threat-modeling.md

Threat Model Analysis for google/tink

Threat: Cryptographic Algorithm Weakness

• Description: An attacker exploits a newly discovered vulnerability or weakness in a cryptographic algorithm used by Tink (e.g., AES, RSA, ECDSA). This could involve cryptanalysis to break encryption, forge signatures, or otherwise undermine the security of data protected by Tink.
• Impact: Confidentiality breach (if encryption algorithm is broken), integrity breach (if signature algorithm is broken), authentication bypass (if MAC algorithm is broken). Potentially widespread impact depending on the algorithm and its usage.
• Tink Component Affected: Core cryptographic primitives (e.g., Aead, PublicKeySign, PublicKeyVerify, Mac). Specifically, the underlying algorithm implementations within Tink.
• Risk Severity: Critical
• Mitigation Strategies:
  • Stay updated with security advisories from Tink and the broader cryptography community.
  • Use recommended key templates and algorithm choices provided by Tink, which are generally considered secure at the time of release.
  • Implement agile cryptography principles: design systems to be algorithm-agnostic where possible, allowing for easier algorithm migration if weaknesses are discovered.
  • Regularly review and update Tink library versions to benefit from security patches and algorithm updates.

Threat: Tink Implementation Bug

• Description: An attacker exploits a bug in the Tink library's code (Java, C++, Go, Python, etc.). This bug could lead to incorrect cryptographic operations, memory corruption, or other vulnerabilities that can be leveraged to bypass security controls, leak data, or cause denial of service.
• Impact: Confidentiality breach, integrity breach, authentication bypass, denial of service, potentially arbitrary code execution depending on the nature of the bug.
• Tink Component Affected: Any Tink module or function, depending on the location of the bug. Could be in core crypto primitives, key management, or API handling.
• Risk Severity: Critical
• Mitigation Strategies:
  • Stay updated with Tink security advisories and patch releases.
  • Use the latest stable version of the Tink library.
  • Report any suspected bugs in Tink to the Google Tink team.
  • Consider using static analysis and fuzzing tools to proactively identify potential bugs in Tink usage within your application.

Threat: Side-Channel Attack on Tink

• Description: An attacker performs a side-channel attack (e.g., timing attack, power analysis) against the application using Tink. By observing subtle variations in execution time, power consumption, or electromagnetic radiation during cryptographic operations, the attacker attempts to extract sensitive information like cryptographic keys.
• Impact: Key compromise, leading to confidentiality breach, integrity breach, or authentication bypass.
• Tink Component Affected: Underlying cryptographic implementations within Tink, particularly those related to key generation, encryption, decryption, signing, and verification.
• Risk Severity: High
• Mitigation Strategies:
  • Deploy applications in secure environments with physical security controls to limit attacker proximity and physical access.
  • Utilize Tink's recommended configurations and primitives, as Tink developers aim to mitigate common side-channel attack vectors.
  • Consider using hardware security modules (HSMs) or trusted execution environments (TEEs) for key storage and cryptographic operations in highly sensitive environments.
  • Perform side-channel analysis testing if the application handles extremely sensitive data and operates in a potentially hostile environment.

Threat: Insecure Key Template Selection

• Description: Developers choose an insecure or inappropriate key template provided by Tink. This could involve using weak algorithms, insecure modes of operation (e.g., ECB), or keys that are too short, significantly reducing the security provided by Tink.
• Impact: Confidentiality breach, integrity breach, authentication bypass, depending on the weakness introduced by the chosen template.
• Tink Component Affected: Key Template selection and usage within the application's code. Specifically, the KeyTemplate and KeysetHandle modules.
• Risk Severity: High
• Mitigation Strategies:
  • Thoroughly understand the security implications of each Tink key template before selecting one.
  • Prefer using recommended "safe" or "recommended" key templates provided by Tink.
  • Consult cryptography experts or security guidelines when choosing key templates for specific use cases.
  • Implement code reviews to ensure developers are selecting appropriate and secure key templates.

Threat: Insecure Key Storage

• Description: Developers store Tink keysets insecurely. This includes hardcoding keys, storing them in plaintext configuration files, using weak encryption for storage, or insufficient access controls. An attacker gaining access to the key storage can compromise all data protected by those keys.
• Impact: Complete confidentiality breach, integrity breach, and authentication bypass for all data protected by the compromised keys.
• Tink Component Affected: Key Management and Storage practices within the application. Specifically, how KeysetHandle and key material are persisted and accessed.
• Risk Severity: Critical
• Mitigation Strategies:
  • Never hardcode keys in application code.
  • Avoid storing keys in plaintext configuration files.
  • Use secure key storage mechanisms provided by Tink or the operating environment (e.g., Tink's CleartextKeysetHandle.write with secure storage, operating system key stores, dedicated key management systems).
  • Encrypt keysets at rest using strong encryption algorithms and separate key management for the key encryption key.
  • Implement strict access control to key storage locations, limiting access to only authorized processes and users.

Threat: Insufficient Key Rotation

• Description: Developers fail to implement regular key rotation for Tink keysets. If a key is compromised, the impact is prolonged, and the window of opportunity for attackers to exploit the compromised key is extended.
• Impact: Increased impact of key compromise, prolonged exposure of sensitive data, and potentially wider data breaches.
• Tink Component Affected: Key Management practices within the application. Specifically, the lack of key rotation mechanisms for KeysetHandle.
• Risk Severity: High
• Mitigation Strategies:
  • Implement a robust key rotation strategy for Tink keysets.
  • Automate key rotation processes where possible.
  • Define clear key rotation schedules based on risk assessments and industry best practices.
  • Use Tink's key management features to facilitate key rotation (e.g., key versioning, key disabling).

Threat: Incorrect Tink API Usage

• Description: Developers misuse Tink's APIs, leading to insecure cryptographic operations. This could involve incorrect parameter passing, mishandling exceptions, or not following Tink's recommended usage patterns, resulting in weakened security or vulnerabilities.
• Impact: Confidentiality breach, integrity breach, authentication bypass, denial of service, or other unexpected security failures depending on the API misuse.
• Tink Component Affected: Tink API usage throughout the application's code. Specifically, all Tink primitives and functions called by the application.
• Risk Severity: High
• Mitigation Strategies:
  • Thoroughly read and understand Tink's documentation and API specifications.
  • Follow Tink's recommended best practices and usage examples.
  • Implement unit and integration tests to verify correct Tink API usage and cryptographic operations.
  • Conduct code reviews to identify potential API misuse and ensure adherence to secure coding practices.
  • Use static analysis tools to detect potential vulnerabilities arising from incorrect API usage.