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Microsoft proves backdoor keys are a bad idea

theregister.co.uk

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Re: Microsoft proves backdoor keys are a bad idea

#31

Post by 45h34jh53k4j »

So from this I think you could say this is a universal microsoft secureboot implementation bypass. all you need is the signed policy file and an older more obscure (signed) non-blacklisted bootmgr and you can exploit secureboot to glory.

its almost certainly going to be used for malware - a return of bootkits for invisibility/persistence?

microsoft will have to keep revoking older bootmgr's as they find them in jailbreak utils and bootkit malware. eventually they will run out, but for now, busted.

tempting to go buy some winRT devices for linux!

Re: Microsoft proves backdoor keys are a bad idea

#32

Post by ge0rg »

Knuff wrote: post #7
bradford wrote: post #5

(disclaimer, MS employee, non-security expert here). I've read through the article, here, and in other places, and I'm seeing sentiment that this is a big fuck up on Microsoft's part. I might be completely misunderstanding, but I just don't see it. In order to use the backdoor, you've got to flash firmware, so, you've got to have physical access to the device. If an attacker has physical access to your device, you're…

The point the register makes is not that this allows unlocking devices (though that's interesting in it's own right), but that is done via a "secret key" that now got exposed. Very similar to what the government wants with key escrows and other backdoor mechanisms for decryption of communication. Maybe to clarify: it highlights the mechanism (golden key) is flawed. That Microsoft uses it for boot loaders is unimporta…

I think thereg didn't get that quite right. From reading the original advisory, I would conclude that this is not a backdoor (a by-design security "override"), but an actual vulnerability in the boot loader, where it does not check the type of the signed data blob (policy vs. supplemental policy) and thus can be exploited to disable further signature checks. The effect is the same of course, both to attackers and to device owners.

One could speculate if this is a backdoor created with plausible deniability, maybe paid for by some three letter agency. But the evidence doesn't really point into the direction of an intentional backdoor.

Re: Microsoft proves backdoor keys are a bad idea

#33

Post by RHSeeger »

theandrewbailey wrote: post #9
bradford wrote: post #5

(disclaimer, MS employee, non-security expert here). I've read through the article, here, and in other places, and I'm seeing sentiment that this is a big fuck up on Microsoft's part. I might be completely misunderstanding, but I just don't see it. In order to use the backdoor, you've got to flash firmware, so, you've got to have physical access to the device. If an attacker has physical access to your device, you're…

From the last section: > To reiterate, these Microsoft-signed resources – the debug-mode policy and the EFI installation tool – are only meant to be used by developers debugging drivers and other low-level operating system code. In the hands of Windows RT slab owners, whose devices are completely locked down, they become surprisingly powerful. > It's akin to giving special secret keys to the police and the Feds that…

Of course, the problem with a digital key is that once it's out in the wild, its out for everyone and forever.

Re: Microsoft proves backdoor keys are a bad idea

#34

Post by mtgx »

bradford wrote: post #26
Knuff wrote: post #7

Earlier quoted context omitted.

The point the register makes is not that this allows unlocking devices (though that's interesting in it's own right), but that is done via a "secret key" that now got exposed. Very similar to what the government wants with key escrows and other backdoor mechanisms for decryption of communication. Maybe to clarify: it highlights the mechanism (golden key) is flawed. That Microsoft uses it for boot loaders is unimporta…

Ok, I get it. The message is "don't use backdoors, because they'll inevitably get leaked", which I agree with. Unfortunately, I don't think that's the message that's being interpreted by the vast majority of readers. I'm delving into opinion territory now, but when the word 'backdoor' is used, aren't most people going to assume that it's an FBI backdoor, instead of a test/development backdoor? This seems like the kin…

A backdoor is a backdoor = unauthorized access to a user's device. What does it matter if it's Microsoft, FBI, or the Chinese government using it? By definition, it can't be "just Microsoft" anyway, as the people who discovered this pointed out, whether it's up to Microsoft or not.

> and no one seems to be doing anything to correct the record.

Maybe Microsoft feels guilty about it? It reminds me of when a journalist asked them about Bitlocker being backdoored, and they refused to comment.

https://www.schneier.com/blog/archives/2015/03/can_the_nsa_b...

Re: Microsoft proves backdoor keys are a bad idea

#35

Post by 45h34jh53k4j »

lawnchair_larry wrote: post #24

What does leaking your private key have to do with backdoor keys? Isn't this like saying that CAs are backdoored because somewhere there exists a private key for those certs?

No private keys were leaked; however a signed policy file, that lets you disable the protections within secureboot was discovered and repurposed.

Its not so much a backdoor key, but an overly permissive mechanism within microsofts secureboot implementation that could be used to implement a backdoor within the system.

A similar analogy in the CA world would be when the Microsoft Terminal Server Licensing CA (which accepted user submitted signing requests) was signing certificates that worked in other contexts (ie: https). This didn't break the CA system globally just one overly permissive implementation.

