httpauth/authz.go

package httpauth

import (
	"encoding/json"
	"net/http"

	"code.nochebuena.dev/go/rbac"
	"code.nochebuena.dev/go/xerrors"
)

// AuthzMiddleware reads the rbac.Identity from context (set by EnrichmentMiddleware)
// and gates the request against the required permission on resource.
// Uses rbac.PermissionProvider directly — no local redefinition of the interface.
// Returns 401 if no identity is in context.
// Returns 403 if the identity lacks the required permission or if the provider errors.
func AuthzMiddleware(provider rbac.PermissionProvider, resource string, required rbac.Permission) func(http.Handler) http.Handler {
	return func(next http.Handler) http.Handler {
		return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
			identity, ok := rbac.FromContext(r.Context())
			if !ok {
				WriteJSONError(w, http.StatusUnauthorized, string(xerrors.ErrUnauthorized), "unauthorized")
				return
			}

			mask, err := provider.ResolveMask(r.Context(), identity.UID, resource)
			if err != nil || !mask.Has(required) {
				WriteJSONError(w, http.StatusForbidden, string(xerrors.ErrPermissionDenied), "forbidden")
				return
			}

			next.ServeHTTP(w, r)
		})
	}
}

// WriteJSONError writes a structured JSON error body matching the httputil.Error format.
// Used by all httpauth-* provider packages to ensure a consistent error format across
// the full middleware stack.
func WriteJSONError(w http.ResponseWriter, status int, code, message string) {
	w.Header().Set("Content-Type", "application/json")
	w.WriteHeader(status)
	_ = json.NewEncoder(w).Encode(map[string]any{
		"code":    code,
		"message": message,
	})
}