1 /* Kernel module to match AH parameters. */ 2 /* (C) 1999-2000 Yon Uriarte <yon@astaro.de> 3 * 4 * This program is free software; you can redistribute it and/or modify 5 * it under the terms of the GNU General Public License version 2 as 6 * published by the Free Software Foundation. 7 */ 8 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt 9 #include <linux/in.h> 10 #include <linux/module.h> 11 #include <linux/skbuff.h> 12 #include <linux/ip.h> 13 14 #include <linux/netfilter_ipv4/ipt_ah.h> 15 #include <linux/netfilter/x_tables.h> 16 17 MODULE_LICENSE("GPL"); 18 MODULE_AUTHOR("Yon Uriarte <yon@astaro.de>"); 19 MODULE_DESCRIPTION("Xtables: IPv4 IPsec-AH SPI match"); 20 21 /* Returns 1 if the spi is matched by the range, 0 otherwise */ 22 static inline bool 23 spi_match(u_int32_t min, u_int32_t max, u_int32_t spi, bool invert) 24 { 25 bool r; 26 pr_debug("spi_match:%c 0x%x <= 0x%x <= 0x%x\n", 27 invert ? '!' : ' ', min, spi, max); 28 r = (spi >= min && spi <= max) ^ invert; 29 pr_debug(" result %s\n", r ? "PASS" : "FAILED"); 30 return r; 31 } 32 33 static bool ah_mt(const struct sk_buff *skb, struct xt_action_param *par) 34 { 35 struct ip_auth_hdr _ahdr; 36 const struct ip_auth_hdr *ah; 37 const struct ipt_ah *ahinfo = par->matchinfo; 38 39 /* Must not be a fragment. */ 40 if (par->fragoff != 0) 41 return false; 42 43 ah = skb_header_pointer(skb, par->thoff, sizeof(_ahdr), &_ahdr); 44 if (ah == NULL) { 45 /* We've been asked to examine this packet, and we 46 * can't. Hence, no choice but to drop. 47 */ 48 pr_debug("Dropping evil AH tinygram.\n"); 49 par->hotdrop = true; 50 return 0; 51 } 52 53 return spi_match(ahinfo->spis[0], ahinfo->spis[1], 54 ntohl(ah->spi), 55 !!(ahinfo->invflags & IPT_AH_INV_SPI)); 56 } 57 58 static int ah_mt_check(const struct xt_mtchk_param *par) 59 { 60 const struct ipt_ah *ahinfo = par->matchinfo; 61 62 /* Must specify no unknown invflags */ 63 if (ahinfo->invflags & ~IPT_AH_INV_MASK) { 64 pr_debug("unknown flags %X\n", ahinfo->invflags); 65 return -EINVAL; 66 } 67 return 0; 68 } 69 70 static struct xt_match ah_mt_reg __read_mostly = { 71 .name = "ah", 72 .family = NFPROTO_IPV4, 73 .match = ah_mt, 74 .matchsize = sizeof(struct ipt_ah), 75 .proto = IPPROTO_AH, 76 .checkentry = ah_mt_check, 77 .me = THIS_MODULE, 78 }; 79 80 static int __init ah_mt_init(void) 81 { 82 return xt_register_match(&ah_mt_reg); 83 } 84 85 static void __exit ah_mt_exit(void) 86 { 87 xt_unregister_match(&ah_mt_reg); 88 } 89 90 module_init(ah_mt_init); 91 module_exit(ah_mt_exit); 92