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Fusée Gelée FAQ by Kate Temkin

http://www.ktemkin.com/faq-fusee-gelee/

Kate has collected and answered the most common questions she's gotten regarding Fusée Gelée. Most notably she explains the three "types" of FG hacks, software, hardware (temporary) and hardware (permanent).

Enjoy!

Kate herself responded to this thread on page 26, thanks Kate!

There's a lot more here than I can easily respond to, so apologies if I miss posts or gloss over points.



This is correct-- while there likely will be software chains around for these things in the future, I don't see them as coming along as quickly as f-g. We don't have a non-coldboot exploit chain at all for 5.0.0-- and we haven't looked yet, as we've had other things to focus on and coldboot works. We do have one for 4.1.0, but it's centered around a couple of exploits that we don't want to burn-- we're hoping to use them to get an opportunity to poke around inside T214/Mariko.



I don't view you as particularly hostile, no. I don't know if challenge is generally a good thing-- sometimes you do have to accept that other people have different ethics or viewpoints from yourself and let that pass, especially if they're just doing stuff for fun-- but I don't view your post as hostile.



Jamais Vu (1.0.0 TrustZone hack) isn't my bug, but has been written up, and is just awaiting someone with the skills to have time to do a public interpretation. Déjà Vu is currently centered around the exploit I mentioned above, and we definitely want to hold onto that for as long as it's applicable. It's entirely a Switch bug, too, so I don't see it as being something that needs responsible disclosure.



For Déjà Vu, absolutely. (explained in last quote)



I don't agree that things like tweeting are ego. This is something I work on because I find it a lot of fun to hack on things, and there's definitely an aspect in which it makes me happy when seeing the results of things makes other people happy. There's also an aspect in which I hope that showing these things are possible inspires people to want to learn e.g. reverse engineering. This stuff is cool; and I want to share the excitement with others and lift them up as much as I can.

You don't have to believe me on that or like that that's my goal. I won't hold it against you if you don't. :)



I honestly support people updating when it makes sense; and I recognize that there's a conflict between holding back information and enabling others to make reasonable decisions about that. I don't like or feel good about secrecy, and I know it has implications. I've tried to be as clear as I can about the costs regarding updating without crossing the line into giving things away.



I think we've been pretty clear that 4.1.0 will eventually see a non-coldboot, software-only exploit with the same level of power. That's actually been posted on the ReSwitched Discord's FAQ for months, but I know the message gets skewed as its gets communicated over to other places. That's part of why I'm here, now-- I want to help clear things up.

The interactions between the operating system and the bootloader-- say on reboot-- are actually fairly limited; and knowing what any of them are is enough to point people at the particular section of bootrom that's vulnerable. That's why I'm not commenting on Fusée Gelée and how it relates to software-only solutions right now. I have said e.g. above that since there's no public way of getting the privileges necessary to run things, 4.1.0 isn't going to see a pure software solution that the public can use at the time that f-g is released. Software exploits will likely come in time; and it's possible we'll come up with things that are even easier than f-g.



I'm not sure if they'll take it seriously enough. I don't know how they are internally-- but I can't just assume they'll fail to do anything and skip disclosure. Honestly, I don't think a "security advisory" is really a bad thing, either-- there are definitely applications of Tegra chips that I and/or the public don't know about. If giving NVIDIA notice gives them time to explain exactly what's dangerous and allow their customers to remove and replace units from places where the vulnerability can cause harm, I consider that a win, and well worth delaying some public switch hacks by a few months.

I'll also say that my fear that vendors won't take the vulnerability seriously is a huge reason I'm so keen to get things out there-- and why I provided a date after which I'll tell the public what's going on that I've said was non-negotiable. I want to make sure this doesn't get hidden, and that people understand exactly what f-g can and can't accomplish, to minimize FUD while also letting people understand the actual risks are associated with using a vulnerable device.



It changes this from an exploit that's going to be usable before the affected people know it's a thing to something that people may have a chance to react to. Making the vulnerability public without disclosure really increases the odds someone is capable of using it to do bad.

I didn't really give NVIDIA a chance to sell-off stock; though. I've said publicly multiple times that there are bugs in Tegra processors well before NVIDIA reached out to me seeking disclosure. If anything, I think telling the public that these vulnerabilities exist while pursuing disclosure helps developers interested in using Tegra chips in the future ask the right question.



I've already said that while pure-software stuff is doable on 4.1.0; it'll be a wait. As far as I'm remembering, the only part of the chain that could require multiple tries to work is PegaSwitch, which is our browser-based entry point, and I haven't even tried the browser entry point that'll eventually be public to see how reliable it is. SciresM did the work to get our non-coldboot exploit working on 4.1.0; not me. :)



Yeah, that's hard-- especially as everyone has a different view as to how inconvenient things are. I don't know of a way to communicate this better without more details.

Incidentally, the 'inconvenience' verbiage came from SciresM and I discussing our respective views on updating. I think SciresM is more towards the opinion that people should hold back more often, where I'm more of the opinion that updating can be a good and reasonable option sometimes. The way we wound up phrasing things is a compromise between views.



