Reset Glitch Hack : Nex exploit for Xbox 360

itchy · Aug 28, 2011

Reset Glitch Hack : New exploit for Xbox 360

The french developer and hacker, GliGli, is proud to release via XboxHacker forums, what most of us are waiting for since more than one year: a new exploit for the Xbox 360. This new Hack is called "Reset Glitch Hack" and needs the installation of a chip. The Reset Glitch Hack is compatible with most 360 models: all the Xbox Slims models and for FAT, Zephyr and Jasper are working for now (Falcon will be released when the devs will have one at hand)

To explain it (very) simply, the chip sends little pulses to the processor in order to distabilize the console and make it believe a modified CB is correctly hashed and signed. This operation doesn't succeed every time, but it is repeated till it works. Once the modified/hacked CB is validated by the console, it has enough rights to launch unsigned code and in our case, XeLL, the Xenon Linux Loader. For full details, read GliGli's explanation of his hack, you can also have a look at the source code of Hack available HERE.

Advantages of this Hack :
- All the 360 expect the Xenons will be compatible.
- It's unpatchable, in fact the CB is involved so early in the console boot process that it can't be revoked

Drawbacks:
- A chip is needed.
- The boot time varies and it can take up to a few minutes to run unsigned code.

Click to expand...

Full explanation :

***************************************
* The Xbox 360 reset glitch hack *
***************************************

Introduction / some important facts
===================================

tmbinc said it himself, software based approaches of running unsigned code on the 360 mostly don't work, it was designed to be secure from a software point of view.

The processor starts running code from ROM (1bl) , which then starts loading a RSA signed and RC4 crypted piece of code from NAND (CB).

CB then initialises the processor security engine, its task will be to do real time encryption and hash check of physical DRAM memory. From what we found, it's using AES128 for crypto and strong (Toeplitz ?) hashing. The crypto is different each boot because it is seeded at least from:
- A hash of the entire fuseset.
- The timebase counter value.
- A truly random value that comes from the hardware random number generator the processor embeds. on fats, that RNG could be electronically deactivated, but there's a check for "apparent randomness" (merely a count of 1 bits) in CB, it just waits for a seemingly proper random number.

CB can then run some kind of simple bytecode based software engine whose task will mainly be to initialise DRAM, CB can then load the next bootloader (CD) from NAND into it, and run it.

Basically, CD will load a base kernel from NAND, patch it and run it.

That kernel contains a small privileged piece of code (hypervisor), when the console runs, this is the only code that would have enough rights to run unsigned code.
In kernel versions 4532/4548, a critical flaw in it appeared, and all known 360 hacks needed to run one of those kernels and exploit that flaw to run unsigned code.
On current 360s, CD contains a hash of those 2 kernels and will stop the boot process if you try to load them.
The hypervisor is a relatively small piece of code to check for flaws and apparently no newer ones has any flaws that could allow running unsigned code.

On the other hand, tmbinc said the 360 wasn't designed to withstand certain hardware attacks such as the timing attack and "glitching".

Glitching here is basically the process of triggering processor bugs by electronical means.

This is the way we used to be able to run unsigned code.

The reset glitch in a few words
=======================

We found that by sending a tiny reset pulse to the processor while it is slowed down does not reset it but instead changes the way the code runs, it seems it's very efficient at making bootloaders memcmp functions always return "no differences". memcmp is often used to check the next bootloader SHA hash against a stored one, allowing it to run if they are the same. So we can put a bootloader that would fail hash check in NAND, glitch the previous one and that bootloader will run, allowing almost any code to run.

Details for the fat hack
=================

On fats, the bootloader we glitch is CB, so we can run the CD we want.

cjak found that by asserting the CPU_PLL_BYPASS signal, the CPU clock is slowed down a lot, there's a test point on the motherboard that's a fraction of CPU speed, it's 200Mhz when the dash runs, 66.6Mhz when the console boots, and 520Khz when that signal is asserted.

