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B2s and Java Permissions

Building Blocks are basically web applications which run in the Blackboard Learn web application container. As such they require specific permissions added to their bb-manifest.xml file to properly install, display, retrieve and persist data, and correctly operate within the Learn application and environment.

In order to interact with the Learn environment a Building Block must supply the necessary set of java permissions in the permissions element located near the bottom of the bb-manifest file. A basic set of permissions may include:

    <permission type="attribute" name="user.personalinfo" actions="get,set"/>
    <permission type="blackboard.persist.PersistPermission" name="user" actions="create,modify"/>
    <permission type="" name="*" actions="resolve,connect"/>
    <permission type="java.util.PropertyPermission" name="*" actions="read,write"/>

One permission often seen is:

    <permission type="" name="&lt;&lt;ALL FILES&gt;&gt;" actions="read,write"/>

While convenient to use this particular ‘wild card’ notation, it provides access to all system files. Thus it is more secure to specify files and paths directly even if this requires multiple permission entries:

    <permission type="" name="BB_HOME/logs/my_b2.log" actions="read,write"/>

A more comprehensive though not all-inclusive set of permissions is listed at the end of this help topic.

How do I know which permissions to include?

Unfortunately AccessControlException< are not discoverable at compile- time as they only manifest when a Building Block is running. So beyond the common permissions noted above, exceptions may be determined by coding practices or by log entry identification. When an installed Building Block encounters a permissions gap at runtime it will throw an AccessControlException permission error. You may use this error to determine the exact permission you need to add to the bb-manifest to correct the AccessControlException condition.

The main indication of an AccessControlException is receiving error 404 when launching your Building Block. This 404 error indicates that the resource is unavailable. This 404 error is a good indication that the Building Block is missing a required permission. The next step is to identify the missing permission.

Using Linux as an example, inspect the /usr/local/blackboard/logs/tomcat/stdout-stderr-xxxxxxxx-log.txt, where xxxxxxxx is the date when the error appeared. Search this log for AccessControlException and you should find something like this:

Caused by: access denied ( resolve)

This is the logged exception and follows the pattern of:

Caused by:**_AccessControlException_**: access denied (<type> <name> [<actions>])

To resolve this error, you simply need to add a new permission element to your bb-manifest.xml file using the logged and if specified [].

The format for the permission element is (notice the same terminology in use):

    <permission type="<type>" name="<name>" actions="<actions>" />

Simply enter the values from the error message into the permission element, add it to your bb-manifest and re-deploy your Building Block. It is important to note that is optional. If your error stack doesn’t have associated with it, simply leave it blank (i.e. actions="").

To illustrate this, we’ll take the above listed error and convert it into a permission element.


Caused by:**_AccessControlException_**: access denied
( resolve)


    <permission actions=resolve />

You will need to re-deploy your Building Block after changing your bb- manifest. Uninstalling and re-deploying your Building Block or changing the version number will update the Building Block with the permissions specified in the bb-manifest. In addition, Blackboard Learn 9.1 October 2014 Release requires a system restart in order to implement the new changes in permissions.

More Permissions

Below are some additional permissions for formatting reference.

Do not include more permissions than are necessary for proper operation of your Building Block as this will impact start times.

    <permission type="" name="sessionmanager" actions="get" />
    <permission type="attribute" name="user.personalinfo" actions="get,set" />
    <permission type="persist" name="groupmembership" actions="create" />
    <permission type="attribute" name="user.authinfo" actions="get" />
    <permission type="java.util.PropertyPermission" name="*" actions="read,write" /> 
    <permission type="persist" name="content" actions="persist" />
    <permission type="persist" name="course" actions="create,modify,delete" /> 
    <permission type="persist" name="user" actions="create,modify,delete" />
    <permission type="persist" name="userrole" actions="create,modify,delete" />
    <permission type="persist" name="coursemembership" actions="persist,create,modify,delete" />             
    <permission type="persist" name="enrollment" actions="persist,create,modify,delete" />
    <permission type="attribute" name="enrollment.rowstatus" actions="get,set" />             
    <!-- Minimum permissions to support Spring -->
    <permission type="java.lang.reflect.ReflectPermission" name="suppressAccessChecks" />
    <permission type="java.lang.RuntimePermission" name="accessDeclaredMembers" />
    <permission type="java.lang.RuntimePermission" name="createClassLoader" />
    <permission type="java.lang.RuntimePermission" name="setContextClassLoader" />             
    <!--  For logback logging -->
    <permission type="" name="${java.home}/lib/*" actions="read" />
    <permission type="" name="BB_HOME/logs/-" actions="read,write" />