security: align with RustSec guidelines and prepare for audit

[kmay89]

Comprehensive security audit preparation bringing VBW into full alignment with RustSec advisory database guidelines and Google's cargo vet auditing standards.

Code hardening:

• Eliminate .unwrap() in production code (main.rs:338 → let-else guard)
• Add security-critical clippy lints: unwrap_used=deny, expect_used=warn, panic=warn, indexing_slicing=warn, missing_docs=warn
• Allow .unwrap()/indexing in test modules via targeted #[allow] attrs
• Add explicit safety comments for all #[allow(clippy::indexing_slicing)]

Supply chain policy:

• Add [advisories] section to deny.toml with unmaintained=deny
• Ban openssl-sys in addition to openssl in deny.toml
• Add .cargo/audit.toml with yanked=deny and show_tree=true
• Enable cargo-deny advisories check in CI and scheduled audit workflows
• Update Makefile deny target to include advisories

Documentation for audit readiness:

• Add comprehensive crate-level docs to lib.rs (security properties, module overview, audit guidance)
• Add module-level //! docs to all 6 source modules explaining purpose, security considerations, and audit notes
• Add /// doc comments to all public functions with error documentation
• Document all Cargo.toml lint allow/deny decisions with rationale
• Document all deny.toml sections with security rationale

Documentation updates:

• Rewrite ARCHITECTURE.md with data flow diagram, cryptographic inventory, trust boundary table, defensive input limits, RustSec alignment section
• Expand SECURITY.md with compile-time/dependency/runtime control tables, RustSec compliance section, audit preparation guide
• Add RustSec compliance posture and lint enforcement sections to AUDIT-BOUNDARY.md with UB-risk-0 classification
• Add security posture section to README.md

All quality gates pass: fmt, clippy -D warnings, 67 tests (28 unit + 11 integration), formatting clean.

https://claude.ai/code/session_01JaWHUAwRXPSeCyt14mNKTL

Summary

Type of Change

• Bug fix (non-breaking change that fixes an issue)
• New feature (non-breaking change that adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)
• Documentation update
• CI/CD or build change
• Dependency update

Security Checklist

• No secrets, credentials, or private keys are committed
• No new dependencies with copyleft or unknown licenses
• No git-sourced dependencies introduced
• Changes do not weaken independence enforcement
• Changes do not introduce symlink-following behavior
• Changes do not increase file size limits without justification

Quality Checklist

• cargo fmt --all -- --check passes
• cargo clippy --all-targets --all-features -- -D warnings passes
• cargo test --all-features passes
• cargo deny check passes
• All commits are signed off (DCO)

Test Plan

Related Issues

[gemini-code-assist]

Summary of Changes

Hello @kmay89, I'm Gemini Code Assist¹! I'm currently reviewing this pull request and will post my feedback shortly. In the meantime, here's a summary to help you and other reviewers quickly get up to speed!

This pull request focuses on a comprehensive security uplift for VBW, bringing its codebase and dependency management into full alignment with industry-standard security guidelines like RustSec and Google's cargo vet. The changes ensure a more resilient application by enforcing stricter code quality, fortifying supply chain integrity, and providing extensive documentation to facilitate future security audits and enhance transparency regarding its defensive mechanisms.

Highlights

• Code Hardening: Eliminated unwrap() in production code by replacing it with a let-else guard in main.rs and introduced security-critical Clippy lints (unwrap_used=deny, expect_used=warn, panic=warn, indexing_slicing=warn, missing_docs=warn) to enforce robust error handling and code quality.
• Supply Chain Policy Enforcement: Configured cargo-audit to deny unmaintained and yanked crates, and updated cargo-deny to include advisory checks and explicitly ban openssl-sys, ensuring stricter dependency hygiene.
• Comprehensive Documentation for Audit Readiness: Significantly expanded documentation across ARCHITECTURE.md, SECURITY.md, AUDIT-BOUNDARY.md, README.md, and all source modules (lib.rs, src/attest.rs, src/bundlehash.rs, src/fs_guard.rs, src/independence.rs, src/main.rs, src/policy.rs) to detail security properties, threat models, cryptographic inventory, audit guidance, and compliance with RustSec and Google's cargo vet standards.

