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 30 /* Returns 1 if the spi is matched by the range, 0 otherwise */ 31 static inline bool 32 spi_match(u_int32_t min, u_int32_t max, u_int32_t spi, bool invert) 33 { 34 bool r; 35 pr_debug("spi_match:%c 0x%x <= 0x%x <= 0x%x\n", 36 invert ? '!' : ' ', min, spi, max); 37 r = (spi >= min && spi <= max) ^ invert; 38 pr_debug(" result %s\n", r ? "PASS" : "FAILED"); 39 return r; 40 } 41 42 static bool comp_mt(const struct sk_buff *skb, struct xt_action_param *par) 43 { 44 struct ip_comp_hdr _comphdr; 45 const struct ip_comp_hdr *chdr; 46 const struct xt_ipcomp *compinfo = par->matchinfo; 47 48 /* Must not be a fragment. */ 49 if (par->fragoff != 0) 50 return false; 51 52 chdr = skb_header_pointer(skb, par->thoff, sizeof(_comphdr), &_comphdr); 53 if (chdr == NULL) { 54 /* We've been asked to examine this packet, and we 55 * can't. Hence, no choice but to drop. 56 */ 57 pr_debug("Dropping evil IPComp tinygram.\n"); 58 par->hotdrop = true; 59 return 0; 60 } 61 62 return spi_match(compinfo->spis[0], compinfo->spis[1], 63 ntohs(chdr->cpi), 64 !!(compinfo->invflags & XT_IPCOMP_INV_SPI)); 65 } 66 67 static int comp_mt_check(const struct xt_mtchk_param *par) 68 { 69 const struct xt_ipcomp *compinfo = par->matchinfo; 70 71 /* Must specify no unknown invflags */ 72 if (compinfo->invflags & ~XT_IPCOMP_INV_MASK) { 73 pr_err("unknown flags %X\n", compinfo->invflags); 74 return -EINVAL; 75 } 76 return 0; 77 } 78 79 static struct xt_match comp_mt_reg[] __read_mostly = { 80 { 81 .name = "ipcomp", 82 .family = NFPROTO_IPV4, 83 .match = comp_mt, 84 .matchsize = sizeof(struct xt_ipcomp), 85 .proto = IPPROTO_COMP, 86 .checkentry = comp_mt_check, 87 .me = THIS_MODULE, 88 }, 89 { 90 .name = "ipcomp", 91 .family = NFPROTO_IPV6, 92 .match = comp_mt, 93 .matchsize = sizeof(struct xt_ipcomp), 94 .proto = IPPROTO_COMP, 95 .checkentry = comp_mt_check, 96 .me = THIS_MODULE, 97 }, 98 }; 99 100 static int __init comp_mt_init(void) 101 { 102 return xt_register_matches(comp_mt_reg, ARRAY_SIZE(comp_mt_reg)); 103 } 104 105 static void __exit comp_mt_exit(void) 106 { 107 xt_unregister_matches(comp_mt_reg, ARRAY_SIZE(comp_mt_reg)); 108 } 109 110 module_init(comp_mt_init); 111 module_exit(comp_mt_exit); 112