Kindle Touch (5.0) Jailbreak/Root and SSH

Update Kindle 5.0.3 has fixed the hole to allow for jailbreak. Upgrading an already jailbroken Kindle Touch is fine as the update does not remove the custom key to allow custom packages. If you on 5.0.3 and have not already installed the key, there is a new jailbreak.

So long story short, we can run custom code on the Kindle Touch now but because the operating system has changed so much from Kindle 3, most Kindle modifications will not run without changes. I hope developers will jump to this device now that it’s unlocked. See the bottom of the post for download links. The directions for using are in the readme. Keep reading for technical details on how this came about.

Obtaining the root image
Before we can look for vulnerabilities in the system that would allow us to break in, we need to break into the system and obtain the files that might contain vulnerabilities. Yes, this is a chicken-and-egg problem, but fortunately Amazon is nice enough to help us with this. On every Kindle device is a TTL serial port. I found this port on the bottom of the device when the cover is opened. Fortunately, I did not even have to mess with it, as hondamarlboro and ramirami both managed to get the dump before me. Once we have the root image, it was only a matter of painstakingly looking through all the files to see possible injection vectors.

Looking for the needle

At first, I was digging deep into the system, disassembling and maping out various native libraries, looking for stack overflows (I found a couple but none could be accessed efficiently). I found the bootloader was unlocked but it would be a pain and danger for users (and even developers) to flash custom kernels and such. I also found that the Java code (the Kindle’s entire GUI is written in Java) is NOT obfuscated (which means it would be easier to reverse and later modify) and Amazon has left in many places to place plugins. For example, once someone has the time to figure things out, it would be very possible to write a EPUB extension to read EPUBs from the native reader. There are some other hidden secrets in the device too. The Kindle Touch has an accelerometer and proximity sensor (and a mic, but we know that) but they aren’t used in the software (yet). The more I looked into the system, I was aware that because it was such a huge rewrite, I had misjudged when I assumed that it would be harder to break as Amazon had years to fix the holes now. In fact, I would say that the Kindle 4 is more secure until I found out that Amazon left in SSH in diagnostics mode. Anyways, as I searched up the complexity chain from the bootloader to the kernel to the libraries to the Java interface, I found something very curious. Much of the operating system is no longer written in Java, but are now in HTML5 and Javascript. In fact, many of the interfaces on the Touch are actually web pages in disguise. For example: the password entry screen, the search bar, the browser (is just an HTML page with a frame), the Wifi selection screen, and even the music player. Obviously, these can’t all run natively in HTML and JS, or the device will be even slower (and it is pretty damn slow). What Amazon did is write a couple of Javascript hooks that are implemented by native libraries and events are read by these libraries and they perform actions accordantly. In short, Javascript will run native code. This is a goldmine, there could be many possible ways of using this to our advantage. There could be buffer overflows, heap overflows, string formatting bugs, etc. However, I didn’t have to look though much before I found a curious function: nativeBridge.dbgCmd();. It seems too good to be true. This function takes any shell command, and runs it (as root). Yup. The web browser will run as root, any command given to it. Don’t go looking for remote code execution yet (although it is highly possible), as the native bridge seems to be disabled when in web browser mode (it may be able to be bypassed, but I haven’t looked into it).

Calling the debug function

So the normal browser (as the one you can enter URLs into) can’t make use of this native bridge. However, as I’ve mentioned, a large part of the GUI in the Kindle Touch is HTML and JavaScript. All we need to do is inject some HTML into one of these and we would be all set. We need something that takes input and displays it to the user. The first thing I thought of was the media player. The Kindle displays the song title, artist, and album name in the music player, so what if we put some HTML into the ID3 tag? Yup, it works. How about some javascript? Running. Let’s try to call the debug function. It works. Well, that was a freebie.

Having some fun

That was a bit too easy and I was disappointed that I didn’t get to talk about how I whipped out IDA Pro and did some master debugging. So, let’s make things harder. We can use a MP3 with custom ID3 tags to execute any command, but how can we make this into a cool one-click solution? First of all, we should limit ourselves to one file to copy. Why make the user keep track of MP3s and shell scripts and where to put them? I took the shell script payload (which installs a developer key into the device so custom packages can be installed) and placed it into the comments section of the ID3 tag in the MP3. Then I used “dd” to extract the script, chmod it, and execute it. Now, another problem in terms of user friendliness is how to let the user know that the process was successful? I quickly whipped up an awesome looking “splash screen” and planned on displaying it while the magic is taking place. At first I tried to encode it into a variable in the shell script payload and extract it, but it was too slow and memory intensive. Instead, I took the image, raw, and appended it into the end of the MP3 (after all, the file was a bit too small). You can see the result in the video attached.

What’s next?

