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• Reverse Engineering Italian Literature

  1er juillet 2014, par Multimedia Mike — Reverse Engineering

  Some time ago, Diego “Flameeyes” Pettenò tried his hand at reverse engineering a set of really old CD-ROMs containing even older Italian literature. The goal of this RE endeavor would be to extract the useful literature along with any structural metadata (chapters, etc.) and convert it to a more open format suitable for publication at, e.g., Project Gutenberg or Archive.org.

  Unfortunately, the structure of the data thwarted the more simplistic analysis attempts (like inspecting for blocks of textual data). This will require deeper RE techniques. Further frustrating the effort, however, is the fact that the binaries that implement the reading program are written for the now-archaic Windows 3.1 operating system.

  In pursuit of this RE goal, I recently thought of a way to glean more intelligence using DOSBox.

  Prior Work
  There are 6 discs in the full set (distributed along with 6 sequential issues of a print magazine named L’Espresso). Analysis of the contents of the various discs reveals that many of the files are the same on each disc. It was straightforward to identify the set of files which are unique on each disc. This set of files all end with the extension “LZn”, where n = 1..6 depending on the disc number. Further, the root directory of each disc has a file indicating the sequence number (1..6) of the CD. Obviously, these are the interesting targets.

  The LZ file extensions stand out to an individual skilled in the art of compression– could it be a variation of the venerable LZ compression ? That’s actually unlikely because LZ — also seen as LIZ — stands for Letteratura Italiana Zanichelli (Zanichelli’s Italian Literature).

  The Unix ‘file’ command was of limited utility, unable to plausibly identify any of the files.

  Progress was stalled.

  Saying Hello To An Old Frenemy
  I have been showing this screenshot to younger coworkers to see if any of them recognize it :

  
  
  

  Not a single one has seen it before. Senior computer citizen status : Confirmed.

  I recently watched an Ancient DOS Games video about Windows 3.1 games. This episode showed Windows 3.1 running under DOSBox. I had heard this was possible but that it took a little work to get running. I had a hunch that someone else had probably already done the hard stuff so I took to the BitTorrent networks and quickly found a download that had the goods ready to go– a directory of Windows 3.1 files that just had to be dropped into a DOSBox directory and they would be ready to run.

  Aside : Running OS software procured from a BitTorrent network ? Isn’t that an insane security nightmare ? I’m not too worried since it effectively runs under a sandboxed virtual machine, courtesy of DOSBox. I suppose there’s the risk of trojan’d OS software infecting binaries that eventually leave the sandbox.

  Using DOSBox Like ‘strace’
  strace is a tool available on some Unix systems, including Linux, which is able to monitor the system calls that a program makes. In reverse engineering contexts, it can be useful to monitor an opaque, binary program to see the names of the files it opens and how many bytes it reads, and from which locations. I have written examples of this before (wow, almost 10 years ago to the day ; now I feel old for the second time in this post).

  Here’s the pitch : Make DOSBox perform as strace in order to serve as a platform for reverse engineering Windows 3.1 applications. I formed a mental model about how DOSBox operates — abstracted file system classes with methods for opening and reading files — and then jumped into the source code. Sure enough, the code was exactly as I suspected and a few strategic print statements gave me the data I was looking for.

  Eventually, I even took to running DOSBox under the GNU Debugger (GDB). This hasn’t proven especially useful yet, but it has led to an absurd level of nesting :

  
  
  

  The target application runs under Windows 3.1, which is running under DOSBox, which is running under GDB. This led to a crazy situation in which DOSBox had the mouse focus when a GDB breakpoint was triggered. At this point, DOSBox had all desktop input focus and couldn’t surrender it because it wasn’t running. I had no way to interact with the Linux desktop and had to reboot the computer. The next time, I took care to only use the keyboard to navigate the application and trigger the breakpoint and not allow DOSBox to consume the mouse focus.

  New Intelligence
  
  By instrumenting the local file class (virtual HD files) and the ISO file class (CD-ROM files), I was able to watch which programs and dynamic libraries are loaded and which data files the code cares about. I was able to narrow down the fact that the most interesting programs are called LEGGENDO.EXE (‘reading’) and LEGGENDA.EXE (‘legend’ ; this has been a great Italian lesson as well as RE puzzle). The first calls the latter, which displays this view of the data we are trying to get at :

  
  
  

  When first run, the program takes an interest in a file called DBBIBLIO (‘database library’, I suspect) :

  === Read(’LIZ98\DBBIBLIO.LZ1’) : req 337 bytes ; read 337 bytes from pos 0x0
  === Read(’LIZ98\DBBIBLIO.LZ1’) : req 337 bytes ; read 337 bytes from pos 0x151
  === Read(’LIZ98\DBBIBLIO.LZ1’) : req 337 bytes ; read 337 bytes from pos 0x2A2
  [...]
  

