Full Report
Rogan brought half of his hardware parts bin to the hackathon! Michael Rodger, Daniel Scragg, Isak van der Walt, Thulani Mabuza and Rogan Dawes formed the Chubby Hackers team to investigate the Wink Hub 2 during SenseCon 2023. This was building on our project from SenseCon 2022 where we looked at the Wink Hub 1, particularly the various debug interfaces for the main i.MX28 and the peripheral radio controller chips. There is quite a lot of detailed information available online for the Wink Hub 1, but not a whole lot for the Wink Hub 2. In fact, there is practically nothing! We aimed to change that.
Analysis Summary
# Tool/Technique: Wink Hub 2 Investigation (SenseCon 2023)
## Overview
This entry summarizes the preliminary hardware investigation conducted by the "Chubby Hackers" team (Michael Rodger, Daniel Scragg, Isak van der Walt, Thulani Mabuza, and Rogan Dawes) into the **Wink Hub 2** IoT device during SenseCon 2023. The goal was to document internal hardware and initial boot processes, contrasting the lack of public information available for the Hub 2 compared to the Hub 1.
## Technical Details
- Type: **Technique** (Hardware Teardown/Firmware Analysis)
- Platform: **Wink Hub 2** (Featuring an **i.MX6UL** CPU)
- Capabilities: Physical access and hardware interface identification (UART, JTAG), boot process monitoring, and observation of security features (Secure Boot/HAB).
- First Seen: SenseCon 2023 (Reported May 26, 2023)
## MITRE ATT&CK Mapping
This research primarily focuses on reconnaissance and initial access vectors related to embedded devices, mapping to the following Tactic for analysis of an organization's assets:
- **TA0011 - Command and Control** (Indirectly, as successful exploitation would lead here)
- T1095 - Non-Application Layer Protocol (Implied, through network service analysis for provisioning)
- **TA0003 - Persistence** (Implied, if firmware modification is successful)
- T1543.003 - Create or Modify System Process: Microcontroller Firmware (If firmware image is modified)
*(Note: Since this is a research/vulnerability discovery effort on an IoT device, direct application of mature malware tactics is limited, focusing instead on hardware access techniques.)*
## Functionality
### Core Capabilities Observed
- **Physical Access:** Successful procedure for opening the case, locating the PCB, and accessing component-side details.
- **Debug Interface Access:** Successful connection to the **UART** interface for the i.MX6 main CPU at **115200 baud** rate.
- **Boot Process Visibility:** Captured the boot log, revealing firmware partitions (`boot`, `updater`, `database`, `dbBackup`, `app`).
- **Firmware Integrity Check:** Confirmed that **Secure Boot** and **High Assurance Boot (HAB)** mechanisms are enabled and active, verifying signatures for U-Boot, the app, and updater partitions using on-chip fuses storing the public key hash.
- **Update Mechanism Trigger:** Identified that the `DO_UPDATE` file in the `database` partition controls whether the device boots the primary app or initiates an update (`1` suggests update).
### Advanced Features
- **High Assurance Boot (HAB):** The i.MX6UL utilizes asymmetric key cryptography enforced by the boot ROM to validate U-Boot and subsequent partitions, significantly hindering unauthorized firmware replacement unless the private key is compromised or a bypass vulnerability is found.
- **Partition Scheme:** Utilizes distinct firmware partitions, suggesting a dual application/fallback setup common in embedded systems.
## Indicators of Compromise
The analysis focused on research artifacts rather than active compromise. No traditional IOCs (like C2 domains) were discovered during this initial stage.
- File Hashes: SHA256 hash provided for the boot log: `aba4b2bb62860c35832a388e7efeb3dc`
- File Names: `DO_UPDATE` (Control file on the database partition)
- Network Indicators: None discovered during initial boot without connecting to network/provisioning services.
- Behavioral Indicators: U-Boot automatically proceeds without user interruption (`Hit any key to stop autoboot: 0` timeout).
## Associated Threat Actors
No specific threat actor groups were associated with the Wink Hub 2 vulnerability discovery reported here. This research was conducted by security professionals performing security testing/hardware analysis.
## Detection Methods
Detection methods relate to recognizing unauthorized hardware access or configuration changes:
- **Behavioral Detection:** Monitoring for anomalous power-on sequences without expected network initialization or attempts to manipulate flash chip control lines (if debugging equipment is attached).
- **Physical Detection:** Detection of tampering indicators on the casing or addition of soldering connections/header pins to debug points (JTAG/UART).
## Mitigation Strategies
Recommendations center on protecting the integrity of the boot chain and controlling physical access:
- **Hardware Hardening:** Utilizing epoxy or tamper-evident seals over debug headers and vulnerable components (like flash chips).
- **Secure Boot Enforcement:** Since HAB is enabled, ensuring that firmware updates originate only from trusted sources that possess the appropriate signing keys.
- **Physical Security:** Restricting physical access to the device to prevent teardown and direct interface probing.
## Related Tools/Techniques
- **Wink Hub 1 Analysis (SenseCon 2022):** The preceding research that established baseline knowledge of the platform's debug interfaces.
- **i.MX6 CPU Vulnerability:** Reference to **CVE-2022-45163** documented by NCC Group, suggesting a potential avenue (if exploitable) to bypass HAB protections, possibly via USB boot alteration.
- **USB Interface Manipulation:** Future planned work involves finding and altering the strapping resistor responsible for selecting the boot source (e.g., forcing boot from USB, though potentially blocked by HAB).