shadow: TOCTOU (time-of-check time-of-use) race condition when copying and removing directory trees

useradd in shadow-utils before 4.0.3, and possibly other versions before 4.0.8, does not provide a required argument to the open function when creating a new user mailbox, which causes the mailbox to be created with unpredictable permissions and possibly allows attackers to read or modify the mailbox.

Unknown vulnerability in the passwdcheck function in Shadow 4.0.4.1, and possibly other versions before 4.0.5, allows local users to conduct unauthorized activities when an error from a pamchauthtok function call is not properly handled.

Quoting first paragraph from [1]: https://bugzilla.redhat.com/showbug.cgi?id=173008

for issue description: ====================== When starting a program via "su - user -c program" the user session can escape to the parent session by using the TIOCSTI ioctl to push characters into the input buffer. This allows for example a non-root session to push "chmod 666 /etc/shadow" or similarly bad commands into the input buffer such that after the end of the session they are executed.

References: [1] https://bugzilla.redhat.com/showbug.cgi?id=173008 [2] http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=628843