Just because the device is jailbroken does not mean it can now magically do anything you want. What needs to happen first is that developers need to take the device and write some code for it. This first jailbreak is really for these developers. For regular users, the only use is to preemptively unlock your device now in case the method is patched in an update or something. No mods for older Kindles will work as-is on the Touch. I’ve included a VERY basic usbnetwork package that will allow you to have SSH access to the device. I think that’s as good of a starting point as anything. From there, developers should be able to rip the root filesystem, test modifications, and write useful tweaks. (And in case of a brick, read my previous post on the bootloader access). Some things I would have to see or do is GUI plugins in the device’s operating system. The Java code is easy to decompile and read as the variable names have not been stripped out (like previous models). Hopefully people can write some reader plugins (like X-Ray) or even format plugins for other ebook formats. Being a touch screen device, one could also write games or useful apps (although the speed and eink are limiting). I need to finish writing the update creation tool so developers can package their modifications.

Download

Download the jailbreak here

Simple custom screensaver mod

Simple usbnet update (supports wifi ssh and resetting root password)

GUI menu launcher and screen rotation hack

Demonstration

Kindle 3.2.1 Jailbreak (Update)

When I first released the Kindle 3.2.1 jailbreak, I called it “temporary.” Although confusing to use and set up, it has gotten thousands of hits and reports of success. However, it was “temporary” because the method used depended on some precise timing and I had a better method that I was saving for Kindle 3.3. Now, I realize that 3.3 will never come, but will instead be 4.0 that will come with Kindle 4, and with a new hardware, everything doesn’t matter. Serge A. Levin has independently discovered a similar bug for what I was going to use on the 3.3 jailbreak, and I’ve asked him to release it because he deserves the credit for the work. If we’re lucky, Amazon will fix the bug in a way that my similar plan for 3.3/4.0 will still work.

(If you are already jailbroken, regardless of what version you’re running, you don’t need to download this. The actual jailbreak hasn’t been updated, just the injection method.)

Also, if you think that the jailbreak didn’t work, try installing a custom package anyways. I have fixed many people’s “I can’t get it working” by telling them that it’s already jailbroken.

Link to jailbreak for all devices on all versions.

EDIT: It seems like there is some confusion so I’ll clear this up. Jailbreaking does NOT remove ads.

PSXperia: Converts any PSX game to work on Xperia Play

After two hard weeks of decompiling, reverse engineering, graphing, and coding, I’m proud to announce PSXperia, a set of tools to extract, patch, and repack the Crash Bandicoot game that comes with all Xperia Play phones to use any PSX game (that you legally own). In addition to allowing you to play any property ripped PSX game, you can also set a custom icon and the game will show up in the phone’s Playstation Pocket app, so you can quickly access it when you flip the gamepad out. I’ve converted and tested 8 games with this tool and they all run flawlessly, but if things don’t work out so smoothly for you, submit your issues to GitHub.

Download the program here and the source here
Setup and usage guide here
Support here
Bug reports here

One more thing: custom recovery kernel for Kindle 3

I didn’t plan to do any more Kindle stuff for a while, but when I made a recovery kernel (prevents your Kindle from bricking) for the Kindle 2/DX as part of my 3.X installer, many asked for a similar protective thing on newer Kindles. Well, here it is.

For now it’s just a kernel with recovery features (export entire filesystem without password or serial port and install custom recovery packages), but maybe if I have the time, one day, I will make it a full custom kernel with additional features or something.

Kindle 3.2.1 Jailbreak

UPDATE: Serge A. Levin has kindly modified my “temporary” jailbreak into a more permanent solution. The information below is now considered old and should be disregarded. Link to jailbreak for all devices on all versions.

 

So I never intended to release a jailbreak for Kindle 3.2.1 because 1) people who got a discount for their Kindles should stick by their commitment and keep the ads and 2) this was an update made purely to disable jailbreaks, so there are no new features. However, from what I heard, more and more people are receiving 3.2.1 as stock firmware (not just ad-supported Kindles) and that people who exchanged their broken Kindles also have 3.2.1. I don’t want to reveal the exploit I found yet (I’m saving it for the next big update), but thankfully, after half an hour of digging, I’ve found another glitch that I can use. The bad news is that this isn’t an “easy one click” jailbreak, it will actually take some effort as some precise timing needs to be correct in order to work.

Technical Details

What is this new glitch you ask? It’s pretty simple and pretty stupid and I feel almost embarrassed to use it (that’s why I’m not even using the word exploit). First of all, the last bug I found was fixed by a regex name check that prevent spaces in names. Now, whenever the Kindle gets an update, before doing anything, it looks for the signature of every file in the update (minus the signature files themselves). They do this by using the “find” command to get a file list and piping the output to “read” where “read” feeds each data (separated by a whitespace) into the signature check function where the function proceeds to use OpenSSL to check the signature. Simple enough. Well, what I want to do is make the signature check ignore a file, and to do it, I make a blank file called “\” (literally a backslash). Now it’s hard to explain what happens, so I’ll show you.

