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Deepak Gupta
Deepak Gupta

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Implementing Continuous Access Control with OpenID CAEP

#webdev #cybersecurity #security #identity

TL;DR

Continuous Access Evaluation Protocol (CAEP) extends the OpenID framework to enable real-time, context-driven access decisions.

This post explains how developers can integrate CAEP into their existing identity infrastructure, including:

  • Implementation patterns
  • Event handling mechanisms
  • Security considerations
  • A full JWT event payload example for testing

Introduction

Most developers are familiar with OAuth 2.0 and OpenID Connect as standards for authentication and authorization. The limitation?

Once a token is issued, access remains valid until expiry — even if conditions change.

In today’s environment, device state, user behavior, and threat intelligence can change instantly. Static token lifetimes are a security risk.

CAEP (Continuous Access Evaluation Protocol), part of the OpenID Foundation’s Shared Signals framework, solves this by enabling real-time access decisions triggered by security events.

Why Continuous Access Matters for Developers

Static access control means:

  • Leaked tokens remain valid until manual revocation or expiration
  • Compromised accounts may still access sensitive resources
  • Real-time threat intelligence is underutilized

Continuous evaluation shifts this model:

  • Apps react instantly to security events (device loss, geo-anomaly, policy changes)
  • Attack surface is reduced by instantly revoking access
  • User experience improves via intelligent session persistence when conditions are safe

What is CAEP and How It Works

CAEP is event-driven access control:

  1. Applications or APIs register for security event subscriptions with the IdP.
  2. The IdP sends real-time signed event payloads (JWTs) when access context changes.
  3. The application enforces updated policy instantly — revoking tokens, forcing re-authentication, or downgrading privileges.

Common CAEP Events:

  • Session revoked
  • Risk score escalation
  • Device compliance check failed
  • User password reset

Key Implementation Components

4.1 Session Context Updates

Your backend session representation should dynamically adjust to incoming CAEP events:

session.securityContext = {
  deviceCompliance: event.deviceCompliance,
  riskLevel: event.riskLevel,
  lastVerified: new Date()
};
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4.2 Event Handling

Use secure endpoints for real-time event delivery.

Webhook Example (Node.js + Express):

app.post("/caep/events", verifySignature, (req, res) => {
  const event = req.body;
  switch(event.type) {
    case "token_revoked":
      revokeSession(event.sessionId);
      break;
    case "policy_update":
      updateAccessPolicy(event.policy);
      break;
  }
  res.sendStatus(200);
});
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4.3 Token Revocation

Invalidate tokens both in the app and API gateway:

def revoke_session(session_id):
    db.sessions.update_one(
        {"_id": session_id},
        {"$set": {"status": "revoked"}}
    )
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4.4 Example CAEP Event JWT Payload

A CAEP event from an IdP is typically sent as a signed JWT to ensure authenticity. Here's a realistic example:

// Compact JWS example (header.payload.signature)
eyJhbGciOiJSUzI1NiIsInR5cCI6IkpXVCJ9.eyJpc3MiOiJodHRwczovL2lkcC5leGFtcGxlLmNvbS8iLCJzdWIiOiJ1c2VyX0lEczEyMyIsImV2ZW50X3R5cGUiOiJ0b2tlbl9yZXZva2VkIiwic2Vzc2lvbl9pZCI6Ijg4ZTM0ZTgtYmQ3YS00ZjI0LTkzNzYtYzBjZTBlOWFjOTZjIiwicmlza19zY29yZSI6IjAuOSIsImRldmljZV9jb21wbGlhbmNlIjpmYWxzZSwiaWF0IjoxNzAxNDU5MjAwLCJjYXBfaWQiOiJhZHAyMDEifQ.SflKxwR...

// Decoded JWT payload:
{
  "iss": "https://idp.example.com/",
  "sub": "user_IDs123",
  "event_type": "token_revoked",
  "session_id": "88e34e8-bd7a-4f24-9376-c0ce0e9ac96c",
  "risk_score": "0.9",
  "device_compliance": false,
  "iat": 1701459200,
  "cap_id": "adp201"
}
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Validation Steps:

  1. Verify Signature: Use IdP’s public key (JWKS endpoint) to verify JWT signature.
  2. Validate Claims:
    • iss matches expected IdP URL
    • iat (issued at) is within acceptable time tolerance
  3. Apply Policy Change: If risk_score > 0.7 or device_compliance == false, revoke token immediately.

Node.js Verification Example:

import jwt from "jsonwebtoken";
import jwksClient from "jwks-rsa";

const client = jwksClient({ jwksUri: "https://idp.example.com/.well-known/jwks.json" });

function getKey(header, callback) {
  client.getSigningKey(header.kid, (err, key) => {
    const signingKey = key.getPublicKey();
    callback(null, signingKey);
  });
}

function verifyCAEPEvent(token) {
  jwt.verify(token, getKey, { algorithms: ["RS256"] }, (err, decoded) => {
    if (err) throw new Error("Invalid CAEP event signature");
    console.log("Verified Event", decoded);
    return decoded;
  });
}
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Sample Implementation Workflow

  1. Register Client with IdP for event subscriptions.
  2. Securely Receive Events over HTTPS with mutual TLS or JWT signatures.
  3. Verify & Decode Payload, checking event_type, session_id, and other claims.
  4. Update Session Store immediately across all distributed nodes.
  5. Trigger User/UI Update if required (e.g., prompt re-authentication).

Architecture in Words

  • IdP (Identity Provider) generates security policies and CAEP events.
  • CAEP Event Service pushes signed JWT events to your backend.
  • Application Webhook Receiver verifies and processes events.
  • Session Store is updated to reflect the current security state.
  • API Gateway blocks revoked tokens in real time.
  • Frontend detects session termination and prompts the user.

Security and Performance Considerations

  • Always verify JWT signatures before trusting event data.
  • Use asynchronous processing (e.g., queues) to avoid blocking threads.
  • Maintain event delivery retries for reliability.
  • Store recent processed event IDs to avoid reprocessing duplicates.

Technical Challenges and Solutions

Challenge: Distributed revocation in microservices

Solution: Use a global session store (Redis, DynamoDB) + pub/sub events.

Challenge: Prevent excessive user disruptions

Solution: Differentiate blocking events vs. informational events.

Challenge: Event authenticity

Solution: Enforce JWT signature checks with key rotation support.

Discussion Point

Have you built real-time JWT event handling for access control yet?

How do you handle low-latency token revocation without introducing downtime?

Conclusion

CAEP moves access control from static timeouts to instant threat-based decisions.

For implementation:

  1. Use secure event delivery
  2. Verify and parse JWT payloads
  3. Apply session policy updates immediately

With this, you can build smarter, more adaptive security for your applications.

This article was adapted from my original blog post. Read the full version here: https://guptadeepak.com/the-future-of-continuous-access-control-openid-caep/

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