1 /* Kernel module to match AH parameters. */ 2 3 /* (C) 2001-2002 Andras Kis-Szabo <kisza@sch.bme.hu> 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 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt 10 #include <linux/module.h> 11 #include <linux/skbuff.h> 12 #include <linux/ip.h> 13 #include <linux/ipv6.h> 14 #include <linux/types.h> 15 #include <net/checksum.h> 16 #include <net/ipv6.h> 17 18 #include <linux/netfilter/x_tables.h> 19 #include <linux/netfilter_ipv6/ip6_tables.h> 20 #include <linux/netfilter_ipv6/ip6t_ah.h> 21 22 MODULE_LICENSE("GPL"); 23 MODULE_DESCRIPTION("Xtables: IPv6 IPsec-AH match"); 24 MODULE_AUTHOR("Andras Kis-Szabo <kisza@sch.bme.hu>"); 25 26 /* Returns 1 if the spi is matched by the range, 0 otherwise */ 27 static inline bool 28 spi_match(u_int32_t min, u_int32_t max, u_int32_t spi, bool invert) 29 { 30 bool r; 31 32 pr_debug("spi_match:%c 0x%x <= 0x%x <= 0x%x\n", 33 invert ? '!' : ' ', min, spi, max); 34 r = (spi >= min && spi <= max) ^ invert; 35 pr_debug(" result %s\n", r ? "PASS" : "FAILED"); 36 return r; 37 } 38 39 static bool ah_mt6(const struct sk_buff *skb, struct xt_action_param *par) 40 { 41 struct ip_auth_hdr _ah; 42 const struct ip_auth_hdr *ah; 43 const struct ip6t_ah *ahinfo = par->matchinfo; 44 unsigned int ptr = 0; 45 unsigned int hdrlen = 0; 46 int err; 47 48 err = ipv6_find_hdr(skb, &ptr, NEXTHDR_AUTH, NULL, NULL); 49 if (err < 0) { 50 if (err != -ENOENT) 51 par->hotdrop = true; 52 return false; 53 } 54 55 ah = skb_header_pointer(skb, ptr, sizeof(_ah), &_ah); 56 if (ah == NULL) { 57 par->hotdrop = true; 58 return false; 59 } 60 61 hdrlen = (ah->hdrlen + 2) << 2; 62 63 pr_debug("IPv6 AH LEN %u %u ", hdrlen, ah->hdrlen); 64 pr_debug("RES %04X ", ah->reserved); 65 pr_debug("SPI %u %08X\n", ntohl(ah->spi), ntohl(ah->spi)); 66 67 pr_debug("IPv6 AH spi %02X ", 68 spi_match(ahinfo->spis[0], ahinfo->spis[1], 69 ntohl(ah->spi), 70 !!(ahinfo->invflags & IP6T_AH_INV_SPI))); 71 pr_debug("len %02X %04X %02X ", 72 ahinfo->hdrlen, hdrlen, 73 (!ahinfo->hdrlen || 74 (ahinfo->hdrlen == hdrlen) ^ 75 !!(ahinfo->invflags & IP6T_AH_INV_LEN))); 76 pr_debug("res %02X %04X %02X\n", 77 ahinfo->hdrres, ah->reserved, 78 !(ahinfo->hdrres && ah->reserved)); 79 80 return (ah != NULL) && 81 spi_match(ahinfo->spis[0], ahinfo->spis[1], 82 ntohl(ah->spi), 83 !!(ahinfo->invflags & IP6T_AH_INV_SPI)) && 84 (!ahinfo->hdrlen || 85 (ahinfo->hdrlen == hdrlen) ^ 86 !!(ahinfo->invflags & IP6T_AH_INV_LEN)) && 87 !(ahinfo->hdrres && ah->reserved); 88 } 89 90 static int ah_mt6_check(const struct xt_mtchk_param *par) 91 { 92 const struct ip6t_ah *ahinfo = par->matchinfo; 93 94 if (ahinfo->invflags & ~IP6T_AH_INV_MASK) { 95 pr_debug("unknown flags %X\n", ahinfo->invflags); 96 return -EINVAL; 97 } 98 return 0; 99 } 100 101 static struct xt_match ah_mt6_reg __read_mostly = { 102 .name = "ah", 103 .family = NFPROTO_IPV6, 104 .match = ah_mt6, 105 .matchsize = sizeof(struct ip6t_ah), 106 .checkentry = ah_mt6_check, 107 .me = THIS_MODULE, 108 }; 109 110 static int __init ah_mt6_init(void) 111 { 112 return xt_register_match(&ah_mt6_reg); 113 } 114 115 static void __exit ah_mt6_exit(void) 116 { 117 xt_unregister_match(&ah_mt6_reg); 118 } 119 120 module_init(ah_mt6_init); 121 module_exit(ah_mt6_exit); 122