The Most Backdoor-Looking Bug I’ve Ever Seen • Hacker News Board

Re: The Most Backdoor-Looking Bug I’ve Ever Seen

#11

Post by Closi » Mon, Jan 11, 2021, 10:03 AM UTC

moepstar wrote: post #3

vbezhenar wrote: post #2

The most backdoor-looking feature for me in supposedly encrypted systems are cloud backups. They are “optional” yet most users will agree (especially when given software constantly nags about it until you give up) and their backups will leak both sides of conversations, despite all end-to-end encryption attempts.

This is something i don't understand (at least for me/my use case): Are historic chats that important to have them backed up? To me, if there's anything of value, i'll save it via other means...

Yes - sometimes you don't realise the value until after the point.

I made a card for my girlfriend on our 5th anniversary by going back and finding our first messages to each other on WhatsApp, and putting a screenshot of them on the front of the card with some corny message. She balled up and was crying for quite some time. Anyway we are broken up now, but that's not the point!

These things really do have sentimental value, and it's not always obvious at the time.

Re: The Most Backdoor-Looking Bug I’ve Ever Seen

#12

Post by joe-collins » Mon, Jan 11, 2021, 10:03 AM UTC

Erlich_Bachman wrote: post #9

Aerroon wrote: post #7

Earlier quoted context omitted.

Sure, but wouldn't you want to have control over these backups yourself? Not only do you get increased privacy from it, you also won't be in for a nasty surprise when the service decides to remove old logs/stop doing business.

An average user doesn't commonly want to have control over anything themselves :P.

I disagree. They'd love to have control, but that control requires tech sophistication that none of the current tooling adequately elides.

Re: The Most Backdoor-Looking Bug I’ve Ever Seen

#13

Post by paveldurov » Mon, Jan 11, 2021, 10:08 AM UTC

Another libelous post by US government affiliated "cryptographer". Perhaps next we will see other familiar faces chipping in like tptacek from matasano )

Impossible to succeed at this level without making a few enemies.

Re: The Most Backdoor-Looking Bug I’ve Ever Seen

#14

Post by 4gotunameagain » Mon, Jan 11, 2021, 10:14 AM UTC

> because an attacker capable of intercepting the messages could simply establish two separate sessions with the two parties, carrying out a PitM attack

Really. That's our new problem now? That it's a person in the middle and not a man in the middle? Plus it goes against the narrative that men are the source of all evil in this world ;)

Re: The Most Backdoor-Looking Bug I’ve Ever Seen

#15

Post by garmaine » Mon, Jan 11, 2021, 10:15 AM UTC

londons_explore wrote: post #8

vbezhenar wrote: post #2

The most backdoor-looking feature for me in supposedly encrypted systems are cloud backups. They are “optional” yet most users will agree (especially when given software constantly nags about it until you give up) and their backups will leak both sides of conversations, despite all end-to-end encryption attempts.

WhatsApps cloud backup on Android sits on Google drive by default. It is encrypted with a per user key known to WhatsApp. That means for a third party to access the chats, they need Google to hand over the data, and Facebook to hand over the key. The logical next step to add would be for Google to additionally encrypt the data with the users logon password or something derived from it. Google won't do this anytime so…

> That means for a third party to access the chats, they need Google to hand over the data, and Facebook to hand over the key.

National intelligence agencies (plural) would already have both.

Re: The Most Backdoor-Looking Bug I’ve Ever Seen

#16

Post by paranoidrobot » Mon, Jan 11, 2021, 10:17 AM UTC

londons_explore wrote: post #8

vbezhenar wrote: post #2

The most backdoor-looking feature for me in supposedly encrypted systems are cloud backups. They are “optional” yet most users will agree (especially when given software constantly nags about it until you give up) and their backups will leak both sides of conversations, despite all end-to-end encryption attempts.

WhatsApps cloud backup on Android sits on Google drive by default. It is encrypted with a per user key known to WhatsApp. That means for a third party to access the chats, they need Google to hand over the data, and Facebook to hand over the key. The logical next step to add would be for Google to additionally encrypt the data with the users logon password or something derived from it. Google won't do this anytime so…

> encrypt the data with the users logon password or something derived from it

This leads to inability to restore a backup if you forget your password and need to reset it.

That's going to lead to screams/tears from a lot of folks who don't realise those implications.

Re: The Most Backdoor-Looking Bug I’ve Ever Seen

#17

Post by Taek » Mon, Jan 11, 2021, 10:22 AM UTC

londons_explore wrote: post #6

If any clients had been logging that nonce, we could retrospectively catch any person in the middle. Far too few services do strategic logging of data useful to catch attackers like this. Many attackers won't attack if they know traces will be left which can point to them.

The more I work with production systems, the more I appreciate healthy logs. We've solved at least a dozen big issues this past year with "just scan the logs and rebuild the historical data, we can pretend like we were monitoring that issue the whole time".

Re: The Most Backdoor-Looking Bug I’ve Ever Seen

#18

Post by tarasmatsyk » Mon, Jan 11, 2021, 10:23 AM UTC

TL;DR

A TG server was sending a "salt" to clients in order to randomize keys (telegram claim) when in fact the "salt" turned out useless in terms of encryption and the only reasonable explanation for the "nonce" was using it as a backdoor to perform MITM attack.

You decide whether it was done intenionally or because of lack of sleep/understanding

PS. an original author got 100k$ for finding/exposing a potential backdoor.

Re: The Most Backdoor-Looking Bug I’ve Ever Seen

#19

Post by londons_explore » Mon, Jan 11, 2021, 10:26 AM UTC

garmaine wrote: post #15

londons_explore wrote: post #8

Earlier quoted context omitted.

WhatsApps cloud backup on Android sits on Google drive by default. It is encrypted with a per user key known to WhatsApp. That means for a third party to access the chats, they need Google to hand over the data, and Facebook to hand over the key. The logical next step to add would be for Google to additionally encrypt the data with the users logon password or something derived from it. Google won't do this anytime so…

> That means for a third party to access the chats, they need Google to hand over the data, and Facebook to hand over the key. National intelligence agencies (plural) would already have both.

True, but it still makes the attack surface much smaller - employees of neither company could steal your data. Your data is now protected by the intersection of the companies privacy policies rather than the union of them.

Re: The Most Backdoor-Looking Bug I’ve Ever Seen

#20

Post by sdflhasjd » Mon, Jan 11, 2021, 10:28 AM UTC

londons_explore wrote: post #8

vbezhenar wrote: post #2

The most backdoor-looking feature for me in supposedly encrypted systems are cloud backups. They are “optional” yet most users will agree (especially when given software constantly nags about it until you give up) and their backups will leak both sides of conversations, despite all end-to-end encryption attempts.

WhatsApps cloud backup on Android sits on Google drive by default. It is encrypted with a per user key known to WhatsApp. That means for a third party to access the chats, they need Google to hand over the data, and Facebook to hand over the key. The logical next step to add would be for Google to additionally encrypt the data with the users logon password or something derived from it. Google won't do this anytime so…

WhatsApp backups are a bit of an anti-feature, as I found out while trying to ditch the app after the recent policy update.

1) The backup can only be made to Google drive, you cannot create a manual backup to a location of your chosing

2) The backup is created in a secret folder that cannot be accessed by the user

3) The backup is deleted if you delete your account. (not much of a backup, eh?)

4) You can only create per-channel exports, but this won't export the entire chat, it will export up to ~12MB of recent media, and ignore the rest, silently. WhatsApp would only share the last 40 messages of a 4-year-old chat because the last few messages contained a few images.