  While we were unable to sort out all of the data files in our cursory investigation, a few things were obvious. The structure of this file looked to contain 336-byte records. Turns out I was off by 1– the records are actually 337 bytes each. The count of records read from disc is equal to the number of items shown in the UI.

  Next, the program is interested in a few more files :

  *** isoFile() : ’DEPOSITO\BLOKCTC.LZ1’, offset 0x27D6000, 2911488 bytes large
  === Read(’DEPOSITO\BLOKCTC.LZ1’) : req 96 bytes ; read 96 bytes from pos 0x0
  *** isoFile() : ’DEPOSITO\BLOKCTX0.LZ1’, offset 0x2A9D000, 17152 bytes large
  === Read(’DEPOSITO\BLOKCTX0.LZ1’) : req 128 bytes ; read 128 bytes from pos 0x0
  === Seek(’DEPOSITO\BLOKCTX0.LZ1’) : seek 384 (0x180) bytes, type 0
  === Read(’DEPOSITO\BLOKCTX0.LZ1’) : req 256 bytes ; read 256 bytes from pos 0x180
  === Seek(’DEPOSITO\BLOKCTC.LZ1’) : seek 1152 (0x480) bytes, type 0
  === Read(’DEPOSITO\BLOKCTC.LZ1’) : req 32 bytes ; read 32 bytes from pos 0x480
  === Read(’DEPOSITO\BLOKCTC.LZ1’) : req 1504 bytes ; read 1504 bytes from pos 0x4A0
  [...]

  Eventually, it becomes obvious that BLOKCTC has the juicy meat. There are 32-byte records followed by variable-length encoded text sections. Since there is no text to be found in these files, the text is either compressed, encrypted, or both. Some rough counting (the program seems to disable copy/paste, which thwarts more precise counting), indicates that the text size is larger than the data chunks being read from disc, so compression seems likely. Encryption isn’t out of the question (especially since the program deems it necessary to disable copy and pasting of this public domain literary data), and if it’s in use, that means the key is being read from one of these files.

  Blocked On Disassembly
  So I’m a bit blocked right now. I know exactly where the data lives, but it’s clear that I need to reverse engineer some binary code. The big problem is that I have no idea how to disassemble Windows 3.1 binaries. These are NE-type executable files. Disassemblers abound for MZ files (MS-DOS executables) and PE files (executables for Windows 95 and beyond). NE files get no respect. It’s difficult (but not impossible) to even find data about the format anymore, and details are incomplete. It should be noted, however, the DOSBox-as-strace method described here lends insight into how Windows 3.1 processes NE-type EXEs. You can’t get any more authoritative than that.

  So far, I have tried the freeware version of IDA Pro. Unfortunately, I haven’t been able to get the program to work on my Windows machine for a long time. Even if I could, I can’t find any evidence that it actually supports NE files (the free version specifically mentions MZ and PE, but does not mention NE or LE).

  I found an old copy of Borland’s beloved Turbo Assembler and Debugger package. It has Turbo Debugger for Windows, both regular and 32-bit versions. Unfortunately, the normal version just hangs Windows 3.1 in DOSBox. The 32-bit Turbo Debugger loads just fine but can’t load the NE file.

  I’ve also wondered if DOSBox contains any advanced features for trapping program execution and disassembling. I haven’t looked too deeply into this yet.

  Future Work
  NE files seem to be the executable format that time forgot. I have a crazy brainstorm about repacking NE files as MZ executables so that they could be taken apart with an MZ disassembler. But this will take some experimenting.

  If anyone else has any ideas about ripping open these binaries, I would appreciate hearing them.

  And I guess I shouldn’t be too surprised to learn that all the literature in this corpus is already freely available and easily downloadable anyway. But you shouldn’t be too surprised if that doesn’t discourage me from trying to crack the format that’s keeping this particular copy of the data locked up.

