Securing Genesys Cloud Webhook Endpoints with Java

What You Will Build

• A production-grade Java Spring Boot service that receives Genesys Cloud webhooks, verifies cryptographic signatures, enforces structural validation, decrypts sensitive fields, prevents replay attacks, and logs every invocation with traceable correlation identifiers.
• This implementation uses the Genesys Cloud Java SDK for webhook registration and Spring Web for the endpoint lifecycle.
• The code covers Java 17 with Spring Boot 3.2, Jackson for JSON processing, NetworkNT for JSON schema validation, and Bouncy Castle for envelope encryption.

Prerequisites

• OAuth client type: Confidential Client (Client Credentials Grant)
• Required scopes: webhooks:read, webhooks:write, webhooks:delete
• SDK version: platform-client-java v130.0.0+
• Language/runtime: Java 17+, Spring Boot 3.2.x
• External dependencies: spring-boot-starter-web, com.networknt:json-schema-validator:1.1.0, org.bouncycastle:bcprov-jdk18on:1.78.1, com.fasterxml.jackson.core:jackson-databind

Authentication Setup

Genesys Cloud requires a bearer token for all administrative API calls. The Java SDK handles token acquisition and caching automatically when configured with client credentials. You must initialize the SDK before registering the webhook endpoint.

import com.genesyscloud.auth.oauth.OAuth;
import com.genesyscloud.auth.oauth.authenticator.OAuthClientCredentials;
import com.genesyscloud.platformclient.v2.ApiClient;
import com.genesyscloud.platformclient.v2.Configuration;

public class GenesysAuthConfig {
    private static final String REGION = "mypurecloud.com";
    private static final String CLIENT_ID = System.getenv("GENESYS_CLIENT_ID");
    private static final String CLIENT_SECRET = System.getenv("GENESYS_CLIENT_SECRET");

    public static ApiClient getAuthenticatedApiClient() throws Exception {
        OAuthClientCredentials credentials = new OAuthClientCredentials(CLIENT_ID, CLIENT_SECRET);
        OAuth oauth = new OAuth(credentials);
        oauth.setRegion(REGION);
        oauth.getAccessToken(); // Forces token acquisition and caching

        Configuration.setDefaultApiClient(oauth.getApiClient());
        return oauth.getApiClient();
    }
}

The SDK caches the access token in memory and automatically refreshes it before expiration. You must ensure your environment variables contain valid credentials for a confidential client. The token acquisition requires no additional scopes beyond what you assign to the client in the Genesys Cloud admin console.

Implementation

Step 1: OAuth Token Acquisition and Webhook Registration

You must register the webhook target in Genesys Cloud before it begins sending events. The registration payload defines the target URL, the event types to subscribe to, and the shared secret used for HMAC verification.

HTTP Request Cycle

• Method: POST
• Path: /api/v2/webhooks
• Headers: Authorization: Bearer <token>, Content-Type: application/json
• OAuth Scope: webhooks:write
• Request Body:

{
  "name": "secure-java-webhook",
  "targetUrl": "https://your-domain.com/api/v1/webhooks/genesys",
  "apiVersion": "v2",
  "events": ["conversation:analyzed", "routing:conversation:created"],
  "secret": "your-pre-shared-hmac-secret"
}

Java SDK Implementation

import com.genesyscloud.platformclient.v2.api.WebhooksApi;
import com.genesyscloud.platformclient.v2.model.CreateWebhookRequest;
import com.genesyscloud.platformclient.v2.model.Webhook;

import java.util.Arrays;
import java.util.List;

public class WebhookRegistrar {
    public static Webhook registerWebhook(ApiClient apiClient, String targetUrl, String secret) throws Exception {
        WebhooksApi webhooksApi = new WebhooksApi(apiClient);
        
        List<String> events = Arrays.asList(
            "routing:conversation:created",
            "routing:conversation:updated",
            "routing:conversation:completed"
        );

        CreateWebhookRequest request = new CreateWebhookRequest()
            .name("secure-java-webhook")
            .targetUrl(targetUrl)
            .apiVersion("v2")
            .events(events)
            .secret(secret);

        Webhook created = webhooksApi.postWebhooks(request);
        System.out.println("Webhook registered with ID: " + created.getId());
        return created;
    }
}

The SDK throws an ApiException on failure. A 403 Forbidden indicates missing webhooks:write scope. A 409 Conflict indicates a duplicate target URL and event combination.

Step 2: HMAC-SHA256 Signature Verification and Replay Attack Prevention

Genesys Cloud attaches two headers to every webhook delivery: X-Genesys-Signature and X-Genesys-Timestamp. The signature is an HMAC-SHA256 hash of the raw request body using the shared secret. The timestamp prevents replay attacks by ensuring the request is recent.

