performing-security-code-review

What this skill does

# Performing Security Code Review

## Overview

Conducts security-focused code reviews by scanning source files for common vulnerability patterns including SQL injection, XSS, authentication flaws, insecure dependencies, and secret exposure. Produces structured severity-rated reports with specific remediation guidance.

## Prerequisites

- Read access to all source files in the target project
- `grep` available on PATH for pattern matching
- Access to `package.json` or equivalent dependency manifest for dependency auditing
- Familiarity with OWASP Top 10 vulnerability categories

## Instructions

1. Identify the scope of the review: specific files, directories, or the entire codebase. Confirm the primary language(s) and framework(s) in use.
2. Scan for hardcoded secrets and credentials:
   - Search for patterns matching API keys, tokens, passwords, AWS access keys (`AKIA...`), and private key headers (`BEGIN PRIVATE KEY`).
   - Flag any `.env` files or configuration files containing plaintext secrets.
3. Analyze code for injection vulnerabilities:
   - Identify raw SQL string concatenation (SQL injection risk).
   - Locate unsanitized user input rendered in HTML (XSS risk).
   - Check for `eval()`, `exec()`, or `Function()` calls with dynamic input (code injection risk).
4. Review authentication and authorization logic:
   - Verify password hashing uses strong algorithms (bcrypt, argon2) rather than MD5/SHA1.
   - Check for missing authentication on sensitive endpoints.
   - Identify overly permissive CORS configurations.
5. Audit dependencies for known vulnerabilities:
   - Run `npm audit` or equivalent package manager audit command.
   - Cross-reference dependency versions against known CVE databases.
6. Check for insecure communication patterns:
   - Flag HTTP URLs where HTTPS is expected.
   - Identify disabled TLS certificate verification.
7. Compile findings into a structured report sorted by severity (Critical, High, Medium, Low), including the vulnerable code location, explanation, and remediation steps.

## Output

A structured security review report containing:

- Summary with total findings count by severity level
- Per-finding entries with: file path, line number, vulnerability type, severity, code snippet, explanation, and recommended fix
- Dependency audit results with CVE identifiers where applicable
- Overall risk assessment (Critical / High / Medium / Low / Clean)

## Error Handling

| Error | Cause | Solution |
|---|---|---|
| No source files found | Incorrect scope path or empty directory | Verify the target directory path and confirm it contains source files |
| Binary files in scan | Non-text files matched by search patterns | Exclude binary extensions and `node_modules/` from scans |
| Dependency manifest missing | No `package.json`, `requirements.txt`, or equivalent | Skip dependency audit; note in report that dependency analysis was not possible |
| Permission denied on files | Restricted file access | Request read permissions or narrow the review scope to accessible files |
| False positive on secret pattern | Benign string matching secret regex | Verify context before reporting; mark as potential false positive if the match appears in test fixtures or documentation |

## Examples

**SQL injection review:**
Trigger: "Review this database query code for SQL injection vulnerabilities."
Process: Scan all files containing SQL query construction. Identify string concatenation with user input (`"SELECT * FROM users WHERE id = " + userId`). Report as High severity with remediation: use parameterized queries or prepared statements.

**Dependency vulnerability scan:**
Trigger: "Check this project's dependencies for known security vulnerabilities."
Process: Run `npm audit` on the project. Parse output for vulnerabilities. Report each finding with CVE identifier, affected package, installed version, and patched version. Recommend `npm audit fix` or manual version pinning.

**Full codebase security audit:**
Trigger: "Run a security scan on this codebase."
Process: Execute all seven scan categories (secrets, injection, auth, dependencies, communication, dangerous commands, obfuscation). Produce a comprehensive report with findings grouped by category and sorted by severity.

## Resources

- [OWASP Top 10](https://owasp.org/www-project-top-ten/) -- industry-standard vulnerability classification
- [Node.js Security Checklist](https://blog.risingstack.com/node-js-security-checklist/) -- Node-specific security guidance
- [CWE/SANS Top 25](https://cwe.mitre.org/top25/) -- most dangerous software weaknesses
- `${CLAUDE_SKILL_DIR}/references/README.md` -- bundled reference materials