sextant-security

name	sextant-security
description	Use for a security-focused audit of code changes or modules. Stronger signals: "security review", "check for vulnerabilities", "is this safe", "audit this", "OWASP", "injection", "auth check", "XSS", "SQL injection". Distinct from sextant-review-code (general quality review); this skill specifically targets security dimensions. Can be run standalone or as a follow-up after sextant-review-code.

!awk 'f;/^---$/{c++}c==2{f=1}' ${CLAUDE_SKILL_DIR}/../principles/SKILL.md

![ -d .gitnexus ] && awk 'f;/^---$/{c++}c==2{f=1}' ${CLAUDE_SKILL_DIR}/../tool-gitnexus/SKILL.md || true

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Security Audit Workflow

Core Principle

Security vulnerabilities are architectural violations in disguise: injection attacks are layer violations (untrusted data reaching logic without sanitization at the entry boundary); privilege escalation is an SRP violation (authorization logic entangled with business logic); secret leakage is a hidden dependency violation (credentials embedded in code rather than injected from outside). Fixing the architecture fixes the vulnerability.

Limitation declaration: This skill performs static code pattern analysis. It cannot execute npm audit, pip-audit, bandit, semgrep, trivy, or any other automated scanner. The dependency findings in Dimension 4 are a preliminary review — they do not substitute for running real tooling.

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Audit Dimensions

Dimension 1: Input Validation

Scope: All public interfaces, API endpoints, and externally-controlled input paths.

Check	Pass condition
Entry-layer validation	All external parameters (request body, query string, headers, file uploads) are validated before entering the logic layer
SQL parameterization	SQL is built with parameterized queries / prepared statements — never string concatenation
HTML output escaping	All user-controlled data is escaped before rendering in HTML (XSS prevention)
Shell command safety	Shell invocations use argument arrays, not string interpolation of user input
Path canonicalization	File paths are resolved (os.path.realpath() / .resolve()) before use to prevent path traversal

Input Validation Findings
─────────────────────────────────────────────
Interface / endpoint: <name>
  [ ] Validated at entry layer before logic layer
  [ ] SQL parameterized (no string concatenation)
  [ ] HTML output escaped
  [ ] Shell commands use argument arrays
  [ ] File paths canonicalized
  Gaps: <list any failing checks>
─────────────────────────────────────────────

Dimension 2: Authentication and Authorization

Scope: All access-controlled endpoints, operations, and data reads/writes.

Check	Pass condition
AuthN at entry layer	Authentication checks are performed at the entry layer (route handler / controller) — not inside the logic layer
AuthZ at entry layer	Authorization checks are performed at the entry layer alongside authentication
Both checked	Both authentication (who are you?) AND authorization (are you allowed to do this?) are verified — not just one
No bypass path	No path to protected resources exists that skips the auth check (e.g., internal endpoint, direct service call)
Tokens out of logs	Session tokens, JWTs, and auth credentials are excluded from application logs
Tenant isolation	For multi-tenant systems: tenant isolation is enforced at the data query level, not only in the UI

Auth Findings
─────────────────────────────────────────────
Endpoint / operation: <name>
  [ ] AuthN check at entry layer
  [ ] AuthZ check at entry layer
  [ ] Both AuthN and AuthZ verified
  [ ] No bypass path identified
  [ ] Session / auth tokens excluded from logs
  [ ] Tenant isolation enforced (if applicable)
  Gaps: <list any failing checks>
─────────────────────────────────────────────

Dimension 3: Sensitive Data Handling

Scope: All data storage, transmission, logging, and serialization paths.