• Broadcast mjpeg stream via websocket using ffmpeg and Python Tornado

  25 février 2016, par Asampaiz

  Well, i have been strugling for weeks now. Searching and reading a hundred of pages and nearly surrender.

  I need your help, this is the story : I want to stream my Logitech C930e webcam (connected to Raspi 2) to web browser. I have tried so many different way, such as using ffserver to pass the stream from ffmpeg to the web browser, but all of that is using same basic, it’s all need a re-encoding. ffserver will always re-encode the stream that passed by ffmpeg, no matter it is already on the right format or not. My webcam have built-in video encoding to mjpeg until 1080p, so that is the reason why i use this webcam, i don’t want using all of Raspi 2 resource just for encoding those stream.

  This approach end up in eating all my Raspi 2 Resources.

  Logitech C930e ---mjpeg 720p (compressed) instead of rawvideo---> ffmjpeg (copy, no reencoding) —http—> ffserver(mjpeg, reencoding to mjpeg ;this is the problem) —http—> Firefox

  My new approach

  Logitech C930e ---mjpeg 720p (compressed) instead of rawvideo---> ffmjpeg (copy, no reencoding —pipe—> Python3 (using tornado as the web framework) —websocket—> Firefox

  The problem of the new approach

  The problem is i can not make sure the stream format that passed by ffmpeg via pipe to Python is ready | compatible to be streamed to browser via websocket. I mean i already do all these step above but the result is unreadable image shown in the browser (like TV lost signal).

  1. I need help figuring out how to feed python the right mjpeg stream format with ffmpeg
  2. I need help on the client side (javascript) how to show the binary message that sent via websocket (the mjpeg stream)

  This is my current script

  Executing ffmpeg in Python (pipe) - Server Side

  --- cut ---
  
          multiprocessing.Process.__init__(self)
  
          self.resultQ = resultQ
  
          self.taskQ = taskQ
  
          self.FFMPEG_BIN = "/home/pi/bin/ffmpeg"
  
          self.video_w = 1280
  
          self.video_h = 720
  
          self.video_res = '1280x720'
  
          self.webcam = '/dev/video0'
  
          self.frame_rate = '10'
  
          self.command = ''
  
          self.pipe = ''
  
          self.stdout = ''
  
          self.stderr = ''
  
  
  
      #Start the ffmpeg, this parameter need to be ajusted,
  
      #video format already tried rawvide, singlejpeg, mjpeg
  
      #mpjpeg, image2pipe
  
      #i need help here (to make sure the format is right for pipe)
  
      def camera_stream_start(self):
  
              self.command = [ self.FFMPEG_BIN,
  
                  '-loglevel', 'debug',
  
                  '-y', 
  
                  '-f', 'v4l2',
  
                  '-input_format', 'mjpeg',
  
                  '-s', self.video_res,
  
                  '-r', self.frame_rate,
  
                  '-i', self.webcam,
  
                  '-c:v', 'copy',
  
                  '-an', 
  
                  '-f', 'rawvideo',
  
                  #'-pix_fmts', 'rgb24',
  
                  '-']
  
              self.pipe = sp.Popen(self.command, stdin=sp.PIPE, stdout = sp.PIPE, shell=False)
  
              #return self.pipe
  
  
  
      #stop ffmpeg
  
      def camera_stream_stop(self):
  
          self.pipe.stdout.flush()
  
          self.pipe.terminate()
  
          self.pipe = ''
  
          #return self.pipe
  
  
  
      def run(self):
  
          #start stream
  
          self.camera_stream_start()
  
          logging.info("** Camera process started")
  
          while True:
  
              #get the stream from pipe,
  
              #this part is also need to be ajusted
  
              #i need help here
  
              #processing the stream read so it can be
  
              #send to browser via websocket
  
              stream = self.pipe.stdout.read(self.video_w*self.video_h*3)
  
  
  
              #reply format to main process
  
              #in main process, the data will be send over binary websocket
  
              #to client (self.write_message(data, binary=True))
  
              rpl = {
  
                  'task' : 'feed',
  
                  'is_binary': True,
  
                  'data' : stream
  
              }
  
              self.pipe.stdout.flush()
  
              self.resultQ.put(rpl)
  
              #add some wait
  
              time.sleep(0.01)
  
          self.camera_stream_stop()
  
          logging.info("** Camera process ended")

  ffmpeg output

  --- Cut ---     
  
  Successfully opened the file.
  
