| Network Working Group | N. Banks |
| Internet-Draft | Microsoft Corporation |
| Intended status: Experimental | August 11, 2020 |
| Expires: February 12, 2021 |
QUIC Disable Encryption
draft-banks-quic-disable-encryption-00
The disable_1rtt_encryption transport parameter can be used to negotiate the disablement of encryption on 1-RTT packets, allowing for reduced CPU load and improved performance. This extension is only meant to be used in environments where both endpoints completely trust the path between themselves; not, for instance, on the open internet.
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By default QUIC Transport Protocol [I-D.ietf-quic-transport] provides secured (authenticated and encrypted) connections via a TLS handshake. The handshake allows for the endpoints to be authenticated by a certificate and then securely generates shared secrets to encrypt the QUIC packet traffic. Post-handshake, this packet encryption can occupy a considerable percentage of CPU usage, depending on the scenario. Additionally, there are scenarios where the protections given by this encryption are either unnecessary or unwanted. For these scenarios, this document defines an extension to the QUIC protocol to allow for mutually participating endpoints to negotiate the disablement of encryption for the 1-RTT packets sent after the handshake.
The keywords "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in BCP 14 [RFC2119] [RFC8174] when, and only when, they appear in all capitals, as shown here.
QUIC connections are generally meant to always be encrypted, to prevent unauthenticated middleboxes from reading or modifying the QUIC packets. This is the desired behavior for most environments; especially any that go over the open internet. There are two possible scenarios where disabling packet encryption makes sense:
The disable_1rtt_encryption transport parameter used for negotiating the use of the extension is defined below.
The disable_1rtt_encryption transport parameter can be sent by both a client and server. The transport parameter is sent with an optional variable-length value by the client and an empty value by the server; a client that understands this transport parameter MUST treat the receipt of a non-empty value as a connection error of type TRANSPORT_PARAMETER_ERROR.
Advertising the disable_1rtt_encryption transport parameter indicates that the endpoint wishes to disable encryption for 1-RTT packets. Both sides must advertise support for the feature for it to be considered successfully negotiated.
If successfully negotiated, all packets that would normally be encrypted with the 1-RTT key are instead sent as cleartext; both header and packet protections are disabled.
The payload sent in the transport parameter by the client, along with any other information the server has about the client (such as IP address) may be used to negotiate the extension on the server side. The TP payload could be considered a key or identifier used by the server to verify the client should be allowed to disable encryption. These additional security measures are optional, but RECOMMENDED to ensure encryption is not accidentally enabled when it should not be.
When the extension is negotiated, all aspects of encryption on 1-RTT packets are removed:
This effectively gives the transport an additional 16 bytes per packet to be used for payload, since it is no longer including an AEAD tag.
Because the AEAD tag is removed along with the encryption, the UDP checksum must be relied upon to determine any packet corruption.
When making the trust determination about the path, each endpoints must take into account possible path changes; NAT rebinding for instance. An endpoint MUST NOT enable enable this extension if it is possible for the path to change during the connection to some untrusted state.
Additionally, a client MUST NOT try to migrate to any path that is untrusted if this extension is negotiated. If a server receives a packet for a connection with this extension negotiated on an untrusted path, it MUST silently drop the packet.
Disabling encryption for 1-RTT packets has some fairly obvious security drawbacks:
This extension is not meant to be used for any practical application protocol on the open internet. Internet facing servers MUST NOT enable this extension. Clients that do not trust their network and path to the server MUST NOT enable this extension.
This extension does not modify the packet protections used during the handshake, so the handshake can still be securely authenticated. This prevents scenarios where one endpoint might trust (or think it trusts) the path, but the other endpoint does not, and a man-in-the-middle tries to force this extension to be used.
To prevent accidental use of the feature on production systems it is RECOMMENDED for servers to have additional measures such as IP filtering or a security key.
This document registers a new value in the QUIC Transport Parameter Registry:
Value: TBD (using value 0xBAAD in early deployments)
Parameter Name: disable_1rtt_encryption
Specification: Indicates disabled 1-RTT encryption is being negotiated
| [I-D.ietf-quic-transport] | Iyengar, J. and M. Thomson, "QUIC: A UDP-Based Multiplexed and Secure Transport", Internet-Draft draft-ietf-quic-transport-29, June 2020. |
| [RFC2119] | Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, DOI 10.17487/RFC2119, March 1997. |
| [RFC8174] | Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, May 2017. |