[dinartem]

Good times. I was the developer at Microsoft who designed the Xbox 360 hardware security, wrote all the boot loaders, and the hypervisor code.

Note to self: you should have added random delays before and after making the POST code visible on the external pins.

[dhx]

Have you seen Tony Chen's (development lead for Xbox One security) description of the Xbox 360 reset glitch hack at [1] and the effect this (and other console exploits of that time) had on Xbox One development?

This is one of my go-to case study videos for the development effort required to architect a computer to resist attackers who have physical access.

[1] https://youtu.be/U7VwtOrwceo?t=536

[spencerflem]

Congratulations, haven't had a reason to mess with it myself, but I've heard it described online as the most secure piece of consumer hardware before or since

[jsheard]

I think you might be mixing up the Xbox 360 with the Xbox One, the former was ultimately compromised in several ways, but the latter's security has held up extremely well for 11 years and counting. The Xbox One and its successor are easily the most secure consoles ever made.

Obligatory: https://www.youtube.com/watch?v=U7VwtOrwceo

[SteveNuts]

I'm curious how it fares against a modern iPhone or similar, has that ever been compared?

[liamwire]

I have a hard time believing the ‘since’ part of that description. Intuition suggests the latest iPhone would take that crown each year.

[notavalleyman]

What are the reasons for why Microsoft wanted to lock down consoles to only run signed code? As a games console manufacturer, what are the business reasons for doing so? Thanks

[nemothekid]

Limiting piracy is the ongoing reason, but there is also the historical reason of the Video game crash of 1983 which led to Nintendo's Seal of Quality.

Essentially as the platform owner, you want to ensure games sold for the platform "just work", and if you have a bunch of third parties running bad software, consumers would lose faith in the platform altogether.

[treyd]

They sell the consoles at a loss, so if you could port your own games to the consoles instead of buying the games that they could take a royalty from then they lose money. It doesn't have to be an effective circumvention to trigger the DMCA making it illegal.

[throwaway48476]

They sell the console at a loss but make 30% on every game sold. The business model is variant of "dumping" but antitrust isn't enforced anymore.

[brokenmachine]

They are rent seekers.

[ashleyn]

business reasons, the console is sold as a loss leader and the real money is made in licensing the games. also serves as brand protection i.e. preventing poor quality third party games from tarnishing the reputation of the console.

[Lammy]

A games console provided a platform where they could more effectively argue that “their” works “““needed””” to be protected so they could farm us (people who want to run their own code on hardware they purchased) for digital-jail technologies which would never otherwise have reason to exist. Then those technologies can metastasize fully-formed over to general-purpose computing in a way that's harder to argue against. They learned with Clipper and Palladium that trying to develop jail tech on PC would be vehemently opposed.

[liamwire]

Can you speak to some of the harder or more interesting challenges you faced during that time?

[dinartem]

One challenge was that while I started working on the Xbox 360 about three years before it would ship, we knew that the custom CPU would not be available until early 2005 (first chips arrived in early February). And there was only supposed to be one hardware spin before final release.

So I had no real hardware to test any of the software I was writing, and no other chips (like the Apple G5 we used as alpha kits) had the custom security hardware or boot sequence like the custom chip would have. But I still needed to provide the first stage boot loader which is stored in ROM inside the CPU weeks before first manufacture.

I ended up writing a simulator of the CPU (instruction level), to make progress on writing the boot code. Obviously my boot code and hypervisor would run perfectly on my simulator since I wrote both!

But IBM had also had a hardware accelerated cycle-accurate simulator that I got to use. I was required to boot the entire Xbox 360 kernel in their simulator before I could release the boot ROM. What takes a few seconds on hardware to boot took over 3 hours in simulation. The POST codes would be displayed every so often to let me know that progress was still being made.

The first CPU arrived on a Friday, by Saturday the electrical engineers flew to Austin to help get the chip on the motherboard and make sure FSB and other busses were all working. I arrived on Monday evening with a laptop containing the source code to the kernel, on Tuesday I compiled and flashed various versions, working through the typical bring-up issues. By Wednesday afternoon the kernel was running Quake, including sound output and controller input.

Three years of preparation to make my contribution to hardware bring-up as short as possible, since I would bottleneck everyone else in the development team until the CPU booted the kernel.

[Dracophoenix]

How did you feel about teenagers and college students exploiting holes in your work? Were you impressed, disappointed, amused, etc.?

Oh and I'd just like to say thank you for your contribution to my childhood/adolescence.

[dvdbloc]

What was the culture like working on this project and back in those days? I’ve always been fascinated by the development of consoles, especially the story of the 360. Any sources you recommend to learn more? I thought the Microsoft documentary on Xbox was the best I’ve found so far.

[jolan]

The Winchester revision is still considered unhackable afaik. It's crazy how many Xbox 360 revisions there were compared to other consoles.

[saturn8601]

Was it ever explained why? This was an unanswered question I always wondered about from time to time. They must have done something to remove RGH capability?

[landr0id]

Wait until you read Grimdoomer’s (yet to be published) write-up on his recent hypervisor exploit that works on the latest OS: https://x.com/grimdoomer/status/1847497275289063676

It’s going to be a doozy

[vlovich123]

I feel like random delays would make the glitch attack harder but it would still be possible given enough attempts. Seems like the bigger issue is that you can glitch the CPU reset line which corrupts the processing rather than having no effect or resetting the CPU.

[kaoD]

I assume those are probably very hard to fix since (again, I assume, I'm just a hobbyist in the hardware space) that sort of glitch relies on propagation delays (e.g. a short burst triggering some latches but not others, or triggering the latches in some specific synchrony).

Can anyone confirm if I'm on the right track with my guess?

[LPisGood]

I’m surprised this was a task that only took a single developer!

[cbanek]

Having a single developer allows fewer offices with their windows completely covered with newspaper. Plus, there's one person doing everything, which can be a lot better than two with people who have different ideas of how to make the system work together.