Changelog

• .cargo/audit.toml
  • Added configuration for cargo-audit to deny unmaintained and yanked dependencies, and to show dependency trees for advisories.
• ARCHITECTURE.md
  • Updated architecture documentation with a data flow diagram, cryptographic inventory, trust boundaries, defensive input limits, and a section on RustSec alignment.
• AUDIT-BOUNDARY.md
  • Expanded audit boundary documentation with new sections on RustSec compliance posture, UB-Risk classification, and lint enforcement.
  • Revised the recommended audit procedure to include new documentation and checks.
• Cargo.toml
  • Configured new security-critical Clippy lints (unwrap_used, expect_used, panic, indexing_slicing) and missing_docs.
  • Added rationales as comments for all allowed pedantic lints.
• Makefile
  • Modified the deny target to include advisories checks for cargo-deny.
• README.md
  • Introduced a new "Security Posture" section outlining VBW's security best practices.
• SECURITY.md
  • Expanded security documentation to include "Dependency vulnerabilities" as a qualification for security issues.
  • Clarified VBW's guarantees and added detailed "Security Controls" (compile-time, dependency, runtime).
  • Added a "RustSec Compliance" section and "Audit Preparation" guidance.
• deny.toml
  • Added an [advisories] section to deny unmaintained crates and configured the RustSec advisory database URL.
  • Explicitly banned openssl-sys in addition to openssl.
  • Enhanced comments for all policy enforcement sections, including licenses, bans, and sources.
• src/attest.rs
  • Documented module purpose, signing delegation, and function behavior with comprehensive module-level and doc comments.
  • Allowed specific clippy lints (unwrap_used, indexing_slicing) within test modules.
• src/bundlehash.rs
  • Documented module purpose, determinism guarantees, security controls, and cryptographic notes with comprehensive module-level and doc comments.
  • Added #[allow(clippy::indexing_slicing)] for a specific line in sha256_file_streaming.
  • Allowed specific clippy lints (unwrap_used, indexing_slicing) within test modules.
• src/fs_guard.rs
  • Documented module purpose, defensive I/O, symlink rejection, size bounding, and TOCTOU window with comprehensive module-level and doc comments.
  • Added doc comments for the read_validated function.
• src/independence.rs
  • Documented module purpose, independence checks, regex safety, and audit notes with comprehensive module-level and doc comments.
  • Refined regex patterns with inline comments for clarity.
  • Allowed specific clippy lints (unwrap_used, indexing_slicing) within test modules.
• src/lib.rs
  • Documented crate-level security properties, module overview, and audit guidance with comprehensive crate-level and module-level comments.
• src/main.rs
  • Documented CLI orchestration, external tool invocation, and audit notes with comprehensive module-level and doc comments for constants and functions.
  • Replaced unwrap() with a let-else guard for improved error handling.
  • Added #[allow(clippy::indexing_slicing)] for JSON indexing operations.
• src/policy.rs
  • Documented policy configuration, design rationale, and function behavior with comprehensive module-level and doc comments for constants, struct fields, and the load function.
  • Allowed specific clippy lints (unwrap_used, indexing_slicing) within test modules.
• tests/integration.rs
  • Added #[allow(clippy::unwrap_used, clippy::expect_used, clippy::indexing_slicing)] to the test module to permit common test practices.

Ignored Files

• Ignored by pattern: .github/workflows/** (2)
  • .github/workflows/audit.yml
  • .github/workflows/ci.yml

Activity

• The pull request author, kmay89, has implemented comprehensive security enhancements across the codebase and documentation.
• All quality gates have passed, including fmt, clippy -D warnings, 67 tests (28 unit + 11 integration), and formatting checks, indicating a high standard of code quality and adherence to new linting rules.

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[gemini-code-assist]

Code Review

This is an excellent pull request that significantly hardens the security posture of the project and prepares it for a formal audit. The changes are comprehensive, including stricter linting, improved supply chain security configuration, removal of panicking code, and extensive documentation updates across the codebase. The attention to detail in documenting security controls and rationale is particularly commendable. I have found two minor issues in configuration and code comments that could be improved for clarity.