Here’s the output of the find command usually:

$ find /tmp/update

/tmp/update/file.ext

/tmp/update/file2.ext

Now, when I insert my slash-file:

$ find /tmp/update

/tmp/update/file.ext

/tmp/update//tmp/update/file2.ext

What happened? The backslash is used in Linux as an escape character. Basically it says to treat the next character as not-special. Remember that “read” splits the data to be read using whitespace (in this case a new line character), so by escaping the whitespace, I can get the system to ignore /tmp/update/file2.ext, and instead get it to read /tmp/update/tmp/update/file2.ext. In that file, I will include an already signed file from an old Amazon update, and when the updater runs, it ignores the extra files and reads the unsigned file. But we’re not done yet. Amazon doesn’t extract the update to a set folder, it extracts it to /tmp/.update-tmp.$$ where $$ means the process id of the script running. This can be any number from 1 to 32768. So what’s the elegant solution to this problem? I don’t know yet. Until someone can come up with a better idea, I’m going to include PIDs 5000-7000. From my tests, if you run it immediately after a reboot, it will be 64xx, so it’s a test of how bad you want to jailbreak ;)

Installation

Since this jailbreak is time and luck based, I’ve included very detailed directions on the exact timing for doing things in the readme. I suggest reading over the directions before starting, because timing is everything. It works only in a certain window of time after startup, so if it doesn’t work you need to restart and try again. If it doesn’t work after three or more tries, it’s mostly my fault as I only tested it with a Kindle 2 so the timing might be different on the Kindle 3. If you have serial port access on your Kindle 3, send me the otaup log and I’ll change the pid set.

Download

Since this is a temporary fix, I’m not going to add this to my projects list.

Download source and binaries here

EDIT: I’ve heard from some users that you have more chance of succeeding if you don’t have any books to load. So, before doing anything, rename the documents folder to documents.bak and the system folder to system.bak, install the jailbreak, and rename everything back. This should allow more chance of succeeding.

EDIT 2: Some people report turning the wireless off before starting also increases success rates.

Kindle 3.X updater for Kindle 2 and Kindle DX released

After a month and a half of testing thanks to the community of MobileRead, I can finally release the first stable version of the Kindle 3.X software updater (help me come up with a better name, please). If you haven’t read my last few Kindle-related posts (read them if you want more technical details of this script), you should know that this allows you to use all the cool new features of the Kindle 3 on a K2 or DX device. Installation is easy and is only three steps: 1) Use “prepare-kindle” script on old Kindle to back up and flash recovery kernel, 2) Copy generated files to Kindle 3 along with “create-updater” script and run it, 3) Copy generated update package back to old Kindle and restart. If that sounds confusing, don’t worry, the readme contains very detailed directions and even how to recover in case anything goes wrong. Speaking of recovery, a “side effect” of using this is that the custom kernel that you flash in order to run the update package allows recovering without a serial cable and the installation of unsigned recovery packages.

Here it is.

Oh, and in case anyone is wondering why I’m not just distributing a full 3.X update package and making you generate it by yourself, it’s because the Kindle framework and OS are proprietary code. I believe that Amazon didn’t release 3.0 for the DX and K2 because they don’t want to lose business for the Kindle 3. So, by making you have a Kindle 3 in order to use this, I can keep Amazon happy.

Kindle 3.1 Jailbreak

I was bored one weekend and decided to jailbreak the new Kindle firmware. It was time consuming to find bugs, but not difficult. Unlike the iPhone, the Kindle doesn’t really have security. They have a verified FS and signed updates and that’s it, but I will still call my jailbreak an “exploit” just to piss you off. Previous Kindle 3 jailbreaks worked (AFAIK, I haven’t really looked into it) by tricking the Kindle into running a custom script by redirecting a signed script using a syslink. This worked because the updater scans only “files” that do not end with “.sig” (signature files to validate the file). They fixed this now by scanning all non-directorys that do no end with “.sig”. This is the first bug I’ve exploited. Part one is getting the files into the update, which I did by conventionally renaming them to “.sig” even though they’re not signature files. Part two is harder, getting the unsigned script to run.

