Set redirect from authorization handler

[justinhelgerson]

I'm creating an AuthorizationHandler to handle authorization to one of my controllers. If the requirement isn't met, I'd like to redirect the user based on route data in the request. I can achieve this with some ugly code in the cookie OnRedirectToAccessDenied method, but I'd like to define it as part of my handler since it seems like a natural place to define this.

I tried putting something together with the code below, but no dice:

protected override async Task HandleRequirementAsync(AuthorizationHandlerContext context, siteAuthorizationRequirement requirement) {
    if (context.Resource is AuthorizationFilterContext mvcContext) {
        var actionFilterContext = (AuthorizationFilterContext)context.Resource;

        object name;
        if (actionFilterContext.RouteData.Values.TryGetValue("urlSlug", out name)) {
            // do a bunch of stuff... omitted for brevity

            if (hasAccess) {
                context.Succeed(requirement);
                return;
            } else {
                actionFilterContext.Result = new RedirectToActionResult("AccessDenied", "Foo", new { urlSlug = name });
                context.Fail();
                return;
            }
        }
    }

    return;
}

If I change the context.Fail() to Succeed, it works. However, that feels wrong so I'm wondering if I'm going about this the wrong way?

[blowdart]

Authorization policies are completely separate from UI concerns. If policy evaluation fails we flow up to the authentication handler which takes care of the response, be it a redirect (for web pages), a 401 or 403 for apis or redirects for things like ADFS/OIDC.

So this isn't the right place to do this, you'd set the forbidden action on the authN handler.

[justinhelgerson]

Thanks @blowdart. That separation makes sense.

Is the OnRedirectToAccessDenied event of the cookie authentication handler really the best spot for this then? It felt a little clunky with not having access to the IActionResult implementations.

[blowdart]

Yea, we've had that feedback, finding a better way to flow information out is on the backlog.

[blowdart]

Linking to https://github.com/aspnet/Security/issues/1359

[justinhelgerson]

Got it, thanks for the info. I'll stick with my string parsing event handler then. Hopefully this will bubble up to a release in 2019.