root/net/ipv4/netfilter/ipt_ah.c

DEFINITIONS

1. spi_match
2. ah_mt
3. ah_mt_check
4. ah_mt_init
5. ah_mt_exit

   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);