FOSDEM: Gnash Developer Deciphers RTMP
Rob Savoye has been engaged in numerous projects, but in his work on Gnash, a free implementation of the Adobe Flash Player, he found a hard nut to crack: how to decipher the protocol details of the Real Time Messaging Protocol (RTMP) it uses. He has now presented his solution at the FOSDEM '09 conference in Belgium.
Savoye, developer with the Open Media Now project funded by Red Hat founder Bob Young, has worked on compilers and debuggers in the past. With Gnash he's been involved in enhancing support for ActionScript 9. Version 8 of the software already serves as a plug-in for Firefox and Konqueror, according to Savoye.
For him, reverse-engineering RTMP for Gnash has not least of all been a mental challenge. He would stare at hex code long enough until a revelation hit him, he said with a smile. He gave an example of his process: at first he searched for certain byte sequences of ASCII code in a collection of as many sample artifacts as possible. He could then determine the boundaries of other data fields and tried to locate a protocol data header. Based on his experience he could then often establish field lengths and checksums for the RTMP protocol.
Numbers are almost always coded in big-endian order in network protocols and checksums rarely consist of anything other than a simple sum or result of a cyclic redundancy check (CRC), according to Savoye. He wrote a log of test code to check his assumptions and warns prospective reverse engineers that they'd have to throw away much of their assumptions if proved false.
Not least of all he cautions imitators about possible legal implications: simple disassembling of proprietary software can lead to claims from respective originators. He therefore recommended involving legal counsel as early as possible in the process. It's also useful, according to Savoye, when a developer reimplements the code, to extract the specification from the network packet and leave just the protocol description for another independent developer in his implementation. Apparently the newest YouTube videos are already viewable using the current Gnash version based on Savoye's work.
Comments
comments powered by DisqusSubscribe to our Linux Newsletters
Find Linux and Open Source Jobs
Subscribe to our ADMIN Newsletters
Support Our Work
Linux Magazine content is made possible with support from readers like you. Please consider contributing when you’ve found an article to be beneficial.
News
-
Linux Servers Targeted by Akira Ransomware
A group of bad actors who have already extorted $42 million have their sights set on the Linux platform.
-
TUXEDO Computers Unveils Linux Laptop Featuring AMD Ryzen CPU
This latest release is the first laptop to include the new CPU from Ryzen and Linux preinstalled.
-
XZ Gets the All-Clear
The back door xz vulnerability has been officially reverted for Fedora 40 and versions 38 and 39 were never affected.
-
Canonical Collaborates with Qualcomm on New Venture
This new joint effort is geared toward bringing Ubuntu and Ubuntu Core to Qualcomm-powered devices.
-
Kodi 21.0 Open-Source Entertainment Hub Released
After a year of development, the award-winning Kodi cross-platform, media center software is now available with many new additions and improvements.
-
Linux Usage Increases in Two Key Areas
If market share is your thing, you'll be happy to know that Linux is on the rise in two areas that, if they keep climbing, could have serious meaning for Linux's future.
-
Vulnerability Discovered in xz Libraries
An urgent alert for Fedora 40 has been posted and users should pay attention.
-
Canonical Bumps LTS Support to 12 years
If you're worried that your Ubuntu LTS release won't be supported long enough to last, Canonical has a surprise for you in the form of 12 years of security coverage.
-
Fedora 40 Beta Released Soon
With the official release of Fedora 40 coming in April, it's almost time to download the beta and see what's new.
-
New Pentesting Distribution to Compete with Kali Linux
SnoopGod is now available for your testing needs
You are right
Actionscript 3 is the most current version
You mean Adobe Flash 9 right? I am an Adobe Flex developer and as per my knowledge and experience Actionscript 3 is the latest version.
Thanks
Faisal