1 files changed, 88 insertions, 0 deletions
diff --git a/net/ipv4/netfilter/ipt_ah.c b/net/ipv4/netfilter/ipt_ah.c
new file mode 100644
index 000000000..161ba412c
--- /dev/null
+++ b/net/ipv4/netfilter/ipt_ah.c
@@ -0,0 +1,88 @@
+// 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);