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 DisqusIssue 262/2022
Buy this issue as a PDF
News
-
Kali Linux 2022.3 Released
From the creators of the most popular penetration testing distributions on the planet, comes a new release with some new tools and a community, real-time chat option.
-
The 14" Pinebook Pro Linux Laptop is Shipping
After a considerable delay, the 14" version of the Pinebook Pro laptop is, once again, available for purchase.
-
OpenMandriva Lx ROME Technical Preview Released
OpenMandriva’s rolling release distribution technical preview has been released for testing purposes and adds some of the latest/greatest software into the mix.
-
Linux Mint 21 is Now Available
The latest iteration of Linux Mint, codenamed Vanessa, has been released with a new upgrade tool and other fantastic features.
-
Firefox Adds Long-Anticipated Feature
Firefox 103 has arrived and it now includes a feature users have long awaited…sort of.
-
System76 Refreshes Their Popular Oryx Pro Laptop with a New CPU
The System76 Oryx Pro laptop has been relaunched with a 12th Gen CPU and more powerful graphics options.
-
Elive Has Released a New Beta
The Elive team is proud to announce the latest beta version (3.8.30) of its Enlightenment-centric Linux distribution.
-
Rocky Linux 9 Has Arrived
The latest iteration of Rocky Linux is now available and includes a host of new features and support for new architecture.
-
Slimbook Executive Linux Ultrabook Upgrading Their CPUs
The Spanish-based company, Slimbook, has made available their next generation Slimbook Executive Linux ultrabooks with a 12th Gen Intel Alder Lake CPU.
-
Fedora Linux is Coming to the Raspberry Pi 4
Thanks to significant work in the upstream, the upcoming release of Fedora 37 will introduce support for the Raspberry Pi 4.
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