misc/91762: Adding a user named ".."

[Werner García]

>Number:         91762
>Category:       misc
>Synopsis:       Adding a user named ".."
>Confidential:   no
>Severity:       serious
>Priority:       medium
>Responsible:    freebsd-bugs
>State:          open
>Quarter:        
>Keywords:       
>Date-Required:
>Class:          sw-bug
>Submitter-Id:   current-users
>Arrival-Date:   Fri Jan 13 17:20:08 GMT 2006
>Closed-Date:
>Last-Modified:
>Originator:     Werner García
>Release:        5.4
>Organization:
OSI de Guatemala, S.A.
>Environment:
FreeBSD kerberos.gua.net 5.4-RELEASE FreeBSD 5.4-RELEASE #0: Wed Aug 10 19:09:11 CST 2005     root at kerberos.gua.net:/usr/src/sys/i386/compile/FIREWALL  i386
>Description:
My question is:

Why can one add a user named "." or ".." with all the problems that this can cause?

Thanks.

>How-To-Repeat:
pw useradd ".."
>Fix:
Modify the user creation mechanisms to disable the use of user names ".", ".." and other critical symbols that have meaning to the operating system.
>Release-Note:
>Audit-Trail:
>Unformatted: