During the past year we had several projects where our target application used Jasper Reports in some way. In a few of the cases we found an API that offered to render a template along with some arguments into a PDF file. This was done with the help of the Jasper Reports Java library. Due to the way the library and the expression mechanism works, this endpoint gave us the possibility to inject Java code and gain remote code execution on the target systems.
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On the insecurity of math.random and it’s siblings
During code reviews we often see developers using weak RNGs like math.random() to generate cryptographic secrets. We think it is commonly known that weak random number generators (RNG) must not be used for any kind of secret and recommend using secure alternatives. I explicitly did not state a specific language yet, because basically every language offers both weak and strong RNGs.
So I asked myself: What if I use a weak RNG to generate a secret? Is it possible to recover the secret from some derived value, like a hash?
Continue readingJenkins Remoting RCE II – The return of the ysoserial
Jenkins is a continuous integration server, widely used in Java environments for building automation and deployment. The project recently disclosed an unauthenticated remote code execution vulnerability discovered by Moritz Bechler. Depending on the development environment, a Jenkins server can be a critical part of the infrastructure: It often creates the application packages that later will be deployed on production application servers. If an attacker can execute arbitrary code, s/he can easily manipulate those packages and inject additional code. Another scenario would be that the attacker stealing credentials, like passwords, private keys that are used for authentication in the deployment process or similar.
Continue readingNew Methods for Exploiting ORM Injections in Java Applications (HITB16)
The HITBSecConf or “Hack In The Box” in Amsterdam is a well known security conference in Europe. We also attended this year too, and there were quite some interesting talks at the HITBSecConf16 conference. One of the talks was about “New Methods for Exploiting ORM Injections in Java Applications” by the security researchers Mikhail Egorov and Sergey Soldatov.
I. What is Object-Relational Mapping (ORM)?
ORM stands for Object-Relational Mapping, which is a technique that automatically converts data from a relational database management system (RDBMS) into objects. This is often used in business applications of today.
Continue readingLiferay Portlet Shell
During one of our pentests in some corporate environment we were to analyze an application-server called Liferay. Liferay comes with a lot of functionalities, runs on top of Apache Tomcat and includes a nice API that makes it very easy to add components or further functionality that are not part of the core. These (potentially selfmade) “addons” are called “portlets” and they can be inserted in any place in the frontend.
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