Process Genesys Cloud Webhook Payloads in AWS Lambda (Node.js)

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Process Genesys Cloud Webhook Payloads in AWS Lambda (Node.js)

What You Will Build

  • A serverless AWS Lambda function that receives HTTP POST requests from Genesys Cloud webhooks.
  • The function validates the request signature, parses the payload, and routes events based on the eventType.
  • This tutorial uses the AWS Lambda Node.js runtime and the crypto module for signature verification.

Prerequisites

  • AWS Account: With permissions to create Lambda functions and IAM roles.
  • Genesys Cloud Organization: With access to the Admin Center to configure Webhooks.
  • Node.js: Version 18.x or later (recommended for AWS Lambda).
  • AWS CLI: Configured with credentials to deploy the Lambda function.
  • Webhook Secret: A secret string generated in the Genesys Cloud Webhook configuration for signature verification.

Authentication Setup

Genesys Cloud webhooks do not use OAuth tokens for delivery. Instead, they use a shared secret to sign the payload. Your Lambda function must verify this signature to ensure the request originates from Genesys Cloud.

The signature is calculated using HMAC-SHA256 over the raw request body. The X-Genesys-Signature header contains the base64-encoded signature.

The Verification Logic

Before processing any data, you must validate the signature. If the signature does not match, the Lambda function must return a 401 Unauthorized status. Genesys Cloud will retry failed deliveries, so failing fast on invalid signatures prevents unnecessary processing.

const crypto = require('crypto');

/**
 * Verifies the Genesys Cloud webhook signature.
 * 
 * @param {string} payload - The raw string body of the request.
 * @param {string} signatureHeader - The value of the X-Genesys-Signature header.
 * @param {string} secret - The shared secret configured in Genesys Cloud.
 * @returns {boolean} True if the signature is valid.
 */
function verifySignature(payload, signatureHeader, secret) {
    if (!signatureHeader || !secret) {
        return false;
    }

    // Genesys Cloud calculates the HMAC-SHA256 of the raw body using the secret
    // and then base64 encodes the result.
    const expectedSignature = crypto
        .createHmac('sha256', secret)
        .update(payload, 'utf8')
        .digest('base64');

    // Use timing-safe comparison to prevent timing attacks
    return crypto.timingSafeEqual(
        Buffer.from(signatureHeader),
        Buffer.from(expectedSignature)
    );
}

Implementation

Step 1: Configure the Lambda Handler for Raw Body Parsing

AWS API Gateway (which triggers Lambda) often parses JSON bodies automatically. However, signature verification requires the raw byte sequence of the request body. If API Gateway parses the JSON, the whitespace and formatting may change, causing the HMAC calculation to fail.

You must configure your Lambda function to receive the raw payload. In the AWS Lambda console, under Configuration > Function URL or API Gateway integration, ensure that the Payload Format Version is set to 2.0 (recommended) or that you are using a Function URL with InvokeMode: BUFFERED.

For API Gateway v2 (HTTP API), the event structure places the body in event.body. If the body is base64 encoded, you must decode it.

/**
 * Decodes the body from the Lambda event.
 * Handles both plain text and base64 encoded bodies.
 */
function getRawBody(event) {
    const { body, isBase64Encoded } = event;

    if (!body) {
        return null;
    }

    if (isBase64Encoded) {
        return Buffer.from(body, 'base64').toString('utf8');
    }

    return body;
}

Step 2: Core Logic and Event Routing

Genesys Cloud sends various event types (e.g., conversation:created, interaction:updated, user:updated). Your Lambda function should route these events to specific handlers.

The payload structure varies by event type. A common pattern is to check event.eventType or look for specific fields like conversationId or interactionId.

