Update 26Sep2018: This post is now a few years old and naturally technology and security have progressed in that time. For more up to date information regarding delegation and, in particular, the requirement for constrained delegation when working with Windows Defender Credential Guard in Windows 10 and Windows Server 2016, please see Stuart Rogers’ very useful SAS Global Forum 2018 Paper: SAS 9.4 on Microsoft Windows: Unleashing Kerberos on Apache Hadoop.
Continuing on the theme of configuring a SAS 9.4 M2 platform on Linux to use Integrated Windows Authentication (IWA), in this post I’m going to jot down some notes on steps 12-15 – configuring the SAS mid-tier on a Linux server for IWA with fallback to form-based authentication (when IWA is not available). This includes delegation, so that IWA users of mid-tier apps like SAS Studio are able to get IWA access to a SAS Workspace Server (and avoid having to store their passwords in metadata or switch to using SAS Token Authentication).
If you’re wondering what happened to steps 1-11, I’ll try get to those earlier steps in future posts. I’m starting at step 12 because someone recently asked me a question about configuring an IWA mid-tier and so it seemed like a good idea to get this blog post done first. Of course, when actual implementing, it’s always good to start at the beginning, building up the foundations, and verifying those first steps are working well before moving on to the next steps. So these steps assume you already have a working implementation where SAS desktop applications (like SAS Management Console & SAS Enterprise Guide) are able to connect to the SAS metadata server using IWA, and also to get IWA access to an appropriately configured SAS Workspace Server.
I have found the best mid-tier related documentation resources for this type of configuration are these ones:
… and there are a few others listed in a previous blog post.
One of the reasons I’m writing this post is to get down some notes on a config that worked for me. The documents referenced above cover a variety of scenarios including plain basic web authentication with an XML file-based UserDatabaseRealm, an LDAP JNDIRealm, IWA (SPNEGO) without fallback, as well as fallback to form-based SAS authentication. Getting the right mix of settings, that didn’t conflict with each other, took me a long time to determine (my mid-tier takes about 20 minutes to restart whenever I want to test a modified config). Along the way I encountered pop-up basic web authentication dialogs when IWA should have worked, and infinite browser-refresh loops for the SAS Logon Manager when IWA was disabled in the browser and I was expecting fallback to SAS authentication. This post is about the final config that worked for me. I know I’ll be referring to this post again, and I hope it proves helpful to others too.
Here goes … Continue reading “Config Notes: SAS Mid-Tier (Linux) IWA with Fallback”
Yesterday I wrote a post about configuring a SAS® 9.4 M2 installation on Linux for Integrated Windows Authentication (IWA) with mid-tier fallback form-based authentication to handle situations where IWA was not available or was disabled. I also repeated this configuration with a SAS Visual Analytics 7.1 installation (based on SAS 9.4 M2). This means that domain users within an organisation, who can participate in IWA, can simply open a browser, navigate to SAS Visual Analytics, and be logged in automatically using their Windows login. Other users without a domain account, on a machine that is not in the domain, or who have deliberately disabled IWA in their browser, will see the familiar SAS Logon Manager login form where they can manually provide a user id and password.
One of the other reasons I built this configuration was to find out what happened with SAS Visual Analytics Guest Access in an IWA fallback configuration like this. Essentially, I wanted to find out if I could get maximum flexibility by supporting IWA users, form-based authentication users, and guest/anonymous access all at the same time.
One of the reasons I wanted to test this was a reference I remembered seeing in the SAS documentation. The Web Authentication section of the SAS 9.4 Intelligence Platform: Security Administration Guide, Second Edition, lists one of the limits of Web Authentication as “Not compatible with anonymous access”. This is also repeated in the PUBLIC Access and Anonymous Access section too.
It makes sense that anonymous access is not compatible with web authentication in a standard non-fallback configuration. If authentication is automatic and it fails then access is denied. An IWA fallback configuration is slightly different though – you have a choice whether to do web authentication or SAS authentication (e.g. IWA or non-IWA). If you choose SAS authentication then perhaps anonymous access might still be available as an option. I decided to test it out.
I ran 4 test scenarios to see how they were handled in an IWA with fallback configuration:
Continue reading “SAS Visual Analytics Guest Access with IWA Fallback”
I’ve just finished a challenging but very rewarding experience configuring a SAS 9.4 M2 platform on Linux to use Integrated Windows Authentication (IWA), for both server and mid-tiers ….. without using Quest Authentication Services.
The SAS platform has supported IWA on Linux since SAS 9.3 but until recently has only supported it when you “purchase, install, and configure an additional third-party product (Quest Authentication Services 4.0)”.
I’ve been wanted to do a SAS + Linux + IWA config for a while but had put it off because of the Quest requirement. What brought it back to the front of my mind was talking to someone recently about implementing IWA for a SAS Visual Analytics installation on Linux. They wanted to provide seamless login via IWA for most users, but also provide form-based logins for people who couldn’t use IWA.
I remembered seeing this section from the What’s New in SAS 9.4 (SAS 9.4 Intelligence Platform):
In the second maintenance release for SAS 9.4, Integrated Windows Authentication on Linux systems no longer requires the use of Quest Authentication Services. SAS can leverage the libraries that are shipped with the supported operating system or that are provided in most third-party authentication solutions.
It sounded like SAS 9.4 M2 would allow me to build such a config, without using Quest, and use the standard Linux libgssapi_krb5 package instead. At the same time I also remembered reading a great SAS Global Forum paper by Zhiyong Li on mid-tier fallback authentication: this is where you can configure the SAS mid-tier to fallback to form-based authentication in situations where IWA is not available or has been disabled (like you might do when you want to login using a different second identity). These both sounded like great challenges [ and fun :) ], so I set about confirming my understanding of these possibilities with SAS 9.4 M2 by doing both at the same time.
After a few days of research, implementation, testing and debugging, I finalized the config last night. I got quite a buzz out of some of the mind-bending troubleshooting sessions and it was a very rewarding outcome. Other than a few relatively minor issues to resolve, it is all working very well now.
If I get some time I’ll try to write up a few blog posts with more detail on the steps, issues, troubleshooting techniques and resolutions. In the meantime here’s an outline of the approach I took:
Continue reading “IWA with SAS 9.4 M2 on Linux”
When testing Integrated Windows Authentication (IWA) based client connections to SAS® platform servers, it is well worth checking the SAS logs to verify the connections are being made the way you expect. SAS has a variety of methods up it’s sleeve to get you authenticated, including cached credentials, retrieving stored credentials from metadata, SAS token authentication etc. Looking in the SAS server logs will help you identify the connection/authentication events and methods used. In the past I’ve thought I was using IWA+Kerberos but when I looked in the log it was obvious I wasn’t! I think it’s essential when testing/troubleshooting a new IWA configuration to review the SAS server logs for both failed and successful connections.
In a previous post “SAS and IWA: Two Hops” I mentioned how sometimes it’s necessary to force the use of Kerberos with IWA to be able to make IWA delegated connections to secondary servers. So here’s some examples of what we might see in SAS server logs Continue reading “SAS & IWA: Check the Logs”
My last post was about configuring additional Service Principal Names (SPNs) in Active Directory to support the use of Integrated Windows Authentication (IWA) in a SAS® platform installation that uses host name aliases in preference to physical host names.
When working on a SAS & IWA setup like this, I’d start by reviewing the currently registered SPNs for all of the SAS servers involved (as well as any other servers that might be accessed from a SAS server using IWA). This gives an idea of what SPNs might have already been added, which ones still need to be added, and potentially which ones might need to be removed.
This is the command I use Continue reading “SAS & IWA: Reviewing SPNs”