Security Devsecops

Security / DevSecOps

This skill covers secure coding practices, dependency and secret hygiene, authentication and authorization, and the security tooling that belongs in a secure software development lifecycle (SSDLC) — from local coding habits through CI/CD gates to production monitoring.

Workflow for Adding a New Feature Securely

1. Identify trust boundaries — Note every place the new code accepts input from a user, another service, or a file, and every place it emits output (HTML, logs, another service).
2. Validate and sanitize at the boundary — Validate all untrusted input on entry; escape output for its destination context (HTML, JS, SQL, shell).
3. Use existing security primitives — Reach for the project's established auth framework, ORM, and secret-management approach rather than writing new ones.
4. Keep secrets out of code and logs — Read credentials from environment variables or a secrets vault; confirm nothing sensitive reaches logs or error messages.
5. Run local security checks before pushing — Lint, SAST, and secret-scanning tools where available (gitleaks, semgrep, npm audit, pip-audit, etc.).
6. Let CI gates run — SAST, SCA, secret scanning, and IaC scanning should run on every PR; treat a failure as a blocker, not a suggestion to suppress.
7. Document the security-relevant decision — Note in the PR description any auth/authz change, new dependency, or deviation from a default-secure pattern, so it's auditable later.

General Security Principles

• Never hardcode secrets, credentials, or API keys in source code. Use environment variables or a secure vault (e.g. AWS Secrets Manager, HashiCorp Vault, Doppler) for sensitive data.
• Never commit .env files, secret config files, or unrecognized tokens to source control. Add them to .gitignore before they're ever staged.
• Never log sensitive data, secrets, or session tokens in application logs — redact or omit them at the point of logging, not after the fact.
• Validate and sanitize all user input at the point it enters the system. Escape output appropriately for its context: HTML-encode for HTML, JS-encode for inline scripts, parameterize for SQL.
• Avoid unsafe dynamic-execution functions such as exec, eval, Function(), pickle.loads on untrusted data, or shell interpolation of user input.

# Unsafe — string interpolation into a query
query = f"SELECT * FROM users WHERE email = '{email}'"
cursor.execute(query)

# Safe — parameterized query
cursor.execute("SELECT * FROM users WHERE email = %s", (email,))

Secret Handling

• Load secrets from environment variables (process.env.API_KEY, os.environ["API_KEY"]) or a vault client, never as literals.
• Rotate any credential that was ever committed to version control, even if the commit was later removed — history retains it.
• Scan for accidentally committed secrets before merge, using tools like gitleaks, trufflehog, or the CI provider's built-in secret scanning.
• Scope credentials narrowly: a CI deploy key should be able to deploy, not administer the whole cloud account.

Database Security

• Use parameterized queries or an ORM for all database access. Never build queries via string concatenation or f-strings with user input.
• Ensure database users have the least privilege required for their role (a reporting service should not have DROP TABLE rights).
• Regularly review and update database access policies as team membership and service responsibilities change.

Dependency Management

• Only add packages from verified, reputable sources — check download counts, maintenance activity, and known-CVE history before adding a new dependency.
• Do not add new dependencies without explicit approval and a brief security review, especially for packages that will run with elevated privileges or process untrusted input.
• Regularly update dependencies and scan for known vulnerabilities using Software Composition Analysis (SCA) tools such as npm audit, pip-audit, Dependabot, Snyk, or Trivy.

# Node.js
npm audit --audit-level=high

# Python
pip-audit

# Container image
trivy image myapp:latest

Authentication & Authorization

• Use established, audited authentication frameworks (e.g. Auth0, Passport, Devise, ASP.NET Identity) — never implement custom cryptographic authentication from scratch.
• Store passwords using strong, salted, adaptive hashes: Argon2id or bcrypt, never MD5, SHA1, or unsalted SHA256.
• Implement Role-Based Access Control (RBAC) — or attribute-based access control for finer granularity — for sensitive operations.
• Enforce the principle of least privilege for both API endpoints and UI actions: check authorization on every request server-side, never trust a hidden UI element as an access control.
• Re-check authorization on every request, even for actions previously permitted — session state and roles can change mid-session.

// Missing authorization check — any authenticated user can access any order
app.get("/orders/:id", requireAuth, async (req, res) => {
  const order = await Order.findById(req.params.id);
  res.json(order);
});

// Correct — verify the resource belongs to the requester
app.get("/orders/:id", requireAuth, async (req, res) => {
  const order = await Order.findById(req.params.id);
  if (!order || order.userId !== req.user.id) {
    return res.status(404).end();
  }
  res.json(order);
});