Application Security

security

Overview

Enforces zero-trust defense-in-depth, OWASP API Top 10 mitigation, cryptographic hardening, sensitive data leakage protection, and AI/LLM safety across all services, endpoints, and agent integrations.

When to Use

Activate whenever writing authentication, authorization, session management, database queries, cryptography, external API integrations, user input handling, or agent tool calling.

Rules & Patterns

Negative Constraints (What NOT to Do)

1. NEVER use standard string comparison (===) for secrets/hashes: Always use crypto.timingSafeEqual to prevent timing attacks.
2. NEVER store sensitive JWT access/refresh tokens in localStorage: Store tokens in httpOnly, Secure, SameSite=Strict cookies.
3. NEVER return raw database/internal error messages or stack traces to the client: Return standardized generic error codes (INTERNAL_SERVER_ERROR) and log details internally.
4. NEVER trust client-provided IDs for authorization without tenant/ownership checks: Always verify where: { id, userId: session.userId } to prevent Broken Object Level Authorization (BOLA/IDOR).
5. NEVER disable CSRF protection, CORS allow-all (*), or TLS verification (NODE_TLS_REJECT_UNAUTHORIZED=0) in production: Always enforce strict origin whitelists and HTTPS.
6. NEVER pass un-sanitized third-party content directly into system prompts or shell execution: Treat all external data as potentially adversarial.

OWASP Top 10 for Modern APIs & Full-Stack

1. Injection (SQL, NoSQL, Command)

• Always use parameterized queries — never concatenate user input into SQL or shell commands.
• Use ORMs (Prisma, Drizzle, SQLAlchemy) with strict schema validation.
• Validate and sanitize all user input before processing.

2. Broken Object Level Authorization (BOLA / IDOR)

• Validate user ownership on EVERY database read, update, or delete:

  // [GOOD] Scoped to authenticated user
  const doc = await db.document.findFirst({
    where: { id: documentId, tenantId: session.tenantId }
  });
  

3. Broken Authentication & Session Management

• Use Argon2id or bcrypt (cost factor ≥ 12) for password hashing.
• Short-lived access tokens (15 min) + secure HTTP-only refresh tokens.
• Enforce rate limiting and brute-force lockouts on auth endpoints.

4. SSRF (Server-Side Request Forgery)

• Restrict server-side URL fetching: validate URL scheme (https: only), resolve IP, and block private CIDR blocks (10.0.0.0/8, 127.0.0.0/8, 169.254.0.0/16, 192.168.0.0/16).

5. Security Misconfiguration & Headers

Enforce modern production security headers:

Content-Security-Policy: default-src 'self'
X-Content-Type-Options: nosniff
X-Frame-Options: DENY
Strict-Transport-Security: max-age=31536000; includeSubDomains
Referrer-Policy: strict-origin-when-cross-origin
Permissions-Policy: camera=(), microphone=(), geolocation=()

AI Agent & LLM Security Invariants

When building AI workflows, tools, or MCP servers:

1. Prompt Injection Defense:
   • Clearly delineate untrusted user/web content using boundary markers (e.g. <untrusted_content> tags).
   • Never allow untrusted content to override system instructions or tool execution permissions.
2. Tool Execution Boundaries:
   • Destructive operations (database drops, file deletions, payment triggers) MUST require explicit user confirmation.
   • Restrict file system tools to the workspace root — block directory traversal (../).
3. Secret Masking & Output Sanitization:
   • Scrub API keys (sk-..., Bearer ...), tokens, and credentials before writing to agent logs or step summaries.

Code Examples

Timing-Safe Secret Verification

import crypto from 'node:crypto';

export function verifyWebhookSignature(payload, signature, secret) {
  const hmac = crypto.createHmac('sha256', secret);
  const digest = Buffer.from(hmac.update(payload).digest('hex'), 'utf8');
  const sigBuffer = Buffer.from(signature, 'utf8');

  if (digest.length !== sigBuffer.length) return false;
  return crypto.timingSafeEqual(digest, sigBuffer);
}

Safe SSRF Prevention Wrapper

import dns from 'node:dns/promises';

export async function validateSafeUrl(urlString: string): Promise<URL> {
  const parsed = new URL(urlString);
  if (parsed.protocol !== 'https:') {
    throw new Error('Only HTTPS protocol is permitted');
  }

  const { address } = await dns.lookup(parsed.hostname);
  if (
    address.startsWith('127.') ||
    address.startsWith('10.') ||
    address.startsWith('192.168.') ||
    address === '169.254.169.254'
  ) {
    throw new Error('Access to private/metadata IP addresses is blocked');
  }

  return parsed;
}

Validation Checklist

• All database queries parameterized or managed by type-safe ORM.
• BOLA/IDOR prevented: all entity queries scoped by tenant/user id.
• Cookies set with HttpOnly, Secure, and SameSite=Strict or Lax.
• Passwords hashed with Argon2id / bcrypt.
• Security headers active in middleware/reverse proxy.
• No secrets or tokens checked into source control or exposed in logs.

Common Mistakes

• Trusting client-side claims: Checking role or permissions only on the frontend without server-side validation.
• Timing attacks on tokens: Comparing tokens with token === expectedToken instead of timingSafeEqual.
• Exposing internal stack traces: Returning full error objects to client in production.
• Unvalidated redirects / URLs: Allowing arbitrary URLs in redirect or fetch parameters.

Integration Notes

• Runs in the REVIEW phase for every backend route, auth flow, and database mutation.
• Integrates with engineering-workflow during Phase 5 (5-axis quality gate).
• Pairs with system-design to mandate secure network boundaries and authorization layers.

