[PATCH net-next v7 21/25] ovpn: implement key add/del/swap via netlink

[Antonio Quartulli <antonio@openvpn.net>]

This change introduces the netlink commands needed to add, delete and
swap keys for a specific peer.

Userspace is expected to use these commands to create, destroy and
rotate session keys for a specific peer.

Signed-off-by: Antonio Quartulli <antonio@openvpn.net>
---
 drivers/net/ovpn/netlink.c | 224 ++++++++++++++++++++++++++++++++++++-
 1 file changed, 221 insertions(+), 3 deletions(-)

diff --git a/drivers/net/ovpn/netlink.c b/drivers/net/ovpn/netlink.c
index 9c9ad1e4cb9a..5d1797accb20 100644
--- a/drivers/net/ovpn/netlink.c
+++ b/drivers/net/ovpn/netlink.c
@@ -678,19 +678,237 @@ int ovpn_nl_del_peer_doit(struct sk_buff *skb, struct genl_info *info)
 	return ret;
 }
 
+static int ovpn_nl_get_key_dir(struct genl_info *info, struct nlattr *key,
+			       enum ovpn_cipher_alg cipher,
+			       struct ovpn_key_direction *dir)
+{
+	struct nlattr *attrs[OVPN_A_KEYDIR_MAX + 1];
+	int ret;
+
+	ret = nla_parse_nested(attrs, OVPN_A_KEYDIR_MAX, key,
+			       ovpn_keydir_nl_policy, info->extack);
+	if (ret)
+		return ret;
+
+	switch (cipher) {
+	case OVPN_CIPHER_ALG_AES_GCM:
+	case OVPN_CIPHER_ALG_CHACHA20_POLY1305:
+		if (NL_REQ_ATTR_CHECK(info->extack, key, attrs,
+				      OVPN_A_KEYDIR_CIPHER_KEY) ||
+		    NL_REQ_ATTR_CHECK(info->extack, key, attrs,
+				      OVPN_A_KEYDIR_NONCE_TAIL))
+			return -EINVAL;
+
+		dir->cipher_key = nla_data(attrs[OVPN_A_KEYDIR_CIPHER_KEY]);
+		dir->cipher_key_size = nla_len(attrs[OVPN_A_KEYDIR_CIPHER_KEY]);
+
+		/* These algorithms require a 96bit nonce,
+		 * Construct it by combining 4-bytes packet id and
+		 * 8-bytes nonce-tail from userspace
+		 */
+		dir->nonce_tail = nla_data(attrs[OVPN_A_KEYDIR_NONCE_TAIL]);
+		dir->nonce_tail_size = nla_len(attrs[OVPN_A_KEYDIR_NONCE_TAIL]);
+		break;
+	default:
+		NL_SET_ERR_MSG_MOD(info->extack, "unsupported cipher");
+		return -EINVAL;
+	}
+
+	return 0;
+}
+
+/**
+ * ovpn_nl_set_key_doit - configure a new key for the specified peer
+ * @skb: incoming netlink message
+ * @info: genetlink metadata
+ *
+ * This function allows the user to install a new key in the peer crypto
+ * state.
+ * Each peer has two 'slots', namely 'primary' and 'secondary', where
+ * keys can be installed. The key in the 'primary' slot is used for
+ * encryption, while both keys can be used for decryption by matching the
+ * key ID carried in the incoming packet.
+ *
+ * The user is responsible for rotating keys when necessary. The user
+ * may fetch peer traffic statistics via netlink in order to better
+ * identify the right time to rotate keys.
+ * The renegotiation follows these steps:
+ * 1. a new key is computed by the user and is installed in the 'secondary'
+ *    slot
+ * 2. at user discretion (usually after a predetermined time) 'primary' and