  Output #0, rawvideo, to 'pipe:':
  
    Metadata:
  
      encoder         : Lavf57.26.100
  
      Stream #0:0, 0, 1/10: Video: mjpeg, 1 reference frame, yuvj422p(center), 1280x720 (0x0), 1/10, q=2-31, -1 kb/s, 10 fps, 10 tbr, 10 tbn, 10 tbc
  
  Stream mapping:
  
    Stream #0:0 -> #0:0 (copy)
  
  Press [q] to stop, [?] for help
  
  --- Cut ---     

  JavaScript websocket - on the client side

  --- Cut ---
  
  socket = new WebSocket(url, protocols || []);
  
  socket.binaryType = "arraybuffer";
  
  
  
  socket.onmessage = function (message) {
  
      //log.debug(message.data instanceof ArrayBuffer);
  
      //This is for the stream that sent via websocket
  
      if(message.data instanceof ArrayBuffer)
  
      {
  
          //I need help here
  
          //How can i process the binary stream
  
          //so its can be shown in the browser (img)
  
          var bytearray = new Uint8Array(message.data);
  
          var imageheight = 720;
  
          var imagewidth = 1280;
  
  
  
          var tempcanvas = document.createElement('canvas');
  
          tempcanvas.height = imageheight;
  
          tempcanvas.width = imagewidth;
  
          var tempcontext = tempcanvas.getContext('2d');
  
  
  
          var imgdata = tempcontext.getImageData(0,0,imagewidth,imageheight);
  
  
  
          var imgdatalen = imgdata.data.length;
  
  
  
          for(var i=8;i/this is for ordinary string that sent via websocket
  
      else{
  
          pushData = JSON.parse(message.data);
  
          console.log(pushData);
  
      }
  
  
  
   --- Cut ---

  Any help, feedback or anything is very appreciated. If something not clear please advice me.

• Vedanti and Max Sound vs. Google

  14 août 2014, par Multimedia Mike — Legal/Ethical

  Vedanti Systems Limited (VSL) and Max Sound Coporation filed a lawsuit against Google recently. Ordinarily, I wouldn’t care about corporate legal battles. However, this one interests me because it’s multimedia-related. I’m curious to know how coding technology patents might hold up in a real court case.

  Here’s the most entertaining complaint in the lawsuit :

  Despite Google’s well-publicized Code of Conduct — “Don’t be Evil” — which it explains is “about doing the right thing,” “following the law,” and “acting honorably,” Google, in fact, has an established pattern of conduct which is the exact opposite of its claimed piety.

  I wonder if this is the first known case in which Google has been sued over its long-obsoleted “Don’t be evil” mantra ?

  Researching The Plaintiffs
  
  I think I made a mistake by assuming this lawsuit might have merit. My first order of business was to see what the plaintiff organizations have produced. I have a strong feeling that these might be run of the mill patent trolls.

  VSL currently has a blank web page. Further, the Wayback Machine only has pages reaching back to 2011. The earliest page lists these claims against a plain black background (I’ve highlighted some of the more boisterous claims and the passages that make it appear that Vedanti doesn’t actually produce anything but is strictly an IP organization) :

  The inventions key :
  The patent and software reduced any data content, without compressing, up to a 97% total reduction of the data which also produces a lossless result. This physics based invention is often called the Holy Grail.

  Vedanti Systems Intellectual Property
  Our strategic IP portfolio is granted in all of the world’s largest technology development and use countries. A major value indemnification of our licensee products is the early date of invention filing and subsequent Issue. Vedanti IP has an intrinsic 20 year patent protection and valuation in royalties and licensing. The original data transmission art has no prior art against it.

  Vedanti Systems invented among other firsts, The Slice and Partitioning of Macroblocks within a RGB Tri level region in a frame to select or not, the pixel.

  Vedanti Systems invention is used in nearly every wireless chipset and handset in the world

  Our original pixel selection system revolutionized wireless handset communications. An example of this system “Slice” and “Macroblock Partitioning” is used throughout Satellite channel expansion, Wireless partitioning, Telecom – Video Conferencing, Surveillance Cameras, and 2010 developing Media applications.

  Vedanti Systems is a Semiconductor based software, applications, and IP Continuations Intellectual Property company.

  Let’s move onto the other plaintiff, Max Sound. They have a significantly more substantive website. They also have an Android app named Spins HD Audio, which appears to be little more than a music player based on the screenshots.

