Harden NGINX against malicious backends

Feature Overview

I would like NGINX to be secure against malicious backends.

Alternatives Considered

Leave NGINX insecure against untrusted backends, preventing the use of Nginx Gateway in multi-tenant Kubernetes clusters with untrusted workloads confined via Kata or similar.

Additional Context

I’m not sure what is required for this. The most obvious fixes needed are:

• Rejecting status codes other than 101 and 103.
• Refusing NUL bytes in HTTP status text.
• Refusing 101 responses without an Upgrade header.
• Refusing 1xx responses in FastCGI.

These are all trivial.

Adding response limits might also be needed. I don’t know which ones already exist.