Security Audit Preparation Guide¶

Version: 1.0.0
Last Updated: January 15, 2026
Contact: security@usl-lang.org

Executive Summary¶

This document prepares security auditors for evaluating the USL compiler. It defines scope, identifies security-critical components, documents test coverage, and provides guidance for comprehensive security assessment.

Audit Objective: Verify that USL provides compile-time security guarantees for policy enforcement, secret management, and generated code security.

Recommended Duration: 2-3 weeks (160-240 hours)

1. Audit Scope¶

In-Scope Components¶

1.1 Parser & Lexer (src/lexer/, src/parser/)¶

Purpose: Parse USL source code into Abstract Syntax Tree (AST)

Security Concerns: - Input validation (malformed syntax) - Denial of service (deeply nested structures) - Unicode handling (homograph attacks) - Buffer overflows (unlikely in Rust, but verify unsafe blocks)

Test Coverage: tests/entity_parser_tests.rs, fuzzing target parser_fuzzer

Lines of Code: ~5,000

1.2 Semantic Analyzer (src/semantic/)¶

Purpose: Type checking, policy validation, secret flow analysis

Security Concerns: - Type confusion vulnerabilities - Policy bypass attempts - Secret leakage through type coercion - Escape validation bypass

Test Coverage: tests/week11_validation_tests.rs, 50+ semantic tests

Lines of Code: ~8,000

1.3 Proof Engines (src/proof/)¶

Purpose: Verify policy totality, invariants, capability safety

Security Concerns: - Proof soundness (false positives/negatives) - Proof completeness (missing cases) - Performance attacks (proof explosion)

Test Coverage: Property-based tests, fuzzing target proof_fuzzer

Lines of Code: ~3,500

1.4 Code Generator (src/codegen/)¶

Purpose: Generate TypeScript, SQL, OpenAPI from validated IR

Security Concerns: - SQL injection in generated queries - XSS in generated API code - Authentication bypass in generated middleware - Secret exposure in generated code

Test Coverage: tests/week10_codegen_tests.rs, tests/week11_openapi_tests.rs

Lines of Code: ~6,000

1.5 Runtime Library (src/runtime/)¶

Purpose: Policy enforcement helpers for generated code

Security Concerns: - Runtime policy bypass - Authentication/authorization flaws - Secret handling in runtime

Test Coverage: tests/week11_runtime_tests.rs

Lines of Code: ~2,000

1.6 Deployment Generator (src/enterprise/deployment/)¶

Purpose: Generate Docker, Kubernetes, monitoring configs

Security Concerns: - Insecure default configurations - Exposed secrets in manifests - Privilege escalation in containers

Test Coverage: tests/deployment_test.rs

Lines of Code: ~1,500

Out-of-Scope¶

• Frontend Tools: VSCode extension, language server (separate audit)
• Documentation Site: Static site generation (low risk)
• Example Applications: Demonstration code (not production)
• Build System: Standard Cargo tooling (community-audited)

2. Security Features¶

2.1 Secret Types¶

Feature: First-class support for sensitive data

Implementation: src/types/secret.rs, src/semantic/secret_flow.rs

Guarantees: - Secrets never appear in logs, error messages, or API responses - Compile-time flow analysis (E401-E404 errors) - Runtime redaction in generated code

Audit Focus: - Verify no secret leakage paths exist - Check error messages don't expose secrets - Validate generated code redacts secrets - Test type coercion doesn't bypass checks

Test Files: - tests/secret_flow_tests.rs - tests/week11_validation_tests.rs (secret validation)

2.2 Policy Enforcement¶

Feature: Mandatory authorization for all behaviors

Implementation: src/semantic/policy_checker.rs, src/proof/policy_totality.rs

Guarantees: - E301: Behavior without authorization fails compilation - E304: Policy totality checking (all code paths authorized) - Runtime enforcement in generated middleware

Audit Focus: - Verify no unauthorized code paths exist - Check policy totality proof soundness - Validate generated code enforces policies correctly - Test edge cases (nested behaviors, async operations)

Test Files: - tests/policy_enforcement_tests.rs - tests/week11_runtime_tests.rs (runtime enforcement)

