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Old 09-30-2010, 11:24 AM   #1
adq
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Working kindlet development without the KDK

Hi, I have managed to persuade my Kindle 3 to load and run a (very simple) kindlet I've written. I do not have access to the KDK: I am using jars I pulled off the kindle itself to develop against.

The trickiest bit was figuring out how to sign a "developer" kindlet properly.

There are details and a demo kindlet source and binary here: http://adq.livejournal.com

BTW: thanks for the jailbreak and usbnetwork patches; they're really cleanly done, and saved me loads of time!
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Old 09-30-2010, 01:12 PM   #2
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Welcome to MobileRead, adq.
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Old 09-30-2010, 03:38 PM   #3
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Looks like a great start without the KDK, well done!
Hope it encourages some other developers to do some interesting things :-)
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Old 09-30-2010, 07:03 PM   #4
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Ta. Some (probably obvious) ideas:

* Better manga reader - the built in one seems rather buggy!
* Something like chrome-to-phone to get links onto the kindle more easily.
* I think the kindle has some sort of USB host capability. I'm not yet sure if the external USB connector is switchable, but if it is, attaching a mobile phone with camera would make an instant document scanner...

Myself, I'm now in the middle of writing a infocom text adventure kindlet for it; I think the kindle is ideally suited for that!
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Old 09-30-2010, 09:58 PM   #5
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Really nice work.

I noticed that there are some very functional java decompilers available, such as
this guy. It's true that the Amazon's binaries are obfuscated, but there are still some informative strings remaining in there. I'll be looking into recompiling the original java binaries, which, if possible, would open the door to modifying the original Kindle software. Though I haven't explored the low-level workings on this yet, one idea that comes to mind is removing the need for signing kindlets - the Home app could instead detect and load jar files directly. Just a thought.
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Old 10-01-2010, 08:47 AM   #6
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I'd suggest http://www.reversed-java.com/fernflower/

Its online only, but gives the most complete output

You'll need to deobfuscate as the method names are all conflicting and many are invalid. I have a nearly working one, but its broken because it doesn't yet deal with preserving the names of overridden methods. I'd not stuck a link to it on my blog yet because of this issue. http://code.google.com/p/adqmisc/sou.../trunk/jrename

The idea is - deobfuscate, decompile, then load into eclipse as a project and use its code refactoring tools to rename things as you figure out what is doing what.

Last edited by adq; 10-01-2010 at 08:51 AM.
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Old 10-04-2010, 01:00 PM   #7
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Thanks adq!

I wonder, if it's possible to build application using some existing cdc sdk . I've tried to build kindlet with cdc_1.0.jar library, but i'm getting error - "An error occured opening thee file".
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Old 10-04-2010, 10:40 PM   #8
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adq, first of all - Wow! I'm impressed with all the work you've done, and in such short time. Thank you for sharing it.

I took a look at the deobfuscator and the fernflower decompiler tonight. My goal was to compile one of the simpler booklet jars: msp.jar (minesweeper). I was unsuccessful, though I think I got a good feel for the process. I'm not sure if you've been able to recompile any of the jars yet, and I'm wondering if I made a mistake somewhere along the way.

Though I'm familiar with Java, I'm more of a C# and C/C++ developer, so I'm not entirely familiar with Eclipse and some of the workings of Java. Anyway, here's what I did:
  1. Pretty dumb, but it took me a little while to figure out that I should deobfuscate the jar files before decompiling them. I did this with all of the relevant lib files individually in addition to msp.jar. The result was a bunch of new deobfuscated jar files, presumably. I'm not sure it was needed, but framework-impl.jar would throw an exception when attempting to deobfuscate, so i skipped it.
  2. I decompiled the deobfuscated msp.jar and threw it into a new Java project in Eclipse
  3. I threw all of the deobfuscated lib jar files into the project and added them to the build path so they became referenced libraries. As I hoped, this killed a ton of compiler errors, but some remained, such as unrecognized classes (which look like they should have been contained in libraries that were already referenced).

Is this generally the procedure you had in mind for deobfuscating / decompiling the files? I'm wondering if, instead of deobfuscating and referencing the lib jar files, I should have instead expanded them into their class files and deobfuscated / referenced those instead.
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Old 10-05-2010, 12:53 PM   #9
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Excellent find. This will get the MPD client I had in mind for a long time done real sone
Should you be evaluating connecting to some non-standard port (such as MPD in my case) it truly is a shame that they only seem to support http and https.

