aenlr/strutt-cve-2014-0114Technical analysis and proof-of-concept for Apache Struts 1 class parameter manipulation (CVE-2014-0114), demonstrating remote code execution on Tomcat and denial-of-service on JBoss/Wildfly.
Parameters in a POST or GET request are handled as properties to be set with the form as a starting point. Parameters can be a path to a nested object.
Apache Struts 1.x can be manipulated to call getClass() on Form Beans. For example, one can directly manipulate attributes on the form's classloader: https://example.com/?class.classLoader.defaultAssertionStatus=true.
Under the hood, Apache Struts 1.x uses commons-beanutils which in version 1.8 (and earlier) does not exclude the class attribute.
Struts 2 has had similar flaws, but here we focus on Struts 1.x where there are no patches to the framework whose latest version was released in 2008 (EOL since 2013).
If the application runs on Tomcat (Catalina), logging can be manipulated so that the attacker can create a JSP file which is then executed when requested from the server. The JSP file can execute arbitrary Java code as the user running the Java process.
See Julián Vila's demonstration for details.
(Tested with JBoss EAP 7.1)
There is a simple method to perform a DOS attack that in the worst case makes JBoss completely unreachable and requires a restart. In the best case, JBoss responds slowly.
Through the class attribute it is possible to access Class#protectionDomain.codeSource.location.
In JBoss, this is a URL object with the vfs protocol.
For a URL of type vfs://, JBoss has registered a URLStreamHandler that returns an object of type org.jboss.vfs.VirtualFile when URL#getContent is called.
class.protectionDomain.codeSource.location.content.pathName points to the directory <PATH>/<application>/WEB-INF/classes.
Via parent you access an object for the directory one level up:
class.protectionDomain.codeSource.location.content.parent.pathName -> <PATH>/<application>/WEB-INF
Question: How many parent references are needed to reach the root of the filesystem?
Question:
What happens when we request class.protectionDomain.codeSource.location.content.parent.parent.[...].childrenRecursively[0].pathName
for the filesystem's root directory?
Answer:
JBoss will go through all files in the filesystem and allocate an org.jboss.vfs.VirtualFile for each file and directory.
Follow-up question: What happens if two requests request all files in the filesystem simultaneously? Three requests? Five? Ten? One hundred?
...
Answer:
If you wait long enough, an error is logged
