attack-surface.md

Attack Surface Analysis for wireguard/wireguard-linux

Attack Surface: 1. Kernel Module Exploitation

• Description: Vulnerabilities within the wireguard-linux kernel module code itself (e.g., buffer overflows, use-after-free, race conditions).
  • How wireguard-linux Contributes: The kernel module is the core component; any flaws in its code directly expose the system. This is a direct involvement.
  • Example: A buffer overflow in the packet processing logic could allow an attacker to inject arbitrary code into the kernel.
  • Impact:
    • Denial of Service (DoS)
    • Privilege Escalation (potentially to root)
    • Information Disclosure (kernel memory, keys)
  • Risk Severity: Critical
  • Mitigation Strategies:
    • Keep Updated: Always run the latest stable kernel and WireGuard module versions.
    • Kernel Hardening: Employ kernel hardening techniques (SELinux, AppArmor, etc.).
    • Code Auditing: (For developers) Conduct thorough code reviews and security audits of the WireGuard codebase.
    • Fuzzing: (For developers) Utilize fuzzing techniques to identify potential vulnerabilities.
    • Userspace Implementation: Consider a userspace implementation (e.g., wireguard-go) if kernel-level risks are unacceptable (trade-off: performance).

Attack Surface: 2. Netlink Interface Manipulation

• Description: Unauthorized access or manipulation of the Netlink interface used to configure WireGuard.
  • How wireguard-linux Contributes: wireguard-linux directly uses the Netlink interface for all configuration and control. This is its primary management interface.
  • Example: A compromised process with CAP_NET_ADMIN could add a malicious peer to the WireGuard configuration, granting unauthorized access.
  • Impact:
    • Configuration Modification (unauthorized peers, altered routes)
    • Information Disclosure (peer keys, allowed IPs)
    • Denial of Service (disrupting connectivity)
  • Risk Severity: High
  • Mitigation Strategies:
    • Capability Restriction: Strictly limit the use of the CAP_NET_ADMIN capability.
    • Dedicated User: Run WireGuard management tools with a dedicated, non-root user account.
    • Monitoring: Monitor Netlink messages for suspicious activity.
    • Access Control Lists (ACLs): If possible, implement ACLs to restrict which processes can interact with the WireGuard Netlink interface.

Attack Surface: 3. Private Key Compromise

• Description: An attacker gains access to a WireGuard private key.
  • How wireguard-linux Contributes: While wireguard-linux itself doesn't store the keys, its entire security model depends on the confidentiality of these keys. This is an indirect, but critical dependency. The use of the keys is directly within wireguard-linux.
  • Example: An attacker compromises a server and steals the WireGuard private key file.
  • Impact:
    • Impersonation of a legitimate peer.
    • Decryption of past and future traffic (depending on key exchange).
  • Risk Severity: Critical
  • Mitigation Strategies:
    • Secure Storage: Store private keys securely, using strong password protection and/or hardware security modules (HSMs).
    • Access Control: Implement strict access controls to prevent unauthorized access to key files.
    • Key Rotation: Regularly rotate private keys.
    • Least Privilege: Ensure the process using the key has the minimum necessary privileges.