(RHSA-2003:224) openssh security update

OpenSSH is a suite of network connectivity tools that can be used to
establish encrypted connections between systems on a network and can
provide interactive login sessions and port forwarding, among other functions.

When configured to allow password-based or challenge-response
authentication, sshd (the OpenSSH server) uses PAM (Pluggable
Authentication Modules) to verify the user’s password. Under certain
conditions, OpenSSH versions prior to 3.6.1p1 reject an invalid
authentication attempt without first attempting authentication using PAM.

If PAM is configured with its default failure delay, the amount of time
sshd takes to reject an invalid authentication request varies widely enough
that the timing variations could be used to deduce whether or not an
account with a specified name existed on the server. This information
could then be used to narrow the focus of an attack against some other
system component.

These updates contain backported fixes that cause sshd to always attempt
PAM authentication when performing password and challenge-response
authentication for clients.