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- // SPDX-License-Identifier: GPL-2.0-only
- /* Kernel module to match AH parameters. */
- /* (C) 1999-2000 Yon Uriarte <yon@astaro.de>
- */
- #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
- #include <linux/in.h>
- #include <linux/module.h>
- #include <linux/skbuff.h>
- #include <linux/ip.h>
- #include <linux/netfilter_ipv4/ipt_ah.h>
- #include <linux/netfilter/x_tables.h>
- MODULE_LICENSE("GPL");
- MODULE_AUTHOR("Yon Uriarte <yon@astaro.de>");
- MODULE_DESCRIPTION("Xtables: IPv4 IPsec-AH SPI match");
- /* Returns 1 if the spi is matched by the range, 0 otherwise */
- static inline bool
- spi_match(u_int32_t min, u_int32_t max, u_int32_t spi, bool invert)
- {
- bool r;
- pr_debug("spi_match:%c 0x%x <= 0x%x <= 0x%x\n",
- invert ? '!' : ' ', min, spi, max);
- r = (spi >= min && spi <= max) ^ invert;
- pr_debug(" result %s\n", r ? "PASS" : "FAILED");
- return r;
- }
- static bool ah_mt(const struct sk_buff *skb, struct xt_action_param *par)
- {
- struct ip_auth_hdr _ahdr;
- const struct ip_auth_hdr *ah;
- const struct ipt_ah *ahinfo = par->matchinfo;
- /* Must not be a fragment. */
- if (par->fragoff != 0)
- return false;
- ah = skb_header_pointer(skb, par->thoff, sizeof(_ahdr), &_ahdr);
- if (ah == NULL) {
- /* We've been asked to examine this packet, and we
- * can't. Hence, no choice but to drop.
- */
- pr_debug("Dropping evil AH tinygram.\n");
- par->hotdrop = true;
- return false;
- }
- return spi_match(ahinfo->spis[0], ahinfo->spis[1],
- ntohl(ah->spi),
- !!(ahinfo->invflags & IPT_AH_INV_SPI));
- }
- static int ah_mt_check(const struct xt_mtchk_param *par)
- {
- const struct ipt_ah *ahinfo = par->matchinfo;
- /* Must specify no unknown invflags */
- if (ahinfo->invflags & ~IPT_AH_INV_MASK) {
- pr_debug("unknown flags %X\n", ahinfo->invflags);
- return -EINVAL;
- }
- return 0;
- }
- static struct xt_match ah_mt_reg __read_mostly = {
- .name = "ah",
- .family = NFPROTO_IPV4,
- .match = ah_mt,
- .matchsize = sizeof(struct ipt_ah),
- .proto = IPPROTO_AH,
- .checkentry = ah_mt_check,
- .me = THIS_MODULE,
- };
- static int __init ah_mt_init(void)
- {
- return xt_register_match(&ah_mt_reg);
- }
- static void __exit ah_mt_exit(void)
- {
- xt_unregister_match(&ah_mt_reg);
- }
- module_init(ah_mt_init);
- module_exit(ah_mt_exit);
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