So it goes like that:
- We assert CPU_PLL_BYPASS around POST code 36 (hex).
- We wait for POST 39 start (POST 39 is the memcmp between stored hash and image hash), and start a counter.
- When that counter has reached a precise value (it's often around 62% of entire POST 39 length), we send a 100ns pulse on CPU_RESET.
- We wait some time and then we deassert CPU_PLL_BYPASS.
- The cpu speed goes back to normal, and with a bit of luck, instead of getting POST error AD, the boot process continues and CB runs our custom CD.

The NAND contains a zero-paired CB, our payload in a custom CD, and a modified SMC image.
A glitch being unreliable by nature, we use a modified SMC image that reboots infinitely (ie stock images reboot 5 times and then go RROD) until the console has booted properly.
In most cases, the glitch succeeds in less than 30 seconds from power on that way.

Details for the slim hack
==================

The bootloader we glitch is CB_A, so we can run the CB_B we want.

On slims, we weren't able to find a motherboard track for CPU_PLL_BYPASS.
Our first idea was to remove the 27Mhz master 360 crystal and generate our own clock instead but it was a difficult modification and it didn't yield good results.
We then looked for other ways to slow the CPU clock down and found that the HANA chip had configurable PLL registers for the 100Mhz clock that feeds CPU and GPU differential pairs.
Apparently those registers are written by the SMC through an I2C bus.
I2C bus can be freely accessed, it's even available on a header (J2C3).
So the HANA chip will now become our weapon of choice to slow the CPU down (sorry tmbinc, you can't always be right, it isn't boring and it does sit on an interesting bus

So it goes like that:
- We send an i2c command to the HANA to slow down the CPU at POST code D8 .
- We wait for POST DA start (POST DA is the memcmp between stored hash and image hash), and start a counter.
- When that counter has reached a precise value, we send a 20ns pulse on CPU_RESET.
- We wait some time and then we send an i2c command to the HANA to restore regular CPU clock.
- The cpu speed goes back to normal, and with a bit of luck, instead of getting POST error F2, the boot process continues and CB_A runs our custom CB_B.

When CB_B starts, DRAM isn't initialised so we chose to only apply a few patches to it so that it can run any CD, the patches are:
- Always activate zero-paired mode, so that we can use a modified SMC image.
- Don't decrypt CD, instead expect a plaintext CD in NAND.
- Don't stop the boot process if CD hash isn't good.

CB_B is RC4 crypted, the key comes from the CPU key, so how do we patch CB_B without knowing the CPU key?
RC4 is basically:
crypted = plaintext xor pseudo-random-keystream
So if we know plaintext and crypted, we can get the keystream, and with the keystream, we can encrypt our own code. It goes like that:
guessed-pseudo-random-keystream = crypted xor plaintext
new-crypted = guessed-pseudo-random-keystream xor plaintext-patch
You could think there's a chicken and egg problem, how did we get plaintext in the first place?
Easy: we had plaintext CBs from fat consoles, and we thought the first few bytes of code would be the same as the new CB_B, so we could encrypt a tiny piece of code to dump the CPU key and decrypt CB_B!

The NAND contains CB_A, a patched CB_B, our payload in a custom plaintext CD, and a modified SMC image.
The SMC image is modified to have infinite reboot, and to prevent it from periodically sending I2C commands while we send ours.

Now, maybe you haven't realised yet, but CB_A contains no checks on revocation fuses, so it's an unpatchable hack !

Caveats
======

Nothing is ever perfect, so there are a few caveats to that hack:
- Even in the glitch we found is pretty reliable (25% success rate per try on average), it can take up to a few minutes to boot to unsigned code.
- That success rate seems to depend on something like the hash of the modified bootloader we want to run (CD for fats and CB_B for slims).
- It requires precise and fast hardware to be able to send the reset pulse.

