Why Smart Light Bulbs Could Be a Gateway for Password Hackers

Smart Light Bulbs Vulnerable to Cryptographic Insecurities

In a recent paper published by a group of researchers split between Italy and the UK, cryptographic insecurities were discovered in the popular smart light bulb, TP-Link Tapo L530E. The researchers chose this specific device because it is currently the best seller on Amazon Italy. While the vulnerabilities found may not directly apply to other smart bulbs, there are valuable lessons to be learned from their report.

Wireless Setup and Imposter Attacks

Like many smart devices, the Tapo L530E can be set up quickly and easily over Wi-Fi. However, this wireless-based configuration opens up the possibility of imposter attacks. By repeatedly turning the light bulb on and off at the wall switch, it can be forced into setup mode, creating a temporary Wi-Fi access point with a recognizable network name. Users then connect to this access point, unprotected by a password, to configure the light bulb to connect to their home Wi-Fi network and cloud account.

The researchers discovered that the protocol used for the setup process lacked strong cryptographic measures to ensure the authenticity of the light bulb. This means that a nearby attacker could potentially create a fake access point and trick users into sending their setup secrets, including their Wi-Fi password and TP-Link account details, to the imposter instead of the genuine light bulb.

Insufficient Protection Against Attacks

The researchers noted that while the Tapo app and L530E firmware included some basic safety checks to prevent these attacks, the protocol itself was designed to avoid mistakes rather than prevent attacks. The app uses a checksum, or keyed hash, to verify the communication between the app and the light bulb. However, the protocol uses fixed key bytes for this checksum, making it easy for attackers to forge the communication.

Additionally, the app establishes a session key with the light bulb for encrypting the data exchanged during the setup process. The researchers found that there was no verification process for this key agreement, meaning that the app could not ensure it was communicating with a genuine light bulb and not an imposter.

Cryptographic Flaws in AES Encryption and Replay Attacks

Further vulnerabilities were discovered in the handling of the session key and the encryption of data. The app uses AES-128-CBC mode for encrypting requests sent to the light bulb. However, the initialisation vector (IV) used for seeding the encryption process was generated at the same time as the session key and remained the same for every subsequent data packet, even when the data was repeated. This violates cryptographic best practices and makes the encryption predictable.

Additionally, the researchers found that old messages, even if an attacker does not understand their content, can be replayed later as if they were new. This poses a significant risk as replay attacks can be used to cause havoc or gain unauthorized access.

Editorial: The Importance of Robust Cryptography in IoT Devices

This research highlights the importance of implementing robust cryptography in Internet of Things (IoT) devices like smart light bulbs. Cryptography serves as a critical component of the “holy trinity” of confidentiality, authenticity, and integrity in ensuring secure communication.

In the case of the Tapo L530E vulnerabilities, the weaknesses in cryptographic measures allowed attackers to exploit the setup process and gain access to sensitive information like Wi-Fi passwords and account details. This demonstrates the need to prioritize not only encryption algorithms but also authentication mechanisms and protection against tampering.

Lessons Learned and Recommendations

As a user of Tapo light bulbs or any other IoT devices, it is essential to stay vigilant and take necessary precautions. Keep an eye out for firmware updates released by TP-Link to address these vulnerabilities. Additionally, developers responsible for securing network traffic and product setups should thoroughly review the research paper to ensure similar mistakes are not made.

When it comes to implementing cryptography, there are several key principles to follow:

1. Confidentiality: Encryption is just one part of the puzzle. Ensure proper measures are in place to protect data from unauthorized access.
2. Authenticity: Verify the identity of devices involved in the communication process. Employ mechanisms like certificates or strong authentication protocols to prevent imposter attacks.
3. Integrity: Implement measures to detect and prevent tampering with data during transmission.
4. Unique Keys and IVs: Never reuse keys or initialisation vectors. Use truly random IVs for each encryption process and ensure nonces or other unique values are used appropriately.
5. Protection Against Replay Attacks: Employ techniques like sequence numbers or timestamps to limit the validity of data packets and prevent replay attacks.

By adhering to these fundamental principles and regularly updating firmware, manufacturers and users can enhance the security of IoT devices and mitigate the risks posed by vulnerabilities like those discovered in the Tapo L530E smart light bulb.