Re: Microsoft proves backdoor keys are a bad idea

#36

Post by bradford »

pipio21 wrote: post #29
bradford wrote: post #26

Earlier quoted context omitted.

Ok, I get it. The message is "don't use backdoors, because they'll inevitably get leaked", which I agree with. Unfortunately, I don't think that's the message that's being interpreted by the vast majority of readers. I'm delving into opinion territory now, but when the word 'backdoor' is used, aren't most people going to assume that it's an FBI backdoor, instead of a test/development backdoor? This seems like the kin…

I s there any difference between a test/development backdoor and a FBI backdoor?. If you let backdoors in the system, of course the secret services will demand to have it. In fact, backdoors that were put in place because secret services' pressure, will be suited as developer backdoors as an excuse when found by the mainstream. First they install backdoors in systems, in order for MS or the US gobertment to have comp…

I think you're missing my point (and my poor wording probably didn't help).

A backdoor that requires physical access isn't a backdoor. If an attacker has such access, you're already screwed.

A backdoor that requires administrative privileges isn't a backdoor. If an attacker has such access, you're already screwed.

The so-called dev/test 'backdoor' really isn't a backdoor. It's a 'unlock' tool that's required for anyone who's going to engineer the device. My main beef is that this article appears to be re-branding the engineering unlock as a backdoor, and confusion is obviously ensuing.

Again, In my original post, I asked "What's the exploit"? and I understand that the existence of an exploit might not be the article's subject, but If you really think that there's a security problem here, I'll ask it again: "What's the exploit?"

Re: Microsoft proves backdoor keys are a bad idea

#37

Post by TheSpiceIsLife »

bradford wrote: post #5

(disclaimer, MS employee, non-security expert here). I've read through the article, here, and in other places, and I'm seeing sentiment that this is a big fuck up on Microsoft's part. I might be completely misunderstanding, but I just don't see it. In order to use the backdoor, you've got to flash firmware, so, you've got to have physical access to the device. If an attacker has physical access to your device, you're…

If an attacker has physical access to your device, you're already screwed.

I'm no security expert, but is this true?

Say I use full drive encryption, with whatever the popular Linux distros are offering at install time, and Say I use a strong password of 30 random characters.

Is it feasible to break this encryption in a reasonable time frame?

Re: Microsoft proves backdoor keys are a bad idea

#38

Post by andrey_utkin »

TheSpiceIsLife wrote: post #37
bradford wrote: post #5

(disclaimer, MS employee, non-security expert here). I've read through the article, here, and in other places, and I'm seeing sentiment that this is a big fuck up on Microsoft's part. I might be completely misunderstanding, but I just don't see it. In order to use the backdoor, you've got to flash firmware, so, you've got to have physical access to the device. If an attacker has physical access to your device, you're…

If an attacker has physical access to your device, you're already screwed. I'm no security expert, but is this true? Say I use full drive encryption, with whatever the popular Linux distros are offering at install time, and Say I use a strong password of 30 random characters. Is it feasible to break this encryption in a reasonable time frame?

See Evil Maid Attack https://www.schneier.com/blog/archives/2009/10/evil_maid_att...

Re: Microsoft proves backdoor keys are a bad idea

#39

Post by Nullabillity »

bradford wrote: post #36
pipio21 wrote: post #29

Earlier quoted context omitted.

I s there any difference between a test/development backdoor and a FBI backdoor?. If you let backdoors in the system, of course the secret services will demand to have it. In fact, backdoors that were put in place because secret services' pressure, will be suited as developer backdoors as an excuse when found by the mainstream. First they install backdoors in systems, in order for MS or the US gobertment to have comp…

I think you're missing my point (and my poor wording probably didn't help). A backdoor that requires physical access isn't a backdoor. If an attacker has such access, you're already screwed. A backdoor that requires administrative privileges isn't a backdoor. If an attacker has such access, you're already screwed. The so-called dev/test 'backdoor' really isn't a backdoor. It's a 'unlock' tool that's required for anyo…

> A backdoor that requires physical access isn't a backdoor. If an attacker has such access, you're already screwed.

> A backdoor that requires administrative privileges isn't a backdoor. If an attacker has such access, you're already screwed.

Then why bother trying to lock it down in the first place?

Re: Microsoft proves backdoor keys are a bad idea

#40

Post by slg »

daenney wrote: post #2

I genuinely hope this will influence the whole government mandated back door debate for the better but I'm afraid that this will just be forgotten in a matter of minutes. Like Gove said "we've had enough of experts", especially when their educated opinions don't suit us.

If a terrorist attack occurred and it was clear that it could have been prevented if the authorities could have read encrypted information, would that change your opinion of backdoors? If not, why are you criticizing the other side for being just as steadfast in their beliefs as you are in yours?

The truth is that no policy is going to be 100% effective so I'm not sure why either side of the debate should overadjust based on a single failure

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