+ *    'secondary' contents are swapped and the new key starts being used for
+ *    encryption, while the old key is kept around for decryption of late
+ *    packets.
+ *
+ * Return: 0 on success or a negative error code otherwise.
+ */
 int ovpn_nl_set_key_doit(struct sk_buff *skb, struct genl_info *info)
 {
-	return -EOPNOTSUPP;
+	struct nlattr *p_attrs[OVPN_A_PEER_MAX + 1];
+	struct nlattr *attrs[OVPN_A_KEYCONF_MAX + 1];
+	struct ovpn_struct *ovpn = info->user_ptr[0];
+	struct ovpn_peer_key_reset pkr;
+	struct ovpn_peer *peer;
+	u32 peer_id;
+	int ret;
+
+	if (GENL_REQ_ATTR_CHECK(info, OVPN_A_PEER))
+		return -EINVAL;
+
+	ret = nla_parse_nested(p_attrs, OVPN_A_PEER_MAX,
+			       info->attrs[OVPN_A_PEER], ovpn_peer_nl_policy,
+			       info->extack);
+	if (ret)
+		return ret;
+
+	if (NL_REQ_ATTR_CHECK(info->extack, info->attrs[OVPN_A_PEER], p_attrs,
+			      OVPN_A_PEER_ID) ||
+	    NL_REQ_ATTR_CHECK(info->extack, info->attrs[OVPN_A_PEER], p_attrs,
+			      OVPN_A_PEER_KEYCONF))
+		return -EINVAL;
+
+	ret = nla_parse_nested(attrs, OVPN_A_KEYCONF_MAX,
+			       p_attrs[OVPN_A_PEER_KEYCONF],
+			       ovpn_keyconf_nl_policy, info->extack);
+	if (ret)
+		return ret;
+
+	if (NL_REQ_ATTR_CHECK(info->extack, p_attrs[OVPN_A_PEER_KEYCONF], attrs,
+			      OVPN_A_KEYCONF_SLOT) ||
+	    NL_REQ_ATTR_CHECK(info->extack, p_attrs[OVPN_A_PEER_KEYCONF], attrs,
+			      OVPN_A_KEYCONF_KEY_ID) ||
+	    NL_REQ_ATTR_CHECK(info->extack, p_attrs[OVPN_A_PEER_KEYCONF], attrs,
+			      OVPN_A_KEYCONF_CIPHER_ALG) ||
+	    NL_REQ_ATTR_CHECK(info->extack, p_attrs[OVPN_A_PEER_KEYCONF], attrs,
+			      OVPN_A_KEYCONF_ENCRYPT_DIR) ||
+	    NL_REQ_ATTR_CHECK(info->extack, p_attrs[OVPN_A_PEER_KEYCONF], attrs,
+			      OVPN_A_KEYCONF_DECRYPT_DIR))
+		return -EINVAL;
+
+	peer_id = nla_get_u32(p_attrs[OVPN_A_PEER_ID]);
+	pkr.slot = nla_get_u8(attrs[OVPN_A_KEYCONF_SLOT]);
+	pkr.key.key_id = nla_get_u16(attrs[OVPN_A_KEYCONF_KEY_ID]);
+	pkr.key.cipher_alg = nla_get_u16(attrs[OVPN_A_KEYCONF_CIPHER_ALG]);
+
+	ret = ovpn_nl_get_key_dir(info, attrs[OVPN_A_KEYCONF_ENCRYPT_DIR],
+				  pkr.key.cipher_alg, &pkr.key.encrypt);
+	if (ret < 0)
+		return ret;
+
+	ret = ovpn_nl_get_key_dir(info, attrs[OVPN_A_KEYCONF_DECRYPT_DIR],
+				  pkr.key.cipher_alg, &pkr.key.decrypt);
+	if (ret < 0)
+		return ret;
+
+	peer = ovpn_peer_get_by_id(ovpn, peer_id);
+	if (!peer) {
+		NL_SET_ERR_MSG_FMT_MOD(info->extack,
+				       "no peer with id %u to set key for",
+				       peer_id);
+		return -ENOENT;
+	}
+
+	ret = ovpn_crypto_state_reset(&peer->crypto, &pkr);
+	if (ret < 0) {
+		NL_SET_ERR_MSG_FMT_MOD(info->extack,
+				       "cannot install new key for peer %u",
+				       peer_id);
+		goto out;
+	}
+
+	netdev_dbg(ovpn->dev, "%s: new key installed (id=%u) for peer %u\n",
+		   __func__, pkr.key.key_id, peer_id);
+out:
+	ovpn_peer_put(peer);
+	return ret;
 }
 