Our current implementation
=====================

We used a Xilinx CoolRunner II CPLD (xc2c64a) board, because it's fast, precise, updatable, cheap and can work with 2 different voltage levels at the same time.
We use the 48Mhz standby clock from the 360 for the glitch counter. For the slim hack, the counter even runs at 96Mhz (incremented on rising and falling edges of clock)
The cpld code is written in VHDL.
We need it to be aware of the current POST code, our first implementations used the whole 8 bits POST port for this, but we are now able to detect the changes of only 1 POST bit, making wiring easier.

Conclusion
========

We tried not to include any MS copyrighted code in the released hack tools.
The purpose of this hack is to run Xell and other free software, I (GliGli) did NOT do it to promote piracy or anything related, I just want to be able to do whatever I want with the hardware I bought, including running my own native code on it.

Credits
=====

GliGli, Tiros: Reverse engineering and hack development.
cOz: Reverse engineering, beta testing.
Razkar, tuxuser: beta testing.
cjak, Redline99, SeventhSon, tmbinc, anyone I forgot... : Prior reverse engineering and/or hacking work on the 360
Click to expand...

Source :
http://www.logic-sunrise.com/
http://www.xboxhacker.org

Xbox hacker topic :
http://www.xboxhacker.org/index.php?topic=16949.0

Hawk · Aug 28, 2011

This could be impressive. Probably wont be too long before the mod chips star coming out if true.

Hawk

ExcruciationX · Aug 28, 2011

Hawk said: ↑

This could be impressive. Probably wont be too long before the mod chips star coming out if true.

Hawk
Click to expand...

yah mang

Hopefully we'll start seeing an actual homebrew scene as well.

hacker360 · Nov 5, 2015

............

adrianc · Aug 28, 2011

Fuckin a!

Gratz to the xbox scene, let's se how m$ responds

-adrianc

ddxcb · Aug 28, 2011

adrianc said: ↑

Fuckin a!

Gratz to the xbox scene, let's se how m$ responds

-adrianc
Click to expand...

They can patch it with trinity 2.0

sneakypeanut · Aug 28, 2011

fuck sake now i blown Â£110 on stuff for this exploit dam you scene dam you

InsaneNutter · Aug 29, 2011

Hopefully the Xbox 360 homebrew scene will now explode, like what happened in the original Xbox days. Unlike the Jtag hack any console on sale today can be exploited now.

In comparison by the time the Jtag hack was developed to a point where it was ready to be released, it had been patched for months making obtaining a Jtaggable console not so easily done. Now there is a massive potential audience for Xbox 360 homebrew i hope some great things will happen.

halo3 · Aug 29, 2011

InsaneNutter said: ↑

Hopefully the Xbox 360 homebrew scene will now explode, like what happened in the original Xbox days. Unlike the Jtag hack any console on sale today can be exploited now.

In comparison by the time the Jtag hack was developed to a point where it was ready to be released, it had been patched for months making obtaining a Jtaggable console not so easily done. Now there is a massive potential audience for Xbox 360 homebrew i hope some great things will happen.
Click to expand...

Only thing is this method requires tools that aren't cheap, and this method requires a good ammount of hardware and software done. So I don't think this will explode the xbox 360 homebrew scene until atleast a cheaper improved method is come up with.

sneakypeanut · Aug 29, 2011

halo3 said: ↑

Only thing is this method requires tools that aren't cheap, and this method requires a good ammount of hardware and software done. So I don't think this will explode the xbox 360 homebrew scene until atleast a cheaper improved method is come up with.
Click to expand...

expensive... bull shit the dev board cost me Â£10 that was cheaper than most modchips were back in the day. the fact that u can now hack any box and the the posibility of some proper modchips for the 360 means the scene is bound to grow

Cancerous1 · Aug 29, 2011

halo3 said: ↑

Only thing is this method requires tools that aren't cheap, and this method requires a good ammount of hardware and software done. So I don't think this will explode the xbox 360 homebrew scene until atleast a cheaper improved method is come up with.
Click to expand...

this method requires a 15$ chip and has schematics to make the programmer required if you cant afford a $12 parallel jtag programmer?? what do you mean? its cheaper than a nandx

_SD_ · Aug 29, 2011

So using this hack, how easy is it to make an Xbox multi-region? I also assume this means no XBL?

