zeroize-audit — Claude Skill

When to Use

• Auditing cryptographic implementations (keys, seeds, nonces, secrets)
• Reviewing authentication systems (passwords, tokens, session data)
• Analyzing code that handles PII or sensitive credentials
• Verifying secure cleanup in security-critical codebases
• Investigating memory safety of sensitive data handling

When NOT to Use

• General code review without security focus
• Performance optimization (unless related to secure wiping)
• Refactoring tasks not related to sensitive data
• Code without identifiable secrets or sensitive values

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Purpose

Detect missing zeroization of sensitive data in source code and identify zeroization that is removed or weakened by compiler optimizations (e.g., dead-store elimination), with mandatory LLVM IR/asm evidence. Capabilities include:

• Assembly-level analysis for register spills and stack retention
• Data-flow tracking for secret copies
• Heap allocator security warnings
• Semantic IR analysis for loop unrolling and SSA form
• Control-flow graph analysis for path coverage verification
• Runtime validation test generation

Scope

• Read-only against the target codebase (does not modify audited code; writes analysis artifacts to a temporary working directory).
• Produces a structured report (JSON).
• Requires valid build context (compile_commands.json) and compilable translation units.
• "Optimized away" findings only allowed with compiler evidence (IR/asm diff).

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Inputs

See {baseDir}/schemas/input.json for the full schema. Key fields:

Field	Required	Default	Description
path	yes	—	Repo root
compile_db	no	null	Path to compile_commands.json for C/C++ analysis. Required if cargo_manifest is not set.
cargo_manifest	no	null	Path to Cargo.toml for Rust crate analysis. Required if compile_db is not set.
config	no	—	YAML defining heuristics and approved wipes
opt_levels	no	["O0","O1","O2"]	Optimization levels for IR comparison. O1 is the diagnostic level: if a wipe disappears at O1 it is simple DSE; O2 catches more aggressive eliminations.
languages	no	["c","cpp","rust"]	Languages to analyze
max_tus	no	—	Limit on translation units processed from compile DB
mcp_mode	no	prefer	off, prefer, or require — controls Serena MCP usage
mcp_required_for_advanced	no	true	Downgrade SECRET_COPY, MISSING_ON_ERROR_PATH, and NOT_DOMINATING_EXITS to needs_review when MCP is unavailable
mcp_timeout_ms	no	—	Timeout budget for MCP semantic queries
poc_categories	no	all 11 exploitable	Finding categories for which to generate PoCs. C/C++ findings: all 11 categories supported. Rust findings: only MISSING_SOURCE_ZEROIZE, SECRET_COPY, and PARTIAL_WIPE are supported; other Rust categories are marked poc_supported=false.
poc_output_dir	no	generated_pocs/	Output directory for generated PoCs
enable_asm	no	true	Enable assembly emission and analysis (Step 8); produces STACK_RETENTION, REGISTER_SPILL. Auto-disabled if emit_asm.sh is missing.
enable_semantic_ir	no	false	Enable semantic LLVM IR analysis (Step 9); produces LOOP_UNROLLED_INCOMPLETE
enable_cfg	no	false	Enable control-flow graph analysis (Step 10); produces MISSING_ON_ERROR_PATH, NOT_DOMINATING_EXITS
enable_runtime_tests	no	false	Enable runtime test harness generation (Step 11)

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Prerequisites

Before running, verify the following. Each has a defined failure mode.

C/C++ prerequisites:

Prerequisite	Failure mode if missing
compile_commands.json at compile_db path	Fail fast — do not proceed
clang on PATH	Fail fast — IR/ASM analysis impossible
uvx on PATH (for Serena)	If mcp_mode=require: fail. If mcp_mode=prefer: continue without MCP; downgrade affected findings per Confidence Gating rules.
{baseDir}/tools/extract_compile_flags.py	Fail fast — cannot extract per-TU flags
{baseDir}/tools/emit_ir.sh	Fail fast — IR analysis impossible
{baseDir}/tools/emit_asm.sh	Warn and skip assembly findings (STACK_RETENTION, REGISTER_SPILL)
{baseDir}/tools/mcp/check_mcp.sh	Warn and treat as MCP unavailable
{baseDir}/tools/mcp/normalize_mcp_evidence.py	Warn and use raw MCP output

