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WhatsApp backdoor allows snooping on encrypted messages

theguardian.com

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Re: WhatsApp backdoor allows snooping on encrypted messages

#191

Post by nickpsecurity »

geocar wrote: post #130

I remember receiving the downvote brigade[1], when Moxie himself said that I should trust WhatsApp without having the source code and the ability to put it on my device. We (even a "smart" community like HN) clearly do not have the ability to think critically about security, and even when our leaders are sincere -- and I really don't mean to suggest Moxie/Signal was complicit in this move -- we still rush to defend o…

More interesting, I stand by my prediction that WhatApp would have a backdoor in it or start selling information once Facebook acquired it regardless of Moxie's improvements. Looks like I called it again. People need to stay away from this messenger unless they absolutely have to be on it for friends and family. Still encourage them to download Signal for anything private.

Re: WhatsApp backdoor allows snooping on encrypted messages

#192

Post by jgaa »

dr_zoidberg wrote: post #185
jgaa wrote: post #182

I think it's pretty obvious that we cannot trust any messenger app that is closed source or relies on some company's service infrastructure. If it's closed source, you cannot possible know what it does. If it's relying on a company's infrastructure, it's likely to be banned by oppressive governments (and that includes most of the so called "free world"). In frustration over my own Government (Norway), I started last…

> If it's closed source, you cannot possible know what it does. You can set up a wifi and try to MitM yourself and see what packets WhatsApp is sending/receiving. Then you can try to snoop on them and test. The fact that it is closed source doesn't mean you can't analyze it, it just means it's a black box that you have to carefully dissect.

You can get some idea by looking at where the packages are going - but in todays ipv4 space, most p2p packages have to transit trough some public IP addresses. That means that, unless you are able to decrypt the traffic, it will be difficult to know if someone is listening in on the conversation. Also, just by looking at the packages, you will not have any means to detect back-doors, unless they are accessed while you are looking. Back-doors potentially requested by intelligence agencies for snooping on high value targets are likely to go undetected.

Re: WhatsApp backdoor allows snooping on encrypted messages

#193

Post by FabHK »

lucastx wrote: post #132
FabHK wrote: post #96

Earlier quoted context omitted.

Hehe, yes, but the point is this: if you had verified fingerprints with Bob and are happily chatting with him, all the messages that reached him (two tick marks in WhatsApp) are safe. Only those that have not yet been delivered (one tick mark) would, when the server sends you you a new key, be re-encrypted and re-sent. All of this, as usual, is predicated on the client behaving as promised.

From the news article: Boelter said: “[Some] might say that this vulnerability could only be abused to snoop on ‘single’ targeted messages, not entire conversations. This is not true if you consider that the WhatsApp server can just forward messages without sending the ‘message was received by recipient’ notification (or the double tick), which users might not notice. Using the retransmission vulnerability, the Whats…

I guess what they're suggesting is to compromise the server in such a way that it does not send "delivered" receipts for any messages anymore (even though it actually delivers them to Bob, and Bob answers, and a "normal" conversation ensues).

Then, at some point later, Eve on the compromised server could send a "oops, here's a new key, send everything undelivered again" message. Then, the client, as it is now, would just re-encrypt and re-send all those messages it deems undelivered so far (and then pop up the "key changed" message, if you had requested it in the settings).

You'd recognise the attack by seeing only single ticks on messages, even if Bob had seen them and answered.

Re: WhatsApp backdoor allows snooping on encrypted messages

#194

Post by hbosch »

kamjam wrote: post #175
MrsPeaches wrote: post #128

Earlier quoted context omitted.

Simple explanation would be that activists use Signal. [1] They don't trust WhatsApp and rely on Signal for secure messaging. Blocking Signal means they are able to target activists without impacting much of the rest of the population. [1] Many of the people I know who are activists in countries where they need to protect their identities use Signal

> Simple explanation would be that activists use Signal. But why do activists simply not use WhatsApp, instead of Signal? If both were suppose to be fully encrypted and secure, why not use the tool that is available. I assume the needing encryption is to prevent the government snooping and eavesdropping on your plans rather than "liking the UI/UX of one system over the other"? Maybe the activists know something we di…

I think the rule of thumb around here is that any system that is closed-source must be treated as inherently untrustworthy from a security standpoint. WhatsApp has therefore always been untrustworthy for the scrupulous, regardless of the relatively flattering PR.

