Sunday, 15 March 2015

Override Java settings on OpenShift


With OpenShift, your server instance in the cloud is prepared with a few mouse clicks or with a single command with the rhc tool.
In most of the cases, this is all you need and you can start right away with your freshly created server instance (named gear in OpenShift terminology).
But in other situations, you want to make some changes to the Java environment, like setting system properties or changing the security settings.

In the case of the security settings, in a normal environment, you can update the file in the JRE_HOME/lib/security folder.  But on the OpenShift environment there are some constraints which makes this task a bit more difficult.  This text shows you an easy way to accomplish your goal.


We have developed a JSF application which uses OAuth2 as authentication means.  So we are using an SSL connection to the OAuth2 provider to verify the tokens which are presented to the applications.
It was working fine on OpenShift with the latest WildFly 8.2 cartridge. And last week, we created a new gear and our application throw an exception EC AlgorithmParameters not available

When we compared this new instance with the instance we had already running, we found out that the java version was different.  The newest one, is using OpenJDK 8u31.  And searching on the web for the combination of this version and the exception we received, revealed that there is an issue with this version related to Elliptic curve algorithm.

So, the next step was to edit the file to exclude the algorithm which causes problems in our cases.  
The key jdk.tls.disabledAlgorithms in the file, needs to contain the codes of the algorithms we don't want, in our situation EC,ECDHE,ECDH.

But when I opened the file and wanted to change the content, I received the warning that the film is read-only.  And you can't change it and you can't become a super user to overrule it.

And I can understand that you want to secure some parts of the server.  But it is no option for us to rewrite the Web application with Java 7 due to a, hopefully, temporarily issue with the Java which is running on the gear.


The solution was found when I found the blog of Eyal Lupu which gives a nice example of how you can override the contents of the file (the documentation in the file itself indicate already this possibility but with the example it became clear for me) and the OpenShift user guide.

So we created a file on the gear to override the key jdk.tls.disabledAlgorithms from the file. And by setting a system property using the JAVA_OPTS_EXT environment variable of the gear, we are able to make the application run again without throwing the exception.

Create the file

  •  rhc ssc gearName
  •  vi
  •  content is jdk.tls.disabledAlgorithms=EC,ECDHE,ECDH
  •  pwd -> and note down (copy) the full path location of the just created file.
  •  exit

Set the environment variable

  •  rhc env set<> -a gearName
Restart your gear/app

  •  rhc app restart -a gearName

The OPENSHIFT_DATA_DIR isn't chosen at random.  It is the only directory which isn't cleared when you push some code to the git repository. So our file is save there and will not be touched by any of the system processes.


The JAVA_OPTS_EXT environment variable is important if you want to change some settings of the Java Environment.  You can add some system properties to configure your application (like setting the JSF project stage) or to override the configuration for instance as explained in this text.

Hope this help you if you have a similar 'issue' with OpenShift.