Screenshot issue on (Molly <-> Signal)

manksudons89231

I am using GrapheneOS with Molly(Signal), and the other person is using Signal on Android.

Signal/Molly has an option called “Screen security: Block screenshots in the recents list and inside the app". If I turn this on, it blocks screenshots inside the app, which is good. However, there are some issues.

Issue 1:
The screenshot-blocking option in Molly/Signal seems like it should apply to both parties, not just one side. If it only applies to one user, what is the point of having this option in Signal/Molly’s settings?
For example, banking apps block screenshots because they run only on a single device. Signal/Molly is a two-party communication app. In this case, the other person(Official_Signal) can still take screenshots, while I am unable to take screenshots myself. This feels inconsistent and unfair.

Issue 2:
There is another setting just above this option called “Screen Lock: Lock app with fingerprint or face recognition". This feature is useful, but when I turn Screen Lock ON, it automatically turns ON Screen security as well. This means that enabling either of these options blocks screenshots.
Fun fact: while my screenshots are blocked, the other party can still freely take screenshots.

chinook

manksudons89231

[when I block screenshots] the other party can still freely take screenshots

Okay? This is a client (application) setting. Not a protocol/chat setting.
This still protects you from accidentally saving private chat screenshot in your gallery.

Screen Lock automatically turns ON Screen security

This is an application setting. If you believe these two should be decoupled, this should be raised with the respective app developers.

Your operating system doesn't control that too.

manksudons89231

chinook

I am aware that this is not a GrapheneOS issue, but I want to clarify what it is and why it exists.

Yes, I understand that posting this discussion in an app developer’s GitHub is not directly related to GrapheneOS. However, I think it is still important for GrapheneOS newcomers like me to understand this, especially for future discussions related to WhatsApp alternatives.

So, you are stating that the screenshot-blocking option is provided for individual client applications, such like banking apps.

In that case, please explain in your own words how this screenshot-blocking feature is useful for an individual client application where communication is two-way (like a chat app). Are you saying that this feature is mainly to protect against people who can physically access my GrapheneOS phone? or why it is for if it is not protecting two-way?

From my perspective, this feels somewhat unnatural because GrapheneOS is already protected with many security features. So what is the purpose of providing a screenshot-blocking option if it belongs to the individual client app?

However, this is also indirectly related to GrapheneOS at the OS level, for example the FLAG_SECURE option, which must be provided by the operating system.

Could you tell me is it belongs to Molly or Signal? Where do i report this?

Novalissoide

manksudons89231 it is less a protection from you deliberately screenshotting in the app, more a mitigation for the risk of rouge software that silently could screenshot your communication, the feature makes this kind of exploit a bit harder to perform.

otterfoghornrainfall

manksudons89231 Could you tell me is it belongs to Molly or Signal? Where do i report this?

Signal

chinook

manksudons89231

So, you are stating that the screenshot-blocking option is provided for individual client applications, such like banking apps.

Well, first it's not an "option provided", it's a flag requested by an app and then respected by the OS.
Other than that it's not my opinion, it's just a fact.

In that case, please explain in your own words how this screenshot-blocking feature is useful for an individual client application where communication is two-way (like a chat app).

This is not my problem TBH. I mentioned one option earlier, another very good reason (rogue app screenshotting) is better one.
This is completely irrelevant to me tbh. An app offers this. You have it on or not. If you turn it on it's presumably useful.

Are you saying that this feature is mainly to protect against people who can physically access my GrapheneOS phone?

I don't think I said anything like that.

or why it is for if it is not protecting two-way?

It is literally disabling screenshotting from being able to capture the contents of the screen.
Why is this not flipping the flag on the ALL the other side of ALL your conversations (and groups)?
I don't know, I suggest you should ask Signal development team.

Blocking screenshots is not a GOS-specific feature, and protocol development happens here: https://github.com/signalapp/libsignal -- just raise the issue there.

At the moment you are suggesting that GrapheneOS team should either:

write and submit a patch to Signal to make sure one chat member flipping this option automatically flips this option for everyone else? Good luck getting that accepted.
somehow exploit Signal on EVERY phone of someone talking with you to somehow forcibly flip the option for everyone because you are using more secure operating system? I don't see it happening anytime soon.

From my perspective, this feels somewhat unnatural because GrapheneOS is already protected with many security features.

Yes.

So what is the purpose of providing a screenshot-blocking option if it belongs to the individual client app?

Blocking screenshots from happening for the particular app: https://blog.ostorlab.co/understanding-android-flag-secure-screen-security.html

However, this is also indirectly related to GrapheneOS at the OS level, for example the FLAG_SECURE option, which must be provided by the operating system.

It's not related to the GoS at all, other than this is a part of the AOSP project, and GrapheneOS is merely respecting the flag in its original scope.

That's it.

This is NOT GrapheneOS problem, this is your problem with the Signal protocol (not blocking screenshots on the phones of everyone who chats with someone with the screenshots blocked).

Feel free to raise it with Signal, GrapheneOS CANNOT FIX this intended behaviour/issue for you.

I agree this thread is solved here.