Rust prerequisites:

Prerequisite	Failure mode if missing
Cargo.toml at cargo_manifest path	Fail fast — do not proceed
cargo check passes	Fail fast — crate must be buildable
cargo +nightly on PATH	Fail fast — nightly required for MIR and LLVM IR emission
uv on PATH	Fail fast — required to run Python analysis scripts
{baseDir}/tools/validate_rust_toolchain.sh	Warn — run preflight manually. Checks all tools, scripts, nightly, and optionally cargo check. Use --json for machine-readable output, --manifest to also validate the crate builds.
{baseDir}/tools/emit_rust_mir.sh	Fail fast — MIR analysis impossible (--opt, --crate, --bin/--lib supported; --out can be file or directory)
{baseDir}/tools/emit_rust_ir.sh	Fail fast — LLVM IR analysis impossible (--opt required; --crate, --bin/--lib supported; --out must be .ll)
{baseDir}/tools/emit_rust_asm.sh	Warn and skip assembly findings (STACK_RETENTION, REGISTER_SPILL). Supports --opt, --crate, --bin/--lib, --target, --intel-syntax; --out can be .s file or directory.
{baseDir}/tools/diff_rust_mir.sh	Warn and skip MIR-level optimization comparison. Accepts 2+ MIR files, normalizes, diffs pairwise, and reports first opt level where zeroize/drop-glue patterns disappear.
{baseDir}/tools/scripts/semantic_audit.py	Warn and skip semantic source analysis
{baseDir}/tools/scripts/find_dangerous_apis.py	Warn and skip dangerous API scan
{baseDir}/tools/scripts/check_mir_patterns.py	Warn and skip MIR analysis
{baseDir}/tools/scripts/check_llvm_patterns.py	Warn and skip LLVM IR analysis
{baseDir}/tools/scripts/check_rust_asm.py	Warn and skip Rust assembly analysis (STACK_RETENTION, REGISTER_SPILL, drop-glue checks). Dispatches to check_rust_asm_x86.py (production) or check_rust_asm_aarch64.py (EXPERIMENTAL — AArch64 findings require manual verification).
{baseDir}/tools/scripts/check_rust_asm_x86.py	Required by check_rust_asm.py for x86-64 analysis; warn and skip if missing
{baseDir}/tools/scripts/check_rust_asm_aarch64.py	Required by check_rust_asm.py for AArch64 analysis (EXPERIMENTAL); warn and skip if missing

Common prerequisite:

Prerequisite	Failure mode if missing
{baseDir}/tools/generate_poc.py	Fail fast — PoC generation is mandatory

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Approved Wipe APIs

The following are recognized as valid zeroization. Configure additional entries in {baseDir}/configs/.

C/C++

• explicit_bzero
• memset_s
• SecureZeroMemory
• OPENSSL_cleanse
• sodium_memzero
• Volatile wipe loops (pattern-based; see volatile_wipe_patterns in {baseDir}/configs/default.yaml)
• In IR: llvm.memset with volatile flag, volatile stores, or non-elidable wipe call

Rust

• zeroize::Zeroize trait (zeroize() method)
• Zeroizing<T> wrapper (drop-based)
• ZeroizeOnDrop derive macro

---

Finding Capabilities

Findings are grouped by required evidence. Only attempt findings for which the required tooling is available.

Finding ID	Description	Requires	PoC Support
MISSING_SOURCE_ZEROIZE	No zeroization found in source	Source only	Yes (C/C++ + Rust)
PARTIAL_WIPE	Incorrect size or incomplete wipe	Source only	Yes (C/C++ + Rust)
NOT_ON_ALL_PATHS	Zeroization missing on some control-flow paths (heuristic)	Source only	Yes (C/C++ only)
SECRET_COPY	Sensitive data copied without zeroization tracking	Source + MCP preferred	Yes (C/C++ + Rust)
INSECURE_HEAP_ALLOC	Secret uses insecure allocator (malloc vs. secure_malloc)	Source only	Yes (C/C++ only)
OPTIMIZED_AWAY_ZEROIZE	Compiler removed zeroization	IR diff required (never source-only)	Yes
STACK_RETENTION	Stack frame may retain secrets after return	Assembly required (C/C++); LLVM IR alloca+lifetime.end evidence (Rust); assembly corroboration upgrades to confirmed	Yes (C/C++ only)
REGISTER_SPILL	Secrets spilled from registers to stack	Assembly required (C/C++); LLVM IR load+call-site evidence (Rust); assembly corroboration upgrades to confirmed	Yes (C/C++ only)
MISSING_ON_ERROR_PATH	Error-handling paths lack cleanup	CFG or MCP required	Yes
NOT_DOMINATING_EXITS	Wipe doesn't dominate all exits	CFG or MCP required	Yes
LOOP_UNROLLED_INCOMPLETE	Unrolled loop wipe is incomplete	Semantic IR required	Yes

