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Mitigation Strategies Analysis for google/flatbuffers

Mitigation Strategy: Schema Validation and Review

  • Description:

    1. Establish Schema Validation Process: Integrate schema validation into your development workflow, specifically for FlatBuffers schemas.
    2. Automated Schema Checks: Use the FlatBuffers schema compiler (flatc) with validation flags (--schema-validation-only) during schema development and in CI/CD to automatically check for FlatBuffers schema errors.
    3. Linting Rules: Implement or adopt schema linting rules specific to FlatBuffers schemas to enforce best practices and catch potential issues related to FlatBuffers schema design.
    4. Manual Peer Reviews: Require peer reviews of all FlatBuffers schema changes by developers knowledgeable in FlatBuffers and security implications of schema design.
    5. Document Schema Changes: Maintain a record of changes to FlatBuffers schemas, including security considerations.

    • Threats Mitigated:

      • Logical Vulnerabilities (Schema-Based): Severity: Medium to High. Poorly designed FlatBuffers schemas can introduce logical flaws exploitable through crafted FlatBuffers messages.
      • Parsing Errors/Unexpected Behavior (Schema Issues): Severity: Low to Medium. Invalid or inconsistent FlatBuffers schemas can cause parsing errors or unexpected behavior when processing FlatBuffers data.

    • Impact:

      • Logical Vulnerabilities (Schema-Based): Medium to High reduction. Proactive FlatBuffers schema validation and review significantly reduce schema-related vulnerabilities.
      • Parsing Errors/Unexpected Behavior (Schema Issues): High reduction. Ensures FlatBuffers schemas are well-formed, minimizing parsing errors due to schema problems.

    • Currently Implemented: Partially implemented. Automated schema checks using flatc --schema-validation-only are in CI/CD. Basic naming conventions are informally followed for FlatBuffers schemas.

    • Missing Implementation: Formal linting rules for FlatBuffers schemas are not defined. Manual peer reviews are inconsistent for FlatBuffers schema changes. Formal documentation of FlatBuffers schema changes is missing.

Mitigation Strategy: Schema Versioning and Management

  • Description:

    1. Adopt Semantic Versioning for FlatBuffers Schemas: Use semantic versioning for FlatBuffers schemas to manage schema evolution.
    2. Central FlatBuffers Schema Registry: Establish a central repository for managing FlatBuffers schema versions.
    3. Schema Identification in FlatBuffers Payloads: Include a mechanism to identify the FlatBuffers schema version within payloads or metadata.
    4. Backward and Forward Compatibility for FlatBuffers Schemas: Design FlatBuffers schemas with backward and forward compatibility in mind to ease schema evolution.
    5. Application-Side FlatBuffers Version Handling: Implement logic to handle different FlatBuffers schema versions in applications.

    • Threats Mitigated:

      • Schema Mismatches (FlatBuffers): Severity: Medium to High. Incompatible FlatBuffers schema versions can cause parsing failures and data corruption when using FlatBuffers.
      • Denial of Service (FlatBuffers Version Mismatch): Severity: Low to Medium. FlatBuffers schema mismatches leading to parsing failures can cause denial of service.

    • Impact:

      • Schema Mismatches (FlatBuffers): High reduction. Clear FlatBuffers schema versioning and management reduce incompatibility risks.
      • Denial of Service (FlatBuffers Version Mismatch): Low to Medium reduction. Minimizes DoS risk from FlatBuffers schema versioning issues.

    • Currently Implemented: Partially implemented. FlatBuffers schemas are in Git, but semantic versioning is not strictly enforced. Version field exists in root table of FlatBuffers messages.

    • Missing Implementation: Formal semantic versioning for FlatBuffers schemas is needed. Dedicated FlatBuffers schema registry is missing. Formal backward/forward compatibility strategy for FlatBuffers schemas is lacking. Application-side FlatBuffers version handling is basic.

Mitigation Strategy: Input Size Limits

  • Description:

    1. Analyze Expected FlatBuffers Data Size: Determine typical and maximum sizes of FlatBuffers messages.
    2. Define Maximum FlatBuffers Size Limit: Set a maximum allowed size for incoming FlatBuffers payloads.
    3. Implement Size Check (FlatBuffers Payloads): Check the size of incoming FlatBuffers messages before parsing.
    4. Reject Oversized FlatBuffers Payloads: Reject FlatBuffers messages exceeding the size limit.
    5. Configuration (FlatBuffers Size Limit): Make the FlatBuffers maximum size limit configurable.

