REDHAT-BUG-834618: Medium severity Red Hat Enterprise Linux 6 vulnerability

A symbol clash issue was found in the pamsshagentauth PAM module as shipped with Red Hat Enterprise Linux 6 and Fedora. In case of certain errors, pamsshagentauth calls error() function to report problems. Due to the way pamsshagentauth was built in Red Hat Enterprise Linux and Fedora packages, this led to glibc's error() function being called instead of the error() function from OpenSSH sources that was meant to be used. As the two error functions expect different arguments, this could cause an application configured to use the pamsshagentauth module (typically su or sudo) to crash, disclose portion of its memory, or, possibly, execute arbitrary code.

This issue did not affect upstream versions of pamsshagentauth and was specific to Red Hat Enterprise Linux / Fedora packages, where pamsshagentauth is part of the openssh source RPM. This bundling is used to avoid duplicating OpenSSH source code. pamsshagentauth embeds a copy of the OpenSSH code. It is not used in Red Hat Enterprise Linux / Fedora packages, instead OpenSSH code from the OpenSSH build is used. This flaw was consequence of this way the PAM module is built.