Application Security — Best Practices

OWASP Top 10

1. Injection (SQL, NoSQL, Command)

• Always use parameterized queries — never concatenate user input into SQL
• Use ORM (Prisma, SQLAlchemy, TypeORM) — they parameterize by default
• Validate and sanitize all user input

2. Broken Authentication

• Use bcrypt/argon2 for password hashing (cost factor ≥ 12)
• JWT: short-lived access tokens (15min), refresh tokens (7 days)
• Rate limit login attempts
• Implement account lockout after N failed attempts
• MFA for sensitive operations

3. Sensitive Data Exposure

• HTTPS everywhere — redirect HTTP to HTTPS
• Encrypt sensitive data at rest (AES-256)
• Never log passwords, tokens, or PII
• Use environment variables for secrets

4. XML/XXE

• Disable external entity processing
• Use JSON instead of XML where possible

5. Broken Access Control

• Default deny — explicitly grant access
• RBAC (Role-Based Access Control) or ABAC (Attribute-Based)
• Check authorization on every request, not just UI
• Don't rely on client-side validation for security

6. Security Misconfiguration

• Remove default credentials
• Disable debug mode in production
• Security headers (see below)
• Keep dependencies updated

7. XSS (Cross-Site Scripting)

• Escape all output by default
• Content-Security-Policy header
• HttpOnly + Secure + SameSite cookies
• Use framework's built-in XSS protection

8. Insecure Deserialization

• Validate and schema-check all input (Zod, Pydantic, class-validator)
• Don't deserialize untrusted data

9. Insufficient Logging

• Log all authentication events
• Log authorization failures
• Log input validation failures
• Include request ID for tracing

10. SSRF (Server-Side Request Forgery)

• Validate and allowlist URLs
• Don't let users control server-side HTTP requests

Security Headers

Content-Security-Policy: default-src 'self'
X-Content-Type-Options: nosniff
X-Frame-Options: DENY
Strict-Transport-Security: max-age=31536000; includeSubDomains
Referrer-Policy: strict-origin-when-cross-origin
Permissions-Policy: camera=(), microphone=(), geolocation=()

Authentication Patterns

JWT Flow

Login → Access Token (15min) + Refresh Token (7d, HttpOnly cookie)
Request → Authorization: Bearer <access_token>
Expired → POST /auth/refresh (sends refresh cookie) → new access token

OAuth2 Flow

Redirect → Provider (Google, GitHub) → Callback → Create/link user → JWT

Checklist Before Deploy

• All secrets in environment variables
• HTTPS enabled
• Security headers configured
• Input validation on all endpoints
• Rate limiting enabled
• CORS configured (not *)
• Error messages don't leak internals
• Dependency audit (npm audit, pip audit)
• Logging for security events

Application Security Examples — Anti-patterns vs ContextOS Standard

Example 1: Timing-Safe Secret Verification

Anti-pattern: Anti-pattern (Vulnerable to side-channel timing attack)

// BAD: string comparison returns early on the first mismatched byte
export function verifyApiKey(providedKey: string, storedKey: string): boolean {
  return providedKey === storedKey; // Vulnerable to timing analysis!
}

Best practice: ContextOS Standard (Constant-time buffer comparison)

// GOOD: crypto.timingSafeEqual executes in constant time
import crypto from 'crypto';

export function verifyApiKey(providedKey: string, storedKey: string): boolean {
  const providedBuffer = Buffer.from(providedKey, 'utf8');
  const storedBuffer = Buffer.from(storedKey, 'utf8');

  if (providedBuffer.length !== storedBuffer.length) {
    return false;
  }

  return crypto.timingSafeEqual(providedBuffer, storedBuffer);
}

Example 2: Preventing IDOR (Insecure Direct Object Reference)

Anti-pattern: Anti-pattern (Trusting client ID without ownership check)

// BAD: any authenticated user can delete any other user's document!
app.delete('/api/documents/:id', requireAuth, async (req, res) => {
  await prisma.document.delete({ where: { id: req.params.id } });
  res.status(204).end();
});

Best practice: ContextOS Standard (Multi-tenant scoped authorization check)

// GOOD: document deletion is strictly scoped to authenticated user or org
app.delete('/api/documents/:id', requireAuth, async (req, res) => {
  const deleted = await prisma.document.deleteMany({
    where: {
      id: req.params.id,
      organizationId: req.user.organizationId, // Tenant isolation
    },
  });

  if (deleted.count === 0) {
    return res.status(404).json({ error: 'Document not found or access denied' });
  }

  return res.status(204).end();
});

security Troubleshooting & Common Mistakes

1. Insecure Direct Object References (IDOR)

• Symptom: User A can access User B's invoices by simply modifying the ID in the URL.
• Root Cause: Querying by record ID without scoping to the authenticated user.id or tenant ID.
• Fix: Always query with ownership predicate: db.invoice.findFirst({ where: { id, userId: auth.user.id } }).

2. SQL Injection via Raw String Concatenation

• Symptom: Database compromised through input fields.
• Root Cause: String templating in raw queries (db.query("SELECT * FROM users WHERE id = " + id)).
• Fix: Always use parameterized queries ($1, $2) or ORM/query-builder methods.

3. Storing Sensitive Secrets in Git or Client Bundles

• Symptom: API keys or JWT signing secrets exposed publicly.
• Root Cause: Hardcoding secrets in source files or prefixing server secrets with NEXT_PUBLIC_.
• Fix: Store all secrets in server-only environment variables; add git-secrets to pre-commit hooks.