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