    • Threats Mitigated:

      • Denial of Service (DoS) - Resource Exhaustion (Large FlatBuffers): Severity: High. Oversized FlatBuffers messages can exhaust server resources.
      • Buffer Overflow (Potential - Large FlatBuffers): Severity: Medium. Extremely large FlatBuffers inputs could theoretically expose vulnerabilities.

    • Impact:

      • Denial of Service (DoS): High reduction. Prevents resource exhaustion from oversized FlatBuffers messages.
      • Buffer Overflow (Potential): Low to Medium reduction. Adds defense against buffer overflows related to FlatBuffers input size.

    • Currently Implemented: Yes, implemented in server network listener for FlatBuffers messages. Limit in server.conf.

    • Missing Implementation: Size limits not consistently applied to all FlatBuffers message receiving points. Client-side limits for outgoing FlatBuffers messages are missing.

Mitigation Strategy: Depth and Nesting Limits

  • Description:

    1. Analyze FlatBuffers Schema Nesting: Understand maximum expected nesting depth in FlatBuffers schemas.
    2. Define Maximum FlatBuffers Nesting Limit: Set a limit on maximum nesting depth for FlatBuffers messages.
    3. Implement Depth Tracking during FlatBuffers Parsing: Track nesting depth while parsing FlatBuffers messages.
    4. Reject Deeply Nested FlatBuffers Payloads: Reject FlatBuffers messages exceeding the nesting limit.
    5. Configuration (FlatBuffers Nesting Limit): Make the FlatBuffers nesting depth limit configurable.

    • Threats Mitigated:

      • Stack Overflow (Deeply Nested FlatBuffers): Severity: High. Deeply nested FlatBuffers messages can cause stack overflow during parsing.
      • Denial of Service (CPU Exhaustion - Deeply Nested FlatBuffers): Severity: Medium. Parsing deeply nested FlatBuffers can exhaust CPU.

    • Impact:

      • Stack Overflow: High reduction. Prevents stack overflow from deeply nested FlatBuffers structures.
      • Denial of Service (CPU Exhaustion): Medium reduction. Reduces DoS risk from complex FlatBuffers structures.

    • Currently Implemented: No. Depth and nesting limits are not implemented in FlatBuffers parsing logic.

    • Missing Implementation: Depth tracking and limit checking needed in FlatBuffers parsing routines.

Mitigation Strategy: Field Range and Value Validation

  • Description:

    1. Identify Critical FlatBuffers Fields: Determine critical fields in FlatBuffers schemas.
    2. Define Validation Rules for FlatBuffers Fields: Define validation rules for critical FlatBuffers fields (type, range, enums, etc.).
    3. Implement Validation Logic (FlatBuffers Parsing): Integrate validation logic into FlatBuffers parsing/deserialization.
    4. Error Handling (FlatBuffers Validation): Handle FlatBuffers validation failures gracefully, reject messages, log errors.
    5. Configuration (FlatBuffers Validation Rules): Consider making FlatBuffers validation rules configurable.

    • Threats Mitigated:

      • Data Integrity Issues (FlatBuffers Data): Severity: Medium to High. Invalid FlatBuffers field values can cause data corruption.
      • Logical Vulnerabilities (Exploitation of Invalid FlatBuffers Values): Severity: Medium to High. Attackers might exploit vulnerabilities via invalid FlatBuffers field values.

    • Impact:

      • Data Integrity Issues (FlatBuffers Data): High reduction. FlatBuffers validation ensures data integrity.
      • Logical Vulnerabilities (Exploitation of Invalid FlatBuffers Values): Medium to High reduction. Reduces attack surface related to invalid FlatBuffers field values.

    • Currently Implemented: Basic type checks are implicit in FlatBuffers parsing. Some manual validation exists, but not systematic for FlatBuffers fields.

    • Missing Implementation: Systematic FlatBuffers field range and value validation is missing. Centralized FlatBuffers validation framework is needed. Consistent FlatBuffers validation rules are lacking.

Mitigation Strategy: String and Vector Length Limits

  • Description:

    1. Analyze FlatBuffers String/Vector Usage: Understand string/vector usage in FlatBuffers schemas and applications.
    2. Define Maximum Length Limits (FlatBuffers Strings/Vectors): Set maximum length limits for strings and vectors in FlatBuffers messages.
    3. Implement Length Checks during FlatBuffers Parsing: Check string/vector lengths during FlatBuffers parsing.
    4. Reject Oversized FlatBuffers Strings/Vectors: Reject FlatBuffers messages with oversized strings/vectors.
    5. Configuration (FlatBuffers String/Vector Length Limits): Make FlatBuffers string/vector length limits configurable.