---

Agent Architecture

The analysis pipeline uses 11 agents across 8 phases, invoked by the orchestrator ({baseDir}/prompts/task.md) via Task. Agents write persistent finding files to a shared working directory (/tmp/zeroize-audit-{run_id}/), enabling parallel execution and protecting against context pressure.

Agent	Phase	Purpose	Output Directory
0-preflight	Phase 0	Preflight checks (tools, toolchain, compile DB, crate build), config merge, workdir creation, TU enumeration	{workdir}/
1-mcp-resolver	Phase 1, Wave 1 (C/C++ only)	Resolve symbols, types, and cross-file references via Serena MCP	mcp-evidence/
2-source-analyzer	Phase 1, Wave 2a (C/C++ only)	Identify sensitive objects, detect wipes, validate correctness, data-flow/heap	source-analysis/
2b-rust-source-analyzer	Phase 1, Wave 2b (Rust only, parallel with 2a)	Rustdoc JSON trait-aware analysis + dangerous API grep	source-analysis/
3-tu-compiler-analyzer	Phase 2, Wave 3 (C/C++ only, N parallel)	Per-TU IR diff, assembly, semantic IR, CFG analysis	compiler-analysis/{tu_hash}/
3b-rust-compiler-analyzer	Phase 2, Wave 3R (Rust only, single agent)	Crate-level MIR, LLVM IR, and assembly analysis	rust-compiler-analysis/
4-report-assembler	Phase 3 (interim) + Phase 6 (final)	Collect findings from all agents, apply confidence gates; merge PoC results and produce final report	report/
5-poc-generator	Phase 4	Craft bespoke proof-of-concept programs (C/C++: all categories; Rust: MISSING_SOURCE_ZEROIZE, SECRET_COPY, PARTIAL_WIPE)	poc/
5b-poc-validator	Phase 5	Compile and run all PoCs	poc/
5c-poc-verifier	Phase 5	Verify each PoC proves its claimed finding	poc/
6-test-generator	Phase 7 (optional)	Generate runtime validation test harnesses	tests/

The orchestrator reads one per-phase workflow file from {baseDir}/workflows/ at a time, and maintains orchestrator-state.json for recovery after context compression. Agents receive configuration by file path (config_path), not by value.

Execution flow

Phase 0: 0-preflight agent — Preflight + config + create workdir + enumerate TUs
           → writes orchestrator-state.json, merged-config.yaml, preflight.json
Phase 1: Wave 1:  1-mcp-resolver              (skip if mcp_mode=off OR language_mode=rust)
         Wave 2a: 2-source-analyzer           (C/C++ only; skip if no compile_db)  ─┐ parallel
         Wave 2b: 2b-rust-source-analyzer     (Rust only; skip if no cargo_manifest) ─┘
Phase 2: Wave 3:  3-tu-compiler-analyzer x N  (C/C++ only; parallel per TU)
         Wave 3R: 3b-rust-compiler-analyzer   (Rust only; single crate-level agent)
Phase 3: Wave 4:  4-report-assembler          (mode=interim → findings.json; reads all agent outputs)
Phase 4: Wave 5:  5-poc-generator             (C/C++: all categories; Rust: MISSING_SOURCE_ZEROIZE, SECRET_COPY, PARTIAL_WIPE; other Rust findings: poc_supported=false)
Phase 5: PoC Validation & Verification
           Step 1: 5b-poc-validator agent      (compile and run all PoCs)
           Step 2: 5c-poc-verifier agent       (verify each PoC proves its claimed finding)
           Step 3: Orchestrator presents verification failures to user via AskUserQuestion
           Step 4: Orchestrator merges all results into poc_final_results.json
Phase 6: Wave 6: 4-report-assembler           (mode=final → merge PoC results, final-report.md)
Phase 7: Wave 7: 6-test-generator             (optional)
Phase 8: Orchestrator — Return final-report.md

