ln-621-security-boundary-auditor

name	ln-621-security-boundary-auditor
description	Checks application security boundaries: secrets, injection, XSS, input validation, and sensitive env defaults. Use when auditing exploitable code paths.
allowed-tools	Read, Grep, Glob, Bash, mcp__hex-graph__trace_dataflow, mcp__hex-line__read_file, mcp__hex-line__grep_search, mcp__hex-line__outline
license	MIT

Paths: File paths (references/, ../ln-*) are relative to this skill directory.

Security Boundary Auditor (L3 Worker)

Type: L3 Worker

Specialized worker auditing exploitable application security boundaries.

Purpose & Scope

• Audit codebase for security boundary vulnerabilities (Category 1: Critical Priority)
• Scan for hardcoded secrets, SQL injection, XSS, missing input validation, and sensitive env defaults
• Emit HARDEN_SECURITY_BOUNDARY, REMOVE_SECRET, or REMOVE_SENSITIVE_DEFAULT
• Return structured findings with severity, location, effort, actions, and recommendations
• Calculate compliance score (X/10) for Security category

Inputs

MANDATORY READ: Load references/audit_worker_core_contract.md and references/mcp_tool_preferences.md. Tool policy: You may run as an isolated subagent where host AGENTS.md is not in scope, so default to hex-line MCP first for file reads, search, and edits. Load references/mcp_integration_patterns.md only when MCP behavior is unclear.

Receives contextStore with: tech_stack, best_practices, principles, codebase_root, output_dir.

Use hex-graph first when dataflow or cross-file reference analysis materially improves confidence. Use hex-line first for local code reads when available. If MCP is unavailable, unsupported, or not indexed, continue with built-in Read/Grep/Glob/Bash and state the fallback in the report.

Workflow

Detection policy: use two-layer detection (candidate scan, then context verification); load references/two_layer_detection.md only when the verification method is ambiguous.

1. Parse Context: Extract tech stack, best practices, codebase root, output_dir from contextStore
2. Scan Codebase (Layer 1): Run security checks using Glob/Grep patterns (see Audit Rules below)
3. Analyze Context (Layer 2): For each candidate, read surrounding code to classify:
   • Secrets: test fixture / example / template -> FP. Production code -> confirmed
   • SQL injection: ORM parameterization nearby -> FP. Raw string concat with user input -> confirmed
   • XSS: framework auto-escapes (React JSX, Go templates) -> FP. Unsafe context (innerHTML, | safe) -> confirmed
   • Sensitive defaults: placeholder/example -> skip. Real fallback for secret/token/key -> confirmed
   • Validation: internal service-to-service endpoint -> downgrade. Public API -> confirmed
4. Collect Findings: Record confirmed violations with severity, location (file:line), effort estimate (S/M/L), recommendation
5. Calculate Score: Count violations by severity, calculate compliance score (X/10)
6. Write Report: Build full markdown report in memory per references/templates/audit_worker_report_template.md, write to {output_dir}/ln-621--global.md in single Write call
7. Return Summary: Return minimal summary (see Output Format)

Audit Rules (Priority: CRITICAL)

1. Hardcoded Secrets

What: API keys, passwords, tokens, private keys in source code

Detection:

• Search patterns: API_KEY = "...", password = "...", token = "...", SECRET = "..."
• File extensions: .ts, .js, .py, .go, .java, .cs
• Exclude: .env.example, README.md, test files with mock data

Severity:

• CRITICAL: Production credentials (AWS keys, database passwords, API tokens)
• HIGH: Development/staging credentials
• MEDIUM: Test credentials in non-test files

Recommendation: Move to environment variables (.env), use secret management (Vault, AWS Secrets Manager)

Effort: S (replace hardcoded value with process.env.VAR_NAME)

2. SQL Injection Patterns

What: String concatenation in SQL queries instead of parameterized queries

Detection:

• Patterns: query = "SELECT * FROM users WHERE id=" + userId, db.execute(f"SELECT * FROM {table}"), `SELECT * FROM ${table}`
• Languages: JavaScript, Python, PHP, Java

Severity:

• CRITICAL: User input directly concatenated without sanitization
• HIGH: Variable concatenation in production code
• MEDIUM: Concatenation with internal variables only

Recommendation: Use parameterized queries (prepared statements), ORM query builders

Effort: M (refactor query to use placeholders)

3. XSS Vulnerabilities

What: Unsanitized user input rendered in HTML/templates

Detection:

• Patterns: innerHTML = userInput, dangerouslySetInnerHTML={{__html: data}}, echo $userInput;
• Template engines: Check for unescaped output ({{ var | safe }}, <%- var %>)

Severity:

• CRITICAL: User input directly inserted into DOM without sanitization
• HIGH: User input with partial sanitization (insufficient escaping)
• MEDIUM: Internal data with potential XSS if compromised

Recommendation: Use framework escaping (React auto-escapes, use textContent), sanitize with DOMPurify

Effort: S-M (replace innerHTML with textContent or sanitize)

4. Sensitive Env Defaults

What: Secret, token, key, credential, or privileged config values with unsafe code defaults

Detection:

• Grep env reads with defaults for sensitive names: SECRET, TOKEN, KEY, PASSWORD, PRIVATE, CREDENTIAL
• Check config/settings classes for hardcoded sensitive fallback values
• Exclude .env.example, tests, docs, and obvious placeholders (changeme, empty string, example)

Severity:

• CRITICAL: production credential fallback or default signing/encryption secret
• HIGH: sensitive default in runtime config reachable in deployed app
• MEDIUM: dev/staging sensitive default outside test-only files

Recommendation: Remove sensitive default, require explicit config, fail fast at startup

Effort: S-M

5. Missing Input Validation

What: Missing validation at system boundaries (API endpoints, user forms, file uploads)

Detection:

• API routes without validation middleware
• Form handlers without input sanitization
• File uploads without type/size checks
• Missing CORS configuration

Severity:

• CRITICAL: File upload without validation, authentication bypass potential
• HIGH: Missing validation on sensitive endpoints (payment, auth, user data)
• MEDIUM: Missing validation on read-only or internal endpoints

Recommendation: Add validation middleware (Joi, Yup, express-validator), implement input sanitization

Effort: M (add validation schema and middleware)

Scoring Algorithm

MANDATORY READ: Load references/audit_scoring.md.

Output Format

MANDATORY READ: Load references/templates/audit_worker_report_template.md.

Write JSON summary per references/audit_summary_contract.md. In managed mode the caller passes both runId and summaryArtifactPath; in standalone mode the worker generates its own run-scoped artifact path per shared contract.

Write report to {output_dir}/ln-621--global.md with category: "Security Boundary" and checks: hardcoded_secrets, sql_injection, xss_vulnerabilities, sensitive_env_defaults, missing_input_validation.

Return summary per references/audit_summary_contract.md.

Standalone mode still writes the same JSON summary to a worker-owned run-scoped artifact path per shared contract.

Critical Rules

Apply the already-loaded references/audit_worker_core_contract.md.

• Do not auto-fix: Report violations only
• Tech stack aware: Use contextStore to apply framework-specific patterns (e.g., React XSS vs PHP XSS)
• False positive reduction: Exclude test files, example configs, documentation
• Effort realism: S = <1 hour, M = 1-4 hours, L = >4 hours
• Location precision: Always include file:line for programmatic navigation
• Unique angle: Audit exploitable application security boundaries only. Do not audit package health or env synchronization.
• Action required: Every finding uses HARDEN_SECURITY_BOUNDARY, REMOVE_SECRET, or REMOVE_SENSITIVE_DEFAULT.

Definition of Done

Apply the already-loaded references/audit_worker_core_contract.md.

• contextStore parsed successfully (including output_dir)
• All 5 security checks completed (secrets, SQL injection, XSS, sensitive env defaults, validation)
• Findings collected with severity, location, effort, recommendation
• Score calculated using penalty algorithm
• Report written to {output_dir}/ln-621--global.md (atomic single Write call)
• Summary written per contract

Reference Files

• Audit output schema: references/audit_output_schema.md
• Security audit rules: references/security_rules.md

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Version: 3.0.0 Last Updated: 2025-12-23