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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

#141

Post by evgen »

mtgx wrote: post #99
mattcoles wrote: post #28

Earlier quoted context omitted.

I don't think this is as serious as it seems, this exploit only applies to undelivered messages, which granted is not great, but is at least something. And any WhatsApp update could potentially include code to snoop on decrypted messages so exploits that can only be performed from the WhatsApp server side - i.e the example in the article about snooping entire conversations - are not really that relevant. Having said…

Did you miss this from the 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 vulnerabi…

It is just as easy to have the clients send a copy of all generated keys to a central server for storage, no need to bother with this re-transmission subterfuge at all.

What you are seeing is not some vast conspiracy, it is a compromise made by some back-end engineer to get a front-end product manager off their ass without anyone thinking through a better UI option.

"So if a user loses their phone you are telling me that all unread messages are lost forever?"

"Yes."

"That won't work. Users will complain, someone will have to deal with those complaints, this just won't work."

"Ok, maybe we just push the unread messages back to the sender's phone and automatically re-send when the recipient gets a new phone."

"Sure, that works. So, about this other problem..."

In retrospect, it is fairly obvious that the send needs some control over re-transmission, but if you have never been a situation like this it is only because no one uses your code.

Re: WhatsApp backdoor allows snooping on encrypted messages

#142

Post by whyever »

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…

> when Moxie himself said that I should trust WhatsApp without having the source code and the ability to put it on my device.

What are you talking about? All I can see there is that you asked for the source code of the QR generator and he delivered. He does not say you should trust WhatsApp.

Re: WhatsApp backdoor allows snooping on encrypted messages

#143

Post by corobo »

FabHK wrote: post #96
yclept wrote: post #78

Earlier quoted context omitted.

Aren't all messages undelivered, until they are?

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.

The next question would be can the server mark a message as undelivered after it's already marked it as delivered.

If it can un-deliver all messages as well as have them re-sent with a new key then there may as well be no keys.

Re: WhatsApp backdoor allows snooping on encrypted messages

#144

Post by samsonradu »

jaymzcampbell wrote: post #2

The key part is this, and it was apparently reported back in April 2016 with Facebook replying it's "expected behavior", it's not something a general attacker can do but it would enable WhatsApp/Facebook to read conversations: > WhatsApp has the ability to force the generation of new encryption keys for offline users, unbeknown to the sender and recipient of the messages, and to make the sender re-encrypt messages wi…

I happened to have the Security Notifications on for a while now. I see the message: "X's security code has changed." pretty often. Under what circumstances does a new pair of encryption keys get generated?

Re: WhatsApp backdoor allows snooping on encrypted messages

#145

Post by whyever »

svkkfnisgkcn3ta wrote: post #139
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…

I'd go further and say Moxie is complicit by way of negligence. It's unethical to assist in the implementation of your protocol when you can't guarantee its privacy protections will actually stand. Otherwise it's free PR for Facebook to tout "Snowden-approved crypto". I have no doubt Moxie acted in good faith and wanted to expand encryption to a large number of users, but this is just another example of why proprieta…

> OWS should denounce these implementations as least as firmly as they do open source Signal client forks.

They don't. Moxie does not want the forks to use his servers or the name of his app, that is all.

Re: WhatsApp backdoor allows snooping on encrypted messages

#146

Post by wlll »

zymhan wrote: post #118
joelhaasnoot wrote: post #19

Earlier quoted context omitted.

According to the article however, the notification is given after the messages are resent. There is nothing the user can seemingly do to prevent retransmission on a forced key change. This prevents further information from being sent, but in case of undelivered messages, they could be snooped on.

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

A way of exploiting it is talked about in the article which would effectively allow Facebook/Whatsapp, or whoever is coercing them, to read all messages sent by a particular device.

Re: WhatsApp backdoor allows snooping on encrypted messages

#147

Post by patrickk »

guidovranken wrote: post #31

From the outset I've always expected that a backdoor was present in Whatsapp. In fact, I'd be surprised if they hadn't granted themselves some special capabilities with regards to the content of the communications. Touting their end-to-end encryption has enticed many people to trust the product, sometimes with strong conviction, while giving themselves a monopoly on access to communication perceived as secure by the…

> In fact, I'd be surprised if they hadn't granted themselves some special capabilities with regards to the content of the communications. Touting their end-to-end encryption has enticed many people to trust the product, sometimes with strong conviction, while giving themselves a monopoly on access to communication perceived as secure by the end users.

It reminds me of this PR puff piece[1] by Google, banging on about how secure their data centre was, the limited access by employees, the amazing information security team, the underfloor lasers to detect intruders, etc. while totally ignoring the elephant in the room, i.e. NSA backdoors which Google is forced to comply with and can't reveal publicly when they do so.

[1]https://www.youtube.com/watch?v=XZmGGAbHqa0

Re: WhatsApp backdoor allows snooping on encrypted messages

#148

Post by mtgx »

ComodoHacker wrote: post #100
hannob wrote: post #25

Some more background: This was presented in the lightning talks at 33c3, starting around minute 48: https://media.ccc.de/v/33c3-8089-lightning_talks_day_4 Here's the congress wiki with some more links: https://events.ccc.de/congress/2016/wiki/Lightning:A_Backdoo... And a blogpost: https://tobi.rocks/2016/04/whats-app-retransmission-vulnerab...

Thank you. The last link should be the source (a note to moderator).

It's news that Facebook still hasn't fixed it (and they're saying they won't fix it).

What do you call a known vulnerability that can be used for eavesdropping that a company refuses to fix ?

1) A mistake

2) A bug

3) A backdoor

Re: WhatsApp backdoor allows snooping on encrypted messages

#149

Post by dmichulke »

samsonradu wrote: post #144
jaymzcampbell wrote: post #2

The key part is this, and it was apparently reported back in April 2016 with Facebook replying it's "expected behavior", it's not something a general attacker can do but it would enable WhatsApp/Facebook to read conversations: > WhatsApp has the ability to force the generation of new encryption keys for offline users, unbeknown to the sender and recipient of the messages, and to make the sender re-encrypt messages wi…

I happened to have the Security Notifications on for a while now. I see the message: "X's security code has changed." pretty often. Under what circumstances does a new pair of encryption keys get generated?

Maybe the very fact that you want to be notified of key change events got you marked as suspicious ;-)

Re: WhatsApp backdoor allows snooping on encrypted messages

#150

Post by kriive »

I'm not a crypto guy, but I'm trying to understand how this backdoor could be used by governments or WhatsApp/Facebook itself. I'm not entirely sure how such an attack based on this backdoor would work.

The article says that WhatsApp servers have the ability to trigger the clients to generate new keys, but even with new keys how can the server read the messages at all? Has the server got a copy of the new generated keys?

Probably there is something big I'm missing.

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