Pitfalls of requesting camera and microphone permission for an Electron app on macOS

Our company’s Electron app would occasionally Crash during device detection. After digging into it, the app didn’t have camera and microphone permission, which caused the crash during device detection.

On macOS 10.14 and later, you have to explicitly grant microphone and camera permission to your own app. Otherwise it cannot use the system camera or microphone. For details, see: Requesting Authorization for Media Capture on macOS (opens in a new tab)

Apple’s docs say that if you want microphone and camera permission, you have to set the related keys in the plist. They are:

• Microphone: NSMicrophoneUsageDescription (opens in a new tab)
• Camera: NSCameraUsageDescription (opens in a new tab)

The Description suffix tells you these keys explain why your app needs the microphone and camera.

Packaging an Electron App is usually done with electron-builder (opens in a new tab). In its docs for Mac packaging there is an extendInfo option: it adds your custom keys to the plist. In electron-builder.yml it looks like this:

mac:
  extendInfo:
    NSMicrophoneUsageDescription: Please allow this app to access your microphone
    NSCameraUsageDescription: Please allow this app to access your camera

After you write that, you’ll find it does nothing. Those two keys only explain why the app is asking for permission. They do not actually request it.

To request camera and microphone permission, you need these keys:

• com.apple.security.device.camera
• com.apple.security.device.audio-input

There is a prerequisite for adding them: you must turn on hardenedRuntime (opens in a new tab).¹ It tightens runtime integrity. For details, see: Hardened Runtime Entitlements (opens in a new tab)

So now we add hardenedRuntime:

mac:
  hardenedRuntime: true
  extendInfo:
    NSMicrophoneUsageDescription: Please allow this app to access your microphone
    NSCameraUsageDescription: Please allow this app to access your camera

The actual request is done with the entitlements option. The config looks like this:

electron-builder.yml

mac:
  entitlements: entitlements.mac.plist
  hardenedRuntime: true
  extendInfo:
    NSMicrophoneUsageDescription: Please allow this app to access your microphone
    NSCameraUsageDescription: Please allow this app to access your camera

entitlements.mac.plist

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE plist PUBLIC "-//Apple//DTD PLIST 1.0//EN" "http://www.apple.com/DTDs/PropertyList-1.0.dtd">
<plist version="1.0">
  <dict>
    <key>com.apple.security.device.audio-input</key>
    <true/>
    <key>com.apple.security.device.camera</key>
    <true/>
  </dict>
</plist>

If you try this, the app will crash on launch, or it won’t even package.

That’s because once you turn on hardenedRuntime to tighten app security, you have to loosen that security a bit. In entitlements.mac.plist you also need:

• com.apple.security.cs.allow-jit (opens in a new tab)
• com.apple.security.cs.allow-unsigned-executable-memory (opens in a new tab)
• com.apple.security.cs.allow-dyld-environment-variables (opens in a new tab)

The final entitlements.mac.plist looks like this:

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE plist PUBLIC "-//Apple//DTD PLIST 1.0//EN" "http://www.apple.com/DTDs/PropertyList-1.0.dtd">
<plist version="1.0">
  <dict>
    <key>com.apple.security.cs.allow-jit</key>
    <true/>
    <key>com.apple.security.cs.allow-unsigned-executable-memory</key>
    <true/>
    <key>com.apple.security.cs.allow-dyld-environment-variables</key>
    <true/>
    <key>com.apple.security.device.audio-input</key>
    <true/>
    <key>com.apple.security.device.camera</key>
    <true/>
  </dict>
</plist>

From here, your Electron app should be able to request and use the camera and microphone on macOS.