Cross-Reference Convention

IDs are namespaced per agent to prevent collisions during parallel execution:

Entity	Pattern	Assigned By
Sensitive object (C/C++)	SO-0001–SO-4999	2-source-analyzer
Sensitive object (Rust)	SO-5000–SO-9999 (Rust namespace)	2b-rust-source-analyzer
Source finding (C/C++)	F-SRC-NNNN	2-source-analyzer
Source finding (Rust)	F-RUST-SRC-NNNN	2b-rust-source-analyzer
IR finding (C/C++)	F-IR-{tu_hash}-NNNN	3-tu-compiler-analyzer
ASM finding (C/C++)	F-ASM-{tu_hash}-NNNN	3-tu-compiler-analyzer
CFG finding	F-CFG-{tu_hash}-NNNN	3-tu-compiler-analyzer
Semantic IR finding	F-SIR-{tu_hash}-NNNN	3-tu-compiler-analyzer
Rust MIR finding	F-RUST-MIR-NNNN	3b-rust-compiler-analyzer
Rust LLVM IR finding	F-RUST-IR-NNNN	3b-rust-compiler-analyzer
Rust assembly finding	F-RUST-ASM-NNNN	3b-rust-compiler-analyzer
Translation unit	TU-{hash}	Orchestrator
Final finding	ZA-NNNN	4-report-assembler

Every finding JSON object includes related_objects, related_findings, and evidence_files fields for cross-referencing between agents.

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Detection Strategy

Analysis runs in two phases. For complete step-by-step guidance, see {baseDir}/references/detection-strategy.md.

Phase	Steps	Findings produced	Required tooling
Phase 1 (Source)	1–6	MISSING_SOURCE_ZEROIZE, PARTIAL_WIPE, NOT_ON_ALL_PATHS, SECRET_COPY, INSECURE_HEAP_ALLOC	Source + compile DB
Phase 2 (Compiler)	7–12	OPTIMIZED_AWAY_ZEROIZE, STACK_RETENTION, REGISTER_SPILL, LOOP_UNROLLED_INCOMPLETE†, MISSING_ON_ERROR_PATH‡, NOT_DOMINATING_EXITS‡	clang, IR/ASM tools

* requires enable_asm=true (default) † requires enable_semantic_ir=true ‡ requires enable_cfg=true

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Output Format

Each run produces two outputs:

1. final-report.md — Comprehensive markdown report (primary human-readable output)
2. findings.json — Structured JSON matching {baseDir}/schemas/output.json (for machine consumption and downstream tools)

Markdown Report Structure

The markdown report (final-report.md) contains these sections:

• Header: Run metadata (run_id, timestamp, repo, compile_db, config summary)
• Executive Summary: Finding counts by severity, confidence, and category
• Sensitive Objects Inventory: Table of all identified objects with IDs, types, locations
• Findings: Grouped by severity then confidence. Each finding includes location, object, all evidence (source/IR/ASM/CFG), compiler evidence details, and recommended fix
• Superseded Findings: Source findings replaced by CFG-backed findings
• Confidence Gate Summary: Downgrades applied and overrides rejected
• Analysis Coverage: TUs analyzed, agent success/failure, features enabled
• Appendix: Evidence Files: Mapping of finding IDs to evidence file paths

Structured JSON

The findings.json file follows the schema in {baseDir}/schemas/output.json. Each Finding object:

{
  "id": "ZA-0001",
  "category": "OPTIMIZED_AWAY_ZEROIZE",
  "severity": "high",
  "confidence": "confirmed",
  "language": "c",
  "file": "src/crypto.c",
  "line": 42,
  "symbol": "key_buf",
  "evidence": "store volatile i8 0 count: O0=32, O2=0 — wipe eliminated by DSE",
  "compiler_evidence": {
    "opt_levels": ["O0", "O2"],
    "o0": "32 volatile stores targeting key_buf",
    "o2": "0 volatile stores (all eliminated)",
    "diff_summary": "All volatile wipe stores removed at O2 — classic DSE pattern"
  },
  "suggested_fix": "Replace memset with explicit_bzero or add compiler_fence(SeqCst) after the wipe",
  "poc": {
    "file": "generated_pocs/ZA-0001.c",
    "makefile_target": "ZA-0001",
    "compile_opt": "-O2",
    "requires_manual_adjustment": false,
    "validated": true,
    "validation_result": "exploitable"
  }
}

See {baseDir}/schemas/output.json for the full schema and enum values.

