[wp-hackers] Allow redirects to subdomain with multisite?

[Otto]

On Thu, Aug 25, 2011 at 1:38 PM, John Reuning <john at ibiblio.org> wrote:
> I have a multisite install with a single-sign on integration that only
> works if the redirect destination from the sso server is the top-level
> url.  i.e. sending the browser to https://example.com/wp-login.php
> works but not https://site.example.com/wp-login.php.

Why exactly is this? Is it a cookie thing? Because if that's the case,
maybe just setting the COOKIE_DOMAIN would work regardless of where
the login is.

Regardless, wp_validate_redirect is a pluggable function. You don't
have to edit the core code to modify it, just define the function
elsewhere, like in a plugin, and your version will replace the one in
the core.

-Otto