1 files changed, 319 insertions, 0 deletions
diff --git a/net/ipv6/seg6_hmac.c b/net/ipv6/seg6_hmac.c
new file mode 100644
index 000000000000..ee6bac0160ac
--- /dev/null
+++ b/net/ipv6/seg6_hmac.c
@@ -0,0 +1,319 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ *  SR-IPv6 implementation -- HMAC functions
+ *
+ *  Author:
+ *  David Lebrun <david.lebrun@uclouvain.be>
+ */
+
+#include <linux/errno.h>
+#include <linux/kernel.h>
+#include <linux/types.h>
+#include <linux/socket.h>
+#include <linux/sockios.h>
+#include <linux/net.h>
+#include <linux/netdevice.h>
+#include <linux/in6.h>
+#include <linux/icmpv6.h>
+#include <linux/mroute6.h>
+#include <linux/rhashtable.h>
+
+#include <linux/netfilter.h>
+#include <linux/netfilter_ipv6.h>
+
+#include <net/sock.h>
+#include <net/snmp.h>
+
+#include <net/ipv6.h>
+#include <net/protocol.h>
+#include <net/transp_v6.h>
+#include <net/rawv6.h>
+#include <net/ndisc.h>
+#include <net/ip6_route.h>
+#include <net/addrconf.h>
+#include <net/xfrm.h>
+
+#include <crypto/sha1.h>
+#include <crypto/sha2.h>
+#include <crypto/utils.h>
+#include <net/seg6.h>
+#include <net/genetlink.h>
+#include <net/seg6_hmac.h>
+#include <linux/random.h>
+
+struct hmac_storage {
+	local_lock_t bh_lock;
+	char hmac_ring[SEG6_HMAC_RING_SIZE];
+};
+
+static DEFINE_PER_CPU(struct hmac_storage, hmac_storage) = {
+	.bh_lock = INIT_LOCAL_LOCK(bh_lock),
+};
+
+static int seg6_hmac_cmpfn(struct rhashtable_compare_arg *arg, const void *obj)
+{
+	const struct seg6_hmac_info *hinfo = obj;
+
+	return (hinfo->hmackeyid != *(__u32 *)arg->key);
+}
+
+static inline void seg6_hinfo_release(struct seg6_hmac_info *hinfo)
+{
+	kfree_rcu(hinfo, rcu);
+}
+
+static void seg6_free_hi(void *ptr, void *arg)
+{
+	struct seg6_hmac_info *hinfo = (struct seg6_hmac_info *)ptr;
+
+	if (hinfo)
+		seg6_hinfo_release(hinfo);
+}
+
+static const struct rhashtable_params rht_params = {
+	.head_offset		= offsetof(struct seg6_hmac_info, node),
+	.key_offset		= offsetof(struct seg6_hmac_info, hmackeyid),
+	.key_len		= sizeof(u32),
+	.automatic_shrinking	= true,
+	.obj_cmpfn		= seg6_hmac_cmpfn,
+};
+
+static struct sr6_tlv_hmac *seg6_get_tlv_hmac(struct ipv6_sr_hdr *srh)
+{
+	struct sr6_tlv_hmac *tlv;
+
+	if (srh->hdrlen < (srh->first_segment + 1) * 2 + 5)
+		return NULL;
+
+	if (!sr_has_hmac(srh))
+		return NULL;
+
+	tlv = (struct sr6_tlv_hmac *)
+	      ((char *)srh + ((srh->hdrlen + 1) << 3) - 40);
+
+	if (tlv->tlvhdr.type != SR6_TLV_HMAC || tlv->tlvhdr.len != 38)
+		return NULL;
+
+	return tlv;
+}
+
+int seg6_hmac_compute(struct seg6_hmac_info *hinfo, struct ipv6_sr_hdr *hdr,
+		      struct in6_addr *saddr, u8 *output)
