net/ipv6/netfilter/ip6t_ah.c

   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);