How the Kindle updater works is that first it gets a list of all files (including files in subfolders, excluding signature files) in the update and checks it’s signature with Amazon’s public keys. If you modify any of the scripts from a previous update, the signature is broken and the Kindle won’t run it. If you add your own scripts, you can’t sign it because you don’t have Amazon’s keys, and finding them would take more then the lifespan of the universe. (SHA256 HMAC). They also use OpenSSL to check the signatures, so trying to buffer overflow or something is out of question (or is it? I haven’t looked into it). Afterwards, when all files are matched with their signatures and checked, the updater reads a “.dat” file which contains a list of all scripts, their MD5 hash and size (to verify, I don’t see the point since they were just signature checked. Maybe a sanity check?). It finds the “.dat” file using “find update*.dat | xargs” which means all the .dat file has to be is start with update and end with .dat. They don’t care what is in between. Next, they read the file using “cat” and with each entry, verify the hash and loads the script. Well, conventionally, “cat” can read multiple files if more then one filename is given in the input. This means if the update*.dat file contains spaces, then “cat” will read every “filename” separated by a space. I took a signed .dat from one of Amazon’s update. Renamed it “update loader.sig .dat” and placed my actual .dat (containing an entry to the script jailbreak.sig, a shell script renamed) in loader.sig. jailbreak.sig untars payload.sig, a renamed tgz file which contains the new keys we want to use to allow custom updates. Amazon’s updater only signature checks “update loader.sig .dat” which is valid. Then cat tries to read the files “update”, “loader.sig”, and “.dat”, one of which exists and the others silently fail. Loader.sig points to the script jailbreak.sig which the updater happily loads thinking it’s already signature checked. Jailbreak.sig, calls tar to extract payload.sig and copies the new keys to /etc/uks and installs a init.d script to allow reverting to Amazon’s keys for installing future updates. Now we own the system again!

tl;dr:

A download to the jailbreak can be found here. Directions are provided in the readme file. Use it at your own risk (I’m not responsible if you somehow brick it) and note that it most likely will void your warranty. Make sure to uninstall all custom updates before you uninstall the jailbreak, as after uninstalling the jailbreak, you cannot run custom packages until you jailbreak again. Directions for switching between custom updates and Amazon updates can be found in the readme file.

Ajax Word Search Solver

I almost forgot about this.

This project was written purely out of my boredom in class. I wanted to learn 1) Javascript, 2) jQuery, 3) JSON, and 4) more Ajax, so I decided to write this simple word search solver. The “backend” (puzzle solving algorithm) is written in PHP not because I didn’t know how to write it in Javascript (ok, maybe it’s because of that),  but because I wanted to try out JSON by allowing PHP to pass the puzzle solutions to Javascript. This word search solver has features such as: solving the puzzle live by highlighting the solution as you type, adding lists of words, removing words from list with delete key or double click, etc.

It’s also very buggy, because as I stated, I wrote this in a few hours with zero knowledge of jQuery/Javascript.

Anyways, here’s the site: http://yifan.lu/wss/ and the source: http://yifan.lu/p/wss

Update: T-Mobile Proxy released: Free unlimited EDGE internet without any plans (for now)

EDIT: This no longer works. If you have the package installed, I would recommend uninstalling it.

I’ve talked about how it works here. In short, I’ve made a proxy server that adds the string “tmobile” to all URL requests on the iPhone because T-Mobile allows internet access to URLs with “tmobile” in it. You can download the deb and install it manually from here. You can also add the repo http://yifan.lu/cydia/ to Cydia. This script works for any unlocked iPhone running T-Mobile including prepaid phones. However, I’m not responsible if you abuse this and get charged. Let’s start the countdown. I predict T-Mobile will have this bug fixed in a month.

Please note that it’s only tested and working on one phone. So it’s pretty beta-ish. If it doesn’t work, please post as much info as you can in the comments, so I can fix it up.

Also, I noticed that it doesn’t work on the internet3.voicestream.com APN. I use wap.voicestream.com and it works there. Another thing that breaks this is any “T-Zones $5.99 hack” (which hasn’t worked for a while now) is installed. The problem is that if you already have a proxy set for ip1 (EDGE/3G) interface, then this won’t work. You can’t modify EDGE/3G proxy information from Preferences.app, so if you manually edited your proxy information in preferences.plist, installed a package that did, or installed a mobile config that did revert the changes to use this.

If all else fails, install my configuration profile by going to http://yifan.lu/cydia/install.mobileconfig from your iPhone and install that configuration profile. It will set the APN and proxy for you.

OSX FaceTime auto-accept script

Another quick half-hour script I wrote. This is an AppleScript that lets you use FaceTime as a video monitor. Just run the script in background, and whenever you want to see your house, just do a FaceTime call to your iMac and the script will accept it.

Assumptions:
1) Nobody else knows your Mac’s FaceTime email. Make it secret, or people can spy on you by calling your email.
2) You haven’t resized FaceTime. I’m lazy so, it closes FaceTime whenever the window size is 638 by 585.

http://pastebin.com/yb3ak41s

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