Annotation validation and set_by_lua_block snippet for auth-realm annotation value

[verdel]

We use the following structure in the Ingress manifests to customize the enabling/disabling of Basic authentication for different path in the requests:

- apiVersion: networking.k8s.io/v1
  kind: Ingress
  metadata:
    annotations:
      nginx.ingress.kubernetes.io/auth-realm: $basic_auth_realm
      nginx.ingress.kubernetes.io/auth-secret: basic-secret
      nginx.ingress.kubernetes.io/auth-type: basic
      nginx.ingress.kubernetes.io/configuration-snippet: |
        set_by_lua_block $basic_auth_realm {
          if ngx.var.uri == "/manifest.webmanifest" then return "off" end
          if ngx.var.uri == "/manifest.json" then return "off" end
          return "Authentication Required"
        }

After enabling the --enable-annotation-validation option for the Ingress Controller, it is not allowed to use the $ symbol in the value of the nginx.ingress.kubernetes.io/auth-realm annotation.

Here is a link to the annotation validation block.

We can use only basic chars and space.

So, we can no longer customize the use of Basic authentication due to the impossibility of using the Lua snippet name as a value for the annotation.

How risky is it in terms of validation to add the $ symbol to the allowed characters for the annotation value?

[k8s-ci-robot]

This issue is currently awaiting triage.

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[verdel]

The same validation issue exists for the annotations nginx.ingress.kubernetes.io/permanent-redirect and nginx.ingress.kubernetes.io/temporal-redirect, where we cannot use the nginx embedded variable $request_uri because of this validation functions.