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0-click deanonymization attack targeting Signal, Discord, other platforms

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Re: 0-click deanonymization attack targeting Signal, Discord, other platforms

#311

Post by angry_octet »

thayne wrote: post #140

What is the benefit of caching images in a cdn for Signal? Assuming local client-side caching, the total number of requests for that resource should be very small, probably one in the vast majority of cases. On an unrelated note, it seems like CloudFront could very easily fix this by not returning the cf-ray header, or at least having an option for the customer to remove it. Although, it might still be possible to ge…

It isn't caching, it's CDNing. It is just an artefact of CDNs that they act as caches for the original content, and for improved distribution response time they cache to the nearest server from the response. ('Nearest' being an approximate heuristic, it is property of the anycast route tables in the BGP routers the request passes through, it is actually a 'best route'.)

Re: 0-click deanonymization attack targeting Signal, Discord, other platforms

#312

Post by bigiain »

lolinder wrote: post #304
alp1n3_eth wrote: post #275

Earlier quoted context omitted.

Not really. Anyone who wants to conceal what continent they're on will also be using a VPN 24/7, or will have the proxy setup in Signal (AKA running 24/7), which defeats this.

Yep: If your threat model includes an attack like this and you're not always on a VPN already, you're likely already compromised. This is a neat demo, but it should not fundamentally alter the way that anyone is using Signal. Either it doesn't matter to you or you already have mitigations in place.

> If your threat model includes an attack like this

The problem is, nobody's threat model includes state level attackers, until one day it does.

Back when Ulbricht was publicly asking questions using an easily uncovered identity, he wasn't thinking that in a few years he'd have the full force of every relevant TLA in the US (and Five Eyes/14 Eyes) trying to track him down.

Re: 0-click deanonymization attack targeting Signal, Discord, other platforms

#313

Post by autoexec »

hedgedoops2 wrote: post #169
lolinder wrote: post #23

Earlier quoted context omitted.

> Given Cloudflare's less-than-straight approach to sales, it is astonishing the words "secure" and "Signal" ever appear in the same sentence. This is an overly binary take. Security is all about threat models, and for most of us the threat model that Signal is solving is "mainstream for-profit apps snoop on the contents of my messages and use them to build an advertising profile". Most of us using it are not using S…

Maybe not individual warrants (at least not warrants to do non-scalable collections like hardware bugs in one's phone - I.e. warrants that, most users, with high probability, are not subject to). But mass surveillance, e.g. NSA, even with 'mass warrants' (e.g. Verizon-FISA warrant), that everyone is subject to, is probably in most people's attacker model. I don't have a study handy, but it seems reasonable that most…

I highly doubt that signal does anything to help with mass surveillance. Signal started keeping people's name, photo, phone number, and contacts in the cloud protected by a "secure" enclave the NSA almost certainly has access to and hackers already got into (https://community.signalusers.org/t/sgx-cacheout-sgaxe-attac...) and even leaving all that aside, all anyone needs is a PIN that can be trivially brute forced. (https://www.vice.com/en/article/signal-new-pin-feature-worri...)

Re: 0-click deanonymization attack targeting Signal, Discord, other platforms

#314

Post by lolinder »

bigiain wrote: post #312
lolinder wrote: post #304

Earlier quoted context omitted.

Yep: If your threat model includes an attack like this and you're not always on a VPN already, you're likely already compromised. This is a neat demo, but it should not fundamentally alter the way that anyone is using Signal. Either it doesn't matter to you or you already have mitigations in place.

> If your threat model includes an attack like this The problem is, nobody's threat model includes state level attackers, until one day it does. Back when Ulbricht was publicly asking questions using an easily uncovered identity, he wasn't thinking that in a few years he'd have the full force of every relevant TLA in the US (and Five Eyes/14 Eyes) trying to track him down.

But he also chose to go on and found a darknet narcotics service. Most people don't do something like that.

Yes, it's vogue right now to speculate that what you're doing right now could suddenly become illegal in a new administration, but if that happens tomorrow, most of us would be one of hundreds of thousands who are all in the same boat. For that reason, most of us won't get targeted retroactively for behaviors that were legal at the time, and we have the option to reevaluate our security posture when the political landscape changes.

But yeah, if you're actively speculating about starting an illegal service today, you should definitely have a better security posture than Ulbricht did.

Re: 0-click deanonymization attack targeting Signal, Discord, other platforms

#315

Post by gtsop »

adamrezich wrote: post #274
gtsop wrote: post #231

Earlier quoted context omitted.

Interesting you touched on his age. I got extremely curious, why did the OP did such a flex?(assumming they are telling the truth). The first sentence is such a weird brag that it felt suspicious. The report is highly technical and extremely well written. We're either dealing with a pure genious or a fraud. But why would a genious flex? Doesn't make sense.

I don't know what you think is genius about any of this, but you're right, the flex is odd. It's something I've been seeing more and more of lately, and I find it off-putting, because, Back In My Day, I never had such a phase, where I felt like I should be given more credit for my 1337 h4xx0r skillz, because I was in high school or whatever—and I don't remember anyone else doing it, either. I can only assume this is…

I find genius being 15 and being in a state to find this issue and write this report. For my understanding there is a ton of context and knowledge packed in this write-up which i can't possibly imagine myself being able to grasp it at the age of 15. That is not to say it's not possible, but it goes to say it is very hard, that's why i characterise it as genius

Re: 0-click deanonymization attack targeting Signal, Discord, other platforms

#316

Post by gabeio »

vel0city wrote: post #280
radicality wrote: post #273

Earlier quoted context omitted.

