For Unix/Linux shops, the security and compliance shortcomings of NIS and NIS+ have become evident in recent years. Lightweight Directory Access Protocol (LDAP) initially seemed a viable alternative that would also allow organisations to manage their Microsoft and Unix user populations in a standard way. So why are LDAP-based management systems now increasingly falling foul of auditors? And what can enterprises do to avoid this?
When it was first introduced, NIS provided a handy mechanism for centrally managing user and host information in large networks. However, the protocol lacks any inherent support for authentication and authorisation, and it is difficult to produce audit trails keeping track of changes to user and host definitions across the system.
With the advent of LDAP, many organisations saw the opportunity of consolidating user data for both Microsoft and Unix/Linux systems in one centralised directory. The problem is that organisations running LDAP are still failing security and compliance audits. LDAP simply does not per se include enough security features to satisfy auditors.
Unmanaged LDAP, that is LDAP implemented as a core provisioning service within the enterprise, but without add-on functionality to secure and control its use, includes support for central controls on passwords, but without integrating security add-ons. LDAP password is the only authentication choice, unless users are allowed to set up their own authentication. In the latter case, a lack of centralised controls over authentication, for example being unable to prevent users from setting up SSH Public Key authentication with no password, can prove costly in audits.
Unmanaged LDAP does not provide enough fine-grained access controls to satisfy IT and compliance auditors. They want to know exactly who can access what resources, when. Unmanaged LDAP cannot control access for individual users or hosts, let alone at the service level.
Audit trails are another problem. Unmanaged LDAP provides no greater central auditing capabilities than NIS, and does not deliver the kind of documented output showing that provisioning and access policies are actually being enforced in the network that auditors require.
Finally, one of the biggest problems with relying on LDAP for network management is the issue of local functional accounts. When business critical applications require these local functional accounts to operate, application managers are rightly reluctant to hand over control of these accounts to external LDAP systems. However, not doing this leaves the enterprise with perhaps dozens of local accounts that are not under centralised control and not subject to policies. This leads to audit failures.
Given recent audit failures, more and more organisations are looking at strategies to manage LDAP across the different operating systems they use, releasing its potential as a provisioning and management tool while ensuring that it does not become a compliance liability.
One strategy on the table is to use Active Directory, Microsoft's implementation of LDAP, to manage all the resources in the network, both Microsoft and non-Microsoft. This category of solutions attempts to extend Active Directory authentication and Group policies to non-Microsoft resources including Unix and Linux systems.
While this approach leverages the investments many organisations have already made in Active Directory, solutions designed to graft Active Directory security models onto Unix and Linux environments typically control access on a host-by-host basis, and do not offer the granularity of managing access to individual Unix/Linux services. When it comes to the pressing problem of controlling the use of privileged accounts on Unix and Linux, a hot potato when it comes to audits, such solutions typically rely on variants of the freeware sudo utility, but do not include features like specific controls on su operations or keystroke logging.
Another approach to centralising identity and access management in the enterprise is to find tools that will manage Unix and Linux systems with sufficient granularity to satisfy auditors and will at the same time integrate with managed LDAP systems, even allowing an LDAP system such as Active Directory to be used as the principal repository of identity data.
This strategy recognises that specialised management systems are needed to control the specifics of the Unix and Linux environment. With a security model that differs from the Microsoft Active Directory Model, controlling Unix and Linux presents a different set of problems, including properly monitoring privileged accounts and the smooth deployment of secure protocols like SSH, to name but two. Such an approach will typically involve deploying a solution that can manage Unix/Linux authorisation at the service level, not the host level, but can also securely integrate with LDAP directories to bring Unix and Linux into the enterprise's central provisioning and identity management system.
When it comes to auditing too, your audit output is only as detailed as the controls you have in place, so if you are controlling access at service level rather than host level, you have more detailed information to present to auditors. Similarly, robust controls on privileged account operations such as keystroke logging provide more evidence of accountability than using sudoers files to guarantee this vital element of Unix/Linux security.
This approach enables functional accounts to be safely run in a local context meaning application managers can rest easy, but at the same time includes these local accounts in a centralised system of controls, subject to enterprise-wide policies, and centrally audited.
As industry searches for a new paradigm to manage mixed Microsoft and Unix/Linux environments, one thing is for sure: unmanaged LDAP systems are failing audits, and it is imperative for companies to assess and determine what their strategy will be moving forward.
Per Eliasson, director at FoxT
FoxT is exhibiting at Infosecurity Europe 2008, Europe's dedicated information security event. Now in its 13th year, the show continues to provide an education programme, new products and services, over 300 exhibitors and 11 700 visitors from every segment of the industry. Held on 22-24 April 2008 in the Grand Hall, Olympia, this is a must attend event for all professionals involved in information security.