Comment 1 for bug 1305440

As stated in the comment of the above mentioned Askubuntu question, the code already states that Unity should use its own pam files:

// FIXME (andy) We should install our own unityshell pam file.
  return pam_start("lightdm", username_.c_str(),
                   &conversation, &pam_handle_) == PAM_SUCCESS;

A trivial patch is to use a specific file name in this code: I used "lightdm-lockscreen", and it works just fine (tested with apt-get source unity + dpkg-buildpackage)

But this raises the question of the specs of this feature request:
- should the specific pam file for the lockscreen be mandatory, or should it fallback to the greeter pam config file ?
- if it is mandatory, what should be the defaults ?
- how to ensure a safe transition for existing installations ?