applock

Prevent user from opening app as penalty.

Features

Prevent user from using the app for certain amount of time. Designed to be used in scenarios when app is ran in a fully offline scenario, assuming the app has been ran at least once in a trusted enviorment.

Who is it for?

• Apps that is ran in airgap scenario without network access
• Assumes that attacker has non-root code execution/physical access to device
• Scenarios that doesn't rely on external OS state, only assumes that app files are intact.

Usage

In your pubspec.yaml

dependencies:
  applock:
    git:
      url: https://github.com/mrcyjanek/applock
      ref: master

Move runApp call into separate function ($main in our example), instead of runApp call await AppLock.instance.registerAppStart(appTheme, $main);

Then, in scenario where user failed to authenticate call following function, after 5 calls to this functions app will lock itself:

await AppLock.instance.fail(appTheme, $main);

and whenever user inputs correct password:

await AppLock.instance.success();

Penalty levels

There are multiple penalty levels in app, and each of these get activated depending on the number of failures

Standard

Forces user to wait while app is awaiting Future.delayed in a loop, very light CPU usage. If at any point app detects that future took over 10% more/less than the time it will invalidate the challenge.

• AppLockPenalty.standardLow => TimeChallenge(timeTotal: 30),
• AppLockPenalty.standardMedium => TimeChallenge(timeTotal: 2 * 60),
• AppLockPenalty.standardHigh => TimeChallenge(timeTotal: 10 * 60),

Tamper

Forces user to wait while app is computing CPU-intensive task (on a single core) that takes on estimate 2 minutes for low and 15 minutes for high difficulty, preventing any time manipulation from being effective, as time is calculated in most wasteful way imaginable.

• AppLockPenalty.tamperLow => HashcashChallenge(difficulty: HashcashChallengeDifficulty.low),
• AppLockPenalty.tamperHigh => HashcashChallenge(difficulty: HashcashChallengeDifficulty.high),

App usually prefer normal time-based wait, unless app is under the risk of being debuggable (adb is enabled, or few other flags for android), then it will skip time-based penalty and go straight to CPU tasks.