netdev - [PATCH net-next v5 22/25] ovpn: kill key and notify userspace in case of IV exhaustion

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Date: Thu, 27 Jun 2024 15:08:40 +0200
From: Antonio Quartulli <antonio@...nvpn.net>
To: netdev@...r.kernel.org
Cc: kuba@...nel.org,
	ryazanov.s.a@...il.com,
	pabeni@...hat.com,
	edumazet@...gle.com,
	andrew@...n.ch,
	sd@...asysnail.net,
	Antonio Quartulli <antonio@...nvpn.net>
Subject: [PATCH net-next v5 22/25] ovpn: kill key and notify userspace in case of IV exhaustion

IV wrap-around is cryptographically dangerous for a number of ciphers,
therefore kill the key and inform userspace (via netlink) should the
IV space go exhausted.

Signed-off-by: Antonio Quartulli <antonio@...nvpn.net>
---
 drivers/net/ovpn/netlink.c | 39 ++++++++++++++++++++++++++++++++++++++
 drivers/net/ovpn/netlink.h |  8 ++++++++
 2 files changed, 47 insertions(+)

diff --git a/drivers/net/ovpn/netlink.c b/drivers/net/ovpn/netlink.c
index 31c58cda6a3d..e43bbc9ad5d2 100644
--- a/drivers/net/ovpn/netlink.c
+++ b/drivers/net/ovpn/netlink.c
@@ -846,6 +846,45 @@ int ovpn_nl_del_key_doit(struct sk_buff *skb, struct genl_info *info)
 	return 0;
 }
 
+int ovpn_nl_notify_swap_keys(struct ovpn_peer *peer)
+{
+	struct sk_buff *msg;
+	int ret = -EMSGSIZE;
+	void *hdr;
+
+	netdev_info(peer->ovpn->dev, "peer with id %u must rekey - primary key unusable.\n",
+		    peer->id);
+
+	msg = nlmsg_new(100, GFP_ATOMIC);
+	if (!msg)
+		return -ENOMEM;
+
+	hdr = genlmsg_put(msg, 0, 0, &ovpn_nl_family, 0, OVPN_CMD_SWAP_KEYS);
+	if (!hdr) {
+		ret = -ENOBUFS;
+		goto err_free_msg;
+	}
+
+	if (nla_put_u32(msg, OVPN_A_IFINDEX, peer->ovpn->dev->ifindex))
+		goto err_cancel_msg;
+
+	if (nla_put_u32(msg, OVPN_A_PEER_ID, peer->id))
+		goto err_cancel_msg;
+
+	genlmsg_end(msg, hdr);
+
+	genlmsg_multicast_netns(&ovpn_nl_family, dev_net(peer->ovpn->dev), msg,
+				0, OVPN_NLGRP_PEERS, GFP_ATOMIC);
+
+	return 0;
+
+err_cancel_msg:
+	genlmsg_cancel(msg, hdr);
+err_free_msg:
+	nlmsg_free(msg);
+	return ret;
+}
+
 /**
  * ovpn_nl_register - perform any needed registration in the NL subsustem
  *
diff --git a/drivers/net/ovpn/netlink.h b/drivers/net/ovpn/netlink.h
index 9e87cf11d1e9..c86cd102eeef 100644
--- a/drivers/net/ovpn/netlink.h
+++ b/drivers/net/ovpn/netlink.h
@@ -12,4 +12,12 @@
 int ovpn_nl_register(void);
 void ovpn_nl_unregister(void);
 
+/**
+ * ovpn_nl_notify_swap_keys - notify userspace peer's key must be renewed
+ * @peer: the peer whose key needs to be renewed
+ *
+ * Return: 0 on success or a negative error code otherwise
+ */
+int ovpn_nl_notify_swap_keys(struct ovpn_peer *peer);
+
 #endif /* _NET_OVPN_NETLINK_H_ */
-- 
2.44.2