2.3 Escape Validation¶

Feature: External code requires explicit adapters

Implementation: src/semantic/escape_validator.rs

Guarantees: - E902: Missing adapter fails compilation - Explicit trust boundary documentation - Clear audit trail of external dependencies

Audit Focus: - Verify escape hatches cannot be bypassed - Check adapter registration is secure - Validate escapes are properly isolated

Test Files: - examples/with_escape.usl - tests/escape_validation_tests.rs

2.4 Layer Boundaries¶

Feature: Compiler-enforced architectural layers

Implementation: src/semantic/layer_validator.rs

Guarantees: - E601-E608: Cross-layer violations fail compilation - E651: Query layer cannot perform writes - Clear separation of concerns

Audit Focus: - Verify layer boundaries cannot be violated - Check query layer is truly read-only - Validate imports respect layer constraints

Test Files: - tests/layer_boundary_tests.rs - tests/query_test.rs

2.5 Generated Code Security¶

Feature: Secure-by-default code generation

Implementation: All codegen modules

Guarantees: - Parameterized SQL queries (no string concatenation) - Input validation in generated APIs - XSS prevention (escaping/sanitization) - CSRF tokens in generated forms

Audit Focus: - Critical: Review all SQL generation for injection vulnerabilities - Critical: Review API generation for authentication/authorization - Check input validation is comprehensive - Verify XSS prevention is correct

Test Files: - tests/week10_codegen_tests.rs - tests/week11_openapi_tests.rs

3. Attack Surface Analysis¶

3.1 Input Validation¶

Attack Vector: Malicious USL source code

Mitigation: - Lexer validates all tokens (E101-E199) - Parser enforces grammar rules (E201-E299) - Semantic analyzer validates semantics (E301-E499)

Test Coverage: 232 integration tests, parser fuzzing

Audit Focus: - Inject malformed syntax (unicode, control chars) - Deeply nested structures (stack overflow) - Large inputs (memory exhaustion) - Homograph attacks (look-alike identifiers)

3.2 Policy Bypass¶

Attack Vector: Circumvent authorization checks

Mitigation: - Compile-time policy totality proof - Runtime enforcement in generated code - No reflection/eval in generated code

Audit Focus: - Attempt to write behaviors without policies - Test policy totality edge cases (nested conditions) - Verify runtime enforcement cannot be disabled - Check for time-of-check/time-of-use vulnerabilities

3.3 Secret Leakage¶

Attack Vector: Extract secret values through side channels

Mitigation: - Secret flow analysis (E401-E404) - Redaction in logs/errors - No serialization of secrets

Audit Focus: - Attempt to leak secrets via error messages - Test type coercion (Secret → T) - Check logging/debugging output - Verify API responses redact secrets

3.4 Escape Abuse¶

Attack Vector: Bypass security through escape hatches

Mitigation: - Adapter requirement (E902) - Explicit trust boundaries - Limited escape capabilities

Audit Focus: - Attempt to use escapes without adapters - Register malicious adapters - Test escape isolation (can't access secrets)

3.5 Generated Code Vulnerabilities¶

Attack Vector: Vulnerabilities in generated TypeScript/SQL

Mitigation: - Parameterized queries - Input validation - Output escaping - Security headers

Audit Focus: - Critical: SQL injection testing (all query generation) - Critical: XSS testing (API responses) - Authentication/authorization in middleware - CSRF protection - Rate limiting - TLS enforcement

3.6 Supply Chain Attacks¶

Attack Vector: Compromised dependencies

Mitigation: - cargo audit (dependency vulnerabilities) - cargo deny (license and advisory checks) - cargo vet (supply chain verification) - Minimal dependencies (60 crates)

Audit Focus: - Review dependency tree - Check for known vulnerabilities - Verify dependency updates are monitored - Assess risk of unmaintained crates

3.7 Denial of Service¶

Attack Vector: Resource exhaustion

Mitigation: - Compilation timeouts - Memory limits - Bounded recursion - Input size limits

Audit Focus: - Test with large inputs (10MB+ files) - Deeply nested structures (1000+ levels) - Exponential proof complexity - Fuzzing for hangs/crashes