However, what you can still do stuff like this:

Code:
	KTextArea ktx = new KTextArea();

	@Override
	public void start() {
		try {

			ctx.getRootContainer().add(ktx);
			ctx.getConnectivity().submitConnectivityRequest(
					new ConnectivityHandler() {

						@Override
						public void disabled(NetworkDisabledDetails arg0)
								throws InterruptedException {
							// TODO Auto-generated method stub

						}

						@Override
						public void connected() throws InterruptedException {
							try {
								URL testUrl = new URL("http", "192.168.2.100", 6600,
                                "");
								URLConnection con = testUrl.openConnection();
								DataInputStream dis = new DataInputStream(con
										.getInputStream());
								String inputLine;

								while ((inputLine = dis.readLine()) != null) {
									ktx.append(inputLine);
								}
								
							} catch (Exception e) {
								ktx.append("exception: " + e.getMessage());
							}
						}
					});

		} catch (Exception e) {
			System.out.println("Error Connecting:" + e.getMessage());
			e.printStackTrace();
		}
	}
Of course the device still sends that bad HTML Header
But after that

Mind that the nasty downside to this is that you can't be on usbnet while doing this...
Seems that the Kindle thinks that there is no W-Lan connection if usb0 is up

Sucks from my point of view, especially as we have to do the connection via that connectivity handler but it can't be helped i guess.

Last edited by th0br0; 10-05-2010 at 01:42 PM.
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Old 10-08-2010, 08:48 PM   #10
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Hiya, sorry been busy kindle hacking for the last few days. I have my infocom interpreter app up and running. please see http://adq.livejournal.com/108011.html for details There's a link to the SVN repos for the source in there as well...
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Old 10-08-2010, 08:53 PM   #11
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Quote:
Originally Posted by mubertmumphrey View Post
adq, first of all - Wow! I'm impressed with all the work you've done, and in such short time. Thank you for sharing it.

I took a look at the deobfuscator and the fernflower decompiler tonight. My goal was to compile one of the simpler booklet jars: msp.jar (minesweeper). I was unsuccessful, though I think I got a good feel for the process. I'm not sure if you've been able to recompile any of the jars yet, and I'm wondering if I made a mistake somewhere along the way.

Though I'm familiar with Java, I'm more of a C# and C/C++ developer, so I'm not entirely familiar with Eclipse and some of the workings of Java. Anyway, here's what I did:
  1. Pretty dumb, but it took me a little while to figure out that I should deobfuscate the jar files before decompiling them. I did this with all of the relevant lib files individually in addition to msp.jar. The result was a bunch of new deobfuscated jar files, presumably. I'm not sure it was needed, but framework-impl.jar would throw an exception when attempting to deobfuscate, so i skipped it.
  2. I decompiled the deobfuscated msp.jar and threw it into a new Java project in Eclipse
  3. I threw all of the deobfuscated lib jar files into the project and added them to the build path so they became referenced libraries. As I hoped, this killed a ton of compiler errors, but some remained, such as unrecognized classes (which look like they should have been contained in libraries that were already referenced).

Is this generally the procedure you had in mind for deobfuscating / decompiling the files? I'm wondering if, instead of deobfuscating and referencing the lib jar files, I should have instead expanded them into their class files and deobfuscated / referenced those instead.


What I did was unzip absolutely everything into one directory, then deobfuscate it all into another directory. After that I kinda had to zip up subdirectories and run them through fernfllower individually, because of the limits.

I'm really just interested in finding out how to use their APIs right now, rather than recompiling stuff, so this works ok for that. My decompiler does still have bugs in it I noticed, I'll try and fix them sometime, but I'm now busy with KIF.

Another suggestion would be to use a bytecode disassembler to disassemble the stuff; I think that generally doesn't have the same problem the obfuscated names that decompiled code does, but obviously you're then just looking at raw java VM assembler...
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Old 10-08-2010, 11:57 PM   #12
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Ah ha. Well that's what I suspected might be necessary, if the deobfuscator would make sure naming was consistent across class files if you process them in batch. Do you know if this is the case, and did you have any success with recompilation using your method? It might be worthwhile for me to add batch jar file processing, as decompressing and then recompressing class files seem to be pretty inconvenient, as you alluded to.

Actually, the first thing I did was run the jar files through a disassembler, but my goal is to be able to add new features into the original Kindle software, and attempting this in Java VM assembly isn't my idea of fun.
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Old 10-09-2010, 05:51 AM   #13
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If you unzip everything and deobs it in one go, the names should be consistent except for occasional deobfuscator bugs.

Yeah, I was using the deobs/decompile it to figure out what I wanted to know; if I actually wanted to change things, I'd probably use a disassembler/assembler.
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Old 02-02-2011, 09:34 PM   #14
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Sorry to revive an old thread but I've been trying to run various kindlets (downloaded from the Kindle store) through Fernflower and keep getting an "Invalid archive file" error. Am I missing a step?
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Old 02-02-2011, 10:37 PM   #15
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Quote:
Originally Posted by ChristianGeek View Post
Sorry to revive an old thread but I've been trying to run various kindlets (downloaded from the Kindle store) through Fernflower and keep getting an "Invalid archive file" error. Am I missing a step?
What do you mean by "through Fernflower"?
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