Blockpass aims to save you from the heart-stopping problem of typing your computer's lock-screen password into a plain text field such as a chat, Twitter, etc., and pressing return before you realize you've just shared your password with a friend, or the world.
Blockpass is a standard Mac OS X application that runs as a "faceless background application." As such it doesn't show up in the Dock. It also has no user NSStatusItem show it won't show up in the menu bar either. It simply runs quietly in the background, waiting for you to type your password (or whatever string you configure it with), and jolts you with an alert condemning the action.
Please note: by default the tool ignores typing that occurs in either Terminal or Screen Sharing.app, it won't interfere with attempts to type your password in those apps.
Blockpass is written in Swift 4.2, and expects to build for a deployment target of 10.10 or higher. It has not been tested in other environments.
Blockpass requires that you enable "access for assistive devices" for the app. The app should prompt you to make this change when it first launches, after which you must reopen the app. If it doesn't prompt you automatically, make the change manually in System Preferences -> Security & Privacy -> Privacy -> Accessibility.
Note that if you run the app directly from Xcode, it is Xcode that will require "access for assistive devices".
To install Blockpass you need to first build the application, run the app, and arrange for the app to be run every time you log in to your Mac. You can arrange this in the "Login Items" section of your user settings in the System Preferences "Users & Groups" pane.
The first time you run Blockpass, it will prompt you for a secret string, which will be saved securely in the keychain. The string you enter will dictate which keystrokes cause Blockpass to later interrupt you and prevent your typing the password in plain text.
If at any time after you first run and configure Blockpass, you wish to change the stored password, you can do so by holding the option key while Blockpass launches. First "killall Blockpass" from the Terminal, then relaunch the app.
Theoretically you should be able to override the built-in default "ignored apps" configuration by declaring your own array of application bundle identifiers, e.g.:
% defaults write com.punkitup.Blockpass IgnoredAppIdentifiers -array com.apple.dt.Xcode com.apple.Safari
% killall Blockpass
% killall cfprefsd
However in my recent tests this does not seem to be working to effectively override the built-in list. It may have something to do with my system, sandboxing, or both.
Blockpass stores your configured password string securely in the System Keychain, using the application name "Blockpass" and account name "main password". It is read from the keychain at launch time unless the option key is held down to override the saved value with a new value.
Because Blockpass has no user interface, to quit the app you will have to "killall Blockpass" from the Terminal.
Should you decide you want to stop using Blockpass entirely, simply delete the app from your computer, remove it from your login items, and "killall Blockpass" from the Terminal, or restart your Mac to be sure it is no longer running.
This project is not particularly supported. I'm sharing this because of the outpouring of requests to do so after I blogged about a related issue. I've tried to make the tool as user-friendly as possible given time constraints, but do not expect the world from me! I hope you enjoy the tool and code.