1 // SPDX-License-Identifier: GPL-2.0-only 2 /* Kernel module to match AH parameters. */ 3 4 /* (C) 2001-2002 Andras Kis-Szabo <kisza@sch.bme.hu> 5 */ 6 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt 7 #include <linux/module.h> 8 #include <linux/skbuff.h> 9 #include <linux/ip.h> 10 #include <linux/ipv6.h> 11 #include <linux/types.h> 12 #include <net/checksum.h> 13 #include <net/ipv6.h> 14 15 #include <linux/netfilter/x_tables.h> 16 #include <linux/netfilter_ipv6/ip6_tables.h> 17 #include <linux/netfilter_ipv6/ip6t_ah.h> 18 19 MODULE_LICENSE("GPL"); 20 MODULE_DESCRIPTION("Xtables: IPv6 IPsec-AH match"); 21 MODULE_AUTHOR("Andras Kis-Szabo <kisza@sch.bme.hu>"); 22 23 /* Returns 1 if the spi is matched by the range, 0 otherwise */ 24 static inline bool 25 spi_match(u_int32_t min, u_int32_t max, u_int32_t spi, bool invert) 26 { 27 bool r; 28 29 pr_debug("spi_match:%c 0x%x <= 0x%x <= 0x%x\n", 30 invert ? '!' : ' ', min, spi, max); 31 r = (spi >= min && spi <= max) ^ invert; 32 pr_debug(" result %s\n", r ? "PASS" : "FAILED"); 33 return r; 34 } 35 36 static bool ah_mt6(const struct sk_buff *skb, struct xt_action_param *par) 37 { 38 struct ip_auth_hdr _ah; 39 const struct ip_auth_hdr *ah; 40 const struct ip6t_ah *ahinfo = par->matchinfo; 41 unsigned int ptr = 0; 42 unsigned int hdrlen = 0; 43 int err; 44 45 err = ipv6_find_hdr(skb, &ptr, NEXTHDR_AUTH, NULL, NULL); 46 if (err < 0) { 47 if (err != -ENOENT) 48 par->hotdrop = true; 49 return false; 50 } 51 52 ah = skb_header_pointer(skb, ptr, sizeof(_ah), &_ah); 53 if (ah == NULL) { 54 par->hotdrop = true; 55 return false; 56 } 57 58 hdrlen = ipv6_authlen(ah); 59 60 pr_debug("IPv6 AH LEN %u %u ", hdrlen, ah->hdrlen); 61 pr_debug("RES %04X ", ah->reserved); 62 pr_debug("SPI %u %08X\n", ntohl(ah->spi), ntohl(ah->spi)); 63 64 pr_debug("IPv6 AH spi %02X ", 65 spi_match(ahinfo->spis[0], ahinfo->spis[1], 66 ntohl(ah->spi), 67 !!(ahinfo->invflags & IP6T_AH_INV_SPI))); 68 pr_debug("len %02X %04X %02X ", 69 ahinfo->hdrlen, hdrlen, 70 (!ahinfo->hdrlen || 71 (ahinfo->hdrlen == hdrlen) ^ 72 !!(ahinfo->invflags & IP6T_AH_INV_LEN))); 73 pr_debug("res %02X %04X %02X\n", 74 ahinfo->hdrres, ah->reserved, 75 !(ahinfo->hdrres && ah->reserved)); 76 77 return spi_match(ahinfo->spis[0], ahinfo->spis[1], 78 ntohl(ah->spi), 79 !!(ahinfo->invflags & IP6T_AH_INV_SPI)) && 80 (!ahinfo->hdrlen || 81 (ahinfo->hdrlen == hdrlen) ^ 82 !!(ahinfo->invflags & IP6T_AH_INV_LEN)) && 83 !(ahinfo->hdrres && ah->reserved); 84 } 85 86 static int ah_mt6_check(const struct xt_mtchk_param *par) 87 { 88 const struct ip6t_ah *ahinfo = par->matchinfo; 89 90 if (ahinfo->invflags & ~IP6T_AH_INV_MASK) { 91 pr_debug("unknown flags %X\n", ahinfo->invflags); 92 return -EINVAL; 93 } 94 return 0; 95 } 96 97 static struct xt_match ah_mt6_reg __read_mostly = { 98 .name = "ah", 99 .family = NFPROTO_IPV6, 100 .match = ah_mt6, 101 .matchsize = sizeof(struct ip6t_ah), 102 .checkentry = ah_mt6_check, 103 .me = THIS_MODULE, 104 }; 105 106 static int __init ah_mt6_init(void) 107 { 108 return xt_register_match(&ah_mt6_reg); 109 } 110 111 static void __exit ah_mt6_exit(void) 112 { 113 xt_unregister_match(&ah_mt6_reg); 114 } 115 116 module_init(ah_mt6_init); 117 module_exit(ah_mt6_exit); 118