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
dccp_find_option(u_int8_t option,const struct sk_buff * skb,unsigned int protoff,const struct dccp_hdr * dh,bool * hotdrop)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
match_types(const struct dccp_hdr * dh,u_int16_t typemask)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
match_option(u_int8_t option,const struct sk_buff * skb,unsigned int protoff,const struct dccp_hdr * dh,bool * hotdrop)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
dccp_mt(const struct sk_buff * skb,struct xt_action_param * par)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
dccp_mt_check(const struct xt_mtchk_param * par)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
dccp_mt_init(void)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
dccp_mt_exit(void)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);
186