教學課程：使用 Lambda 函式 URL 建立 Webhook 端點

開啟 Lambda 主控台中的函數頁面。

執行下列動作，建立基本的 'Hello world' 函式：

1. 選擇 Create function (建立函數)。

2. 選取從頭開始撰寫。

3. 針對函數名稱，請輸入 myLambdaWebhook。

4. 針對執行期，選取 python3.14。

5. 選擇 Create function (建立函數)。

在程式碼來源窗格中，複製並貼上以下項目來取代現有程式碼：

import json
import hmac
import hashlib
import os

def lambda_handler(event, context):
    
    # Get the webhook secret from environment variables
    webhook_secret = os.environ['WEBHOOK_SECRET']
    
    # Verify the webhook signature
    if not verify_signature(event, webhook_secret):
        return {
            'statusCode': 401,
            'body': json.dumps({'error': 'Invalid signature'})
        }
    
    try:
        # Parse the webhook payload
        payload = json.loads(event['body'])
        
        # Handle different event types
        event_type = payload.get('type')
        
        if event_type == 'payment.success':
            # Handle successful payment
            order_id = payload.get('orderId')
            print(f"Processing successful payment for order {order_id}")
            
            # Add your business logic here
            # For example, update database, send notifications, etc.
            
        elif event_type == 'payment.failed':
            # Handle failed payment
            order_id = payload.get('orderId')
            print(f"Processing failed payment for order {order_id}")
            
            # Add your business logic here
            
        else:
            print(f"Received unhandled event type: {event_type}")
        
        # Return success response
        return {
            'statusCode': 200,
            'body': json.dumps({'received': True})
        }
        
    except json.JSONDecodeError:
        return {
            'statusCode': 400,
            'body': json.dumps({'error': 'Invalid JSON payload'})
        }
    except Exception as e:
        print(f"Error processing webhook: {e}")
        return {
            'statusCode': 500,
            'body': json.dumps({'error': 'Internal server error'})
        }

def verify_signature(event, webhook_secret):
    """
    Verify the webhook signature using HMAC
    """
    try:
        # Get the signature from headers
        signature = event['headers'].get('x-webhook-signature')

        if not signature:
            print("Error: Missing webhook signature in headers")
            return False
        
        # Get the raw body (return an empty string if the body key doesn't exist)
        body = event.get('body', '')
        
        # Create HMAC using the secret key
        expected_signature = hmac.new(
            webhook_secret.encode('utf-8'),
            body.encode('utf-8'),
            hashlib.sha256
        ).hexdigest()
        
        # Compare the expected signature with the received signature to authenticate the message
        is_valid = hmac.compare_digest(signature, expected_signature)
        if not is_valid:
            print(f"Error: Invalid signature. Received: {signature}, Expected: {expected_signature}")
            return False
            
        return True
    except Exception as e:
        print(f"Error verifying signature: {e}")
        return False

在 DEPLOY 區段中，選擇部署以更新函數的程式碼。

開啟 Lambda 主控台中的函數頁面。

執行下列動作，建立基本的 'Hello world' 函式：

1. 選擇 Create function (建立函數)。

2. 選取從頭開始撰寫。

3. 針對函數名稱，請輸入 myLambdaWebhook。

4. 針對執行期，選取 nodejs24.x。

5. 選擇 Create function (建立函數)。

在程式碼來源窗格中，複製並貼上以下項目來取代現有程式碼：

import crypto from 'crypto';

export const handler = async (event, context) => {
    // Get the webhook secret from environment variables
    const webhookSecret = process.env.WEBHOOK_SECRET;

    // Verify the webhook signature
    if (!verifySignature(event, webhookSecret)) {
        return {
            statusCode: 401,
            body: JSON.stringify({ error: 'Invalid signature' })
        };
    }

    try {
        // Parse the webhook payload
        const payload = JSON.parse(event.body);

        // Handle different event types
        const eventType = payload.type;

        switch (eventType) {
            case 'payment.success': {
                // Handle successful payment
                const orderId = payload.orderId;
                console.log(`Processing successful payment for order ${orderId}`);

                // Add your business logic here
                // For example, update database, send notifications, etc.
                break;
            }

            case 'payment.failed': {
                // Handle failed payment
                const orderId = payload.orderId;
                console.log(`Processing failed payment for order ${orderId}`);

                // Add your business logic here
                break;
            }

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

        // Return success response
        return {
            statusCode: 200,
            body: JSON.stringify({ received: true })
        };

    } catch (error) {
        if (error instanceof SyntaxError) {
            // Handle JSON parsing errors
            return {
                statusCode: 400,
                body: JSON.stringify({ error: 'Invalid JSON payload' })
            };
        }

        // Handle all other errors
        console.error('Error processing webhook:', error);
        return {
            statusCode: 500,
            body: JSON.stringify({ error: 'Internal server error' })
        };
    }
};

// Verify the webhook signature using HMAC

const verifySignature = (event, webhookSecret) => {
    try {
        // Get the signature from headers
        const signature = event.headers['x-webhook-signature'];
  
        if (!signature) {
            console.log('No signature found in headers:', event.headers);
            return false;
        }
  
        // Get the raw body (return an empty string if the body key doesn't exist)
        const body = event.body || '';
  
        // Create HMAC using the secret key
        const hmac = crypto.createHmac('sha256', webhookSecret);
        const expectedSignature = hmac.update(body).digest('hex');
  
        // Compare expected and received signatures
        const isValid = signature === expectedSignature;
        if (!isValid) {
            console.log(`Invalid signature. Received: ${signature}, Expected: ${expectedSignature}`);
            return false;
        }
        
        return true;
    } catch (error) {
        console.error('Error during signature verification:', error);
        return false;
    }
  };

在 DEPLOY 區段中，選擇部署以更新函數的程式碼。

將下列程式碼儲存為名為 calculate_signature.py 的檔案。將程式碼中的 Webhook 秘密取代為您自己的值。

import secrets
import hmac
import json
import hashlib

webhook_secret = "arlbSDCP86n_1H90s0fL_Qb2NAHBIBQOyGI0X4Zay4M"

body = json.dumps({"type": "payment.success", "orderId": "1234", "amount": "99.99"})

signature = hmac.new(
            webhook_secret.encode('utf-8'),
            body.encode('utf-8'),
            hashlib.sha256
        ).hexdigest()

print(signature)

從儲存程式碼的同一目錄中執行下列命令來計算簽章。複製程式碼輸出的簽章。

python calculate_signature.py

將下列程式碼儲存為名為 calculate_signature.mjs 的檔案。將程式碼中的 Webhook 秘密取代為您自己的值。

import crypto from 'crypto';

const webhookSecret = "arlbSDCP86n_1H90s0fL_Qb2NAHBIBQOyGI0X4Zay4M"
const body = "{\"type\": \"payment.success\", \"orderId\": \"1234\", \"amount\": \"99.99\"}";

let hmac = crypto.createHmac('sha256', webhookSecret);
let signature = hmac.update(body).digest('hex');

console.log(signature);

從儲存程式碼的同一目錄中執行下列命令來計算簽章。複製程式碼輸出的簽章。

node calculate_signature.mjs