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FBI used iPhone notification data to retrieve deleted Signal messages

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Re: FBI used iPhone notification data to retrieve deleted Signal messages

#91

Post by vlovich123 »

satvikpendem wrote: post #89
aftbit wrote: post #86

Earlier quoted context omitted.

Wait... why does Signal need to send notification content to Firebase to trigger a push notification on device? I would instead expect that Signal would send a push to my Android saying nothing more than "wake up, you've got a message in convo XYZ", then the app would take over and handle the rest of it locally. I also didn't realize that Android stores message history even after I've replied or swiped them away. Tha…

If your app needs to send a notification while it's not currently a running process, it must go through Firebase on Google's side and APNS on Apple's side. There is no way for a non running app to send a notification entirely locally, this is by design of both companies.

> this is by design of both companies.

I’ll note that whatever other reasons it’s also the only way to make this battery efficient. Having a bunch of different TCP connections signaling events at random times is not what you want.

Ideally the app also is responsible for rendering rather than having to disclose the message but that can be challenging to accomplish for all sorts of reasons).

Re: FBI used iPhone notification data to retrieve deleted Signal messages

#92

Post by SergeAx »

tbrownaw wrote: post #72
SergeAx wrote: post #55

Probably stupid question: why won't they e2e-encrypt push notifications too? The vector is obvious and has been open since forever.

The "e" in e2e encryption is a computing device, not the device's user's brain.

Right. So I send a push notification with the "silent" flag and encrypted content; the app receives it, decrypts the text, and displays the notification locally. Google/Apple has only ciphertext in their FBI/CIA/NSA-accessible databases.

Re: FBI used iPhone notification data to retrieve deleted Signal messages

#93

Post by tayk47999 »

nickburns wrote: post #53
hammock wrote: post #52

Earlier quoted context omitted.

Wait so if I do iOS setting notifications > never show previews it’s still caching them in the background? Unencrypted?

Yes. And technically, from a privacy perspective, it's even worse than that. What's additionally happening is they're still 'syncing' back to Apple servers via APNS (and to Alphabet servers via Firebase on Android)—even with notifications completely disabled , that's correct. If the app generates them, the OS receives them. That's why the Signal app offers this setting.

Any idea if this works the same or differently for Hidden apps specifically?

Normally no notifications are shown for hidden apps, and even if you unhide the apps, prior notifications which were sent do not reappear IIRC. I'm curious if notifications like that are still hitting the phone into the notifications database, or get silently dropped, or something else.

Re: FBI used iPhone notification data to retrieve deleted Signal messages

#94

Post by 9dev »

satvikpendem wrote: post #89
aftbit wrote: post #86

Earlier quoted context omitted.

Wait... why does Signal need to send notification content to Firebase to trigger a push notification on device? I would instead expect that Signal would send a push to my Android saying nothing more than "wake up, you've got a message in convo XYZ", then the app would take over and handle the rest of it locally. I also didn't realize that Android stores message history even after I've replied or swiped them away. Tha…

If your app needs to send a notification while it's not currently a running process, it must go through Firebase on Google's side and APNS on Apple's side. There is no way for a non running app to send a notification entirely locally, this is by design of both companies.

> […] this is by design of both companies.

This is more of a fundamental technical limitation of operating systems and networks; I don't think it is possible to design distributed communication between arbitrary service provider infrastructure and end-user devices without an always-online intermediary reachable from anywhere (a bouncer, in IRC terms) that accepts messages for non-present consumers.

Re: FBI used iPhone notification data to retrieve deleted Signal messages

#95

Post by 1vuio0pswjnm7 »

"However, it appears the defendant did not have that setting enabled, which, in turn, seemingly allowed the system to store the content in the database."

"[A]llowing the system to store the content in the database" where a third party, such as Apple or a government, can access it is the default

Only a small minority of users know about settings and how to change them. The vast majority of users do not change default settings. Apple knows this

Re: FBI used iPhone notification data to retrieve deleted Signal messages

#96

Post by llacane »

aftbit wrote: post #86
nickburns wrote: post #53

Earlier quoted context omitted.

Yes. And technically, from a privacy perspective, it's even worse than that. What's additionally happening is they're still 'syncing' back to Apple servers via APNS (and to Alphabet servers via Firebase on Android)—even with notifications completely disabled , that's correct. If the app generates them, the OS receives them. That's why the Signal app offers this setting.

Wait... why does Signal need to send notification content to Firebase to trigger a push notification on device? I would instead expect that Signal would send a push to my Android saying nothing more than "wake up, you've got a message in convo XYZ", then the app would take over and handle the rest of it locally. I also didn't realize that Android stores message history even after I've replied or swiped them away. Tha…

Signal does NOT send notification content througth APN/Firebase, their push notification is literaly a ping as you expected.

Source: https://mastodon.world@Mer__edith/111563866152334347 (Meredith Whittaker is the current CEO of Signal)

I can't link you rigth now to the actual code on their repo but it is verifiable.

Re: FBI used iPhone notification data to retrieve deleted Signal messages

#98

Post by JumpCrisscross »

nickburns wrote: post #58
JumpCrisscross wrote: post #45

Earlier quoted context omitted.

Signal should switch the default to being less verbose.

The default should be "No name or content".

Name only strikes me as a fairer compromise between security and usability.

Re: FBI used iPhone notification data to retrieve deleted Signal messages

#99

Post by commandersaki »

chasil wrote: post #7

First, a critical setting for Signal users: "Signal’s settings include an option that prevents the actual message content from being previewed in notifications. However, it appears the defendant did not have that setting enabled, which, in turn, seemingly allowed the system to store the content in the database." Second, how can I see this notification history?

So I wonder about this. The quote from the 404 media article [0] is:

“We learned that specifically on iPhones, if one’s settings in the Signal app allow for message notifications and previews to show up on the lock screen, [then] the iPhone will internally store those notifications/message previews in the internal memory of the device,” a supporter of the defendants who was taking notes during the trial told 404 Media

The default setting appears to be to only show notification preview when unlocked. Will that notification still be stored unencrypted in notification storage or is it in an encrypted store because it will preview after unlock?

It makes sense that any notification that previews on the lock screen would be unencrypted (including the case where it is encrypted but the encryption key is adjacently stored).

This all reads to me that this was a user induced OPSEC issue and Signal had the right defaults.

[0] https://archive.is/bSQhD#selection-619.0-622.0

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