  Max Sound also has a stock ticker symbol : MAXD. Something clicked into place when I looked up their ticker symbol : While worth only a few pennies, it was worth a few more pennies after this lawsuit was announced, which might be one of the motivations behind the lawsuit.

  Here’s a trick I learned when I was looking for a new tech job last year : When I first look at a company’s website and am trying to figure out what they really do, I head straight to their jobs/careers page. A lot of corporate websites have way too much blathering corporatese that can be tough to cut through. But when I see what mix of talent and specific skills they are hoping to hire, that gives me a much better portrait of what the company does.

  The reason I bring this up is because this tech company doesn’t seem to have jobs/careers page.

  The Lawsuit
  The core complaint centers around Patent 7974339 : Optimized data transmission system and method. It was filed in July 2004 (or possibly as early as January 2002), issued in July 2011, and assigned (purchased ?) by Vedanti in May 2012. The lawsuit alleges that nearly everything Google has ever produced (or, more accurately, purchased) leverages the patented technology.

  The patent itself has 5 drawings. If you’ve ever seen a multimedia codec patent, or any whitepaper on a multimedia codec, you’ve seen these graphs before. E.g., “Raw pixels come in here -> some analysis happens here -> more analysis happens over here -> entropy coding -> final bitstream”. The text of a patent document isn’t meant to be particularly useful. I’ve tried to understand this stuff before and it never goes well. Skimming the text, I just see a blur of the words data, transmission, pixel, and matrix.

  So I read the complaint to try to figure out what this is all about. To summarize the storyline as narrated by the lawsuit, some inventors were unhappy with the state of video compression in 2001 and endeavored to create something better. So they did, and called it the VSL codec. This codec is so far undocumented on the MultimediaWiki, so it probably has yet to be seen “in the wild”. Good luck finding hard technical data on it now since searches for “VSL codec” are overwhelmed by articles about this lawsuit. Also, the original codec probably wasn’t called VSL because VSL is apparently an IP organization formed much later.

  Then, the protagonists of the lawsuit patented the codec. Then, years later, Google wanted to purchase a video codec that they could open source and use to supplant H.264.

  The complaint goes on to allege that in 2010, Google specifically contacted VSL to possibly license or acquire this mysterious VSL technology. Google was allegedly allowed to study the technology, eventually decided not to continue discussions, and shipped back the proprietary materials.

  Here’s where things get weird. When Google shipped back the materials, they allegedly shipped back a bunch of Post-It notes. The notes are alleged to contain a ton of incriminating evidence. The lawsuit claims that the notes contained such tidbits as :

  • Google was concerned that its infringement could be considered “recklessness” (the standard applicable to willful infringement) ;
  • Google personnel should “try” to destroy incriminating emails ;
  • Google should consider a “design around” because it was facing a “risk of litigation.”

  Actually, given Google’s acquisition of On2, I can totally believe that last one (On2’s codecs have famously contained a lot of weirdness which is commonly suspected to be attributable to designing around known patents).

  Anyway, a lot of this case seems to hinge on the authenticity of these Post-It notes :

  “65. The Post-It notes are unequivocal evidence of Google’s knowledge of the ’339 Patent and infringement by Defendants”

  I wish I could find a stock photo of a stack of Post-It notes in an evidence bag.

  I’ve worked at big technology companies. Big tech companies these days are very diligent about indoctrinating employees about IP liability issues. The reason this Post-It situation strikes me as odd is because the alleged contents of the notes basically outline everything the corporate lawyers tell you NOT to do.

  Analysis
  I’m trying to determine what specific algorithms and coding techniques. I guess I was expecting to see a specific claim that, “Our patent outlines this specific coding technique and here is unequivocal proof that Google A) uses the same technique, and B) specifically did so after looking at our patent.” I didn’t find that (well, a bit of part B, c.f., the Post-It note debacle), but maybe that’s not how these patent lawsuits operate. I’ve never kept up before.

  Maybe it’s just a patent troll. Maybe it’s for the stock bump. I’m expecting to see pump-n-dump stock spam featuring the stock symbol MAXD anytime now.

  I’ve never been interested in following a lawsuit case carefully before. I suddenly find myself wondering if I can subscribe to the RSS feed for this case ? Too much to hope for. But I found this item through Pando and maybe they’ll stay on top of it.