This is quite technical. As you can see in the provider, the method is called
sometimes when the User changes, and so the token becomes de-authenticated (e.g.
someone else changes the password between requests).
In practice, the user should be unauthenticated. Using the anonymous token did this,
but throwing an AccountStatusException seems like a better idea. It needs to be an
AccountStatusException because the ExceptionListener from the Firewall looks for exceptions
of this class and logs the user out when they are found (because this is their purpose).
This solution is a copy of what AbstractAuthenticationListener does. Scenario:
1) Login
2) Go back to the log in page
3) Put in a bad user/pass
You *should* still be logged in after a failed attempt. This commit gives that behavior.
This looks like a subjective change (one more method, but the method implementations are
simpler), but it wasn't. The problem was that the UserChecker checkPreAuth should happen
*after* we get the user, but *before* the credentials are checked, and that wasn't possible
before this change. Now it is.
Here is the flow:
A) You login using guard and are given a PostAuthGuardToken
B) Your user changes between requests - AbstractToken::setUser() and hasUserChanged() - which
results in the Token becoming "not authenticated"
C) Something calls out to the security system, which then passes the no-longer-authed
token back into the AuthenticationProviderManager
D) Because the PostauthGuardToken implements GuardTokenInterface, the provider responds
to it. But, seeing that this is a no-longer-authed PostAuthGuardToken, it returns
an AnonymousToken, which triggers logout
The reason is that the GuardAuthenticationProvider *must* respond to *all* tokens
created by the system - both "pre auth" and "post auth" tokens. The reason is that
if a "post auth" token becomes not authenticated (e.g. because the user changes between
requests), then it may be passed to the provider system. If no providers respond (which
was the case before this commit), then AuthenticationProviderManager throws an exception.
The next commit will properly handle these "post auth" + "no-longer-authenticated" tokens,
which should cause a log out.
