1 | // SPDX-License-Identifier: GPL-2.0-or-later |
2 | /* Kernel module to match IPComp parameters for IPv4 and IPv6 |
3 | * |
4 | * Copyright (C) 2013 WindRiver |
5 | * |
6 | * Author: |
7 | * Fan Du <fan.du@windriver.com> |
8 | * |
9 | * Based on: |
10 | * net/netfilter/xt_esp.c |
11 | */ |
12 | |
13 | #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt |
14 | #include <linux/in.h> |
15 | #include <linux/module.h> |
16 | #include <linux/skbuff.h> |
17 | #include <linux/ip.h> |
18 | |
19 | #include <linux/netfilter/xt_ipcomp.h> |
20 | #include <linux/netfilter/x_tables.h> |
21 | |
22 | MODULE_LICENSE("GPL" ); |
23 | MODULE_AUTHOR("Fan Du <fan.du@windriver.com>" ); |
24 | MODULE_DESCRIPTION("Xtables: IPv4/6 IPsec-IPComp SPI match" ); |
25 | MODULE_ALIAS("ipt_ipcomp" ); |
26 | MODULE_ALIAS("ip6t_ipcomp" ); |
27 | |
28 | /* Returns 1 if the spi is matched by the range, 0 otherwise */ |
29 | static inline bool |
30 | spi_match(u_int32_t min, u_int32_t max, u_int32_t spi, bool invert) |
31 | { |
32 | bool r; |
33 | pr_debug("spi_match:%c 0x%x <= 0x%x <= 0x%x\n" , |
34 | invert ? '!' : ' ', min, spi, max); |
35 | r = (spi >= min && spi <= max) ^ invert; |
36 | pr_debug(" result %s\n" , r ? "PASS" : "FAILED" ); |
37 | return r; |
38 | } |
39 | |
40 | static bool comp_mt(const struct sk_buff *skb, struct xt_action_param *par) |
41 | { |
42 | struct ip_comp_hdr _comphdr; |
43 | const struct ip_comp_hdr *chdr; |
44 | const struct xt_ipcomp *compinfo = par->matchinfo; |
45 | |
46 | /* Must not be a fragment. */ |
47 | if (par->fragoff != 0) |
48 | return false; |
49 | |
50 | chdr = skb_header_pointer(skb, offset: par->thoff, len: sizeof(_comphdr), buffer: &_comphdr); |
51 | if (chdr == NULL) { |
52 | /* We've been asked to examine this packet, and we |
53 | * can't. Hence, no choice but to drop. |
54 | */ |
55 | pr_debug("Dropping evil IPComp tinygram.\n" ); |
56 | par->hotdrop = true; |
57 | return false; |
58 | } |
59 | |
60 | return spi_match(min: compinfo->spis[0], max: compinfo->spis[1], |
61 | ntohs(chdr->cpi), |
62 | invert: !!(compinfo->invflags & XT_IPCOMP_INV_SPI)); |
63 | } |
64 | |
65 | static int comp_mt_check(const struct xt_mtchk_param *par) |
66 | { |
67 | const struct xt_ipcomp *compinfo = par->matchinfo; |
68 | |
69 | /* Must specify no unknown invflags */ |
70 | if (compinfo->invflags & ~XT_IPCOMP_INV_MASK) { |
71 | pr_info_ratelimited("unknown flags %X\n" , compinfo->invflags); |
72 | return -EINVAL; |
73 | } |
74 | return 0; |
75 | } |
76 | |
77 | static struct xt_match comp_mt_reg[] __read_mostly = { |
78 | { |
79 | .name = "ipcomp" , |
80 | .family = NFPROTO_IPV4, |
81 | .match = comp_mt, |
82 | .matchsize = sizeof(struct xt_ipcomp), |
83 | .proto = IPPROTO_COMP, |
84 | .checkentry = comp_mt_check, |
85 | .me = THIS_MODULE, |
86 | }, |
87 | { |
88 | .name = "ipcomp" , |
89 | .family = NFPROTO_IPV6, |
90 | .match = comp_mt, |
91 | .matchsize = sizeof(struct xt_ipcomp), |
92 | .proto = IPPROTO_COMP, |
93 | .checkentry = comp_mt_check, |
94 | .me = THIS_MODULE, |
95 | }, |
96 | }; |
97 | |
98 | static int __init comp_mt_init(void) |
99 | { |
100 | return xt_register_matches(match: comp_mt_reg, ARRAY_SIZE(comp_mt_reg)); |
101 | } |
102 | |
103 | static void __exit comp_mt_exit(void) |
104 | { |
105 | xt_unregister_matches(match: comp_mt_reg, ARRAY_SIZE(comp_mt_reg)); |
106 | } |
107 | |
108 | module_init(comp_mt_init); |
109 | module_exit(comp_mt_exit); |
110 | |