Adobe @ DefCon 2017

A few weeks ago we joined fellow members of the Adobe security team at Defcon 2017. The conference attendance has grown in size over the years as security has become a mainstream in today’s world. We were looking forward to the great line up of briefings, villages, and capture the flag (CTF) contests – Defcon never disappoints.

Here are some of the briefings this year that we found interesting and valuable to our work here at Adobe.

“A New Era of SSRF – Exploiting URL Parser in Trending Programming Languages” by Orange Tsai

The best part of this presentation was that it was very hands-on and less theoretical – something we look forward to in a presentation at DefCon. The presentation discussed zero-day vulnerabilities in URL parsers and requesters for widely-used languages like Java, Python, Ruby, JavaScript, and more. It was really helpful since Adobe is a multilingual shop. They also discussed about the mitigation strategies. Orange Tsai, the presenter, followed the talk with an interesting demo. He chained 4 different vulnerabilities together including SSRF, CRLF injection, unsafe marshal in memcache, and ruby gem to perform a RCE (Remote Code Execution) on Github Enterprise. The combined technique was called “Protocol Smuggling.” It earned him a bounty of $12,500 from GitHub.

“First SHA-1 collision” presented by Elie Bursztein from Google

This was one of the presentations most looked forward to by attendees – there was a significant wait to even get in. This presentation was super helpful since they demoed how an attacker could forge PDF documents to have the same hash yet different content. We really appreciated the effort that has been put into the research from the anti-abuse team within Google. This work was based on cryptanalysis – considered to be 100,000 times more effective than a brute-force attack. For the tech community, these findings emphasize the need for reducing SHA-1 usage. Google has advocated the deprecation of SHA-1 for many years, particularly when it comes to signing TLS certificates. The team also briefly discussed safer hashing algorithms such as SHA256 and bcrypt. They also spent some time discussing the future of hash security.

“Friday the 13th: JSON Attacks!” by Alvaro Muñoz and Oleksandr Mirosh

The briefing kicked off with examples of deserialization attacks and an explanation of how 2016 came to be known as the year of the “Java Deserialization Apocalypse.” The talk focused on JSON libraries which allow arbitrary code execution upon deserialization of untrusted data. It was followed by a walkthrough of deserialization vulnerabilities in some of the most common Java and .NET libraries. The talk emphasized that the format used for serialization is irrelevant for deserialization attacks. It could be binary data, text such as XML, JSON, or even custom binary formats. The presenter noted that serializers cannot be trusted with untrusted data. The talk provided guidance on detecting if a serializer could be attacked. The briefing ended with the speakers providing mitigation advice to help avoid vulnerable configurations that could leave serialization libraries vulnerable. This briefing was particularly valuable as it helped us better understand JSON attacks, how to discover vulnerable deserialization library configurations, and how to mitigate known issues.

“CableTap: Wirelessly Tapping Your Home Network” by Chris Grayson, Logan Lamb, and Marc Newlin

At this briefing, presenters discussed 26 critical vulnerabilities they discovered in some of the major ISP provided network devices. They also showcased some cool attack chains enabling someone to take complete control over these devices and their network.

Hacking Village

One of the other major highlights of Defcon 25 was the Voting Machine Village. For the first time ever US voting machines were brought into the Hacking Village. Many vulnerabilities were found in these machines over the course of DefCon. It was also reported that the machines were hacked in under 2 hours. The Recon-village also never fails to deliver the best of social engineering exploits. It reminds us of the importance of security training and education. Additionally, the demo labs were thought provoking. We found a lot of tools to potentially add to our toolkits. A couple of the cool ones included Android Tamer by Anant Srivastava which focused on Android Security and EAPHammer – a toolkit for targeted twin attacks on WPA2-Enterprise networks by Gabriel Ryan.

Overall these industry events provide a great opportunity for our own security researchers to mingle with and learn from the broader security community. They help keep our knowledge and skills up-to-date. They also provide invaluable tools to help us better mitigate threats and continue to evolve our Adobe SPLC (Secure Product Lifecycle) process.

Lakshmi Sudheer & Narayan Gowraj
Security Researchers

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