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WhatsApp end-to-end encrypted backups security assessment

research.nccgroup.com

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Re: WhatsApp end-to-end encrypted backups security assessment

#21

Post by reissbaker »

bsaul wrote: post #10
triumphantomato wrote: post #3

Earlier quoted context omitted.

Wrong. 1. Backups are opt-in - just as they have always been. 2. The E2EE backups do not rely on HSM's - they rely on a client-side only key derived by the WhatsApp client, on the user's phone. 3. The client-side key backup does not rely solely on HSM's - naturally, the client-side key must be backed up in case the user loses their phone. This key is itself encrypted and stored remotely (whether this is on third-part…

what's the threat this hsm is adding protection against ? i don't mean to be ironic, i genuinely couldn't understand after reading the paper.

The HSM is a server-side HSM. I believe it helps prevent brute-forcing weak passwords/PINs by non-WhatsApp attackers, in case non-WhatsApp attackers gain access to the encrypted backup keys.

Re: WhatsApp end-to-end encrypted backups security assessment

#22

Post by orf »

ivanmontillam wrote: post #20
vorpalhex wrote: post #14

Earlier quoted context omitted.

View once media is always susceptible to this problem. I can always put a capture card between my screen and the device or use a vm - or just take a picture using a second device. Likewise touching file storage makes sense, the media files have to sit somewhere. Any vaguely modern android phone has full disk encryption, so it's only apps with global filesystem access that present a threat.

That's not true. It's possible to manipulate file-like objects without ever touching the filesystem. BytesIO in Python for example ([0]). I'm not an expert in Java Android, but I'm pretty certain there must be something like that. [0]: https://docs.python.org/3/library/io.html

Let’s assume we don’t want to make memory constrained devices keep large video files buffered in memory and constantly re-download them over the network?

Re: WhatsApp end-to-end encrypted backups security assessment

#23

Post by jb_s »

orf wrote: post #22
ivanmontillam wrote: post #20

Earlier quoted context omitted.

That's not true. It's possible to manipulate file-like objects without ever touching the filesystem. BytesIO in Python for example ([0]). I'm not an expert in Java Android, but I'm pretty certain there must be something like that. [0]: https://docs.python.org/3/library/io.html

Let’s assume we don’t want to make memory constrained devices keep large video files buffered in memory and constantly re-download them over the network?

encrypt with in-memory nonce

Re: WhatsApp end-to-end encrypted backups security assessment

#24

Post by epolanski »

r00fus wrote: post #17
jakecopp wrote: post #15

Why on earth do people trust a closed source messenger owned by Facebook, which backs up to Google? Signal and Matrix are open source and full-featured.

Most likely because their contacts don't want to switch. I've migrated extended family off WhatsApp to Signal but it was a nontrivial effort since their contacts don't want to use anything but WhatsApp.

Just imagine the world we live in, how numb average joe is.

I said same things to most of my closer people and in the end they tell me “well they have all our data anyway”.

And all they have to do is just download an application.

Re: WhatsApp end-to-end encrypted backups security assessment

#25

Post by ivanmontillam »

orf wrote: post #22
ivanmontillam wrote: post #20

Earlier quoted context omitted.

That's not true. It's possible to manipulate file-like objects without ever touching the filesystem. BytesIO in Python for example ([0]). I'm not an expert in Java Android, but I'm pretty certain there must be something like that. [0]: https://docs.python.org/3/library/io.html

Let’s assume we don’t want to make memory constrained devices keep large video files buffered in memory and constantly re-download them over the network?

For the View Once media, have it buffered in memory and be done with it. Delete from the server once it's inaccessible (or keep it a few days it need be... for reporting reasons).

For the non-private media, just write it to storage straight away.

Re: WhatsApp end-to-end encrypted backups security assessment

#26

Post by jensensbutton »

jakecopp wrote: post #15

Why on earth do people trust a closed source messenger owned by Facebook, which backs up to Google? Signal and Matrix are open source and full-featured.

Because the number of people who can actually validate the security of the open source options is vanishingly small and assessments like this provide sufficient evidence that WhatsApp's claims are not bunk.

Re: WhatsApp end-to-end encrypted backups security assessment

#27

Post by vorpalhex »

jb_s wrote: post #23
orf wrote: post #22

Earlier quoted context omitted.

Let’s assume we don’t want to make memory constrained devices keep large video files buffered in memory and constantly re-download them over the network?

encrypt with in-memory nonce

Still hit the issue with large media that doesn't fit in memory and your gain is still minor (resist a compromised filesystem.. maybe.. if they didn't compromise the binary too)

Re: WhatsApp end-to-end encrypted backups security assessment

#28

Post by vorpalhex »

ivanmontillam wrote: post #25
orf wrote: post #22

Earlier quoted context omitted.

Let’s assume we don’t want to make memory constrained devices keep large video files buffered in memory and constantly re-download them over the network?

For the View Once media, have it buffered in memory and be done with it. Delete from the server once it's inaccessible (or keep it a few days it need be... for reporting reasons). For the non-private media, just write it to storage straight away.

You're still susceptible to me owning a second device that can take photos. If it can be displayed, it can be copied.

Re: WhatsApp end-to-end encrypted backups security assessment

#29

Post by robryk »

ivanmontillam wrote: post #11

For the work I do, I also conducted a mini-experiment where I checked the WhatsApp security in regards to the media transmitted. In the cited documentation below ([0]), it claims that media will not be saved for either method 1 or 2 ("To stop media from all your individual chats and groups from being saved" and "To stop media from a particular individual chat or group from being saved"). I found out that the media is…

Regarding storing files: They either are using https://developer.android.com/training/data-storage/app-spec... and other apps would not be able to access those files at all, or they should be using it instead of just using "external storage".

Re: WhatsApp end-to-end encrypted backups security assessment

#30

Post by smoldesu »

jb_s wrote: post #23
orf wrote: post #22

Earlier quoted context omitted.

Let’s assume we don’t want to make memory constrained devices keep large video files buffered in memory and constantly re-download them over the network?

encrypt with in-memory nonce

How does that prevent me from lifting it right off the framebuffer?
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