pam-krb5 To-Do List

PAM API:

• Support PAM_CHANGE_EXPIRED_AUTHTOK properly in pam_chauthtok. This will require prompting for the current password (if it's not already available in the PAM data) and trying a regular authentication first to see if the account is expired.

• Tighter verification that all of our flags are valid might be a good idea.

• For informational messages followed by a prompt, find a way to combine these into one PAM conversation call for better GUI presentation behavior.

Functionality:

• Change the authentication flow so that both Heimdal and MIT use the same logic for attempting PKINIT first and then falling back to password. This will fix failure to store passwords in the PAM data with try_pkinit and MIT Kerberos on password fallback and will allow implementation of use_pkinit for MIT. Based on discussion with MIT Kerberos upstream, the best approach is probably to configure a custom prompter that refuses to reply to any prompt.

• Add a daemon that can be used to verify TGTs that can be used when pam-krb5 is run as a non-root user and hence doesn't have access to the system keytab. Jeff Hutzelman has a daemon and protocol for doing this developed for a different PAM authentication module, and it would be good to stay consistent with that protocol if possible. (Debian Bug#399001)

• The alt_auth_map parsing to find realms doesn't take into account escaped @-signs and doesn't do proper principal parsing.

• Fix password expiration handling for the search_k5login and alt_auth_map cases. Right now, we may return expired password errors that would trigger password expiration handling, which probably isn't correct.

• Support authentication from a keytab.

• Support disabling of user canonicalization so that the PAM user is retained even if the module did an aname to lname mapping.

• Use set_out_ccache to write the resulting ticket cache, if it is available. This ensures the correct flags are set in the ticket cache. This poses some challenges due to the two-step ticket cache mechanism currently used. Perhaps there's a cache copying API?

• Use krb5_chpw_message to parse password change messages from Active Directory.

• Consider exposing the Kerberos principal in the password prompt for a password change. (Debian Bug#667928)

Code Cleanup:

• The PKINIT code for Heimdal involves too many #ifdefs right now for my taste. Find a way to restructure it to only wrap the main PKINIT function for Heimdal.

• The current handling of error return codes is a mess. We need to find a way to return a rich set of error codes from the underlying functions and then map error codes appropriately in the interface functions. Helpful for this would be improved documentation of what error codes are permitted and where.

• Tracking when to free the Kerberos context and other things stored in the PAM context is currently too complicated. It should be possible to simplify it with a reference counting scheme.

Documentation:

• Document PKINIT configuration with MIT in krb5.conf. It looks like the library supports configuration in [realms] with similar names to the PAM module configuration.

Portability:

• If pam_modutil_getpwnam is not available but getpwnam_r is, roll our own using getpwnam_r.

Logging:

• Log the information that the Kerberos library asks us to display, or at least the info and error messages.

• Log unknown PAM flags on module entry. Currently, only the symbolic flags we know about will be logged.

Test suite:

• Ensure that the test suite covers all possible PAM options.

• Figure out why the pin-mit script for module/pkinit prompts twice and check if it's a bug in the module.

• Find a way of testing the PKINIT identity selection for MIT Kerberos with use_pkinit enabled.