1 // SPDX-License-Identifier: GPL-2.0-only 2 /* Kernel module to match AH parameters. */ 3 /* (C) 1999-2000 Yon Uriarte <yon@astaro.de> 4 */ 5 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt 6 #include <linux/in.h> 7 #include <linux/module.h> 8 #include <linux/skbuff.h> 9 #include <linux/ip.h> 10 11 #include <linux/netfilter_ipv4/ipt_ah.h> 12 #include <linux/netfilter/x_tables.h> 13 14 MODULE_LICENSE("GPL"); 15 MODULE_AUTHOR("Yon Uriarte <yon@astaro.de>"); 16 MODULE_DESCRIPTION("Xtables: IPv4 IPsec-AH SPI match"); 17 18 /* Returns 1 if the spi is matched by the range, 0 otherwise */ 19 static inline bool 20 spi_match(u_int32_t min, u_int32_t max, u_int32_t spi, bool invert) 21 { 22 bool r; 23 pr_debug("spi_match:%c 0x%x <= 0x%x <= 0x%x\n", 24 invert ? '!' : ' ', min, spi, max); 25 r = (spi >= min && spi <= max) ^ invert; 26 pr_debug(" result %s\n", r ? "PASS" : "FAILED"); 27 return r; 28 } 29 30 static bool ah_mt(const struct sk_buff *skb, struct xt_action_param *par) 31 { 32 struct ip_auth_hdr _ahdr; 33 const struct ip_auth_hdr *ah; 34 const struct ipt_ah *ahinfo = par->matchinfo; 35 36 /* Must not be a fragment. */ 37 if (par->fragoff != 0) 38 return false; 39 40 ah = skb_header_pointer(skb, par->thoff, sizeof(_ahdr), &_ahdr); 41 if (ah == NULL) { 42 /* We've been asked to examine this packet, and we 43 * can't. Hence, no choice but to drop. 44 */ 45 pr_debug("Dropping evil AH tinygram.\n"); 46 par->hotdrop = true; 47 return false; 48 } 49 50 return spi_match(ahinfo->spis[0], ahinfo->spis[1], 51 ntohl(ah->spi), 52 !!(ahinfo->invflags & IPT_AH_INV_SPI)); 53 } 54 55 static int ah_mt_check(const struct xt_mtchk_param *par) 56 { 57 const struct ipt_ah *ahinfo = par->matchinfo; 58 59 /* Must specify no unknown invflags */ 60 if (ahinfo->invflags & ~IPT_AH_INV_MASK) { 61 pr_debug("unknown flags %X\n", ahinfo->invflags); 62 return -EINVAL; 63 } 64 return 0; 65 } 66 67 static struct xt_match ah_mt_reg __read_mostly = { 68 .name = "ah", 69 .family = NFPROTO_IPV4, 70 .match = ah_mt, 71 .matchsize = sizeof(struct ipt_ah), 72 .proto = IPPROTO_AH, 73 .checkentry = ah_mt_check, 74 .me = THIS_MODULE, 75 }; 76 77 static int __init ah_mt_init(void) 78 { 79 return xt_register_match(&ah_mt_reg); 80 } 81 82 static void __exit ah_mt_exit(void) 83 { 84 xt_unregister_match(&ah_mt_reg); 85 } 86 87 module_init(ah_mt_init); 88 module_exit(ah_mt_exit); 89