/**
 * Main Lambda handler.
 * 
 * @param {Object} event - The Lambda event object.
 * @param {Object} context - The Lambda context object.
 */
exports.handler = async (event, context) => {
    // 1. Extract raw body and headers
    const rawBody = getRawBody(event);
    const signatureHeader = event.headers?.['x-genesys-signature'] || event.headers?.['X-Genesys-Signature'];
    const secret = process.env.GENESYS_WEBHOOK_SECRET;

    // 2. Validate Signature
    if (!verifySignature(rawBody, signatureHeader, secret)) {
        return {
            statusCode: 401,
            headers: { 'Content-Type': 'application/json' },
            body: JSON.stringify({ error: 'Invalid signature' })
        };
    }

    try {
        // 3. Parse JSON Payload
        const payload = JSON.parse(rawBody);

        // 4. Route based on eventType
        const eventType = payload.eventType;

        if (eventType === 'conversation:created') {
            await handleConversationCreated(payload);
        } else if (eventType === 'interaction:updated') {
            await handleInteractionUpdated(payload);
        } else {
            console.warn(`Unhandled event type: ${eventType}`);
        }

        // 5. Return 200 OK
        return {
            statusCode: 200,
            headers: { 'Content-Type': 'application/json' },
            body: JSON.stringify({ success: true })
        };

    } catch (error) {
        console.error('Error processing webhook:', error);
        return {
            statusCode: 500,
            headers: { 'Content-Type': 'application/json' },
            body: JSON.stringify({ error: 'Internal server error' })
        };
    }
};

Step 3: Processing Specific Events

Let us implement a handler for conversation:created. This event is triggered when a new conversation (call, chat, email, etc.) is initiated. You might use this to log the conversation start time or update an external CRM.

The payload for conversation:created includes the conversationId, type (e.g., call, chat), and createdTimestamp.

/**
 * Handles the conversation:created event.
 * 
 * @param {Object} payload - The parsed webhook payload.
 */
async function handleConversationCreated(payload) {
    const { conversationId, type, createdTimestamp, participants } = payload;

    console.log(`New ${type} conversation created: ${conversationId} at ${createdTimestamp}`);

    // Example: Filter for Voice calls only
    if (type === 'call') {
        // You can integrate with the Genesys Cloud API here using the SDK
        // to fetch more details or update a custom attribute.
        await updateExternalCRM(conversationId, 'CREATED');
    }
}

/**
 * Placeholder for external system integration.
 * In production, replace this with actual API calls to your database or CRM.
 */
async function updateExternalCRM(conversationId, status) {
    // Simulate async operation
    console.log(`Updating CRM for conversation ${conversationId} with status ${status}`);
    return true;
}

Step 4: Handling Interaction Updates

The interaction:updated event is more complex. It provides a delta of changes. You must check the updates array to see what changed.

/**
 * Handles the interaction:updated event.
 * 
 * @param {Object} payload - The parsed webhook payload.
 */
async function handleInteractionUpdated(payload) {
    const { interactionId, updates } = payload;

    if (!updates || updates.length === 0) {
        return;
    }

    for (const update of updates) {
        // Check for specific field changes, e.g., disposition
        if (update.type === 'disposition') {
            console.log(`Interaction ${interactionId} disposition changed to: ${update.value}`);
            // Trigger downstream logic based on disposition
        }
    }
}

Complete Working Example

This is the full, deployable Lambda function code. It includes signature verification, raw body handling, and event routing.

const crypto = require('crypto');

/**
 * Verifies the Genesys Cloud webhook signature.
 */
function verifySignature(payload, signatureHeader, secret) {
    if (!signatureHeader || !secret) {
        return false;
    }

    const expectedSignature = crypto
        .createHmac('sha256', secret)
        .update(payload, 'utf8')
        .digest('base64');

    return crypto.timingSafeEqual(
        Buffer.from(signatureHeader),
        Buffer.from(expectedSignature)
    );
}

/**
 * Decodes the body from the Lambda event.
 */
function getRawBody(event) {
    const { body, isBase64Encoded } = event;

    if (!body) {
        return null;
    }

    if (isBase64Encoded) {
        return Buffer.from(body, 'base64').toString('utf8');
    }

    return body;
}

/**
 * Handles the conversation:created event.
 */
async function handleConversationCreated(payload) {
    const { conversationId, type, createdTimestamp } = payload;
    console.log(`[INFO] New ${type} conversation: ${conversationId} at ${createdTimestamp}`);
    