(I'm going to assume this meant "on the hacking side". If not I'm not sure what hacking site you're referring to.)

Updating to latest just closes the possibility of using software exploits launched from Horizon, which can make setup more difficult. I know you'd like to know how much, but I unfortunately don't have a good way of qualifying that. As I've mentioned, if you're suffering from not being able to use your 3.0.1+ Switch, you probably do want to upgrade and just risk things being more inconvenient in the future. Worst comes to worst, if you decide you can't tolerate the inconvenience, you upgrade and then wind up having to figure out a modchip.

The downgrade protection fuses literally mean nothing to a system with f-g, which can entirely skip the downgrade check. Incidentally, SciresM actually accidentally bricked one of his systems in a way such that it was always failing the downgrade checks, and he's been able to use f-g to get that system up and running again.



I don't think that's clear at all, nor do I want to confirm or deny this. Sorry.



I think you're making a bunch of assumptions here, and that's maybe not a great idea. I'm not saying you're necessarily right or wrong; just that I don't think your assumptions are founded.



I don't think this contradicts. This is talking about vulnerabilities that aren't f-g; not because f-g doesn't work on 4.1.0, but because it's possible we may come up with vulnerabilities that are even nicer on 4.1.0 in the future.



I'm being as clear as I feel I can, and adding clarifications e.g. here where I think it helps. There will be different names for the the ways you can use f-g eventually; and I'll be fully open about everything once the summer rolls around and I'm not putting the disclosure timeline in jeopardy.



I know and have said about that this "bring your own exploit" business makes development exclusive, and that's exclusionary and I really don't like it-- I just don't see a way around it. I would love to get more developers and more perspective, and that's why my release date for f-g is tied to my disclosure timeline and not in particular to Atmosphère's release.




I've tried to point out approximately what the difficulty would be for some of the options to kind of provide this, but this is a hard thing to accomplish. In this case, providing details that are more specific really points a finger at vulnerability details, so there's not much I'm comfortable sharing. I've shared what I could-- as a data point, some of the other teams have outright stated that they think I've shared too much already and made things obvious. I don't agree or necessarily care about their opinons, but c'est la vie.



Well, this isn't the case. This has been disclosed to Nintendo, too-- as NVIDIA shares their vulnerability findings with downstream customers. It's more general malicious actors that I'd be worried about.



See above-- but I don't think I'd advise specifically updating to 4.1.0 unless that gives you enough access to the games you want.



I'm also super glad that we can do a lot of our work in the open. I hope there's a lot more of it in the future-- and I'd love to stream some of it. :)



I find the requirement disheartening as well, but I think this is the right way to do things, for now. I've explained my rationale above; feel free to ask questions.



I'm not sure why people are against communication, here. There were definite benefits to talking about f-g in the first place; including that it demonstrates that Tegra chips are vulnerable-- which hopefully influences buying decisions in the future and puts pressure on NVIDIA to seek as much of a fix as they can. After that there seemed to be definitely benefits to talking about more details, even in the limited sense that I'm able to. I've tried to give people more information than the nothing they would have had so they could have more of an idea whether it's be a good idea to e.g. pre-order a modchip or update their system. I know it can be frustrating to not get full disclosure, and that more information would help people to make a better or more conclusive decision, but full disclosure isn't an option until this summer. I don't think that's a reason to hold back information.



I don't have specific answers to your questions, unfortunately-- but I think it sounds like the main purpose of this Switch is as a gaming device and maybe you should upgrade and enjoy playing games with your son.



I don't think that asking for clarification is criticism. It might be rude to push me to answer something I said I wouldn't, but I don't think there's harm in answer.



I don't think I've said anything about opening the console or not. See above for my views on updating?



I'm not sure where you got this impression, or why you're confident about things enough to claim you know about the internal values or working of ReSwitched. This is also easily disprovable just from public information--Hedgeberg has tested out f-g on stream. I don't see it as great opsec to enumerate how many people have access to the vulnerability, but we've long had a policy of only giving exploit details to those who actually want to know them and are in a position where they can use them to help. This is a basic security precaution and not about trust.

I'm actually not sure how this is relevant to the broader discussion. Based on your post history, I can tell that you strongly support TX and the option they're providing, and you're welcome to that, but I think throwing around generic unfounded criticism of RS doesn't do much good and distracts from me answering community questions. :)



I don't think they're obviously more convenient, as they exist right now. They're both inherently however-tethered-you-consider-PegaSwitch, take a bunch of time to run, and rely on a pegaswitch entry point.



That's not correct-- everyone on a current hardware revision will be able to install and use CFW the day it's released, if they're willing to put in the effort and potentially take on some minor risk.



