize = sizeof(struct xt_dccp_info), | |
153 | .proto = IPPROTO_DCCP, | |
154 | .me = THIS_MODULE, | |
155 | }, | |
156 | }; | |
157 | ||
158 | static int __init dccp_mt_init(void) | |
159 | { | |
160 | int ret; | |
161 | ||
162 | /* doff is 8 bits, so the maximum option size is (4*256). Don't put | |
163 | * this in BSS since DaveM is worried about locked TLB's for kernel | |
164 | * BSS. */ | |
165 | dccp_optbuf = kmalloc(256 * 4, GFP_KERNEL); | |
166 | if (!dccp_optbuf) | |
167 | return -ENOMEM; | |
168 | ret = xt_register_matches(dccp_mt_reg, ARRAY_SIZE(dccp_mt_reg)); | |
169 | if (ret) | |
170 | goto out_kfree; | |
171 | return ret; | |
172 | ||
173 | out_kfree: | |
174 | kfree(dccp_optbuf); | |
175 | return ret; | |
176 | } | |
177 | ||
178 | static void __exit dccp_mt_exit(void) | |
179 | { | |
180 | xt_unregister_matches(dccp_mt_reg, ARRAY_SIZE(dccp_mt_reg)); | |
181 | kfree(dccp_optbuf); | |
182 | } | |
183 | ||
184 | module_init(dccp_mt_init); | |
185 | module_exit(dccp_mt_exit); |