Re: Kerberos and DIGEST-MD5

[Howard Chu <hyc@symas.com>]

Jose Gonzalez Gomez wrote:
> > The cleanest way to make this work is to use Heimdal Kerberos and set 
> > its KDC to store the Kerberos authentication data in LDAP. Then use 
> > the smbk5pwd module in OpenLDAP's CVS to keep the userPassword and 
> > krb5Key in sync. Synchronization is one-way - when you change 
> > passwords using LDAP then both LDAP and Kerberos will be updated at 
> > once, but if you change passwords using Kerberos only Kerberos will 
> > change. Note that this approach only works with OpenLDAP 2.2 and 
> > Heimdal Kerberos. Also there is no need to use saslauthd when using 
> > this method; the LDAP userPassword simply holds the user's cleartext 
> > password. Obviously there are other security considerations from 
> > storing a cleartext password in LDAP.

>    So you gain the ability to offer DIGEST-MD5 authentication without 
> having duplicated password information, but then you lose the 
> possibility of letting users change their passwords using the standard 
> unix/linux/kerberos tools. The first obvious implication of this 
> approach is that you will have a hard time trying to enforce any 
> password policy in your network, as this usually involves an expired 
> password that must be changed at logon time using pam, and enforcing the 
> quality of the password using kerberos policies... am I missing anything 
> here? Should I use a combination of cracklib/ldap modules for password 
> and kerberos modules for auth/account/session in pam? Would such a setup 
> work?

Use pam_ldap instead of pam_krb, and you'll be able to change your 
passwords using the standard Unix/Linux tools. Password policy 
enforcement is also available in OpenLDAP CVS.

>    Regarding the smbk5pwd... will this be included in a future release 
> of OpenLDAP?

Don't know; I wrote this following a request from Andrew Bartlett on the 
Samba project but he went quiet and no one else provided any feedback so 
it seems there hasn't been any demand/interest.

> And a final question regarding Kerberos... until now I've 
> been using mit-krb5, do you recommend heimdal over mit for any reason?

Well, the most obvious reason is that the MIT KDC doesn't support LDAP. 
There are other reasons that have been hashed out on this list countless 
times, read the mailing list archive.
--
  -- Howard Chu
  Chief Architect, Symas Corp.       Director, Highland Sun
  http://www.symas.com               http://highlandsun.com/hyc
  Symas: Premier OpenSource Development and Support