Broadcom chips are used in approximately a billion of devices, such as all iPhones, MacBooks, the Samsung Galaxy S series, the older Google Nexus series, older Thinkpads, Raspberry Pis, various IoT devices, and more. In 2016, Cypress acquired the IoT division of Broadcom. Since then, firmware variants slightly diverged, as Broadcom kept non-IoT customers like Apple and Samsung. However, the firmware interaction and update mechanism stayed the same. We reverse-engineered how the operating systems patch this firmware and interact with it. Based on that we developed a Bluetooth experimentation framework, which is able to patch the firmware. This enables various features that otherwise would only be possible with a full-stack software-defined radio implementation, such as injecting and monitoring packets on the link layer.
InternalBlue has not only been used for our own research at the Secure Mobile Networking Lab (SEEMOO). Also, the KNOB and BIAS attack prototype were implemented using InternalBlue LMP messages and the SweynTooth attacks also experimented with InternalBlue for crafting LCP messages. Note that in contrast to tools like btlejack or Ubertooth, InternalBlue does not aim at performing Machine-in-the-Middle attacks. However, the device running InternalBlue can send arbitrary packets and also inject these into existing connections. During monitoring, all packets that are received by the device running InternalBlue are captured, and there is no packet loss. InternalBlue does not have any issues with analysis of encrypted connections or Classic Bluetooth. If you have specific feature requests for your security research, feel free to open a ticket.
In addition to security research, InternalBlue also opens possibilities for further analysis such as Bluetooth Low Energy performance statistics and improvements. Anything that can be improved within a Bluetooth stack can be directly tested on off-the-shelf devices.
Our recent research features Frankenstein, which emulates the firmware including thread switches and virtual modem input. The emulated firmware can be attached to a Linux host. Thus, the approach is full-stack. We mainly used it for fuzzing and found vulnerabilities that include host responses to be triggered. Frankenstein is in a separate repository, but depends on InternalBlue to take state snapshots etc. on a physical device.
Moreover, we just published Polypyus. It enables binary-only binary diffing, independent of IDA and Ghidra. However, it integrates into that workflow by identifying good starting points for further analysis. We already tried it across various Broadcom Wi-Fi and Bluetooth firmware.
Looking for our random number generator measurements that we did within the analysis of CVE-2020-6616? You can find them here.
There are also some more dynamic hooks for HCI with Frida on iOS and Android. We used this to study the warning behavior in the user interface upon MitM attacks. Likely useful for a lot of other experiments, though.
Due to Spectra
Table of Contents
- Feature overview
- General setup and usage
- Operating system specific setup
- Firmware overview
- SEEMOO talks and publications
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