Verification Logic

import com.genesyscloud.platformclient.v2.ApiException;
import org.springframework.http.ResponseEntity;
import org.springframework.web.bind.annotation.*;
import javax.crypto.Mac;
import javax.crypto.spec.SecretKeySpec;
import java.nio.charset.StandardCharsets;
import java.security.InvalidKeyException;
import java.security.NoSuchAlgorithmException;
import java.time.Instant;
import java.time.temporal.ChronoUnit;

@RestController
@RequestMapping("/api/v1/webhooks")
public class WebhookController {
    
    private static final String HMAC_ALGORITHM = "HmacSHA256";
    private static final long MAX_TIMESTAMP_DRIFT_SECONDS = 300; // 5 minutes
    private final String sharedSecret;

    public WebhookController(@Value("${genesys.webhook.secret}") String sharedSecret) {
        this.sharedSecret = sharedSecret;
    }

    @PostMapping(value = "/genesys", consumes = "application/json")
    public ResponseEntity<String> handleWebhook(
            @RequestBody String rawPayload,
            @RequestHeader(value = "X-Genesys-Signature", required = false) String signature,
            @RequestHeader(value = "X-Genesys-Timestamp", required = false) String timestamp,
            @RequestHeader(value = "X-Correlation-Id", defaultValue = "unknown") String correlationId) {

        // 1. Verify timestamp to prevent replay attacks
        if (timestamp == null || !isTimestampValid(timestamp)) {
            return ResponseEntity.status(403).body("{\"error\": \"Invalid or missing timestamp\"}");
        }

        // 2. Verify HMAC signature
        if (signature == null || !verifyHmacSignature(rawPayload, signature)) {
            return ResponseEntity.status(401).body("{\"error\": \"Signature verification failed\"}");
        }

        // 3. Process payload (delegated to service)
        try {
            WebhookProcessor.process(rawPayload, correlationId);
            return ResponseEntity.ok("{\"status\": \"processed\", \"correlation_id\": \"" + correlationId + "\"}");
        } catch (Exception e) {
            return ResponseEntity.status(500).body("{\"error\": \"Internal processing failure\", \"details\": \"" + e.getMessage() + "\"}");
        }
    }

    private boolean isTimestampValid(String timestampHeader) {
        try {
            Instant receivedTime = Instant.parse(timestampHeader);
            Instant now = Instant.now();
            long diff = Math.abs(ChronoUnit.SECONDS.between(receivedTime, now));
            return diff <= MAX_TIMESTAMP_DRIFT_SECONDS;
        } catch (Exception e) {
            return false;
        }
    }

    private boolean verifyHmacSignature(String payload, String expectedSignature) {
        try {
            Mac mac = Mac.getInstance(HMAC_ALGORITHM);
            SecretKeySpec keySpec = new SecretKeySpec(sharedSecret.getBytes(StandardCharsets.UTF_8), HMAC_ALGORITHM);
            mac.init(keySpec);
            byte[] hash = mac.doFinal(payload.getBytes(StandardCharsets.UTF_8));
            String computedSignature = bytesToHex(hash);
            return MessageDigest.isEqual(computedSignature.getBytes(StandardCharsets.UTF_8), expectedSignature.getBytes(StandardCharsets.UTF_8));
        } catch (NoSuchAlgorithmException | InvalidKeyException e) {
            throw new RuntimeException("HMAC computation failed", e);
        }
    }

    private String bytesToHex(byte[] bytes) {
        StringBuilder hexString = new StringBuilder();
        for (byte b : bytes) {
            String hex = Integer.toHexString(0xff & b);
            if (hex.length() == 1) hexString.append('0');
            hexString.append(hex);
        }
        return hexString.toString();
    }
}

The MessageDigest.isEqual method prevents timing attacks during signature comparison. The timestamp validation rejects requests older than 300 seconds. Spring Boot automatically reads the raw body into rawPayload when consumes = "application/json" is specified.

Step 3: JSON Schema Validation and Envelope Decryption

Genesys Cloud payloads follow a consistent structure, but you must enforce strict validation before processing. Additionally, sensitive fields such as customer phone numbers or emails may be transmitted using envelope encryption. This step validates the payload structure and decrypts protected fields.

