Save Your Cloud: DoS on VMs in OpenNebula 4.6.1

This is a post about an old vulnerability that I finally found the time to blog about. It dates back to 2014, but from a technical point of view it is nevertheless interesting: An XML parser that tries to fix structural errors in a document caused a DoS problem.

All previous posts of this series focused on XSS. This time, we present a vulnerability which is connected another Cloud Management Platform: OpenNebula. This Infrastructure-as-a-Service platform started as a research project in 2005. It is used by information technology companies like IBM, Dell and Akamai as well as academic institutions and the European Space Administrations (ESA). By relying on standard Linux tools as far as possible, OpenNebula reaches a high level of customizability and flexibility in hypervisors, storage systems, and network infrastructures. OpenNebula is distributed using the Apache-2 license.

XML Parser Evaluation

XML Parser Evaluation

For some time now, we've been researching in excruciating detail the prevalence of DTD attacks on different XML parsers.

For a quick recap which attacks are possible, see our DTD Cheat Sheet post.


In this post, we present you the results in a nutshell.
The information presented here is based on this masterthesis which covers the respective results in greater detail.

Test Methodology

We identified 16 test vectors, each testing a specific attack vector (e.g. XXE, various kinds of DoS, XXE parameter entity,...). We ran these tests against the default parser configuration and call these therefore core tests.

Additional tests are based on the same test vectors, however, we executed them against custom (modified) parser configurations, indicating the effect of specific features of a parser.

The complete test set is available on github.

Results

We analyzed the following parsers and summarized the test results in Table 1. In addition, we show which attacks cannot be mitigated indicated by an asterisk.

DTD Cheat Sheet

When evaluating the security of XML based services, one should always consider DTD based attack vectors, such as XML External Entities (XXE) as,for example, our previous post XXE in SAML Interfaces demonstrates.

In this post we provide a comprehensive list of different DTD attacks.

The attacks are categorized as follows:

• Denial-of-Service Attacks
• Classic XXE
• Advanced XXE
• Server-Side Requst Forgery (SSRF)
• XInclude
• XSLT

EsPReSSO - A good morning starts with coffee!

In this posts I describe the tool, I wrote for my Bachelor thesis at the Chair for Network and Data Security, with support of Context Information Security Ltd.. EsPReSSO is a apronym for "Extension for Recognition and Processing of Single Sing on Protocols". The basic idea behind EsPReSSO is to automate standard tasks to detect and classify the Single Sign-On (SSO) Protocols OpenID, BrowserID, SAML, OAuth, OpenID-Connect, Facebook Connect and Microsoft Account. The tool is integrate with PortSwigger's HTTP Proxy, Burp Suite. Furthermore EsPReSSO integrates the WS-Attacker, to attack SAML services semi-automated or manually.

Not so Smart: On Smart TV Apps

One of the main characteristics of Smart TVs are apps. Apps extend the Smart TV behavior with various functionalities, ranging from usage of social networks or payed streaming services, to buying articles on Ebay. These actions demand usage of critical data like authentication tokens and passwords, and thus raise a question on new attack scenarios and general security of Smart TV apps.

These reasons make it interesting enough to do some research on smart TVs. We wrote a paper with the title "Not so Smart: On Smart TV Apps", which will be presented in a few days at the "International Workshop on Secure Internet of Things" (SIoT 2015). In this paper, we investigate attack models for Smart TVs and their apps, and systematically analyze security of Smart TV devices. We point out that some popular apps, including Facebook, Ebay or Watchever, send login data over unencrypted channels. Even worse, we show that an arbitrary app installed on devices of the market share leader Samsung can gain access to the credentials of a Samsung Single Sign-On account. Therefore, such an app can hijack a complete user account including all his devices like smartphones and tablets connected with it. Based on our findings, we provide recommendations that are of general importance and applicable to areas beyond Smart TVs.

Introduction to WS-Attacker: XML Signature Wrapping (XSW) on Web services

This post introduces WS-Attacker. We start with how to build it from source. After that we setup an example Axis2 Web service and finally we perform an XSW Attack on it.