1 /* Kernel module to match IPComp parameters for IPv4 and IPv6 2 * 3 * Copyright (C) 2013 WindRiver 4 * 5 * Author: 6 * Fan Du <fan.du@windriver.com> 7 * 8 * Based on: 9 * net/netfilter/xt_esp.c 10 * 11 * This program is free software; you can redistribute it and/or 12 * modify it under the terms of the GNU General Public License 13 * as published by the Free Software Foundation; either version 14 * 2 of the License, or (at your option) any later version. 15 */ 16 17 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt 18 #include <linux/in.h> 19 #include <linux/module.h> 20 #include <linux/skbuff.h> 21 #include <linux/ip.h> 22 23 #include <linux/netfilter/xt_ipcomp.h> 24 #include <linux/netfilter/x_tables.h> 25 26 MODULE_LICENSE("GPL"); 27 MODULE_AUTHOR("Fan Du <fan.du@windriver.com>"); 28 MODULE_DESCRIPTION("Xtables: IPv4/6 IPsec-IPComp SPI match"); 29 MODULE_ALIAS("ipt_ipcomp"); 30 MODULE_ALIAS("ip6t_ipcomp"); 31 32 /* Returns 1 if the spi is matched by the range, 0 otherwise */ 33 static inline bool 34 spi_match(u_int32_t min, u_int32_t max, u_int32_t spi, bool invert) 35 { 36 bool r; 37 pr_debug("spi_match:%c 0x%x <= 0x%x <= 0x%x\n", 38 invert ? '!' : ' ', min, spi, max); 39 r = (spi >= min && spi <= max) ^ invert; 40 pr_debug(" result %s\n", r ? "PASS" : "FAILED"); 41 return r; 42 } 43 44 static bool comp_mt(const struct sk_buff *skb, struct xt_action_param *par) 45 { 46 struct ip_comp_hdr _comphdr; 47 const struct ip_comp_hdr *chdr; 48 const struct xt_ipcomp *compinfo = par->matchinfo; 49 50 /* Must not be a fragment. */ 51 if (par->fragoff != 0) 52 return false; 53 54 chdr = skb_header_pointer(skb, par->thoff, sizeof(_comphdr), &_comphdr); 55 if (chdr == NULL) { 56 /* We've been asked to examine this packet, and we 57 * can't. Hence, no choice but to drop. 58 */ 59 pr_debug("Dropping evil IPComp tinygram.\n"); 60 par->hotdrop = true; 61 return 0; 62 } 63 64 return spi_match(compinfo->spis[0], compinfo->spis[1], 65 ntohs(chdr->cpi), 66 !!(compinfo->invflags & XT_IPCOMP_INV_SPI)); 67 } 68 69 static int comp_mt_check(const struct xt_mtchk_param *par) 70 { 71 const struct xt_ipcomp *compinfo = par->matchinfo; 72 73 /* Must specify no unknown invflags */ 74 if (compinfo->invflags & ~XT_IPCOMP_INV_MASK) { 75 pr_err("unknown flags %X\n", compinfo->invflags); 76 return -EINVAL; 77 } 78 return 0; 79 } 80 81 static struct xt_match comp_mt_reg[] __read_mostly = { 82 { 83 .name = "ipcomp", 84 .family = NFPROTO_IPV4, 85 .match = comp_mt, 86 .matchsize = sizeof(struct xt_ipcomp), 87 .proto = IPPROTO_COMP, 88 .checkentry = comp_mt_check, 89 .me = THIS_MODULE, 90 }, 91 { 92 .name = "ipcomp", 93 .family = NFPROTO_IPV6, 94 .match = comp_mt, 95 .matchsize = sizeof(struct xt_ipcomp), 96 .proto = IPPROTO_COMP, 97 .checkentry = comp_mt_check, 98 .me = THIS_MODULE, 99 }, 100 }; 101 102 static int __init comp_mt_init(void) 103 { 104 return xt_register_matches(comp_mt_reg, ARRAY_SIZE(comp_mt_reg)); 105 } 106 107 static void __exit comp_mt_exit(void) 108 { 109 xt_unregister_matches(comp_mt_reg, ARRAY_SIZE(comp_mt_reg)); 110 } 111 112 module_init(comp_mt_init); 113 module_exit(comp_mt_exit); 114