Re: WhatsApp backdoor allows snooping on encrypted messages

#195

Post by drdaeman »

whyever wrote: post #154
tim333 wrote: post #60

Earlier quoted context omitted.

It seems hard to expect full privacy from any company based in the US given the government's tendency to force them to allow access.

When the US government asked OWS for data on some users, all they got was the telephone number and the date of the last login.

Ahem. Don't they also have contact information? From https://whispersystems.org/blog/contact-discovery/ and lack of future follow-ups on the subject, I believe they do. Possibly, hashed or obfuscated, but still recoverable.

Which must mean either I'm misunderstanding something (e.g. things had changed since the blog post was published and relevant GitHub issues were closed), or they had not disclosed some information they have to the US government, or they (or word of mouth, retelling the story) is misinforming users about what was disclosed.

(Upd: Yes, it would be a good idea to go through Signal source code and see what exactly is sent, before making any suggestions that may look like an accusation, but... sorry, the code is quite complicated and I don't think I can figure this out any fast. I found ContactTokenDetails class, but lost my way trying to trace its usage and how it's wrapped/encrypted/etc.)

Re: WhatsApp backdoor allows snooping on encrypted messages

#196

Post by formerly_ta »

reitanqild wrote: post #134
FabHK wrote: post #70

Earlier quoted context omitted.

So, just to clarify my understanding: Basically, what we have here is a weakness in the client , namely a provision that allows the server to send the client a fresh key and ask for re-encryption and re-sending with the new key. This, in turn, would allow for a good old MITM attack if the server were to be compromised. This re-encryption and re-sending of messages would be without intervention by the user, though a m…

> if the server were to be compromised. IMO they have been since they joined Facebook.

If you're serious about security, every computer outside your control should be considered compromised, regardless of what you think about the owning company.

With Signal, I have an E2E connection where if I trust both clients, I can trust the connection. WhatsApp, however, has client code that will essentially reveal any unsent messages to the server on request. And then you just have to trust this compromised computer with any message you send.

Re: WhatsApp backdoor allows snooping on encrypted messages

#197

Post by Johnny_Brahms »

dromen wrote: post #169
zymhan wrote: post #118

Earlier quoted context omitted.

Sure, this could certainly leak some information, but it's hard to argue that this is a "backdoor".

It makes WhatsApp effectively not E2E encrypted. All messages can be recovered by Facebook. How is that NOT a backdoor?

All messages, sent while a person is offline. It is bad, but not nearly as bad as "all messages"

Re: WhatsApp backdoor allows snooping on encrypted messages

#198

Post by disgusting_guy »

dromen wrote: post #169
zymhan wrote: post #118

Earlier quoted context omitted.

Sure, this could certainly leak some information, but it's hard to argue that this is a "backdoor".

It makes WhatsApp effectively not E2E encrypted. All messages can be recovered by Facebook. How is that NOT a backdoor?

No, all messages cannot be recovered by Facebook. Read the article - messages that are not yet delivered can potentially be read; if it has been delivered it cannot be retrieved.

Re: WhatsApp backdoor allows snooping on encrypted messages

#199

Post by jdjb »

arjie wrote: post #188
mtgx wrote: post #168

Earlier quoted context omitted.

If a user loses their phone, I think they have a lot more to worry about than a few missed WhatsApp messages anyway. I don't think this is a "common sense" compromise that WhatsApp made here, especially in the context of them promising end-to-end encryption. It's kind of like that other nonsense tech companies are doing these days, by supporting U2F auth, but then requiring you also set-up SMS auth in parallel, so th…

If I lose my phone, I expect my new phone to have proper continuity on the messages. I'd rather have that than any encryption, to be honest. I don't care if the government spies on me. I do care if something someone sent me gets lost.

Then don't use a messenger that promises end-to-end encryption. Client side encryption is all about ensuring only clients that hold private keys can read messages delivered to them.

Re: WhatsApp backdoor allows snooping on encrypted messages

#200

Post by jdjb »

leecarraher wrote: post #157

C'mon we know this already, it's not a backdoor. This has been known and is discussed in the protocol and forums as the trade off in ease-of-use versus validation. For people wanting security, they simply check the verify keys, warn on key change. For people who don't care as much about verifying the recipient, they don't know about the feature, and don't use it, but they still get pretty good security, can upgrade t…

They should also add a toggle that prevents the client from retransmission to unknown keys without human approval.
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