How do I stack Plack authentication handlers?

Question

I would like to have my Plack app try several different means of authorizing the user. Specifically, check if the user is already authorized via a session cookie, then check for Digest authentication and then fall back to Basic.

I figured I could just enable a bunch of Auth handlers in the order I wanted them to be checked (Session, Digest, Basic). Unfortunately, the way that Plack::Middleware::Auth::Digest and Plack::Middleware::Auth::Basic are written they both return 401 if digest or basic auth doesn't exist, respectively.

How is this normally dealt with in Plack?

Don't have an answer for you, but isn't 404 is completely wrong for that? — ysth
@ysth Yeah, that's one of the things miyagawa suggested when I asked him. More importantly, I'm more deeply redesigning this project so it doesn't require effectively writing its own framework in raw Plack to match its historical quirks. Then I can use Catalyst or Dancer or something. — Schwern

Ashley Ashley · Accepted Answer · 2011-01-17T03:53:06

I do not have an implementation but I think I have the approach. You can do this "in-line" with Plack::Middleware::Conditional. So it would look like this but you'll have to fill in the missing conditions/tests. I didn't see an easy/obvious way but I suspect you might. Since you have the $env to pass around you should be able to set/check HTTP_/session stuff in the order you want and keep the state for the next handler to know if it should be enabled or not.

use Plack::Builder;

my $app = sub {
    [ 200,
      [ "Content-Type" => "text/plain" ],
      [ "O HAI, PLAK!" ]
    ];
};

builder {
    enable "Session::Cookie";
    enable_if { my $env = shift;
                # I don't know...
            } "Auth::Digest",
                realm => "Secured", secret => "BlahBlah",
                    authenticator => sub { $_[0] eq $_[1] };
    enable_if { my $env = shift;
                # I don't know...
            } "Auth::Basic",
                authenticator => sub { $_[0] eq $_[1] };
    $app;
};

How do I stack Plack authentication handlers?

2 Answers