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Fri, 06 Dec 2024 13:19:05 -0800 (PST) From: Antonio Quartulli Date: Fri, 06 Dec 2024 22:18:44 +0100 Subject: [PATCH net-next v13 19/22] ovpn: kill key and notify userspace in case of IV exhaustion Precedence: bulk X-Mailing-List: linux-kselftest@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Message-Id: <20241206-b4-ovpn-v13-19-67fb4be666e2@openvpn.net> References: <20241206-b4-ovpn-v13-0-67fb4be666e2@openvpn.net> In-Reply-To: <20241206-b4-ovpn-v13-0-67fb4be666e2@openvpn.net> To: netdev@vger.kernel.org, Eric Dumazet , Jakub Kicinski , Paolo Abeni , Donald Hunter , Antonio Quartulli , Shuah Khan , sd@queasysnail.net, ryazanov.s.a@gmail.com, Andrew Lunn Cc: Simon Horman , linux-kernel@vger.kernel.org, linux-kselftest@vger.kernel.org X-Mailer: b4 0.14.2 X-Developer-Signature: v=1; a=openpgp-sha256; l=5711; i=antonio@openvpn.net; h=from:subject:message-id; bh=BmSG4nFIoJPZgNxaXPPXP4Eer5fmr9CpUdYsd+yrONM=; b=owEBbQGS/pANAwAIAQtw5TqgONWHAcsmYgBnU2pYczM/3wcBBdc0TsbtPLXzTa7vHA0lVmOEp jmZlmuuYnCJATMEAAEIAB0WIQSZq9xs+NQS5N5fwPwLcOU6oDjVhwUCZ1NqWAAKCRALcOU6oDjV h4pWCACAo9XvxVLUXHLuPoD4P6l5dAII1FgYj2xdCSOvP3e5pswxJ3pZ/UG63eJweOhVLe6SELG xN8FzGRmpYT6pvrzb+r9ZACAVc7gw3RoQqD4Yj/cilQSZ+3UvZM6dQC1T8PmPxKk0KC7Xy4Laqt CKjOHX2/AUQDpbbaEJWP9OapSuVbF/LWXa3NYOJC2owlnKTdzJ78CiXwVn/jsGGtqBYQqHpdzmn 3/9H8Djs9lulEk0gaZ3dKxk0WUr9RhMQFryvKkPDRYIWp4obII+0QOn6tQNNRgypRT6+Q6/qC/b G7NIWfj79ufJ2zDVrr5DVaBx9jKzAbBd3bz2rvQLwBz102VO X-Developer-Key: i=antonio@openvpn.net; a=openpgp; fpr=CABDA1282017C267219885C748F0CCB68F59D14C 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 --- drivers/net/ovpn/crypto.c | 19 ++++++++++++++++ drivers/net/ovpn/crypto.h | 2 ++ drivers/net/ovpn/io.c | 13 +++++++++++ drivers/net/ovpn/netlink.c | 55 ++++++++++++++++++++++++++++++++++++++++++++++ drivers/net/ovpn/netlink.h | 2 ++ 5 files changed, 91 insertions(+) diff --git a/drivers/net/ovpn/crypto.c b/drivers/net/ovpn/crypto.c index 6fccd73c6cf7d2566d1b819cb6d5d7b2ea98e81d..47a627822e95e3a1079a710c66037ec74173e653 100644 --- a/drivers/net/ovpn/crypto.c +++ b/drivers/net/ovpn/crypto.c @@ -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. */ diff --git a/drivers/net/ovpn/crypto.h b/drivers/net/ovpn/crypto.h index 05ca312765a4551b3493dc6a27228e8ad48e99f6..2e338ea3b9542a067c1c53cb18bd12648d832cd9 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); +void 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 b1e2f976b4cfdf1a6f8a644eb5406f21830026e6..04a57685a546f0eeac4e9a68910adeff246f5284 100644 --- a/drivers/net/ovpn/io.c +++ b/drivers/net/ovpn/io.c @@ -243,6 +243,19 @@ 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; diff --git a/drivers/net/ovpn/netlink.c b/drivers/net/ovpn/netlink.c index f4dfcaafdb9501999d25464a4ec9f096a16826c2..355cd3aa4849b518bc794152e6d9d0bce7ed0f6b 100644 --- a/drivers/net/ovpn/netlink.c +++ b/drivers/net/ovpn/netlink.c @@ -1044,6 +1044,61 @@ 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 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); + + genlmsg_multicast_netns(&ovpn_nl_family, sock_net(peer->sock->sock->sk), + msg, 0, OVPN_NLGRP_PEERS, GFP_KERNEL); + + 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 9e87cf11d1e9813b7a75ddf3705ab7d5fabe899f..33390b13c8904d40b629662005a9eb92ff617c3b 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_ */