> Does Signal save history? Or does it save your encryption keys in a file?
Even on Signal Desktop, retrieving things from an outside app is very-hard-to-impossible depending on configuration and what you're after.
There's a reason most Signal bots (even benign ones) hook up an event stream to a specially configured Signal daemon and build an external record of data from Signal by watching for events over time.
> More, a compromized app can execute Signal itself, attach a debugger to it, fake inputs, read outputs, read it's memory...
I think you're missing a lot of the attack surface here. "Local execution is game over" is a technically-true-but-incomplete thought-terminating statement; it's more useful to assess "if I grant local execution, what attackers are likely to be interested in that, and what attacks are they likely to perform?"
Like sure, if you install something containing a full userland rootkit designed to attack a given application, and that application isn't running in a container such that you have to pivot through root to access it, you're screwed.
Those do exist, but there are a ton of local attack vectors that aren't that. Many pieces of malicious code that install with local apps aren't that complex, since complexity begets size and suspicious-behavior detection. Less complex malware would prefer to e.g. read Firefox's sqlite database files rather than try to execute new instances of trusted programs like Signal to get data out of them. We know from analysis of a lot of malware that it overwhelmingly prefers low-hanging fruit that's easy to harvest quickly and without doing much that risks detection. Some malware's scarier, but like Mickens said, most people a) aren't gonna get Mossad'd on, and b) can't do much about it if they are: https://www.usenix.org/system/files/1401_08-12_mickens.pdf
There are also local attack vectors that don't involve installing malware directly. Local programs that run code (browsers) and plenty of other exploits in e.g. decoders are limited enough in what's possible within the exploit chain that they can't calc.exe you and instead rely on info harvesting from speculative execution
Flatpak/Snap/etc., also can assist with a layer of local-app security here.
Put all that together, and you end up at the conclusion that a large volume of data is only practically accessible to a lot of malware by accessing another running app's memory. Two significant ways to do that are 1) reading memory directly (significantly mitigated by hardware permissioning/segmentation/ASLR) and 2) reading data those apps publish to the display system. Wayland makes that second one a lot harder.
Even on Signal Desktop, retrieving things from an outside app is very-hard-to-impossible depending on configuration and what you're after.
There's a reason most Signal bots (even benign ones) hook up an event stream to a specially configured Signal daemon and build an external record of data from Signal by watching for events over time.
> More, a compromized app can execute Signal itself, attach a debugger to it, fake inputs, read outputs, read it's memory...
I think you're missing a lot of the attack surface here. "Local execution is game over" is a technically-true-but-incomplete thought-terminating statement; it's more useful to assess "if I grant local execution, what attackers are likely to be interested in that, and what attacks are they likely to perform?"
Like sure, if you install something containing a full userland rootkit designed to attack a given application, and that application isn't running in a container such that you have to pivot through root to access it, you're screwed.
Those do exist, but there are a ton of local attack vectors that aren't that. Many pieces of malicious code that install with local apps aren't that complex, since complexity begets size and suspicious-behavior detection. Less complex malware would prefer to e.g. read Firefox's sqlite database files rather than try to execute new instances of trusted programs like Signal to get data out of them. We know from analysis of a lot of malware that it overwhelmingly prefers low-hanging fruit that's easy to harvest quickly and without doing much that risks detection. Some malware's scarier, but like Mickens said, most people a) aren't gonna get Mossad'd on, and b) can't do much about it if they are: https://www.usenix.org/system/files/1401_08-12_mickens.pdf
There are also local attack vectors that don't involve installing malware directly. Local programs that run code (browsers) and plenty of other exploits in e.g. decoders are limited enough in what's possible within the exploit chain that they can't calc.exe you and instead rely on info harvesting from speculative execution
Flatpak/Snap/etc., also can assist with a layer of local-app security here.
Put all that together, and you end up at the conclusion that a large volume of data is only practically accessible to a lot of malware by accessing another running app's memory. Two significant ways to do that are 1) reading memory directly (significantly mitigated by hardware permissioning/segmentation/ASLR) and 2) reading data those apps publish to the display system. Wayland makes that second one a lot harder.