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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 <[email protected]>
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
21MODULE_LICENSE("GPL");
22MODULE_AUTHOR("Harald Welte <[email protected]>");
23MODULE_DESCRIPTION("Xtables: DCCP protocol packet match");
24MODULE_ALIAS("ipt_dccp");
25MODULE_ALIAS("ip6t_dccp");
26
27#define DCCHECK(cond, option, flag, invflag) (!((flag) & (option)) \
28 || (!!((invflag) & (option)) ^ (cond)))
29
30static unsigned char *dccp_optbuf;
31static DEFINE_SPINLOCK(dccp_buflock);
32
33static inline bool
34dccp_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 || i == optlen - 1)
66 i++;
67 else
68 i += op[i + 1] ? : 1;
69 }
70
71 spin_unlock_bh(&dccp_buflock);
72 return false;
73
74partial:
75 spin_unlock_bh(&dccp_buflock);
76invalid:
77 *hotdrop = true;
78 return false;
79}
80
81
82static inline bool
83match_types(const struct dccp_hdr *dh, u_int16_t typemask)
84{
85 return typemask & (1 << dh->dccph_type);
86}
87
88static inline bool
89match_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
95static bool
96dccp_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
124static 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
137static 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
158static int __init dccp_mt_init(void)
159{
160 int ret;
161
162 pr_warn_once("The DCCP match is deprecated and scheduled to be removed in 2027.\n"
163 "Please contact the netfilter-devel mailing list or update your iptables rules\n");
164
165 /* doff is 8 bits, so the maximum option size is (4*256). Don't put
166 * this in BSS since DaveM is worried about locked TLB's for kernel
167 * BSS. */
168 dccp_optbuf = kmalloc(256 * 4, GFP_KERNEL);
169 if (!dccp_optbuf)
170 return -ENOMEM;
171 ret = xt_register_matches(dccp_mt_reg, ARRAY_SIZE(dccp_mt_reg));
172 if (ret)
173 goto out_kfree;
174 return ret;
175
176out_kfree:
177 kfree(dccp_optbuf);
178 return ret;
179}
180
181static void __exit dccp_mt_exit(void)
182{
183 xt_unregister_matches(dccp_mt_reg, ARRAY_SIZE(dccp_mt_reg));
184 kfree(dccp_optbuf);
185}
186
187module_init(dccp_mt_init);
188module_exit(dccp_mt_exit);