Integrity Failures in Chi with Jwt Tokens

In Chi, an Integrity Failure involving JWT tokens typically occurs when a service accepts and acts upon a token whose contents have been altered or whose cryptographic integrity cannot be verified. This can expose endpoints to tampering attacks, such as changing the algorithm to none, swapping the signing key, or modifying claims like roles or scopes, leading to privilege escalation or unauthorized actions.

Chi’s default JSON Web Token handling relies on explicit configuration. If the token validation settings are incomplete (for example, omitting expected issuer or audience, or failing to enforce token binding), an attacker who can influence the request path or headers may supply a modified token that the server mistakenly trusts. Because Chi routes are often defined with pattern-based parameter extraction, a mismatch between the intended route constraint and the token usage can allow a tampered token to bypass intended authorization checks.

One common pattern is to read the token from an Authorization header and pass claims into the route pipeline without strict validation. For example, if a route expects a specific claim format but does not verify the token’s signature or the alg header, an attacker could replace a signed token with an unsigned one or with a token signed using a different key. This is especially risky when the application uses a weak or default secret, or when secrets are shared across environments.

Real-world attack patterns mirror the OWASP API Top 10 2023 category A07:2023 (Identification and Authentication Failures) and align with known CVE behaviors where token validation logic is bypassed. Because Chi encourages minimal configuration for rapid development, developers might skip steps like explicitly setting validateIssuer or validateAudience, inadvertently enabling tokens from unexpected issuers or for different audiences to be accepted.

Additionally, if the application deserializes token payloads into loosely typed objects and then uses those values in routing or business logic, an attacker can inject unexpected types or values that change control flow. This can lead to Insecure Direct Object References (IDOR) or BOLA when combined with weak ownership checks. The interplay between Chi’s route resolution and JWT claim usage means that integrity failures in token handling can propagate into broader authorization flaws.

To detect such issues, scans exercise unauthenticated and authenticated paths, submitting tokens with modified headers or claims to observe whether access controls or data scopes are improperly relaxed. Findings will highlight missing validation settings, overly permissive algorithms, or missing checks that should be enforced before processing requests.

Remediation focuses on strict token validation and avoiding implicit trust in any part of the token. Always specify expected signing algorithms, explicitly validate issuer and audience, and avoid using tokens to dynamically alter routing in ways that bypass authorization checks.

Example: secure token validation in a Chi endpoint using a well-configured JWT library.

// config.jwt.js
export const jwtConfig = {
  issuer: 'https://auth.example.com/',
  audience: 'https://api.example.com/',
  algorithms: ['RS256'],
  clockTolerance: 60,
};

// server.chi
import { jwtDecode } from 'jose';
import { jwtConfig } from './config.jwt.js';

export const verifyToken = (token) => {
  if (!token?.startsWith('Bearer ')) {
    throw new Error('Unauthorized');
  }
  const raw = token.slice(7);
  // Enforce algorithm and validate claims
  const { payload, protectedHeader } = jwtDecode(raw, { issuer: jwtConfig.issuer, audience: jwtConfig.audience, algorithms: jwtConfig.algorithms });
  if (!payload || !protectedHeader) {
    throw new Error('Invalid token');
  }
  return payload;
};

// routes/secure.chi
import { verifyToken } from '../jwt.js';

middleware('auth') = (req) => {
  const token = req.header('Authorization');
  const claims = verifyToken(token);
  req.claims = claims;
};

get '/admin' = (req) => {
  if (req.claims.role !== 'admin') {
    throw 'Forbidden';
  }
  return { message: 'admin area' };
};

Example: enforce algorithm and reject none in a Chi middleware.

// enforce-jwt-alg.chi
export const enforceJwt = (req) => {
  const auth = req.header('Authorization');
  if (!auth || !auth.startsWith('Bearer ')) {
    return { error: 'Unauthorized' };
  }
  const token = auth.slice(7);
  const segments = token.split('.');
  if (segments.length !== 3) {
    return { error: 'Invalid token structure' };
  }
  const header = JSON.parse(Buffer.from(segments[0], 'base64url').toString());
  if (header.alg !== 'RS256') {
    return { error: 'Unsupported algorithm' };
  }
  // Further validation (issuer, audience, signature) should be performed server-side
  return null;
};

get '/resource' = [enforceJwt, (req) => {
  return { data: 'protected' };
}];

Example: avoid using token-derived values to influence route parameters directly; keep authorization checks explicit.

// bad: using claim to select route logic
get '/:userRole/dashboard' = (req) => {
  // Do not trust URL or token-derived role for route selection
};

// good: derive access inside handler after strict validation
get '/dashboard' = (req) => {
  const token = req.header('Authorization')?.slice(7);
  const claims = verifyToken(token);
  if (claims.role !== 'admin') {
    throw 'Forbidden';
  }
  return { view: 'admin-dashboard' };
};

Additional recommendations: rotate signing keys, store secrets/keys securely, prefer asymmetric algorithms (RS256/ES256), and set short expirations. Regularly scan with tools that include JWT integrity checks to catch configuration drift.