Support TLS Session Resumption settings

[guydc]

Description:
TLS Session in envoy can be resumed using stateful (session id) and/or stateless (session ticket) approaches.

Envoy Proxy docs on TLS mention the importance of session resumption for performance and security in front proxy scenarios:

Session resumption: Server connections support resuming previous sessions via TLS session tickets (see RFC 5077). Resumption can be performed across hot restarts and between parallel Envoy instances (typically useful in a front proxy configuration).

The default Envoy Gateway settings for session resumption are sub-optimal from a performance perspective and can have some security implications.

Since Envoy Gateway typically deploys multiple Envoy Proxy instances, in-memory session id caches and session ticket encryption keys are not synchronized. As a result, a TLS session would only be resumed if a new connection is established against the same Envoy Proxy Instance.

From a security perspective, envoy users previously requested the option to disable both stateful and stateless session resumption, due to various risks associated with resumption.

Envoy Gateway could:

• Allow users to opt-out of session resumption for security purposes
• Allow users to synchronize session ticket encryption keys across instances to improve the chance of successful resumption
• Allow users to control session ticket encryption key LCM to meet security requirements (e.g. rotation frequency).

This can be achieve by extending the TLS parameter support in Client Traffic Policy.

[optional Relevant Links:]

• https://www.envoyproxy.io/docs/envoy/latest/intro/arch_overview/security/ssl#tls
• Config to disable TLS session tickets envoy#9951
• tls: validate client cert on session resumption envoy#28758