    • Threats Mitigated:

      • Buffer Overflow (FlatBuffers String/Vector Length): Severity: Medium to High. Long strings/vectors in FlatBuffers can cause buffer overflows.
      • Denial of Service (Memory Exhaustion - FlatBuffers Strings/Vectors): Severity: Medium to High. Long FlatBuffers strings/vectors can exhaust memory.
      • Denial of Service (CPU Exhaustion - FlatBuffers Strings/Vectors): Severity: Medium. Operations on long FlatBuffers strings/vectors can exhaust CPU.

    • Impact:

      • Buffer Overflow (FlatBuffers String/Vector Length): Medium to High reduction. Limits buffer overflow risk from long FlatBuffers strings/vectors.
      • Denial of Service (Memory Exhaustion - FlatBuffers Strings/Vectors): Medium to High reduction. Prevents memory exhaustion from large FlatBuffers string/vector data.
      • Denial of Service (CPU Exhaustion - FlatBuffers Strings/Vectors): Medium reduction. Reduces CPU exhaustion risk from long FlatBuffers strings/vectors.

    • Currently Implemented: No. String and vector length limits are not enforced during FlatBuffers parsing.

    • Missing Implementation: Length checks needed in FlatBuffers parsing for strings/vectors. Configurable FlatBuffers length limits are needed.

Mitigation Strategy: Fuzzing and Security Testing

  • Description:

    1. Choose Fuzzing Tools (FlatBuffers): Select fuzzing tools for FlatBuffers parsing.
    2. Generate Fuzzing Corpus (FlatBuffers): Create a corpus of valid and invalid FlatBuffers messages for fuzzing.
    3. Run Fuzzing Campaigns (FlatBuffers Parsing): Fuzz FlatBuffers parsing code.
    4. Analyze Fuzzing Results (FlatBuffers): Analyze crashes/errors from FlatBuffers fuzzing.
    5. Fix Vulnerabilities (FlatBuffers Parsing): Patch FlatBuffers parsing code based on fuzzing findings.
    6. Automate Fuzzing (FlatBuffers): Integrate FlatBuffers fuzzing into CI/CD.

    • Threats Mitigated:

      • Buffer Overflows (FlatBuffers Parsing): Severity: High. Fuzzing finds buffer overflows in FlatBuffers parsing.
      • Memory Corruption (FlatBuffers Parsing): Severity: High. Fuzzing detects memory corruption in FlatBuffers parsing.
      • Denial of Service (Parsing Errors - FlatBuffers): Severity: Medium to High. Fuzzing reveals parsing errors causing DoS in FlatBuffers processing.
      • Unexpected Behavior (FlatBuffers Parsing): Severity: Medium. Fuzzing uncovers unexpected behavior in FlatBuffers parsing.

    • Impact:

      • Buffer Overflows (FlatBuffers Parsing): High reduction. Fuzzing is effective for finding FlatBuffers buffer overflows.
      • Memory Corruption (FlatBuffers Parsing): High reduction. Fuzzing is effective for detecting FlatBuffers memory corruption.
      • Denial of Service (Parsing Errors - FlatBuffers): Medium to High reduction. Fuzzing helps find FlatBuffers parsing errors leading to DoS.
      • Unexpected Behavior (FlatBuffers Parsing): Medium reduction. Fuzzing can uncover various unexpected behaviors in FlatBuffers parsing.

    • Currently Implemented: No. FlatBuffers-specific fuzzing and security testing are not performed.

    • Missing Implementation: FlatBuffers fuzzing infrastructure needs setup, corpus creation, CI/CD integration.

Mitigation Strategy: Resource Limits during Parsing

  • Description:

    1. Identify Resource Bottlenecks (FlatBuffers Parsing): Analyze resource bottlenecks in FlatBuffers parsing.
    2. Implement Parsing Timeouts (FlatBuffers): Set timeouts for FlatBuffers parsing operations.
    3. Monitor Memory Usage (FlatBuffers Parsing): Monitor memory usage during FlatBuffers parsing.
    4. Resource Limits per Request (FlatBuffers Parsing): Set resource limits per FlatBuffers parsing request in multi-threaded environments.
    5. Configuration (FlatBuffers Resource Limits): Make FlatBuffers resource limits configurable.

