i don't know if this is going to help you but i sovled a related issue for single sign on as described below to log in to my seam application from a URL.

usage : https://host:port/appdomain/SingleSignOn.seam?login=aaa&password=bbb

for your problem, i guess a similar approach could be taken, while also consuming an extra parameter being the url parameter.

at the end of the flow you than can redirect to the original URL with

@In("#{facesContext.externalContext}")
 private ExternalContext externalContext;

and

externalContext.redirect(documentURL);

a quick and dirty approach I use:

from pages.xml

<page view-id="/singleSignOn.xhtml"
 action="#{identity.login}">
 <navigation from-action="#{identity.login}">
 <rule if="#{identity.loggedIn}">
 <redirect view-id="/home.xhtml"/>
 </rule>
 </navigation>
 </page>

with an empty singleSignOn.xhtml page

while reading two request parameters within my AuthenticationAction bean

@Stateless
@Name("authenticator")
public class AuthenticatorAction implements AuthenticatorI {

 @Logger
 Log log;

 @RequestParameter
 String login;

 @RequestParameter
 String password;

...