Server-side request forgery in Boruta OAuth request_uri and OpenID jwks_uri fetching

Summary

Server-Side Request Forgery vulnerability in malach-it Boruta allows an unauthenticated remote attacker to cause the OAuth/OpenID authorization server to issue outbound HTTP requests to attacker-chosen URIs, including internal services and cloud metadata endpoints. Three code paths fetch remote URIs supplied by the requester without sufficient validation of the target. Boruta.Oauth.Request.Base.fetch_unsigned_request/1 in lib/boruta/oauth/request/base.ex dereferences the OAuth request_uri parameter from the authorization request via Finch.build(:get, request_uri) |> Finch.request(OpenIDHttpClient). Boruta.Openid.parse_registration_params/2 in lib/boruta/openid.ex dereferences the jwks_uri supplied in an OpenID Connect dynamic client registration request. Boruta.Ecto.Clients.refresh_jwk_from_jwks_uri/1 in lib/boruta/adapters/ecto/clients.ex later refreshes the stored jwks_uri for an existing client. In all three paths the only validation is that the URI parses with a scheme (and one of the two request_uri clauses does not even restrict the scheme to http or https). The implementations do not require HTTPS, do not enforce a host or IP allowlist, do not reject loopback, private, link-local, or other non-public ranges after DNS resolution, do not cap response size, and do not constrain redirects. An attacker can therefore steer the server's HTTP client at arbitrary network targets reachable from the Boruta host. This issue affects boruta: from 2.3.2 before 2.3.7.