Support metadata input in Mathching API

[zhaohuabing]

Title: Support metadata input in Matching API

Description:
The Matching API currently doesn't support Metata Input. It would be valuable if Envoy could support it.

For instance, we prefer using Matcher over RBAC rules for authorization due to its flexibility. However, while RBAC allows specifying metadata as the principal, the matcher API currently lacks this capability, limiting use cases such as JWT claims as principals.

The supported Matching Inputs: https://www.envoyproxy.io/docs/envoy/latest/intro/arch_overview/advanced/matching/matching_api#extension-category-envoy-matching-http-input

@arkodg

[kyessenov]

Sure, this would be a great addition, and can follow similar code to filter state input.

[vikaschoudhary16]

Hey @zhaohuabing Are you working to implement it?

[zhaohuabing]

Hey @zhaohuabing Are you working to implement it?

No, feel free to go ahead if you get time.

[vikaschoudhary16]

/assign

[zetaab]

@vikaschoudhary16 when you start implementing this, my use case is that I would like to use JWT claim like "email": "foo@bar.com" for RBAC. Also I would like to use JWT []string claims. That can be like "roles": ["foo", "bar"]. If these array claims are forwarded currently to backends as headers, these will be shown in headers as base64 encoded string. It is pretty difficult to do authorization for base64 encoded string. So is there somekind of shortcut to base64 decode and check is there value in array?

[vikaschoudhary16]

@zetaab I have tested changes in the linked PR. If there is a claim like "roles": ["foo", "bar"] in the token, matcher which is added in the linked PR is able to authorize on specific claims like foo allowed and bar denied etc.

So is there somekind of shortcut to base64 decode and check is there value in array?

You can test with my PR your usecase, if you want to give it a quick try. Functionally it should be working.