[PATCH net-next v20 22/25] ovpn: kill key and notify userspace in case of IV exhaustion

@@ -54,6 +54,25 @@ void ovpn_crypto_state_release(struct ovpn_crypto_state *cs)
 	}
 }
 
+/* removes the key matching the specified id from the crypto context */
+void ovpn_crypto_kill_key(struct ovpn_crypto_state *cs, u8 key_id)
+{
+	struct ovpn_crypto_key_slot *ks = NULL;
+
+	spin_lock_bh(&cs->lock);
+	if (rcu_access_pointer(cs->slots[0])->key_id == key_id) {
+		ks = rcu_replace_pointer(cs->slots[0], NULL,
+					 lockdep_is_held(&cs->lock));
+	} else if (rcu_access_pointer(cs->slots[1])->key_id == key_id) {
+		ks = rcu_replace_pointer(cs->slots[1], NULL,
+					 lockdep_is_held(&cs->lock));
+	}
+	spin_unlock_bh(&cs->lock);
+
+	if (ks)
+		ovpn_crypto_key_slot_put(ks);
+}
+
 /* Reset the ovpn_crypto_state object in a way that is atomic
  * to RCU readers.
  */

@@ -140,4 +140,6 @@ int ovpn_crypto_config_get(struct ovpn_crypto_state *cs,
 			   enum ovpn_key_slot slot,
 			   struct ovpn_key_config *keyconf);
 
+void ovpn_crypto_kill_key(struct ovpn_crypto_state *cs, u8 key_id);
+
 #endif /* _NET_OVPN_OVPNCRYPTO_H_ */

@@ -255,6 +255,19 @@ void ovpn_encrypt_post(void *data, int ret)
 	if (likely(ovpn_skb_cb(skb)->req))
 		aead_request_free(ovpn_skb_cb(skb)->req);
 
+	if (unlikely(ret == -ERANGE)) {
+		/* we ran out of IVs and we must kill the key as it can't be
+		 * use anymore
+		 */
+		netdev_warn(peer->ovpn->dev,
+			    "killing key %u for peer %u\n", ks->key_id,
+			    peer->id);
+		ovpn_crypto_kill_key(&peer->crypto, ks->key_id);
+		/* let userspace know so that a new key must be negotiated */
+		ovpn_nl_key_swap_notify(peer, ks->key_id);
+		goto err;
+	}
+
 	if (unlikely(ret < 0))
 		goto err;
 

@@ -1094,6 +1094,70 @@ int ovpn_nl_key_del_doit(struct sk_buff *skb, struct genl_info *info)
 	return 0;
 }
 
+/**
+ * ovpn_nl_key_swap_notify - notify userspace peer's key must be renewed
+ * @peer: the peer whose key needs to be renewed
+ * @key_id: the ID of the key that needs to be renewed
+ *
+ * Return: 0 on success or a negative error code otherwise
+ */
+int ovpn_nl_key_swap_notify(struct ovpn_peer *peer, u8 key_id)
+{
+	struct ovpn_socket *sock;
+	struct nlattr *k_attr;
+	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(NLMSG_DEFAULT_SIZE, GFP_ATOMIC);
+	if (!msg)
+		return -ENOMEM;
+
+	hdr = genlmsg_put(msg, 0, 0, &ovpn_nl_family, 0, OVPN_CMD_KEY_SWAP_NTF);
+	if (!hdr) {
+		ret = -ENOBUFS;
+		goto err_free_msg;
+	}
+
+	if (nla_put_u32(msg, OVPN_A_IFINDEX, peer->ovpn->dev->ifindex))
+		goto err_cancel_msg;
+
+	k_attr = nla_nest_start(msg, OVPN_A_KEYCONF);
+	if (!k_attr)
+		goto err_cancel_msg;
+
+	if (nla_put_u32(msg, OVPN_A_KEYCONF_PEER_ID, peer->id))
+		goto err_cancel_msg;
+
+	if (nla_put_u16(msg, OVPN_A_KEYCONF_KEY_ID, key_id))
+		goto err_cancel_msg;
+
+	nla_nest_end(msg, k_attr);
+	genlmsg_end(msg, hdr);
+
+	rcu_read_lock();
+	sock = rcu_dereference(peer->sock);
+	if (!sock) {
+		ret = -EINVAL;
+		goto err_unlock;
+	}
+	genlmsg_multicast_netns(&ovpn_nl_family, sock_net(sock->sock->sk),
+				msg, 0, OVPN_NLGRP_PEERS, GFP_ATOMIC);
+	rcu_read_unlock();
+
+	return 0;
+err_unlock:
+	rcu_read_unlock();
+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
  *

@@ -12,4 +12,6 @@
 int ovpn_nl_register(void);
 void ovpn_nl_unregister(void);
 
+int ovpn_nl_key_swap_notify(struct ovpn_peer *peer, u8 key_id);
+
 #endif /* _NET_OVPN_NETLINK_H_ */