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Threat Model Analysis for dotnet/roslyn

Threat: Analyzer/Code Fix Injection

  • Threat: Analyzer/Code Fix Injection

    • Description: If the application allows users to provide custom analyzers or code fixes (e.g., in a plugin system or online code analysis tool), an attacker could submit a malicious analyzer that performs unauthorized actions. The attacker's goal could be to tamper with the compilation of other users' code, exfiltrate data, or execute arbitrary code. This directly exploits the extensibility mechanisms provided by Roslyn.
    • Impact:
      • Compromise of other users' code.
      • Data exfiltration.
      • Elevation of privilege if the analyzer runs with higher permissions.
      • Denial of service.
    • Roslyn Component Affected:
      • Microsoft.CodeAnalysis.Diagnostics.DiagnosticAnalyzer (and derived classes)
      • Microsoft.CodeAnalysis.CodeFixes.CodeFixProvider (and derived classes)
      • Microsoft.CodeAnalysis.Workspace (methods for loading and applying analyzers/fixes)
    • Risk Severity: Critical
    • Mitigation Strategies:
      • Strict Isolation: Run user-provided analyzers/code fixes in a highly restricted environment (e.g., a separate AppDomain with minimal permissions, a sandboxed process, or a container).
      • Permission Whitelist: Define a whitelist of allowed Roslyn API calls for user-provided code. Block any attempts to call unauthorized APIs.
      • Code Review: If feasible, manually review user-submitted analyzers/code fixes before allowing them to be used.
      • Static Analysis of Analyzers: Use Roslyn itself (in a secure environment!) to analyze the submitted analyzers for potentially malicious behavior before allowing them to run.
      • Digital Signatures: Require user-provided analyzers to be digitally signed by a trusted authority.

Threat: Code Injection via Dynamic Compilation

  • Threat: Code Injection via Dynamic Compilation

    • Description: If the application uses Roslyn to dynamically generate and execute code based on user input, an attacker could inject malicious code into the input, leading to arbitrary code execution. This directly leverages Roslyn's code generation and execution capabilities.
    • Impact: Complete system compromise. The attacker could gain full control of the application and potentially the underlying server.
    • Roslyn Component Affected:
      • Microsoft.CodeAnalysis.CSharp.Scripting.CSharpScript.RunAsync (and related methods)
      • Microsoft.CodeAnalysis.CSharp.CSharpCompilation.Create (and related methods)
      • Microsoft.CodeAnalysis.Emit.EmitResult
    • Risk Severity: Critical
    • Mitigation Strategies:
      • Strict Input Validation: Implement extremely rigorous input validation and sanitization to prevent any malicious code from being included in the dynamically generated code. Use a whitelist approach whenever possible.
      • Sandboxing: Execute the dynamically generated code in a highly restricted environment (e.g., a separate AppDomain with minimal permissions, a sandboxed process, or a container). Never run user-provided code with the application's privileges.
      • Principle of Least Privilege: Ensure the application itself runs with the minimum necessary privileges.
      • Avoid Dynamic Compilation (If Possible): If the application's functionality can be achieved without dynamic code generation, this is the safest approach.

Threat: Roslyn Vulnerability Exploitation

  • Threat: Roslyn Vulnerability Exploitation

    • Description: An attacker exploits a previously unknown (zero-day) or unpatched vulnerability in the Roslyn compiler or libraries themselves. This is a direct attack on the Roslyn implementation.
    • Impact: Varies depending on the vulnerability, but could potentially lead to denial of service, code execution, or information disclosure.
    • Roslyn Component Affected: Any part of the Roslyn codebase could be vulnerable.
    • Risk Severity: High to Critical
    • Mitigation Strategies:
      • Keep Roslyn Updated: Regularly update to the latest version of the Roslyn NuGet packages to receive security patches.
      • Monitor Security Advisories: Stay informed about any security advisories related to Roslyn.
      • Defense in Depth: Implement other security measures (e.g., sandboxing, input validation) to reduce the impact of a potential Roslyn vulnerability.
      • Fuzz Testing: Consider fuzz testing the Roslyn APIs used by the application to proactively identify potential vulnerabilities.

Threat: Compiler Bomb (Resource Exhaustion)

  • Threat: Compiler Bomb (Resource Exhaustion)

    • Description: An attacker submits specially crafted code designed to consume excessive CPU, memory, or disk space during compilation or analysis, leveraging Roslyn's parsing and semantic analysis capabilities. The attacker aims to cause a denial-of-service condition.
    • Impact: Application becomes unresponsive or crashes, preventing legitimate users from accessing the service. Potentially, the entire server could become unstable.
    • Roslyn Component Affected:
      • Microsoft.CodeAnalysis.CSharp.SyntaxTree.ParseText (and VB.NET equivalent)
      • Microsoft.CodeAnalysis.Compilation.Create
      • Microsoft.CodeAnalysis.SemanticModel (various methods)
      • Any analyzer that performs complex code analysis.
    • Risk Severity: High
    • Mitigation Strategies:
      • Resource Limits: Use CancellationTokenSource with a timeout to limit the overall compilation time. Use CompilationOptions.WithMemoryConstraints to limit memory usage.
      • Input Size Limits: Impose strict limits on the size of the input code.
      • Sandboxing: Execute Roslyn in a separate process or AppDomain with restricted resources. Consider using containers (e.g., Docker) for stronger isolation.
      • Complexity Analysis (Pre-Roslyn): Implement a lightweight pre-parser or heuristic check to detect potentially problematic code patterns before passing it to Roslyn. This can filter out obvious compiler bombs.
      • Monitoring: Monitor resource usage during compilation and terminate any processes exceeding thresholds.