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attack-surface.md

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Attack Surface Analysis for wireguard/wireguard-linux

Attack Surface: Kernel Exploits via Malformed Packets

  • Description: Vulnerabilities in the WireGuard kernel module's packet processing logic can be exploited by sending specially crafted or malformed network packets.
  • WireGuard-linux Contribution: wireguard-linux implements packet parsing and processing in the kernel module (wireguard.ko). Bugs in this code can lead to exploitable vulnerabilities.
  • Example: Sending a packet with an oversized header field that triggers a buffer overflow in the kernel module when processing the header length, leading to arbitrary code execution in the kernel.
  • Impact: System compromise, kernel-level code execution, denial of service, data corruption.
  • Risk Severity: Critical
  • Mitigation Strategies:
    • Developers:
      • Thoroughly audit and fuzz test the kernel module's packet processing code.
      • Implement robust input validation and bounds checking for all packet fields.
      • Utilize memory-safe programming practices in kernel module development.
      • Regularly update wireguard-linux to the latest version with security patches.
    • Users:
      • Keep the operating system and kernel updated to receive security patches for wireguard-linux.
      • Implement network firewalls to filter potentially malicious traffic before it reaches the WireGuard interface.
      • Monitor system logs for suspicious activity related to WireGuard.

Attack Surface: Cryptographic Implementation Flaws

  • Description: Vulnerabilities in the implementation of cryptographic algorithms (ChaCha20, Poly1305, Curve25519, BLAKE2s) within the wireguard-linux kernel module.
  • WireGuard-linux Contribution: wireguard-linux directly implements these cryptographic algorithms in its kernel module for encryption, authentication, and key exchange.
  • Example: A subtle flaw in the Curve25519 implementation could potentially weaken the key exchange process, making it susceptible to attacks that could reveal session keys or compromise forward secrecy.
  • Impact: Information disclosure, cryptographic bypass, man-in-the-middle attacks, loss of confidentiality and integrity.
  • Risk Severity: High
  • Mitigation Strategies:
    • Developers:
      • Utilize well-vetted and audited cryptographic libraries or implementations.
      • Perform rigorous testing and formal verification of cryptographic code.
      • Stay up-to-date with cryptographic best practices and security advisories.
      • Regularly review and update the cryptographic implementations used in wireguard-linux.
    • Users:
      • Use the latest stable version of wireguard-linux which incorporates the most recent security updates and cryptographic improvements.
      • Monitor security advisories related to the cryptographic libraries used by WireGuard and update accordingly.

Attack Surface: Handshake Protocol Vulnerabilities

  • Description: Flaws in the Noise protocol implementation within the wireguard-linux kernel module's handshake state machine.
  • WireGuard-linux Contribution: wireguard-linux implements the Noise protocol for establishing secure connections between peers. Vulnerabilities in this implementation can compromise the handshake process.
  • Example: A flaw in the state machine logic could allow an attacker to inject messages during the handshake, leading to a man-in-the-middle attack where the attacker can intercept and potentially decrypt traffic.
  • Impact: Man-in-the-middle attacks, authentication bypass, denial of service, compromise of session keys.
  • Risk Severity: High
  • Mitigation Strategies:
    • Developers:
      • Thoroughly analyze and test the Noise protocol implementation for state machine vulnerabilities and protocol weaknesses.
      • Utilize formal verification techniques to ensure the correctness of the handshake protocol implementation.
      • Adhere strictly to the Noise protocol specification and best practices.
      • Regularly review and update the handshake implementation based on security research and findings.
    • Users:
      • Use the latest stable version of wireguard-linux which includes fixes for any known handshake protocol vulnerabilities.
      • Ensure proper peer configuration and authentication mechanisms are in place.

Attack Surface: Userspace Tool Command Injection (wg-quick)

  • Description: Vulnerabilities in the wg-quick script that could allow attackers to inject arbitrary shell commands through maliciously crafted configuration files.
  • WireGuard-linux Contribution: wg-quick is a userspace tool provided with wireguard-linux for simplifying WireGuard interface configuration. It parses configuration files and executes shell commands based on their content.
  • Example: A malicious user could create a wg0.conf file with a crafted PostUp or PreDown directive containing shell commands that are executed with root privileges when wg-quick up wg0 is run.
  • Impact: Privilege escalation to root, system compromise, arbitrary code execution.
  • Risk Severity: High
  • Mitigation Strategies:
    • Developers:
      • Sanitize and validate all input from configuration files parsed by wg-quick to prevent command injection.
      • Avoid using shell commands directly in wg-quick where possible. Use safer alternatives or libraries for system configuration.
      • Implement secure coding practices in shell scripting to minimize injection risks.
    • Users:
      • Carefully review and understand the contents of WireGuard configuration files, especially if obtained from untrusted sources.
      • Restrict access to WireGuard configuration files to trusted users only.
      • Avoid running wg-quick with configuration files from untrusted sources.