threat-modeling.md

Threat Model Analysis for kezong/fat-aar-android

Threat: Threat 1: Malicious AAR Substitution (Due to fat-aar-android Packaging)

• Description: An attacker creates a malicious AAR with the same name and structure as a legitimate AAR produced by fat-aar-android. Because fat-aar-android bundles all dependencies into a single unit, the attacker can replace the entire set of libraries, not just a single dependency. This makes the attack more impactful than a typical dependency confusion attack. The attacker uses social engineering, a compromised repository, or other means to trick a developer into using the malicious AAR.
• Impact: Complete application compromise. The attacker can execute arbitrary code within the application's context, leading to data theft, privilege escalation, or other malicious actions. The attack bypasses standard dependency management security checks because the entire bundle is replaced.
• Affected Component: The fat-aar-android output (the resulting AAR file). The attack leverages the fact that fat-aar-android creates a single, self-contained AAR, making it a single point of failure.
• Risk Severity: Critical
• Mitigation Strategies:
  • Strict Checksum Verification: Developers must verify the SHA-256 (or stronger) checksum of the downloaded AAR against a known-good checksum published by the original library author through a secure channel (e.g., their official website, signed release notes). Do not rely on checksums from the repository itself.
  • Digital Signature Verification: If the AAR is digitally signed by the library author, verify the signature using the author's public key. This is stronger than checksums.
  • Private, Controlled Repository: Use a private repository (e.g., Artifactory, Nexus) with strict access controls and auditing to store and distribute AARs built with fat-aar-android.

Threat: Threat 2: Tampering with Embedded Libraries Post-Build (Facilitated by fat-aar-android)

• Description: After the AAR is built using fat-aar-android, an attacker gains access to the AAR file. Because fat-aar-android embeds all dependencies as internal JAR files, the attacker can modify these JARs without affecting external dependency metadata. This makes tampering harder to detect with standard tools. The attacker injects malicious code or alters existing code within the embedded libraries.
• Impact: Application compromise. The attacker's code runs within the application, potentially with elevated privileges. The lack of external dependency tracking makes detection difficult.
• Affected Component: The embedded JAR files within the AAR produced by fat-aar-android. The vulnerability is amplified by fat-aar-android's embedding process, which obscures the individual components and makes integrity checks more complex.
• Risk Severity: Critical
• Mitigation Strategies:
  • AAR Signing (Pre-APK): Sign the AAR before it's included in the final APK. This provides an additional layer of integrity checking, specifically for the fat-aar-android output. Use a separate key for AAR signing.
  • Runtime Integrity Checks (Complex): Implement a mechanism to verify the integrity of the embedded libraries at runtime. This is challenging and may impact performance. It could involve calculating checksums of the embedded JARs and comparing them to known-good values stored securely.

Threat: Threat 3: Vulnerable Dependency Inclusion (Amplified by fat-aar-android)

• Description: A developer uses fat-aar-android to include a library with a known vulnerability. fat-aar-android embeds this vulnerable library. The key difference here is that fat-aar-android makes updating this dependency significantly harder. A new vulnerability in any embedded library requires rebuilding the entire AAR.
• Impact: The impact depends on the specific vulnerability, ranging from DoS to RCE. The "fat" nature of the AAR means a single vulnerable dependency can compromise the whole application, and updating is a major undertaking.
• Affected Component: The dependency resolution and embedding process of fat-aar-android. The plugin's core function of merging dependencies into a single AAR exacerbates the risk of vulnerable dependencies by making updates difficult and infrequent.
• Risk Severity: High (Potentially Critical, depending on the vulnerability)
• Mitigation Strategies:
  • Pre-Embedding Dependency Scanning: Use SCA tools (OWASP Dependency-Check, Snyk, etc.) before using fat-aar-android to identify known vulnerabilities.
  • Automated AAR Rebuilds: Implement a fully automated build and release process that triggers a rebuild of the AAR whenever any embedded dependency has a security update. This is crucial but complex to achieve reliably. This is the most important mitigation, and the most difficult with fat-aar-android.

Threat: Threat 4: Build Process Compromise (Targeting fat-aar-android)

• Description: An attacker compromises the build environment where fat-aar-android is used. The attacker modifies the fat-aar-android plugin itself or its configuration to inject malicious code during the AAR creation process. This is a direct attack on the tool.
• Impact: Complete application compromise. The attacker's code is embedded within the AAR and executed within the application.
• Affected Component: The fat-aar-android plugin itself and the build environment. This is a supply chain attack specifically targeting the fat-aar-android tool.
• Risk Severity: Critical
• Mitigation Strategies:
  • Secure, Isolated Build Environment: Use a secure and isolated build environment (containers, VMs). Minimize access.
  • fat-aar-android Plugin Integrity Verification: Verify the integrity of the fat-aar-android plugin (checksums, digital signatures, if available) before each build. This is crucial to detect tampering with the tool itself.
  • CI/CD Pipeline Security: Implement robust security practices for the CI/CD pipeline, including access controls, auditing, and automated security checks.