    • Threats Mitigated:

      • Denial of Service (CPU Exhaustion - FlatBuffers Parsing): Severity: Medium to High. Complex FlatBuffers messages can exhaust CPU during parsing.
      • Denial of Service (Memory Exhaustion - FlatBuffers Parsing): Severity: Medium to High. Parsing complex FlatBuffers can exhaust memory.
      • Time-Based Attacks (Slow FlatBuffers Parsing): Severity: Low to Medium. Slow FlatBuffers parsing can be exploited for time-based attacks.

    • Impact:

      • Denial of Service (CPU Exhaustion - FlatBuffers Parsing): Medium to High reduction. FlatBuffers parsing timeouts and CPU limits prevent CPU exhaustion.
      • Denial of Service (Memory Exhaustion - FlatBuffers Parsing): Medium to High reduction. FlatBuffers parsing memory limits prevent memory exhaustion.
      • Time-Based Attacks (Slow FlatBuffers Parsing): Low to Medium reduction. FlatBuffers parsing timeouts mitigate some time-based attacks.

    • Currently Implemented: No. Resource limits during FlatBuffers parsing are not implemented.

    • Missing Implementation: FlatBuffers parsing timeout mechanisms and memory monitoring are needed. Configurable FlatBuffers resource limits are required.

Mitigation Strategy: Use Latest Stable flatc Version

  • Description:

    1. Track flatc Releases: Monitor for new stable flatc compiler versions.
    2. Update flatc Regularly: Update to the latest stable flatc compiler version.
    3. Version Pinning (flatc): Pin the flatc version in the project build system.
    4. Test After flatc Updates: Re-run tests after updating flatc.

    • Threats Mitigated:

      • Compiler Vulnerabilities (flatc): Severity: Medium to High. Older flatc versions might have vulnerabilities.
      • Bugs in Generated Code (flatc): Severity: Low to Medium. Bugs in older flatc can cause errors in generated code.

    • Impact:

      • Compiler Vulnerabilities (flatc): Medium to High reduction. Latest flatc reduces risk of compiler vulnerabilities.
      • Bugs in Generated Code (flatc): Low to Medium reduction. Latest flatc reduces bugs in generated code.

    • Currently Implemented: Partially implemented. Project uses flatc, but updates are not immediate. Version pinning is used but not strictly enforced for latest stable flatc.

    • Missing Implementation: Formal process for updating to latest stable flatc is needed. Strict flatc version pinning is required.

Mitigation Strategy: Static Analysis of Generated Code

  • Description:

    1. Choose Static Analysis Tools (Generated FlatBuffers Code): Select static analysis tools for the language of generated FlatBuffers code.
    2. Integrate Static Analysis into CI/CD (FlatBuffers Code): Integrate static analysis for generated FlatBuffers code into CI/CD.
    3. Configure Analysis Rules (FlatBuffers Code): Configure static analysis rules for security issues in generated FlatBuffers code.
    4. Review Analysis Results (FlatBuffers Code): Review static analysis results for generated FlatBuffers code.
    5. Code Audits (Manual - Generated FlatBuffers Code): Conduct manual audits of critical generated FlatBuffers code.

    • Threats Mitigated:

      • Buffer Overflows (in Generated FlatBuffers Code): Severity: High. Static analysis can detect buffer overflows in generated FlatBuffers parsing code.
      • Memory Leaks (in Generated FlatBuffers Code): Severity: Medium. Static analysis can identify memory leaks in generated FlatBuffers code.
      • Null Pointer Dereferences (in Generated FlatBuffers Code): Severity: Medium. Static analysis can detect null pointer dereferences in generated FlatBuffers code.
      • Other Code Defects (in Generated FlatBuffers Code): Severity: Low to Medium. Static analysis can find other defects in generated FlatBuffers code.

    • Impact:

      • Buffer Overflows (in Generated FlatBuffers Code): Medium to High reduction. Static analysis helps find buffer overflows in generated FlatBuffers code.
      • Memory Leaks (in Generated FlatBuffers Code): Medium reduction. Static analysis helps reduce memory leak risks in generated FlatBuffers code.
      • Null Pointer Dereferences (in Generated FlatBuffers Code): Medium reduction. Static analysis helps reduce null pointer dereference risks in generated FlatBuffers code.
      • Other Code Defects (in Generated FlatBuffers Code): Low to Medium reduction. Static analysis improves generated FlatBuffers code quality.

    • Currently Implemented: No. Static analysis is not performed on generated FlatBuffers code.

    • Missing Implementation: Static analysis tools need selection and CI/CD integration for generated FlatBuffers code. Analysis rules need configuration. Review process for analysis findings is needed. Manual audits of generated FlatBuffers code are not regular.