From 89d3c0e4612afa1c6429ed68d298e35592fbe208 Mon Sep 17 00:00:00 2001 From: Antonio Quartulli Date: Tue, 15 Apr 2025 13:17:37 +0200 Subject: [PATCH] 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. Userspace has two ways of deciding when the key has to be renewed before exhausting the IV space: 1) time based approach: after X seconds/minutes userspace generates a new key and sends it to the kernel. This is based on guestimate and normally default timer value works well. 2) packet count based approach: after X packets/bytes userspace generates a new key and sends it to the kernel. Userspace keeps track of the amount of traffic by periodically polling GET_PEER and fetching the VPN/LINK stats. Signed-off-by: Antonio Quartulli Link: https://patch.msgid.link/20250415-b4-ovpn-v26-20-577f6097b964@openvpn.net Reviewed-by: Sabrina Dubroca Tested-by: Oleksandr Natalenko Signed-off-by: Paolo Abeni --- drivers/net/ovpn/crypto.c | 22 +++++++++++++ drivers/net/ovpn/crypto.h | 2 ++ drivers/net/ovpn/io.c | 14 +++++++++ drivers/net/ovpn/netlink.c | 64 ++++++++++++++++++++++++++++++++++++++ drivers/net/ovpn/netlink.h | 2 ++ 5 files changed, 104 insertions(+) diff --git a/drivers/net/ovpn/crypto.c b/drivers/net/ovpn/crypto.c index deeefffc0981..90580e32052f 100644 --- a/drivers/net/ovpn/crypto.c +++ b/drivers/net/ovpn/crypto.c @@ -54,6 +54,28 @@ void ovpn_crypto_state_release(struct ovpn_crypto_state *cs) } } +/* removes the key matching the specified id from the crypto context */ +bool 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); + + /* let the caller know if a key was actually killed */ + return ks; +} + /* Reset the ovpn_crypto_state object in a way that is atomic * to RCU readers. */ diff --git a/drivers/net/ovpn/crypto.h b/drivers/net/ovpn/crypto.h index 487d24a7d266..0e284fec3a75 100644 --- a/drivers/net/ovpn/crypto.h +++ b/drivers/net/ovpn/crypto.h @@ -140,4 +140,6 @@ int ovpn_crypto_config_get(struct ovpn_crypto_state *cs, enum ovpn_key_slot slot, struct ovpn_key_config *keyconf); +bool ovpn_crypto_kill_key(struct ovpn_crypto_state *cs, u8 key_id); + #endif /* _NET_OVPN_OVPNCRYPTO_H_ */ diff --git a/drivers/net/ovpn/io.c b/drivers/net/ovpn/io.c index fd8820c7d133..dd8a8055d967 100644 --- a/drivers/net/ovpn/io.c +++ b/drivers/net/ovpn/io.c @@ -245,6 +245,20 @@ void ovpn_encrypt_post(void *data, int ret) kfree(ovpn_skb_cb(skb)->sg); 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); + if (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; diff --git a/drivers/net/ovpn/netlink.c b/drivers/net/ovpn/netlink.c index 1f4220021df3..f0b571605936 100644 --- a/drivers/net/ovpn/netlink.c +++ b/drivers/net/ovpn/netlink.c @@ -1103,6 +1103,70 @@ 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 * diff --git a/drivers/net/ovpn/netlink.h b/drivers/net/ovpn/netlink.h index 0d6c34e17082..5dc84c8e5e80 100644 --- a/drivers/net/ovpn/netlink.h +++ b/drivers/net/ovpn/netlink.h @@ -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_ */ -- 2.50.1