4. Test Coverage¶

4.1 Unit Tests¶

4.2 Fuzzing Targets¶

Located in compiler/fuzz/fuzz_targets/:

• parser_fuzzer.rs: Fuzz parser with random input
• semantic_fuzzer.rs: Fuzz semantic analyzer
• proof_fuzzer.rs: Fuzz proof engines
• codegen_fuzzer.rs: Fuzz code generation

Corpus: 500+ generated test cases

Coverage: Fuzzing reaches ~85% of code paths

4.3 Integration Tests¶

• Complete Stack Tests: End-to-end compilation + codegen
• Import/Export Tests: Cross-module dependencies
• Deployment Tests: Full deployment manifests
• OpenAPI Tests: API specification generation

4.4 Security-Specific Tests¶

• Secret Flow: 15 tests for secret leakage prevention
• Policy Enforcement: 20 tests for authorization
• Layer Boundaries: 12 tests for architectural constraints
• Escape Validation: 8 tests for adapter requirements

5. Dependencies¶

5.1 Direct Dependencies (Production)¶

Total Production Dependencies: ~40 crates (including transitive)

5.2 Development Dependencies¶

5.3 Dependency Auditing¶

Tools: - cargo audit: Scans for known vulnerabilities (RustSec database) - cargo deny: Checks licenses and advisories - cargo vet: Supply chain verification - cargo outdated: Identifies outdated dependencies

Policy: - Security vulnerabilities must be addressed within 7 days - Major dependency updates reviewed quarterly - Unmaintained crates replaced within 30 days

6. Known Issues¶

6.1 Current Vulnerabilities¶

None identified as of January 15, 2026.

6.2 Limitations¶

1. Adapter Trust: External adapters are trusted. USL cannot verify adapter security.
2. Risk: Medium
3. Mitigation: Documentation requires users to audit adapters

4. Future: Sandboxed adapter execution (v2.0)

5. Time-of-Check/Time-of-Use: Policies checked at compile-time, enforced at runtime.

6. Risk: Low (generated code includes runtime checks)
7. Mitigation: Both compile-time and runtime enforcement

8. Future: Formal verification of codegen correctness (v1.2)

9. Generated Code Security: Depends on runtime environment (Node.js, PostgreSQL).

10. Risk: Medium
11. Mitigation: Generated code follows best practices

12. Future: Runtime security SDK (v1.1)

13. Supply Chain: Dependencies audited but not formally verified.

14. Risk: Low
15. Mitigation: cargo audit, cargo vet, minimal dependencies
16. Future: Certified dependency set (v1.2)

6.3 Future Work¶

• Runtime policy monitoring and alerting
• Dynamic policy updates (without recompilation)
• Real-time threat detection
• Distributed tracing with security events
• Formal verification of codegen correctness

7. Audit Timeline¶

Recommended Schedule (2-3 weeks)¶

Week 1: Code Review¶

• Days 1-2: Setup, architecture overview, threat model review
• Days 3-4: Parser and lexer security review
• Day 5: Semantic analyzer review

Week 2: Security Features & Testing¶

• Days 6-7: Secret flow analysis and policy enforcement
• Days 8-9: Code generation security (SQL, TypeScript, OpenAPI)
• Day 10: Proof engines and runtime library

Week 3: Testing & Reporting¶

• Days 11-12: Fuzzing, penetration testing, exploit attempts
• Days 13-14: Supply chain review, dependency audit
• Day 15: Final report preparation and presentation

8. RFP Template for Security Firms¶

8.1 Project Overview¶

Project: USL Compiler Security Audit
Version: 1.0.0
Language: Rust
Lines of Code: ~26,000 (compiler only)

Description: USL is a policy-first specification language that generates secure-by-default backend systems. The compiler enforces security at compile-time through secret flow analysis, policy totality proofs, and layer boundaries.