Check	Pass condition
No hardcoded credentials	No literal credential values assigned to variables matching: password, api_key, secret, token, private_key, access_key (case-insensitive)
PII out of logs	Personally identifiable information (names, emails, phone numbers, national IDs) is not written to logs
Sanitized error messages	Error messages returned to external callers do not expose stack traces, file paths, SQL queries, or internal structure
Response field masking	Sensitive fields (passwords, tokens, PII) are stripped or masked from API response objects before serialization
Secrets from environment	Secrets are loaded from environment variables or a secrets manager — not from committed config files

Sensitive Data Findings
─────────────────────────────────────────────
  [ ] No hardcoded credentials (password/key/secret/token literals)
  [ ] PII excluded from logs
  [ ] Error messages sanitized for external callers
  [ ] Sensitive fields stripped from API responses
  [ ] Secrets sourced from env vars / secrets manager (not committed config)
  Gaps: <list any failing checks>
─────────────────────────────────────────────

Dimension 4: Dependency Review

Scope: Dependency manifest files (package.json, requirements.txt, go.mod, Cargo.toml, pom.xml, pyproject.toml).

Scope boundary: Claude cannot query live CVE databases or confirm current compromise status of packages. This dimension covers checks that can be performed reliably from the manifest file alone. For vulnerability scanning, authoritative tooling is required (see note below).

Check	Pass condition
Exact version pinning	All production dependencies use exact versions — no ^, ~, *, or latest ranges; floating ranges in production create non-reproducible builds
Lock file committed	A lock file exists and is committed: package-lock.json, yarn.lock, pnpm-lock.yaml, poetry.lock, Cargo.lock, go.sum
Dev/prod separation	Dev tools, test frameworks, and linters are in devDependencies / [dev-dependencies] — not in production dependencies
No self-referential or phantom imports	No dependencies listed that are not used by the codebase, and no imports used in code that are absent from the manifest

Authoritative scan required: Run npm audit, pip-audit, cargo audit, or trivy to check for known CVEs and supply-chain issues. Claude cannot execute these tools and cannot reliably identify compromised or vulnerable packages from the manifest text alone.

Dependency Review Findings
─────────────────────────────────────────────
  [ ] Production dependencies use exact version pinning (no ^ ~ * latest)
  [ ] Lock file exists and is committed
  [ ] Dev dependencies correctly separated from production dependencies
  [ ] No unused or phantom dependencies found
  Gaps: <list any failing checks>
  ⚠️ Authoritative scan required: run npm audit / pip-audit / cargo audit / trivy
─────────────────────────────────────────────

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Finding Severity Levels

Level	Meaning	Action
CRITICAL	Directly exploitable with no prerequisites (SQL injection, auth bypass, hardcoded admin credential)	Block merge; fix immediately
HIGH	Exploitable under specific but realistic conditions (missing auth on an endpoint reachable with a valid session)	Fix before shipping
MEDIUM	Defense-in-depth gap (error message leaks stack trace, no direct exploit path)	Fix in near-term follow-up
LOW	Best-practice gap with no current exploit path (PII in debug logs, dev dependency in prod bundle)	Track as tech debt

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Forbidden Actions

• Do not run shell commands, execute scanners, or call external APIs
• Do not mark a finding as "not a vulnerability" because "this code isn't reachable in production" without tracing the actual call path — reachability must be verified, not assumed
• Do not skip Dimension 2 for "internal-only" endpoints — network perimeters can be breached; internal endpoints without auth checks are still vulnerabilities

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Reply Format

─── Security Audit Summary ──────────────────────────
① Scope:          <files / endpoints / modules reviewed>
② Findings:
   CRITICAL: <count> — <brief list or "none">
   HIGH:     <count> — <brief list or "none">
   MEDIUM:   <count> — <brief list or "none">
   LOW:      <count> — <brief list or "none">
③ Dimension status:
   Input validation:  ✅ clean / ⚠️ N gaps found
   Auth / AuthZ:      ✅ clean / ⚠️ N gaps found
   Sensitive data:    ✅ clean / ⚠️ N gaps found
   Dependencies:      ✅ clean / ⚠️ N concerns — authoritative scan still required
④ Needs your input: <CRITICAL / HIGH items requiring immediate decision before merge>
─────────────────────────────────────────────────────