Hawk · Aug 29, 2011

_SD_ said: ↑

So using this hack, how easy is it to make an Xbox multi-region? I also assume this means no XBL?
Click to expand...

Pretty easy if you know what you are doing.

And yeah this is really cheap, I bought everything for under $50 USD, wait until the modchips come out those will be expensive, but will also make it really easy.

Hawk

halo3 · Aug 29, 2011

Cancerous1 said: ↑

this method requires a 15$ chip and has schematics to make the programmer required if you cant afford a $12 parallel jtag programmer?? what do you mean? its cheaper than a nandx
Click to expand...

The chip is $17 and then with shipping it comes to about $30; if you need a flasher and dont have an lpt port thats another $20-$50, + there are some other small parts you need to get and ship.
Now compare that to a $20 flasher and 5cent diodes for the normal jtag hack, or if you have an ltp all you need is diodes and resistors.

I still love this hack and I already have everything purchased and being shipped to me, just the only thing is, this is more expensive then the traditional jtag hack, thats all.

Hawk · Aug 29, 2011

halo3 said: ↑

The chip is $17 and then with shipping it comes to about $30; if you need a flasher and dont have an lpt port thats another $20-$50, + there are some other small parts you need to get and ship.

Now compare that to a $20 flasher and 5cent diodes for the normal jtag hack. Ntm the normal jtag hack is only a 7 wire install and the 2 diodes while atm this hack requires more hardware and software done.
Click to expand...

the C-Mod, plus LPT programmer =$42 shipped, $8 ebay for sockets, and caps.

And the wires wow there is soooooo many, like 7. Go mod a PS2 from back in the day then complain about wires.

If you was selecting the difficulty in a game this would be like normal as apposed to before it was easy.

Either way this is a great mod, and is pretty cheap and easy to do, if you know what you are doing, get a couple friends in real life to buy chips and just share a programmer that cuts down the cost right there. Once you have a programmer the cost is around $20 for chip and parts, buy from ebay in bulk and its like 1 cent for a cap, 25 cent for a socket.

Or just wait until the dedicated mod chips come out and they'll be more expensive but easier to install.

Cygnos should come back out with a dual nand chip now since you can have one for live and one for the mod now.

Hawk

halo3 · Aug 29, 2011

hawk what are you doing instead of the $50usd jtag programmable cable?

Cancerous1 · Aug 29, 2011

halo3 said: ↑

hawk what are you doing instead of the $50usd jtag programmable cable?
Click to expand...

50$ jtag programming cable?! you should google/read before you post

http://www.ebay.com/itm/Xilinx-Para...920?pt=LH_DefaultDomain_2&hash=item2a1394e2c8

try $12 and free shipping,

and as to your post about $30 shipping on the chip, use google for that too and save money, so the hack isn't expensive you just aren't good at shopping.

billcosbymon · Aug 29, 2011

Damn, I was going to post this.

sneakypeanut · Aug 29, 2011

many hours of googerling later i found it was cheaper to buy it in the states and ship it over to england yeah aparently i live in a country that dosnt have any dev boards in atall

Hawk · Aug 29, 2011

I just bought the jtag3 lpt cable from digilent.com. it was $12.

Hawk

Reset Glitch Hack : Nex exploit for Xbox 360

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Reset Glitch Hack : Nex exploit for Xbox 360

itchy Guest

Hawk Peppy Member

ExcruciationX Active Member

hacker360 Spirited Member

adrianc Spirited Member

ddxcb Gota J.T.A.G. That Xbone Yo.

sneakypeanut Pika CHUUUUUU!!!

InsaneNutter Spirited Member

halo3 Robust Member

sneakypeanut Pika CHUUUUUU!!!

Cancerous1 Rapidly Rising Member

_SD_ Resolute Member

Hawk Peppy Member

halo3 Robust Member

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billcosbymon Guru Meditation Error

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