Provide alternative for (and deprecate) twistd ftp --userAnonymous

	@cyli reported
Trac ID	trac#5313
Type	enhancement
Created	2011-10-16 00:07:54Z

Originally part of #4752

It would be nice if --userAnonymous could also be eliminated, with the determination about whether a user is anonymous delegated to the credentials checker. However, it appears as though the server wants to return "331.2" instead of "331.1" when an anonymous login is being attempted, which requires the server to know if it is going to be an anonymous login before the "password" is sent (hence before the login is attempted).

Perhaps we can get rid of --userAnonymous.

After FTP receives the username, it can log in to the portal with UsernamePassword(username, ""). If this succeeds, the server can proceed to prompt for the "password" (ie, email address) and log it or whatever. If it fails, the server can prompt for the password and re-try login with UsernamePassword(username, password).

This would let an IUsernamePassword credentials checker decide which username corresponds to the anonymous user and return ANONYMOUS when it sees a login attempt for that username. If the realm also allows anonymous users, this would succeed with a usable avatar.

trac-id__5313 5313
type__enhancement enhancement
reporter__cyli cyli
priority__normal normal
milestone__ 
branch__ 
branch_author__ 
status__new new
resolution__None None
component__core core
keywords__ 
time__1318723674000000 1318723674000000
changetime__1318723674000000 1318723674000000
version__None None
owner__ 

Start by tracing how twistd ftp handles --userAnonymous, FTP usernames and passwords, and the credentials checker described in the issue. Determine how anonymous-login detection can move to the checker while preserving the required 331 response, then deprecate or remove the option and verify the resulting FTP behavior.