+{
+	__be32 hmackeyid = cpu_to_be32(hinfo->hmackeyid);
+	int plen, i, ret = 0;
+	char *ring, *off;
+
+	/* saddr(16) + first_seg(1) + flags(1) + keyid(4) + seglist(16n) */
+	plen = 16 + 1 + 1 + 4 + (hdr->first_segment + 1) * 16;
+
+	/* this limit allows for 14 segments */
+	if (plen >= SEG6_HMAC_RING_SIZE)
+		return -EMSGSIZE;
+
+	/* Let's build the HMAC text on the ring buffer. The text is composed
+	 * as follows, in order:
+	 *
+	 * 1. Source IPv6 address (128 bits)
+	 * 2. first_segment value (8 bits)
+	 * 3. Flags (8 bits)
+	 * 4. HMAC Key ID (32 bits)
+	 * 5. All segments in the segments list (n * 128 bits)
+	 */
+
+	local_bh_disable();
+	local_lock_nested_bh(&hmac_storage.bh_lock);
+	ring = this_cpu_ptr(hmac_storage.hmac_ring);
+	off = ring;
+
+	/* source address */
+	memcpy(off, saddr, 16);
+	off += 16;
+
+	/* first_segment value */
+	*off++ = hdr->first_segment;
+
+	/* flags */
+	*off++ = hdr->flags;
+
+	/* HMAC Key ID */
+	memcpy(off, &hmackeyid, 4);
+	off += 4;
+
+	/* all segments in the list */
+	for (i = 0; i < hdr->first_segment + 1; i++) {
+		memcpy(off, hdr->segments + i, 16);
+		off += 16;
+	}
+
+	switch (hinfo->alg_id) {
+	case SEG6_HMAC_ALGO_SHA1:
+		hmac_sha1(&hinfo->key.sha1, ring, plen, output);
+		static_assert(SEG6_HMAC_FIELD_LEN > SHA1_DIGEST_SIZE);
+		memset(&output[SHA1_DIGEST_SIZE], 0,
+		       SEG6_HMAC_FIELD_LEN - SHA1_DIGEST_SIZE);
+		break;
+	case SEG6_HMAC_ALGO_SHA256:
+		hmac_sha256(&hinfo->key.sha256, ring, plen, output);
+		static_assert(SEG6_HMAC_FIELD_LEN == SHA256_DIGEST_SIZE);
+		break;
+	default:
+		WARN_ON_ONCE(1);
+		ret = -EINVAL;
+		break;
+	}
+	local_unlock_nested_bh(&hmac_storage.bh_lock);
+	local_bh_enable();
+	return ret;
+}
+EXPORT_SYMBOL(seg6_hmac_compute);
+
+/* checks if an incoming SR-enabled packet's HMAC status matches
+ * the incoming policy.
+ *
+ * called with rcu_read_lock()
+ */
+bool seg6_hmac_validate_skb(struct sk_buff *skb)
+{
+	u8 hmac_output[SEG6_HMAC_FIELD_LEN];
+	struct net *net = dev_net(skb->dev);
+	struct seg6_hmac_info *hinfo;
+	struct sr6_tlv_hmac *tlv;
+	struct ipv6_sr_hdr *srh;
+	struct inet6_dev *idev;
+	int require_hmac;
+
+	idev = __in6_dev_get(skb->dev);
+
+	srh = (struct ipv6_sr_hdr *)skb_transport_header(skb);
+
+	tlv = seg6_get_tlv_hmac(srh);
+
+	require_hmac = READ_ONCE(idev->cnf.seg6_require_hmac);
+	/* mandatory check but no tlv */
+	if (require_hmac > 0 && !tlv)
+		return false;
+
+	/* no check */
+	if (require_hmac < 0)
+		return true;
+
+	/* check only if present */
+	if (require_hmac == 0 && !tlv)
+		return true;
+
+	/* now, seg6_require_hmac >= 0 && tlv */
+
+	hinfo = seg6_hmac_info_lookup(net, be32_to_cpu(tlv->hmackeyid));
