Hacker News Board Hacker News, browsed like a classic message board
Live data from Hacker News

WhatsApp end-to-end encrypted backups security assessment

research.nccgroup.com

Post reply on HN
Print view View original

11–20 of 121 posts

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

#11

Post by ivanmontillam »

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 in fact written to storage, straight to the "Private" directory ("Internal Storage/WhatsApp/Media/WhatsApp Images/Private"). Said directory includes a ".nomedia" file which inhibits the Gallery app from your phone to see such media. So if you were to copy the "Media" directory into your PC, such "unsaved media" would come with it.

Also, when sending View Once media ([1]), it can be easily screenshot on your smartphone, or if you're using WhatsApp Web, use the DevTools while image is open, so you can grab it in their transmitted resolution.

Want to grab a status from a contact? Go to "Internal Storage/WhatsApp/Media/.Statuses" (enable view hidden directories in your Files Explorer application) and copy/move the file elsewhere, so it goes out of reach when WhatsApp tries to delete it.

Not to spill poisonous words around here, but I highly doubt they take security seriously.

[0]: https://faq.whatsapp.com/android/how-to-stop-saving-whatsapp... [1]: https://faq.whatsapp.com/general/chats/about-view-once/?lang...

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

#12

Post by vorpalhex »

That this audit was published helps build faith that WhatsApp is trying to do the right thing but it sounds like they still have some kinks to work out.

This is not a trivial problem and I don't want to downplay their effort and transparency. Seeing their struggle and audits is a good sign - they are doing the right things.

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

#13

Post by reissbaker »

alerighi wrote: post #7
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…

Last time I looked at it, WhatsApp backup key was simply stored server side. Also, backup encryption key never changes, basically. I tell you this because I needed to extract an old backup that I did on Android years ago to recover some messages: well it was as simple as extracting the key from another phone where I was signed into (need root privileges, but of course you can just access the account from an emulator,…

I believe you are mistaken, and the NCC group analysis makes it quite clear that the locally-stored backup key is not the same as the "export key": the export key is the encrypted version of the local backup key. WhatsApp servers only have access to the export key, not the local backup key. The fact that you could extract the local backup key with physical access to your device and root privileges does not mean that the key is stored remotely in plaintext.

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

#14

Post by vorpalhex »

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…

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.

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

#16

Post by pytlicek »

WillSmithPro wrote: post #6

I came across this twitter thread during the last Facebook outage. Apparently something very wrong is happening there with their backups. I would definitely check similar cases. Confirmed by multiple people :/ I quote the author: This is really weird. In #WhatsApp, I started to see messages that I know 100% that I deleted 2 days ago?! WTF is happening there? I think this is a really big violation of privacy! I see th…

I completely forgot about this issue :) I'm glad someone was interested in looking at how those backups work. Perhaps my complaints also contributed to this investigation :)))

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

#17

Post by r00fus »

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.

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

#18

Post by ivanmontillam »

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…

Additional pills:

If you have your phone rooted, go to the "/data/data/com.whatsapp" using a terminal, and copy the messages database to the Internal Storage (wherever that is, I don't have any rooted device right now with me).

Then extract that file to your computer and use any SQLite3 viewer. It's not encrypted.

You'll find messages since the very first install of WhatsApp, even if you deleted these.

Last tested: about the year 2017.

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

#20

Post by ivanmontillam »

vorpalhex wrote: post #14
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…

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

Post reply on HN