I'm actually not sure what you mean by this entire post? Sorry about that-- I'd love to address your ideas, but unfortunately I can't figure out your meaning. :(



That was about me having fun by trying to see if a DIY, cheap modchip option is reasonable. It turns out it is. As you've noted, it's not necessary on any firmware. I just really like the idea that the open exchange of knowledge -- especially when profit's not a motive -- can result in creation of neat options for the community. ^-^



Yep; that's exactly what it means. :)



I don't think this has been at all implied-- and you'd be hard pressed to find a way to make a solder-less Arduino option that even remotely fits in the Switch case. :)

I should also clarify that the DIY option isn't solderless. :)


If you have or are going to get the game anyway, you can. Those versions are pretty much interchangeable in the long-term. :)



Yep-- and it's possible at some point that we'll allow you to install Fake News without Puyo using f-g/Atmosphère. The original plan was to release Atmosphère for 1.0.0 first while we tried to figure out how to deal with Fusée Gelée, but we actually wound up with a disclosure schedule that was faster than we'd thought. :)
 
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smf

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The difference is not every one is rocking 1.0.0 :)

Are you worried that you won't feel superior?

Not really, you also need to press "Volume +" to enter RCM.

The disclosure doesn't mention that, it claims without a valid BCT and bootloader then it will enter RCM anyway.

"Tegra processors include a USB Recovery Mode (RCM), which we can observe to be activated under a number of conditions:

  • If the processor fails to find a valid Boot Control Table (BCT) + bootloader on its boot media;
  • If processor straps are pulled to a particular value e.g. by holding a button combination; or
  • If the processor is rebooted after a particular value is written into a power management controller scratch register."
 

sarkwalvein

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The disclosure doesn't mention that, it claims without a valid BCT and bootloader then it will enter RCM anyway.

"Tegra processors include a USB Recovery Mode (RCM), which we can observe to be activated under a number of conditions:

  • If the processor fails to find a valid Boot Control Table (BCT) + bootloader on its boot media;
  • If processor straps are pulled to a particular value e.g. by holding a button combination; or
  • If the processor is rebooted after a particular value is written into a power management controller scratch register."
This is about case 2: "If processor straps are pulled to a particular value e.g. by holding a button combination", not about case 1.

Source: Page 10 of the disclosure PDF, and sorry, it was "Volume -", not "Volume +",

Disclosure PDF said:
...Boot the Switch in RCM mode. There are three ways to do this, but the first- unseating its eMMC board- is likely the most straightforward:
1. Ensure the Switch cannot boot off its eMMC. The most straightforward way to to this is to open the back cover and remove the socketed eMMC board; corrupting the BCT or bootloader on the eMMC boot partition would also work.
2. Trigger the RCM straps. Hold VOL_DOWN and short pin 10 on the right JoyCon connector to ground while engaging the power button.
3. Set bit 2 of PMC scratch register zero. On modern firmwares, this requires EL3 or pre-sleep BPMP execution.
 
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charlieb

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Are you worried that you won't feel superior?
Not at all, I paid a considerable premium for 1.0.0 on the basis that it would lead to a better end use experience. I also avoided playing games for a very long time which was difficult, so I just want to see that I didnt waste my time and money and that the benefits of 1.0.0 are realised.
 

smf

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This is about case 2: "If processor straps are pulled to a particular value e.g. by holding a button combination", not about case 1.

EDIT: looking for sources to link here...

The question that was asked was essentially "do I need to hold those buttons every time to load CFW" (case 2) and I basically said "no you can remove the BCT" (case 1). I'm not sure what your point is.

Not at all, I paid a considerable premium for 1.0.0 on the basis that it would lead to a better end use experience. I also avoided playing games for a very long time which was difficult, so I just want to see that I didnt waste my time and money and that the benefits of 1.0.0 are realised.

kate has been deliberately vague, but it's unclear whether there are any long term benefits of 1.0.0. On a hunch I sold my <3.0.0 switch when the prices rocketed. I now have a new cheap imported 4.0.1 switch and I am thinking of buying a mariko switch when they come out, having double the memory bandwidth and faster gpu seems like something I would take some inconvenience for.
 

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What I don't see now, do I need to open the switch? Screw something off? Or can I do this short circuit just like that?
fusee.png
 

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Now that its open to everyone, kate could release more info obout it!
And the things that she couldn't talk earlier !

She could, but what is the point? We all know it now.

I believe SciresM has a completely different untethered coldboot exploit for < 5.0

upload_2018-4-24_19-50-49-png.121188


The detail he goes into on his potential "sysmodule save file parse method" sounds like someone already has discovered it. Whether he has broken ASLR and has gone to a lot of trouble is less clear.
 

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So if the pins are shorted and no button combination is pressed, will the console simply boot as usual? Having a button combination to enter recovery mode sounds perfectly reasonable as long as we don't need to mess with the pins every time.
 

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So going by iPhone terminology, it’s semi-tethered rather than tethered? I have no issue having to send the payload by USB every time as long as I’m not opening the Joy-Con every time.
As long as having a PC near to you to send the payload every time you power cycle is not a problem for you, then you are good to go, I guess.
 
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