The PAM patch to 'su' does not support pam_putenv(). Some
PAM modules expect to be able to set environment variables
in the child process. A prime example is Kerberos PAM
modules, which want to set the KRBTKFILE environment
variables both for security reasons and to allow a single
user to have multiple 'Kerberos sessions' each with
different ticket files.

Here is a patch that enables this functionality; please
apply it or something like it to the next version of Red
Hat:

http://www.engin.umich.edu/caen/systems/Linux/code/patches/sh-utils-1.16-morepam.patch


Thank you very much,

Chris Wing
wingc.edu