 int ovpn_nl_swap_keys_doit(struct sk_buff *skb, struct genl_info *info)
 {
-	return -EOPNOTSUPP;
+	struct ovpn_struct *ovpn = info->user_ptr[0];
+	struct nlattr *attrs[OVPN_A_PEER_MAX + 1];
+	struct ovpn_peer *peer;
+	u32 peer_id;
+	int ret;
+
+	if (GENL_REQ_ATTR_CHECK(info, OVPN_A_PEER))
+		return -EINVAL;
+
+	ret = nla_parse_nested(attrs, OVPN_A_PEER_MAX, info->attrs[OVPN_A_PEER],
+			       ovpn_peer_nl_policy, info->extack);
+	if (ret)
+		return ret;
+
+	if (NL_REQ_ATTR_CHECK(info->extack, info->attrs[OVPN_A_PEER], attrs,
+			      OVPN_A_PEER_ID))
+		return -EINVAL;
+
+	peer_id = nla_get_u32(attrs[OVPN_A_PEER_ID]);
+
+	peer = ovpn_peer_get_by_id(ovpn, peer_id);
+	if (!peer) {
+		NL_SET_ERR_MSG_FMT_MOD(info->extack,
+				       "no peer with id %u to swap keys for",
+				       peer_id);
+		return -ENOENT;
+	}
+
+	ovpn_crypto_key_slots_swap(&peer->crypto);
+	ovpn_peer_put(peer);
+
+	return 0;
 }
 
 int ovpn_nl_del_key_doit(struct sk_buff *skb, struct genl_info *info)
 {
-	return -EOPNOTSUPP;
+	struct nlattr *p_attrs[OVPN_A_PEER_MAX + 1];
+	struct nlattr *attrs[OVPN_A_KEYCONF_MAX + 1];
+	struct ovpn_struct *ovpn = info->user_ptr[0];
+	enum ovpn_key_slot slot;
+	struct ovpn_peer *peer;
+	u32 peer_id;
+	int ret;
+
+	if (GENL_REQ_ATTR_CHECK(info, OVPN_A_PEER))
+		return -EINVAL;
+
+	ret = nla_parse_nested(p_attrs, OVPN_A_PEER_MAX,
+			       info->attrs[OVPN_A_PEER], ovpn_peer_nl_policy,
+			       info->extack);
+	if (ret)
+		return ret;
+
+	if (NL_REQ_ATTR_CHECK(info->extack, info->attrs[OVPN_A_PEER], p_attrs,
+			      OVPN_A_PEER_ID) ||
+	    NL_REQ_ATTR_CHECK(info->extack, info->attrs[OVPN_A_PEER], p_attrs,
+			      OVPN_A_PEER_KEYCONF))
+		return -EINVAL;
+
+	ret = nla_parse_nested(attrs, OVPN_A_KEYCONF_MAX,
+			       p_attrs[OVPN_A_PEER_KEYCONF],
+			       ovpn_keyconf_nl_policy, info->extack);
+	if (ret)
+		return ret;
+
+	if (NL_REQ_ATTR_CHECK(info->extack, p_attrs[OVPN_A_PEER_KEYCONF], attrs,
+			      OVPN_A_KEYCONF_SLOT))
+		return -EINVAL;
+
+	peer_id = nla_get_u32(p_attrs[OVPN_A_PEER_ID]);
+	slot = nla_get_u8(attrs[OVPN_A_KEYCONF_SLOT]);
+
+	peer = ovpn_peer_get_by_id(ovpn, peer_id);
+	if (!peer) {
+		NL_SET_ERR_MSG_FMT_MOD(info->extack,
+				       "no peer with id %u to delete key for",
+				       peer_id);
+		return -ENOENT;
+	}
+
+	ovpn_crypto_key_slot_delete(&peer->crypto, slot);
+	ovpn_peer_put(peer);
+
+	return 0;
 }
 
 /**
-- 
2.44.2