SiriSpy flaw allows eavesdropping on users’ conversations with Siri

SiriSpy is a vulnerability affecting Apple iOS and macOS that allowed apps to eavesdrop on users’ conversations with Siri.

SiriSpy is a now-patched vulnerability, tracked as CVE-2022-32946, in Apple’s iOS and macOS that could have potentially allowed any app with access to Bluetooth to eavesdrop on conversations with Siri and audio.

“An app may be able to record audio using a pair of connected AirPods.” reads the advisory published by Apple. “This issue was addressed with improved entitlements.”

The malicious app with access to Bluetooth could record the conversations from the iOS keyboard dictation feature when using AirPods or Beats headsets.

According to app developer Guilherme Rambo, who reported SiriSpy to Apple, the app doesn’t request microphone access permission and doesn’t leave any trace that it was listening to the microphone.

“Any app with access to Bluetooth could record your conversations with Siri and audio from the iOS keyboard dictation feature when using AirPods or Beats headsets.” reads a blog post published by Rambo. “This would happen without the app requesting microphone access permission and without the app leaving any trace that it was listening to the microphone.”

While testing AirBuddy’s features, the experts noticed that the AirPods included a service with the UUID 9bd708d7-64c7-4e9f-9ded-f6b6c4551967, and with characteristics that supported notifications. Further investigation allowed him to associated the above UUID to the DoAP service used for Siri and Dictation support.

An attacker can create a malicious app that could be connected to the AirPods via Bluetooth and record the audio in the background.

“In a real-world exploit scenario, an app that already has Bluetooth permission for some other reason could be doing this without any indication to the user that it’s going on, because there’s no request to access the microphone, and the indication in Control Center only lists “Siri & Dictation”, not the app that was bypassing the microphone permission by talking directly to the AirPods over Bluetooth LE.” added the expert.

Investigating the same issue on macOS, Rambo discovered that exploiting the issue can allow to completely bypass of the Transparency, Consent and Control (TCC) security framework. This means that a malicious app can eavesdrop conversations with Siri without requesting any permissions.

On Apple’s platforms, the BTLEServerAgent (or BTLEServer, depending on the platform) is responsible for handling of the DoAP protocol. It provides an interface over the mach service com.apple.BTLEAudioController.xpc, which other processes on the system can use to request audio from the AirPods DoAP service.

The experts explained that the lack of entitlement checks for BTLEServerAgent is the root cause of the problem.

“For services that are exposed to third-party apps, system daemons usually check for a specific entitlement before allowing an app to send requests to them, or put up a TCC prompt on the app’s behalf, only allowing the communication to go through once the user has approved it. You can probably see where this is going: BTLEServerAgent did not have any entitlement checks or TCC prompts in place for its com.apple.BTLEAudioController.xpc service, so any process on the system could connect to it, send requests, and receive audio frames from AirPods.” concludes the expert. “This exploit would only work on macOS, because the more restricted sandbox of iOS prevents apps from accessing most global mach services directly.”

Apple addressed the issue with the release of  iOS 16.1 and iPadOS 16 (October 24, 2022) and updates for macOS.

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Pierluigi Paganini

(SecurityAffairs – hacking, SiriSpy)

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