8.2 Audit Objectives¶

1. Verify compile-time security guarantees (policy enforcement, secret management)
2. Assess generated code security (SQL injection, XSS, authentication)
3. Evaluate proof engine soundness and completeness
4. Review supply chain security and dependencies
5. Identify vulnerabilities and recommend mitigations

8.3 Deliverables¶

• Security Assessment Report: Comprehensive findings and recommendations
• Vulnerability Report: Detailed description of any vulnerabilities found
• Threat Model Validation: Review and update of threat model
• Compliance Assessment: GDPR, HIPAA, PCI-DSS considerations
• Executive Summary: High-level findings for non-technical stakeholders

8.4 Questions for Auditors¶

1. Experience: Have you audited compilers or code generators before?
2. Rust Expertise: What is your team's experience with Rust security?
3. Formal Methods: Do you have experience with proof systems and formal verification?
4. Generated Code: Can you assess security of generated TypeScript/SQL?
5. Tools: What tools do you use (SAST, DAST, fuzzing)?
6. Timeline: What is your estimated duration and cost?
7. Remediation: Do you provide support for fixing identified issues?
8. References: Can you provide references from similar audits?

8.5 Access Provided¶

• Source Code: Full access to GitHub repository
• Documentation: All design docs, security docs, API references
• Test Suite: 232 tests, fuzzing targets, benchmarks
• Collaboration: Direct access to development team for questions
• Environment: Pre-configured development environment (Docker)

8.6 Expected Cost¶

Estimate: $40,000 - $80,000 (2-3 weeks, 2-3 auditors)

Budget Breakdown: - Code review: 60-80 hours - Security testing: 40-60 hours - Report writing: 20-30 hours - Collaboration: 20-30 hours

9. Audit Preparation Checklist¶

Pre-Audit¶

• Clean up TODO/FIXME comments in security-critical code
• Update all documentation (security, API, architecture)
• Run full test suite (ensure 100% passing)
• Run security scans (cargo audit, cargo deny)
• Generate coverage reports
• Prepare development environment (Docker, docs)
• Brief development team on audit process

During Audit¶

• Provide timely responses to auditor questions (< 24 hours)
• Schedule daily standups (15 minutes)
• Document all findings in tracking system
• Prioritize critical findings for immediate remediation
• Maintain open communication channels (Slack, email)

Post-Audit¶

• Review final report with team
• Create remediation plan with timelines
• Address critical vulnerabilities immediately (< 7 days)
• Update documentation based on findings
• Re-audit after remediations (if needed)
• Publish summary of findings (after fixes)

10. Contact Information¶

Security Team: - Primary Contact: security@usl-lang.org - Project Lead: [Name], lead@usl-lang.org - Response Time: 24 hours for audit inquiries

Availability: - Timezone: UTC-8 (Pacific Time) - Hours: Monday-Friday, 9am-5pm PT - Emergency Contact: +1-XXX-XXX-XXXX

Appendix A: Threat Model Summary¶

See threat-model.md for complete threat model.

High-Priority Threats: 1. SQL Injection in generated queries 2. Policy bypass attempts 3. Secret leakage through error messages 4. Supply chain attacks

Medium-Priority Threats: 5. XSS in generated API code 6. Denial of service (resource exhaustion) 7. Escape hatch abuse 8. Time-of-check/time-of-use vulnerabilities

Appendix B: Code Structure¶

compiler/src/
├── lexer/          # Input validation (5,000 LOC)
├── parser/         # AST construction (4,500 LOC)
├── semantic/       # Type checking, policy validation (8,000 LOC)
├── proof/          # Policy totality, invariants (3,500 LOC)
├── codegen/        # Code generation (6,000 LOC)
├── runtime/        # Runtime library (2,000 LOC)
├── enterprise/     # Deployment generation (1,500 LOC)
├── error/          # Error handling (1,200 LOC)
└── types/          # Type system (2,000 LOC)

Security-Critical Files: - src/semantic/secret_flow.rs (secret leakage prevention) - src/semantic/policy_checker.rs (authorization enforcement) - src/codegen/typescript/query.rs (SQL injection prevention) - src/codegen/openapi/mod.rs (API security) - src/proof/policy_totality.rs (proof soundness)

End of Audit Preparation Guide

For questions or clarifications, contact security@usl-lang.org.