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1da177e4 LT |
1 | /* Kernel module to match ESP parameters. */ |
2 | ||
3 | /* (C) 1999-2000 Yon Uriarte <yon@astaro.de> | |
4 | * | |
5 | * This program is free software; you can redistribute it and/or modify | |
6 | * it under the terms of the GNU General Public License version 2 as | |
7 | * published by the Free Software Foundation. | |
8 | */ | |
9 | ||
10 | #include <linux/module.h> | |
11 | #include <linux/skbuff.h> | |
12 | #include <linux/ip.h> | |
13 | ||
14 | #include <linux/netfilter_ipv4/ipt_esp.h> | |
15 | #include <linux/netfilter_ipv4/ip_tables.h> | |
16 | ||
17 | MODULE_LICENSE("GPL"); | |
18 | MODULE_AUTHOR("Yon Uriarte <yon@astaro.de>"); | |
19 | MODULE_DESCRIPTION("iptables ESP SPI match module"); | |
20 | ||
21 | #ifdef DEBUG_CONNTRACK | |
22 | #define duprintf(format, args...) printk(format , ## args) | |
23 | #else | |
24 | #define duprintf(format, args...) | |
25 | #endif | |
26 | ||
27 | /* Returns 1 if the spi is matched by the range, 0 otherwise */ | |
28 | static inline int | |
29 | spi_match(u_int32_t min, u_int32_t max, u_int32_t spi, int invert) | |
30 | { | |
31 | int r=0; | |
32 | duprintf("esp spi_match:%c 0x%x <= 0x%x <= 0x%x",invert? '!':' ', | |
33 | min,spi,max); | |
34 | r=(spi >= min && spi <= max) ^ invert; | |
35 | duprintf(" result %s\n",r? "PASS" : "FAILED"); | |
36 | return r; | |
37 | } | |
38 | ||
39 | static int | |
40 | match(const struct sk_buff *skb, | |
41 | const struct net_device *in, | |
42 | const struct net_device *out, | |
43 | const void *matchinfo, | |
44 | int offset, | |
45 | int *hotdrop) | |
46 | { | |
47 | struct ip_esp_hdr _esp, *eh; | |
48 | const struct ipt_esp *espinfo = matchinfo; | |
49 | ||
50 | /* Must not be a fragment. */ | |
51 | if (offset) | |
52 | return 0; | |
53 | ||
54 | eh = skb_header_pointer(skb, skb->nh.iph->ihl * 4, | |
55 | sizeof(_esp), &_esp); | |
56 | if (eh == NULL) { | |
57 | /* We've been asked to examine this packet, and we | |
58 | * can't. Hence, no choice but to drop. | |
59 | */ | |
60 | duprintf("Dropping evil ESP tinygram.\n"); | |
61 | *hotdrop = 1; | |
62 | return 0; | |
63 | } | |
64 | ||
65 | return spi_match(espinfo->spis[0], espinfo->spis[1], | |
66 | ntohl(eh->spi), | |
67 | !!(espinfo->invflags & IPT_ESP_INV_SPI)); | |
68 | } | |
69 | ||
70 | /* Called when user tries to insert an entry of this type. */ | |
71 | static int | |
72 | checkentry(const char *tablename, | |
73 | const struct ipt_ip *ip, | |
74 | void *matchinfo, | |
75 | unsigned int matchinfosize, | |
76 | unsigned int hook_mask) | |
77 | { | |
78 | const struct ipt_esp *espinfo = matchinfo; | |
79 | ||
80 | /* Must specify proto == ESP, and no unknown invflags */ | |
81 | if (ip->proto != IPPROTO_ESP || (ip->invflags & IPT_INV_PROTO)) { | |
82 | duprintf("ipt_esp: Protocol %u != %u\n", ip->proto, | |
83 | IPPROTO_ESP); | |
84 | return 0; | |
85 | } | |
86 | if (matchinfosize != IPT_ALIGN(sizeof(struct ipt_esp))) { | |
87 | duprintf("ipt_esp: matchsize %u != %u\n", | |
88 | matchinfosize, IPT_ALIGN(sizeof(struct ipt_esp))); | |
89 | return 0; | |
90 | } | |
91 | if (espinfo->invflags & ~IPT_ESP_INV_MASK) { | |
92 | duprintf("ipt_esp: unknown flags %X\n", | |
93 | espinfo->invflags); | |
94 | return 0; | |
95 | } | |
96 | ||
97 | return 1; | |
98 | } | |
99 | ||
100 | static struct ipt_match esp_match = { | |
101 | .name = "esp", | |
102 | .match = &match, | |
103 | .checkentry = &checkentry, | |
104 | .me = THIS_MODULE, | |
105 | }; | |
106 | ||
107 | static int __init init(void) | |
108 | { | |
109 | return ipt_register_match(&esp_match); | |
110 | } | |
111 | ||
112 | static void __exit cleanup(void) | |
113 | { | |
114 | ipt_unregister_match(&esp_match); | |
115 | } | |
116 | ||
117 | module_init(init); | |
118 | module_exit(cleanup); |