Isn’t that because the URL parameters are so long that by design they effectively _are_ the password protection for the resource ? They shouldn’t be able to ‘leak’ to unintended recipients. Personally, like you I’m also not a huge fan of this, but URLs like that basically should be treated as the passwords. Don’t post them publicly / don’t give them out to people you don’t trust.

There's a part of me that's fine with it for a short-lived URL which contains a temporary access key but for a forever URL with a forever access key I'm not entirely happy with it. I use it to share memes and shitpost but definitely not something to share sensitive content IMO.

For signal then the issue becomes saving who owns what image (so that you can re-issue “passwords”) and THAT is much more dangerous to the users than simply allowing users to grab semi-anonymous links into their cdn with enough of a url to be nearly impossible to iterate through every combination without hitting tons of rate limits. (Ignoring this location cache timing issue.)

Edit: Actually... (in signal's case) it might be possible to provide the user's device 2 tokens, 1 to access the url and 1 to issue new access links. Then the user can request a new access link with their second token when their url access token expires. Signatures would help prevent it from needing to be stored in the database. It would be interesting to try.

Edit2: Also I am now curious... does this mean only text messages are e2ee? yikes.

Re: 0-click deanonymization attack targeting Signal, Discord, other platforms

#317

Post by bigiain »

genewitch wrote: post #214
lxgr wrote: post #142

Earlier quoted context omitted.

It's not stretching it. The expectation is that Signal does not reveal any observable aspect of your IP address or location when receiving messages on it. Whether this specific level/type of deanonymization is a problem for your particular use case is an entirely different question. Personally, I wouldn't even care if mutual contacts were to see my IP address outright (and they do for calls), but I'm not every user.

I don't care if users see "my" ipv4 because cgnat. I think i don't care if they can see my ipv6 because each machine gets a /64 to itself, that's the logic, right? But my PBX and my matrix server both use coturn. Our 10 user "private" PBX we have to VPN into a fortigate in a DC to use, but to my understanding, there's literally no way to eavesdrop on those calls without already compromising the server it's running on…

> to my understanding, there's literally no way to eavesdrop on those calls without already compromising the server it's running on

That's probably correct (with the caveat that I suspect NSA/FSB/MSS/Mossad/whoever can reasonably be assumed to have backdoored Fortinet)

There is still the problem that an attacker with "global passive observer" capabilities (which almost certainly includes most non 3rd world nation states, and probably a few of the more problematic 3rd world ones too) can still do traffic analysis to uncover your social network (or criminal/terrorist/whistleblower/journalistic network) by identifying the call traffic endpoints.

Re: 0-click deanonymization attack targeting Signal, Discord, other platforms

#318

Post by iforgot22 »

internet_points wrote: post #2

So if you send a picture to a Signal user, it's retrieved via cloudflare, and cached in a data center near that user; now you can look up the cache status and find the data center used. I'd say "deanonymization" is stretching it, unless the user is in the middle of nowhere (no other users near the data center). But interesting writeup anyway.

Looks like it's possible to hit 2 datacenters due to load-balancing, which would narrow it down a bit more. Suppose you do this repeatedly as the target is moving around, hitting even more datacenters.

Re: 0-click deanonymization attack targeting Signal, Discord, other platforms

#319

Post by bigiain »

genewitch wrote: post #214
lxgr wrote: post #142

Earlier quoted context omitted.

It's not stretching it. The expectation is that Signal does not reveal any observable aspect of your IP address or location when receiving messages on it. Whether this specific level/type of deanonymization is a problem for your particular use case is an entirely different question. Personally, I wouldn't even care if mutual contacts were to see my IP address outright (and they do for calls), but I'm not every user.

I don't care if users see "my" ipv4 because cgnat. I think i don't care if they can see my ipv6 because each machine gets a /64 to itself, that's the logic, right? But my PBX and my matrix server both use coturn. Our 10 user "private" PBX we have to VPN into a fortigate in a DC to use, but to my understanding, there's literally no way to eavesdrop on those calls without already compromising the server it's running on…

> I think i don't care if they can see my ipv6 because each machine gets a /64 to itself, that's the logic, right?

I suspect you're looking at that wrong.

It's each internet connection that gets a /64, not each machine. Your ISP hands you a /64 and you can do whatever you like with it on your home(/corporate) network.

So you can choose from 18 thousand trillion IPV6 addresses for any machine behind your ISP/internet connection, but the top half of your IPV6 address uniquely identifies that ISP and they can connect that to your account/payment details, with 4 billion times as much precision as an IPV4 address.

Re: 0-click deanonymization attack targeting Signal, Discord, other platforms

#320

Post by iforgot22 »

gtsop wrote: post #231
byearthithatius wrote: post #223

Earlier quoted context omitted.

I would guess some are just jealous of his age, but some do find the claim of de anonymizing to simply be overblown given it doesn't tell you nearly enough to find anyone except in very niche cases. This "attack" is easily defeated with a VPN or living in any major city.

Interesting you touched on his age. I got extremely curious, why did the OP did such a flex?(assumming they are telling the truth). The first sentence is such a weird brag that it felt suspicious. The report is highly technical and extremely well written. We're either dealing with a pure genious or a fraud. But why would a genious flex? Doesn't make sense.

I can believe a very talented 15yo pulling this off. But the number of anonymous "I'm 15 and this is my impressive feat" posts on HN made me wonder if it's just a joke.
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