I understand Signal’s stance on this. For this vulnerability, the attacker needs physical access to computer. If the attacker has already gained physical access, the attacker can already access your messages, crypto wallets, password managers.
Many password managers also have this flaw. For example, Someone can change Keepass master password if the user is already logged in to the session, if they have physical access to the PC and lock you out of all your accounts.
Yeah, this is why I added a hardware key to my db. The hardware key is required not just for reading the db, but writing to it as well.
Another tip: use something like an OnlyKey that has its own locking and self-destruct mechanisms so this method isn’t foiled by simply acquiring the key.
For example, Someone can change Keepass master password if the user is already logged in to the session, if they have physical access to the PC and lock you out of all your accounts.
This seems like easy fix is available. On Windows, Access Shadow copies, restore previous version from $DayBeforeLockout. Or on Linux, specific file systems have automatic volume level snapshotting available. Or on either…restore the keepass file from a backup before the change.
They don’t need physical access (hold the device in their hand), they just need a command execution, which is a much lower bar. I expect some defence in depth for an application that holds some of the most private information there is about me.
The argument still holds. If they have remote execution access, they already have your data. Encryption can’t protect your data here because encrypted data will automatically become unencrypted once the user logs into the computer. If the attacker has remote access they can log into your account and the data will be unencrypted.
No, defense in depth is still important.
It’s true that full-disk encryption is useless against remote execution attacks, because the attacker is already inside that boundary. (i.e., As you say, the OS will helpfully decrypt the file for the attacker.)
However, it’s still useful to have finer-grained encryption of specific files. (Preferably in addition to full-disk encryption, which remains useful against other attack vectors.) i.e., Prompt the user for a password when the program starts, decrypt the data, and hold it in RAM that’s only accessible to that running process. This is more secure because the attacker must compromise additional barriers. Physical access is harder than remote execution with root, which is harder than remote execution in general.
They don’t necessarily need RCE access.
Also this isn’t how security works. Please refer to the Swiss cheese model.
Unless you can guarantee that every application ever installed on every computer will always be secure under every circumstances then you’re already breaking your security model.
An application may expose a vulnerable web server which may allow read only file system access without exposing the user to any direct control of their computer from an attacker. Now your lack of security posture for your application (signal) now has a shared fate to any other application anyone else built.
This is just one of many easy examples that are counter to your argument here.
