Secure code review

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Secure Code Review

Apply OWASP Top 10 and CWE Top 25 patterns during code generation and review

ALWAYS

• Use parameterized queries / prepared statements for all database access. Never build SQL by string concatenation, even for "trusted" inputs.
• Validate input at the trust boundary — type, length, allowed characters, allowed range — and reject before processing.
• Encode output for the rendering context (HTML escape for HTML, URL encode for query params, JSON encode for JSON output).
• Use the language's built-in cryptography library, never custom-rolled crypto. Prefer AES-GCM for symmetric encryption, Ed25519 / RSA-PSS for signatures, Argon2id / bcrypt for password hashing.
• Use crypto/rand (Go), secrets module (Python), crypto.randomBytes (Node.js), or the platform CSPRNG for any random value involved in security (tokens, IDs, session keys).
• Set explicit security headers on HTTP responses: Content-Security-Policy, Strict-Transport-Security, X-Content-Type-Options: nosniff, Referrer-Policy.
• Use the principle of least privilege for file paths, database users, IAM policies, and process privileges.

NEVER

• Build SQL/NoSQL queries by string concatenation with user input.
• Pass user input directly to exec, system, eval, Function(), child_process, subprocess.run(shell=True), or any other command-execution path.
• Trust client-side validation. Always re-validate server-side.
• Use MD5 or SHA1 for any new security-sensitive purpose (passwords, signatures, HMAC). Use SHA-256 / SHA-3 / BLAKE2 / Argon2id instead.
• Use ECB mode for any encryption, ever. Prefer GCM, CCM, or ChaCha20-Poly1305.
• Use == for password comparison — use a constant-time comparison (hmac.compare_digest, crypto.timingSafeEqual, subtle.ConstantTimeCompare).
• Allow user input to determine file paths without canonicalization and allowlist checks (defends against ../../../etc/passwd style path traversal).
• Disable TLS certificate verification in production code — verify=False, InsecureSkipVerify: true, rejectUnauthorized: false.

KNOWN FALSE POSITIVES

• Internal admin tools intentionally executing shell commands against trusted, fixed arguments are acceptable when documented and code-reviewed.
• Cryptographic test vectors using MD5 / SHA1 for compatibility with documented protocols (e.g. legacy interop tests) are acceptable.
• Constant-time comparison is overkill for non-secret comparisons (string equality in logs, tag matching).