Threat: Malicious Custom Rule Execution
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Threat: Malicious Custom Rule Execution
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Description: An attacker crafts a malicious ktlint rule set (JAR file) and distributes it through a compromised repository, social engineering, or a compromised dependency. A developer unknowingly downloads and integrates this rule set. When ktlint runs, the malicious rule executes arbitrary code on the developer's machine or within the CI/CD pipeline. The attacker could steal credentials, modify source code, install malware, or pivot to other systems. This is a classic supply chain attack.
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Impact:
- Complete system compromise (developer machine or CI/CD server).
- Data exfiltration (source code, credentials, sensitive data).
- Code modification (introduction of backdoors, vulnerabilities, or malicious logic).
- Lateral movement within the network.
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Affected ktlint Component: Custom rule loading mechanism (
RuleSetProvider
, class loading, and the ServiceLoader mechanism). The core vulnerability is ktlint's ability to load and execute arbitrary code from external JAR files provided as rule sets. -
Risk Severity: Critical
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Mitigation Strategies:
- Source Verification: Strictly obtain rule sets only from trusted, official sources (e.g., the official ktlint GitHub repository, extremely well-known and vetted community providers with a strong security track record). Avoid any unknown or unverified sources.
- Code Review: Mandate thorough, manual code review of the source code of any custom rule set before integration. Treat it as a high-risk third-party dependency. Do not rely solely on automated scanning.
- Checksum Verification: Always verify the SHA-256 (or other strong cryptographic hash) checksum of the downloaded rule set JAR against a known good value published by the trusted source. Automate this verification in build scripts.
- Sandboxing: Run ktlint within a strictly sandboxed environment (e.g., a Docker container with minimal privileges and network access) to contain the potential impact of malicious code execution. This is essential for CI/CD pipelines.
- Dependency Management: Use a dependency management system (e.g., Gradle, Maven) that supports and enforces checksum verification for external JAR dependencies. Configure it to fail the build if checksums do not match.
- Least Privilege: Run ktlint with the absolute minimum necessary privileges. Never run it as root or with administrator access.
- Network Restrictions: If possible, restrict network access for the environment where ktlint is executed, especially during CI/CD, to limit the attacker's ability to exfiltrate data or communicate with command-and-control servers.
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Threat: Exploitation of ktlint Vulnerability (Leading to Code Execution)
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Description: An attacker discovers a zero-day vulnerability in ktlint itself (e.g., in the parsing logic, rule engine, or a specific built-in rule) that allows for arbitrary code execution. They craft a specially designed Kotlin file that, when processed by ktlint, triggers the vulnerability and executes malicious code. This is less likely than the malicious rule scenario but still a significant risk.
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Impact:
- Remote code execution on the developer's machine or CI/CD server.
- Data exfiltration.
- Code modification.
- System compromise.
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Affected ktlint Component: Potentially any part of ktlint, depending on the specific vulnerability. Likely areas include:
KtLint.kt
(main entry point and processing logic)com.pinterest.ktlint.core.ast
(Abstract Syntax Tree parsing)- Specific rule implementations within
com.pinterest.ktlint.ruleset.standard
orcom.pinterest.ktlint.ruleset.experimental
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Risk Severity: High (Potentially Critical if a readily exploitable RCE is found)
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Mitigation Strategies:
- Keep Updated: Maintain a strict policy of updating to the latest version of ktlint immediately upon release. Automate this process in CI/CD.
- Monitor Advisories: Actively monitor ktlint's security advisories, release announcements, and any relevant security mailing lists for vulnerability disclosures.
- Sandboxing: As with malicious rules, running ktlint in a sandboxed environment (e.g., Docker) significantly reduces the impact of a potential code execution vulnerability.
- Fuzzing (Advanced): For organizations with high security requirements, consider implementing fuzz testing of ktlint to proactively discover vulnerabilities before attackers do. This is a specialized security testing technique.
- Vulnerability Scanning (Advanced): Integrate static analysis tools that can scan ktlint's codebase itself for potential vulnerabilities.
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