+	if (!hinfo)
+		return false;
+
+	if (seg6_hmac_compute(hinfo, srh, &ipv6_hdr(skb)->saddr, hmac_output))
+		return false;
+
+	if (crypto_memneq(hmac_output, tlv->hmac, SEG6_HMAC_FIELD_LEN))
+		return false;
+
+	return true;
+}
+EXPORT_SYMBOL(seg6_hmac_validate_skb);
+
+/* called with rcu_read_lock() */
+struct seg6_hmac_info *seg6_hmac_info_lookup(struct net *net, u32 key)
+{
+	struct seg6_pernet_data *sdata = seg6_pernet(net);
+	struct seg6_hmac_info *hinfo;
+
+	hinfo = rhashtable_lookup_fast(&sdata->hmac_infos, &key, rht_params);
+
+	return hinfo;
+}
+EXPORT_SYMBOL(seg6_hmac_info_lookup);
+
+int seg6_hmac_info_add(struct net *net, u32 key, struct seg6_hmac_info *hinfo)
+{
+	struct seg6_pernet_data *sdata = seg6_pernet(net);
+	int err;
+
+	switch (hinfo->alg_id) {
+	case SEG6_HMAC_ALGO_SHA1:
+		hmac_sha1_preparekey(&hinfo->key.sha1,
+				     hinfo->secret, hinfo->slen);
+		break;
+	case SEG6_HMAC_ALGO_SHA256:
+		hmac_sha256_preparekey(&hinfo->key.sha256,
+				       hinfo->secret, hinfo->slen);
+		break;
+	default:
+		return -EINVAL;
+	}
+
+	err = rhashtable_lookup_insert_fast(&sdata->hmac_infos, &hinfo->node,
+					    rht_params);
+
+	return err;
+}
+EXPORT_SYMBOL(seg6_hmac_info_add);
+
+int seg6_hmac_info_del(struct net *net, u32 key)
+{
+	struct seg6_pernet_data *sdata = seg6_pernet(net);
+	struct seg6_hmac_info *hinfo;
+	int err = -ENOENT;
+
+	hinfo = rhashtable_lookup_fast(&sdata->hmac_infos, &key, rht_params);
+	if (!hinfo)
+		goto out;
+
+	err = rhashtable_remove_fast(&sdata->hmac_infos, &hinfo->node,
+				     rht_params);
+	if (err)
+		goto out;
+
+	seg6_hinfo_release(hinfo);
+
+out:
+	return err;
+}
+EXPORT_SYMBOL(seg6_hmac_info_del);
+
+int seg6_push_hmac(struct net *net, struct in6_addr *saddr,
+		   struct ipv6_sr_hdr *srh)
+{
+	struct seg6_hmac_info *hinfo;
+	struct sr6_tlv_hmac *tlv;
+	int err = -ENOENT;
+
+	tlv = seg6_get_tlv_hmac(srh);
+	if (!tlv)
+		return -EINVAL;
+
+	rcu_read_lock();
+
+	hinfo = seg6_hmac_info_lookup(net, be32_to_cpu(tlv->hmackeyid));
+	if (!hinfo)
+		goto out;
+
+	memset(tlv->hmac, 0, SEG6_HMAC_FIELD_LEN);
+	err = seg6_hmac_compute(hinfo, srh, saddr, tlv->hmac);
+
+out:
+	rcu_read_unlock();
+	return err;
+}
+EXPORT_SYMBOL(seg6_push_hmac);
+
+int __net_init seg6_hmac_net_init(struct net *net)
+{
+	struct seg6_pernet_data *sdata = seg6_pernet(net);
+
+	return rhashtable_init(&sdata->hmac_infos, &rht_params);
+}
+
+void __net_exit seg6_hmac_net_exit(struct net *net)
+{
+	struct seg6_pernet_data *sdata = seg6_pernet(net);
+
+	rhashtable_free_and_destroy(&sdata->hmac_infos, seg6_free_hi, NULL);
+}
+EXPORT_SYMBOL(seg6_hmac_net_exit);