    // Add your business logic here
    // Example: Send to SQS, update DynamoDB, etc.
}

/**
 * Handles the interaction:updated event.
 */
async function handleInteractionUpdated(payload) {
    const { interactionId, updates } = payload;
    
    if (updates) {
        for (const update of updates) {
            console.log(`[INFO] Interaction ${interactionId} updated: ${update.type} -> ${update.value}`);
        }
    }
}

/**
 * Main Lambda handler.
 */
exports.handler = async (event, context) => {
    const secret = process.env.GENESYS_WEBHOOK_SECRET;

    if (!secret) {
        console.error('GENESYS_WEBHOOK_SECRET environment variable is not set');
        return {
            statusCode: 500,
            body: JSON.stringify({ error: 'Configuration error' })
        };
    }

    const rawBody = getRawBody(event);
    
    // Handle both header casing variations
    const signatureHeader = event.headers?.['x-genesys-signature'] || 
                            event.headers?.['X-Genesys-Signature'];

    if (!verifySignature(rawBody, signatureHeader, secret)) {
        console.warn('Signature verification failed');
        return {
            statusCode: 401,
            headers: { 'Content-Type': 'application/json' },
            body: JSON.stringify({ error: 'Invalid signature' })
        };
    }

    try {
        const payload = JSON.parse(rawBody);
        const eventType = payload.eventType;

        console.log(`Received event: ${eventType}`);

        switch (eventType) {
            case 'conversation:created':
                await handleConversationCreated(payload);
                break;
            case 'interaction:updated':
                await handleInteractionUpdated(payload);
                break;
            default:
                console.log(`No handler for event type: ${eventType}`);
                break;
        }

        return {
            statusCode: 200,
            headers: { 'Content-Type': 'application/json' },
            body: JSON.stringify({ success: true })
        };

    } catch (error) {
        console.error('Error processing webhook:', error);
        return {
            statusCode: 500,
            headers: { 'Content-Type': 'application/json' },
            body: JSON.stringify({ error: 'Internal server error' })
        };
    }
};

Common Errors & Debugging

Error: 401 Unauthorized (Signature Mismatch)

Cause: The HMAC signature calculated by your Lambda does not match the X-Genesys-Signature header.

How to Fix:

  1. Check Environment Variable: Ensure GENESYS_WEBHOOK_SECRET is set correctly in the Lambda environment variables. Copy the exact secret from the Genesys Cloud Webhook configuration.
  2. Raw Body Integrity: Ensure you are using the raw body string. If API Gateway parses the JSON, the whitespace may differ. Use the getRawBody function provided above to handle base64 decoding.
  3. Encoding: Ensure the secret is treated as a UTF-8 string in createHmac.

Debug Code:
Add temporary logging to compare signatures:

const expected = crypto.createHmac('sha256', secret).update(rawBody, 'utf8').digest('base64');
console.log('Expected:', expected);
console.log('Received:', signatureHeader);

Error: 502 Bad Gateway from Genesys Cloud

Cause: Your Lambda function returned a non-2xx status code or did not respond within the timeout.

How to Fix:

  1. Timeout: Increase the Lambda timeout to at least 10 seconds. Genesys Cloud expects a response within a reasonable window.
  2. Response Format: Ensure the Lambda handler returns a valid JSON response with a statusCode of 200 on success.
  3. Logs: Check CloudWatch Logs for unhandled exceptions. If the function crashes, Genesys Cloud will retry.

Error: Payload Too Large

Cause: The webhook payload exceeds the Lambda payload limit (6 MB for synchronous, 256 KB for API Gateway).

How to Fix:
Genesys Cloud webhook payloads are typically small. If you encounter this, you are likely misconfiguring the webhook to send large attachments or extensive history. Configure the webhook in Genesys Cloud to send only the necessary fields.

Official References