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Android Security Auditing: Investigating Unauthorized Screenshots

tech.michaelaltfield.net

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Re: Android Security Auditing: Investigating Unauthorized Screenshots

#31

Post by oliwarner »

saagarjha wrote: post #26
izacus wrote: post #22

Earlier quoted context omitted.

How is messaging confidental data? Remember, FLAG_SECURE prevents users from taking screenshots themselves as well and prevents display of content in several other cases (e.g. screen mirroring). Your conversations aren't nearly as sensitive to require such a large breach of usability.

> Your conversations aren't nearly as sensitive to require such a large breach of usability. Yours might not be, but this isn’t true for everyone.

I think the broader point is that it stops the user doing something they want to. Something they could still do with a camera.

The flag should secure it from other apps but the user screenshot tool should be able to override it. The cap framework should be able to do this, you just need to insulate the app itself to ensure only real people can use it.

Re: Android Security Auditing: Investigating Unauthorized Screenshots

#32

Post by Confiks »

izacus wrote: post #22
RafiqM wrote: post #6

Earlier quoted context omitted.

The conclusion is there's no problem, that it wasn't the nefarious activity that he originally thought it was. The additional point he's trying to make is that app developers should use FLAG_SECURE if its confidential data - messaging probably should be, and his bitcoin app should almost certainly be.

How is messaging confidental data? Remember, FLAG_SECURE prevents users from taking screenshots themselves as well and prevents display of content in several other cases (e.g. screen mirroring). Your conversations aren't nearly as sensitive to require such a large breach of usability.

Preventing screenshots and showing up in the active apps list is an option within the Signal preferences. So Signal provides a precautious default, but allows you to turn it off.

Re: Android Security Auditing: Investigating Unauthorized Screenshots

#33

Post by zczc »

jancsika wrote: post #14

FLAG_SECURE: * overworked, out-of-coffee developer of "secure" messaging app forgets to set FLAG_SECURE. Oops. vs. FLAG_CACHE_ARBITRARY_IMAGE_OF_MY_INTERFACE_TO_HELP_ANDROID_APPEAR_MORE_RESPONSIVE: * overworked developer of "secure" messaging app who is out of coffee forgets to set this flag. App doesn't appear more responsive but also doesn't cache an image of the interface . Yay security! * But... app devs default…

Correction: FLAG_SECURE doesn't make app "less responsive". It makes it appear as a header with a blank rectangle beneath in Recent apps, which lessens the UX but not responsiveness

Re: Android Security Auditing: Investigating Unauthorized Screenshots

#34

Post by izacus »

Confiks wrote: post #32
izacus wrote: post #22

Earlier quoted context omitted.

How is messaging confidental data? Remember, FLAG_SECURE prevents users from taking screenshots themselves as well and prevents display of content in several other cases (e.g. screen mirroring). Your conversations aren't nearly as sensitive to require such a large breach of usability.

Preventing screenshots and showing up in the active apps list is an option within the Signal preferences. So Signal provides a precautious default, but allows you to turn it off.

This is the right way to do it in my opinion.

Re: Android Security Auditing: Investigating Unauthorized Screenshots

#35

Post by OnlyRepliesToBS »

brodyprice wrote: post #3

The screenshots were for "recent apps" navigation, they weren't being uploaded anywhere, apps can set "FLAG_SECURE" to prevent it, the device was rooted, and the files were "...inaccessible to most apps, except those to which I grant root access." ? Can someone explain to me what the problem is? Why are the screenshots considered unauthorized?

are you fucking kidding?

Re: Android Security Auditing: Investigating Unauthorized Screenshots

#36

Post by esotericn »

Why can manual screenshots be prevented by applications?

Automated screenshots - makes sense.

But manual? I've lost count of the number of times I've had to resort to stupid nonsense like taking a photo of my phone with another phone.

It provides zero security benefit whilst making the end user's life harder.

Re: Android Security Auditing: Investigating Unauthorized Screenshots

#37

Post by tjoff »

solarkraft wrote: post #27
RafiqM wrote: post #6

Earlier quoted context omitted.

The conclusion is there's no problem, that it wasn't the nefarious activity that he originally thought it was. The additional point he's trying to make is that app developers should use FLAG_SECURE if its confidential data - messaging probably should be, and his bitcoin app should almost certainly be.

I hate apps using FLAG_SECURE with full passion. I want to take a fucking screenshot and you don't allow me to.

Yeah, for some reason web browsers feel the need to do that when browsing in private mode.

It is one thing to block automatic screenshots or screen recordings. Another when the user explicitly tries to take a screenshot.

Re: Android Security Auditing: Investigating Unauthorized Screenshots

#38

Post by kbenson »

tjoff wrote: post #37
solarkraft wrote: post #27

Earlier quoted context omitted.

I hate apps using FLAG_SECURE with full passion. I want to take a fucking screenshot and you don't allow me to.

Yeah, for some reason web browsers feel the need to do that when browsing in private mode. It is one thing to block automatic screenshots or screen recordings. Another when the user explicitly tries to take a screenshot.

I imagine the reasoning is that if you can do it, some other app might be able to trigger it, and at that point, it's all downhill.

Re: Android Security Auditing: Investigating Unauthorized Screenshots

#39

Post by FactolSarin »

esotericn wrote: post #36

Why can manual screenshots be prevented by applications? Automated screenshots - makes sense. But manual? I've lost count of the number of times I've had to resort to stupid nonsense like taking a photo of my phone with another phone. It provides zero security benefit whilst making the end user's life harder.

How can the API ever be 100% sure it's a user-initiated screenshot?

Re: Android Security Auditing: Investigating Unauthorized Screenshots

#40

Post by esotericn »

FactolSarin wrote: post #39
esotericn wrote: post #36

Why can manual screenshots be prevented by applications? Automated screenshots - makes sense. But manual? I've lost count of the number of times I've had to resort to stupid nonsense like taking a photo of my phone with another phone. It provides zero security benefit whilst making the end user's life harder.

How can the API ever be 100% sure it's a user-initiated screenshot?

It's a physical button press.
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