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Confidence Gating

Evidence thresholds

A finding requires at least 2 independent signals to be marked confirmed. With 1 signal, mark likely. With 0 strong signals (name-pattern match only), mark needs_review.

Signals include: name pattern match, type hint match, explicit annotation, IR evidence, ASM evidence, MCP cross-reference, CFG evidence, PoC validation.

PoC validation as evidence signal

Every finding is validated against a bespoke PoC. After compilation and execution, each PoC is also verified to ensure it actually tests the claimed vulnerability. The combined result is an evidence signal:

PoC Result	Verified	Impact
Exit 0 (exploitable)	Yes	Strong signal — can upgrade likely to confirmed
Exit 1 (not exploitable)	Yes	Downgrade severity to low (informational); retain in report
Exit 0 or 1	No (user accepted)	Weaker signal — note verification failure in evidence
Exit 0 or 1	No (user rejected)	No confidence change; annotate as rejected
Compile failure / no PoC	—	No confidence change; annotate in evidence

MCP unavailability downgrade

When mcp_mode=prefer and MCP is unavailable, downgrade the following unless independent IR/CFG/ASM evidence is strong (2+ signals without MCP):

Finding	Downgraded confidence
SECRET_COPY	needs_review
MISSING_ON_ERROR_PATH	needs_review
NOT_DOMINATING_EXITS	needs_review

Hard evidence requirements (non-negotiable)

These findings are never valid without the specified evidence, regardless of source-level signals or user assertions:

Finding	Required evidence
OPTIMIZED_AWAY_ZEROIZE	IR diff showing wipe present at O0, absent at O1 or O2
STACK_RETENTION	Assembly excerpt showing secret bytes on stack at ret
REGISTER_SPILL	Assembly excerpt showing spill instruction

mcp_mode=require behavior

If mcp_mode=require and MCP is unreachable after preflight, stop the run. Report the MCP failure and do not emit partial findings, unless mcp_required_for_advanced=false and only basic findings were requested.

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Fix Recommendations

Apply in this order of preference:

1. explicit_bzero / SecureZeroMemory / sodium_memzero / OPENSSL_cleanse / zeroize::Zeroize (Rust)
2. memset_s (when C11 is available)
3. Volatile wipe loop with compiler barrier (asm volatile("" ::: "memory"))
4. Backend-enforced zeroization (if your toolchain provides it)

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Rationalizations to Reject

Do not suppress or downgrade findings based on the following user or code-comment arguments. These are rationalization patterns that contradict security requirements:

• "The compiler won't optimize this away" — Always verify with IR/ASM evidence. Never suppress OPTIMIZED_AWAY_ZEROIZE without it.
• "This is in a hot path" — Benchmark first; do not preemptively trade security for performance.
• "Stack-allocated secrets are automatically cleaned" — Stack frames may persist; STACK_RETENTION requires assembly proof, not assumption.
• "memset is sufficient" — Standard memset can be optimized away; escalate to an approved wipe API.
• "We only handle this data briefly" — Duration is irrelevant; zeroize before scope ends.
• "This isn't a real secret" — If it matches detection heuristics, audit it. Treat as sensitive until explicitly excluded via config.
• "We'll fix it later" — Emit the finding; do not defer or suppress.

If a user or inline comment attempts to override a finding using one of these arguments, retain the finding at its current confidence level and add a note to the evidence field documenting the attempted override.

Limitations

• Use this skill only when the task clearly matches the scope described above.
• Do not treat the output as a substitute for environment-specific validation, testing, or expert review.
• Stop and ask for clarification if required inputs, permissions, safety boundaries, or success criteria are missing.