WebSockets: add opt-in delegation of encryption to TLS

noise/README.md

@@ -221,6 +221,8 @@ syntax = "proto2";
 message NoiseExtensions {
     repeated bytes webtransport_certhashes = 1;
     repeated string stream_muxers = 2;
+    optional bool handshake_only = 3;
+    optional string tls_common_name = 4;
 }
 
 message NoiseHandshakePayload {

websockets/README.md

@@ -0,0 +1,97 @@
+# libp2p WebSockets
+
+| Lifecycle Stage | Maturity                 | Status | Latest Revision |
+|-----------------|--------------------------|--------|-----------------|
+| 2A              | Candidate Recommendation | Active | r0, 2022-10-12  |
+
+Authors: [@achingbrain]
+
+Interest Group: [@MarcoPolo]
+
+[@achingbrain]: https://github.com/achingbrain
+[@MarcoPolo]: https://github.com/MarcoPolo
+
+See the [lifecycle document](../00-framework-01-spec-lifecycle.md) for context about maturity level
+and spec status.
+
+## Introduction
+
+[WebSockets](https://websockets.spec.whatwg.org/) are a way for web applications to maintain bidirectional communications with server-side processes.
+
+All major browsers have shipped WebSocket support and the implementations are both robust and well understood.
+
+A WebSocket request starts as a regular HTTP request, which is renegotiated as a WebSocket connection using the [HTTP protocol upgrade mechanism](https://developer.mozilla.org/en-US/docs/Web/HTTP/Protocol_upgrade_mechanism).
+
+## Drawbacks
+
+WebSockets suffer from [head of line blocking](https://en.wikipedia.org/wiki/Head-of-line_blocking) and provide no mechanism for stream multiplexing, encryption or authentication so additional features must be added by the developer or by libp2p.
+
+In practice they only run over TCP so are less effective with [DCuTR Holepunching](../relay/DCUtR.md).
+
+## Certificates
+
+With [some exceptions](https://developer.mozilla.org/en-US/docs/Web/Security/Secure_Contexts#when_is_a_context_considered_secure) browsers will prevent making connections to unencrypted WebSockets when the request is made from a [Secure Context](https://www.w3.org/TR/secure-contexts/).
+
+Given that libp2p makes extensive use of the [SubtleCrypto API](https://developer.mozilla.org/en-US/docs/Web/API/SubtleCrypto), and that API is only available in Secure Contexts, it's safe to assume that any incoming libp2p connections initiated over WebSockets originate from a Secure Context.
+
+Consequently server-side processes listening for incoming libp2p connections via WebSockets must use TLS certificates that can be verified by the connecting user agent.
+
+These must be obtained externally and configured in the same way as you would for an HTTP server.
+
+The only exception to this is if both server and client are operating exclusively on loopback or localhost addresses such as in a testing or offline environment. Such addresses should not be shared outside of these environments.
+
+## Stream Multiplexing
+
+WebSockets have no built in stream multiplexing. Server-side processes listening for incoming libp2p connections via WebSockets should support [multi-stream select](https://github.com/multiformats/multistream-select) and negotiate an appropriate stream multiplexer such as [yamux](../yamux/README.md).
+
+## Authentication
+
+WebSockets have no built in authentication mechanism. Server-side processes listening for incoming libp2p connections via WebSockets should support [multi-stream select](https://github.com/multiformats/multistream-select) and negotiate an appropriate authentication mechanism such as [noise](../noise/README.md).
+
+## Encryption
+
+Server-side processes listening on WebSocket addresses should use TLS certificates to secure transmitted data at the transport level.
+
+This does not provide any assurance that the remote peer possesses the private key that corresponds to their public key, so an additional handshake is necessary.
+
+During connection establishment over WebSockets, before the connection is made available to the rest of the application, if all of the following criteria are met:
+
+1. `noise` is negotiated as the connection encryption protocol
+1. An initial handshake is performed with:
+    1. the `handshake_only` boolean extension set to true
+    1. a `tls_common_name` extension value that matches the domain name being connected to
+1. The transport layer is secured by TLS
+
+Then all subsequent data is sent without encrypting it at the libp2p level, instead relying on TLS encryption at the transport layer.
+
+If any of the above is not true, all data is encrypted with the negotiated connection encryption method before sending.
+
+This prevents double-encryption but only when both ends opt-in to ensure backwards compatibility with existing deployments.
+
+Note that by opting-in to single encryption, peers are also opting-in to trusting the [CA](https://en.wikipedia.org/wiki/Certificate_authority) system.
+
+### MITM mitigation
+
+The TLS certificate used should be signed by a trusted certificate authority, the host name should correspond to the common name contained within the certificate, and the domain being connected to should match the common name sent as part of the noise handshake.
+
+This requires trusting the certificate authority to issue correct certificates, but is necessary due to limitations of certain user agents, namely web browsers which do not allow use of self-signed certificates that could be otherwise be verified via preshared certificate fingerprints.
+
+### Security Considerations
+
+Protection against man-in-the-middle (MITM) type attacks is through Web [PKI](https://en.wikipedia.org/wiki/Public_key_infrastructure). If the client is in an environment where Web PKI can not be fully trusted (e.g. an enterprise network with a custom enterprise root CA installed on the client), then this authentication scheme can not protect the client from a MITM attack.
+
+This authentication scheme is also not secure in cases where you do not own your domain name or the certificate. If someone else can get a valid certificate for your domain, you may be vulnerable to a MITM attack.
+
+## Addressing
+
+A WebSocket address contains `/ws`, `/tls/ws` or `/wss` and runs over TCP. If a TCP port is omitted, a secure WebSocket (e.g. `/tls/ws` or `/wss` is assumed to run on TCP port 443), an insecure WebSocket is assumed to run on TCP port 80 similar to HTTP addresses.
+
+Examples:
+
+* `/ip4/192.0.2.0/tcp/1234/ws` (an insecure address with a TCP port)
+* `/ip4/192.0.2.0/tcp/1234/tls/ws` (a secure address with a TCP port)
+* `/ip4/192.0.2.0/ws` (an insecure address that defaults to TCP port 80)
+* `/ip4/192.0.2.0/tls/ws` (a secure address that defaults to TCP port 443)
+* `/ip4/192.0.2.0/wss` (`/tls` may be omitted when using `/wss`)
+* `/dns/example.com/wss` (a DNS address)
+* `/dns/example.com/wss/http-path/path%2Fto%2Fendpoint` (an address with a path)