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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

#71

Post by lucb1e »

qznc wrote: post #66
lucb1e wrote: post #23

Earlier quoted context omitted.

He never said it was. Google services aren't isolated like normal apps either, as far as I know they can access other app's data (when installing cyanogenmod, I had to install google apps in some weird way from the bootloader because it has to change protected things on the phone). His point of requiring google's stuff to be installed is valid, even if he wrote it thinking payload gets sent over it.

Even if you don't install Gapps, large parts of Android/CyanogenMod are from Google as well. How does installing Gapps make the security worse?

Because it's likely someone would have noticed if every AOSP phone called third party servers (or something like that). Plenty of people made Android derivatives, modded it, or just compiled it to toy with. Of course there's no guarantee without a full audit (and even with an audit, they might miss something), but I trust AOSP a lot more than a closed source app suite.

Re: WhatsApp backdoor allows snooping on encrypted messages

#72

Post by thinkloop »

discordianfish wrote: post #43
feral wrote: post #35

I am flagging this article, as the headline and first few paragraphs are very misleading, based on my understanding from: https://tobi.rocks/2016/04/whats-app-retransmission-vulnerab... They make it sound like an intentional backdoor has been introduced to WhatsApp to facilitate monitoring. Rather, it seems like there's a weakness in the implementation, where if a message is undelivered, an attacker could trick the s…

Agree, also think it's likely this is an intentional trade off: Alice sends Bob a message but Bob's phone is broken, so he gets a new one. The message is marked as not delivered. Since Bob's old keys are lost, WhatsApp needs to generate new ones. The trade off here allows in this scenario to accept new keys transparently. Not ideal from a security perspective but what would be the alternative? Bob meeting Alice so th…

What if the originating client (Alice) was responsible for re-encrypting undelivered messages?

Re: WhatsApp backdoor allows snooping on encrypted messages

#73

Post by Arathorn »

At the risk of stating the obvious: there is real benefit to using an entirely decentralised open source comms system like Riot.im (Matrix) or Conversations (XMPP), where you can pick precisely which app to run, who to trust to build that app, who to trust to advertise your public keys, and who to host your server.

It's inevitable that big centralised services like WhatsApp or even Signal are going to be under pressure from governments to support lawful intercept; in many countries it's essentially illegal to run a communication service that can't be snooped under a court order. Multinationals like Facebook are neither going to want to break the law (as it ends up with their senior management getting arrested: https://www.theguardian.com/technology/2016/mar/01/brazil-po...) - nor pull out of those territories (given WhatsApp market penetration in Brazil is 98.5% or similar).

Re: WhatsApp backdoor allows snooping on encrypted messages

#77

Post by vorticalbox »

rahilb wrote: post #21

Doesn't this mean that only subsequent messages can be decrypted? i.e. Whatsapp has provided forward secrecy (as long as they haven't been using this trick from the initial secrets that were set up)?

Pretty sure that is the case. the key is changed while you're offline making any unsent messages use the new key that they know.

But if they can change the key while you're offline that means they can change the key and know everything from that point on.

Re: WhatsApp backdoor allows snooping on encrypted messages

#78

Post by yclept »

FabHK wrote: post #70
wirelessest wrote: post #59

Earlier quoted context omitted.

I thought that was the whole point of end-to-end. That you don't need trust in the server because the messages are opaque. If this is an exploit that can be performed by a compromised server, it's very much relevant

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…

Aren't all messages undelivered, until they are?

Re: WhatsApp backdoor allows snooping on encrypted messages

#79

Post by rakoo »

hellofunk wrote: post #48
d33 wrote: post #34

Earlier quoted context omitted.

The fact that you have a PhD in cryptography doesn't necessarily mean you know how to write secure code. Especially C code. Lot of people hated OpenSSL quality long before Heartbleed, but it took that vuln for people to actually realize how bad it is. I can imagine a good, secure SSL library being written by somebody without a PhD, in a safer language.

> Especially C code Isn't WhatsApp an Erlang app?

Whatsapp is both a server and a client. The server might be written in Erlang, but the client (where all the end-to-end encryption happens) is written in whatever the device can run.

Re: WhatsApp backdoor allows snooping on encrypted messages

#80

Post by Arathorn »

Arathorn wrote: post #73

At the risk of stating the obvious: there is real benefit to using an entirely decentralised open source comms system like Riot.im (Matrix) or Conversations (XMPP), where you can pick precisely which app to run, who to trust to build that app, who to trust to advertise your public keys, and who to host your server. It's inevitable that big centralised services like WhatsApp or even Signal are going to be under pressu…

oh, and one other thing - there's also real value to independently published public security audits of the crypto to pick up on things like WhatsApp's retransmission 'bug', at least as of a given snapshot of the codebase. E.g. https://www.nccgroup.trust/us/our-research/matrix-olm-crypto... for Matrix or https://conversations.im/omemo/audit.pdf for OMEMO & Conversations.
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