Internet-Draft WebSocket Extension to disable masking May 2023
Damjanovic Expires 20 November 2023 [Page]
Workgroup:
HTTP
Internet-Draft:
draft-damjanovic-websockets-nomasking-00
Published:
Intended Status:
Experimental
Expires:
Author:
D. Damjanovic
Microsoft

WebSocket Extension to disable masking

Abstract

The WebSocket protocol specifies that all frames sent from the client to the server must be masked. This was introduced as a protection against a possible attack on the infrastructure. With careful consideration, the masking could be omitted when intermediaries do not have access to the unencrypted traffic.

This specification introduces a WebSocket extension that disables the mandatory masking of frames sent from the client to the server. The extension is allowed only under special circumstances where masking is known to be unnecessary.

Status of This Memo

This Internet-Draft is submitted in full conformance with the provisions of BCP 78 and BCP 79.

Internet-Drafts are working documents of the Internet Engineering Task Force (IETF). Note that other groups may also distribute working documents as Internet-Drafts. The list of current Internet-Drafts is at https://datatracker.ietf.org/drafts/current/.

Internet-Drafts are draft documents valid for a maximum of six months and may be updated, replaced, or obsoleted by other documents at any time. It is inappropriate to use Internet-Drafts as reference material or to cite them other than as "work in progress."

This Internet-Draft will expire on 20 November 2023.

Table of Contents

1. Introduction

The WebSocket protocol specifies that all frames sent from the client to the server must be masked [RFC6455]. This was introduced as a protection against a possible attack on the infrastructure described in Section 10.3 of [RFC6455]. The attack can be performed on intermediaries, such as proxies and it could cause cache poisoning. Using end-to-end encryption, the attack can be mitigated without the use of masking. This is because every intermediary will be denied access to the unencrypted traffic, which prevents the caching attack. The masking has been made mandatory for the connection using TLS to protect the infrastructure that is behind TLS terminating proxies.

This specification introduces a WebSocket extension that disables the masking of frames sent from the client to the server. The support for the extension will be advertised by the client (see Section 9 of [RFC6455]). The server may accept the extension only after careful consideration discussed in Section Section 3.1. The extension may only be advertised if secure transport is used.

2. Conventions and Definitions

The key words "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.

3. The "no-masking" extension

The "no-masking" extension is negotiated using the WebSocket extension mechanism described in Section 9 of [RFC6455]. The client advertises support for the extension by sending "no-masking" in the list of supported extensions sent in the "Sec-WebSocket-Extensions" header field. The server accepts the extension, by sending "no-masking" in the "Sec-WebSocket-Extensions" header value.

The client MUST NOT send the extension if a non-secure connection is not used on the connection. The server MUST reject the upgrade request if the "no-masking" extension is advertised on a non-secure connection.

If the "no-masking" extension is negotiated the client and the server behavior are:

3.1. Server behavior considerations

If a WebSocket connection is end-to-end encrypted the server can accept the "no-masking" extension.

In case the connection is not end-to-end encrypted MUST NOT accept the "no-masking" extension.

Intermediaries that terminate TLS connection should remove the extension from the "Sec-WebSocket-Extensions" header field.

4. Security Considerations

TBA

5. IANA Considerations

IANA has registered the following WebSocket extension name in the "WebSocket Extension Name Registry" defined in [RFC6455].

Extension Identifier: no-masking

Extension Common Name: Disable the WebSocket client-to-server masking

Extension Definition: This document.

Known Incompatible Extensions: None

The "no-masking" extension name is used in the "Sec-WebSocket-Extensions" header in the WebSocket opening handshake to negotiate disabling of the client-to-server masking.

6. Normative References

[RFC6455]
Fette, I. and A. Melnikov, "The WebSocket Protocol", RFC 6455, DOI 10.17487/RFC6455, , <https://www.rfc-editor.org/info/rfc6455>.
[RFC2119]
Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, DOI 10.17487/RFC2119, , <https://www.rfc-editor.org/info/rfc2119>.
[RFC8174]
Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, , <https://www.rfc-editor.org/info/rfc8174>.

Acknowledgments

Author's Address

Dragana Damjanovic
Microsoft