Schema Definition and Validation Service

import com.networknt.schema.JsonSchema;
import com.networknt.schema.JsonSchemaFactory;
import com.networknt.schema.SpecVersion;
import com.networknt.schema.ValidationMessage;
import com.fasterxml.jackson.databind.JsonNode;
import com.fasterxml.jackson.databind.ObjectMapper;
import org.bouncycastle.jce.provider.BouncyCastleProvider;
import org.bouncycastle.jce.spec.OAEPParameterSpec;
import org.bouncycastle.jce.spec.PSource;
import org.springframework.stereotype.Service;

import javax.crypto.Cipher;
import javax.crypto.spec.GCMParameterSpec;
import javax.crypto.spec.SecretKeySpec;
import java.nio.charset.StandardCharsets;
import java.security.Security;
import java.security.spec.MGF1ParameterSpec;
import java.util.Base64;
import java.util.Set;

@Service
public class WebhookProcessor {
    private static final ObjectMapper MAPPER = new ObjectMapper();
    private static final JsonSchema GENESYS_SCHEMA;
    private static final String RSA_PRIVATE_KEY = System.getenv("ENCRYPTION_RSA_PRIVATE_KEY");
    private static final String RSA_PUBLIC_KEY_FOR_VALIDATION = System.getenv("ENCRYPTION_RSA_PUBLIC_KEY");

    static {
        Security.addProvider(new BouncyCastleProvider());
        try {
            String schemaJson = """
                {
                  "$schema": "http://json-schema.org/draft-07/schema#",
                  "type": "object",
                  "required": ["event", "payload", "correlationId"],
                  "properties": {
                    "event": { "type": "string" },
                    "payload": { "type": "object" },
                    "correlationId": { "type": "string" },
                    "encryptedData": { "type": "object" }
                  }
                }
                """;
            GENESYS_SCHEMA = JsonSchemaFactory.getInstance(SpecVersion.VersionFlag.V7)
                    .getSchema(schemaJson);
        } catch (Exception e) {
            throw new RuntimeException("Schema initialization failed", e);
        }
    }

    public static void process(String rawPayload, String correlationId) throws Exception {
        JsonNode rootNode = MAPPER.readTree(rawPayload);

        // Validate against JSON schema
        Set<ValidationMessage> errors = GENESYS_SCHEMA.validate(rootNode);
        if (!errors.isEmpty()) {
            throw new IllegalArgumentException("Payload validation failed: " + errors);
        }

        // Decrypt sensitive fields if present
        if (rootNode.has("encryptedData") && rootNode.get("encryptedData").isObject()) {
            JsonNode encryptedNode = rootNode.get("encryptedData");
            String encryptedKey = encryptedNode.get("encryptedKey").asText();
            String encryptedPayload = encryptedNode.get("data").asText();
            String iv = encryptedNode.get("iv").asText();

            byte[] decryptedSymmetricKey = decryptRsaOaep(encryptedKey, RSA_PRIVATE_KEY);
            String decryptedPayload = decryptAesGcm(encryptedPayload, decryptedSymmetricKey, iv);
            
            // Replace encrypted node with decrypted JSON for downstream processing
            JsonNode decryptedJson = MAPPER.readTree(decryptedPayload);
            rootNode.put("decryptedPayload", decryptedJson);
        }

        // Log and forward to business logic
        System.out.println("Processed webhook. Correlation: " + correlationId + " | Payload: " + rootNode);
    }

    private static byte[] decryptRsaOaep(String encryptedBase64, String privateKeyPem) throws Exception {
        Cipher cipher = Cipher.getInstance("RSA/ECB/OAEPWithSHA-256AndMGF1Padding", "BC");
        OAEPParameterSpec oaepParams = new OAEPParameterSpec("SHA-256", "MGF1", MGF1ParameterSpec.SHA1, PSource.PSpecified.DEFAULT);
        cipher.init(Cipher.DECRYPT_MODE, loadPrivateKey(privateKeyPem), oaepParams);
        return cipher.doFinal(Base64.getDecoder().decode(encryptedBase64));
    }

    private static String decryptAesGcm(String encryptedBase64, byte[] key, String ivBase64) throws Exception {
        Cipher cipher = Cipher.getInstance("AES/GCM/NoPadding", "BC");
        GCMParameterSpec spec = new GCMParameterSpec(128, Base64.getDecoder().decode(ivBase64));
        SecretKeySpec keySpec = new SecretKeySpec(key, "AES");
        cipher.init(Cipher.DECRYPT_MODE, keySpec, spec);
        byte[] decryptedBytes = cipher.doFinal(Base64.getDecoder().decode(encryptedBase64));
        return new String(decryptedBytes, StandardCharsets.UTF_8);
    }

    private static java.security.PrivateKey loadPrivateKey(String pem) throws Exception {
        // Simplified PEM loader for tutorial brevity. In production, use a key store or vault.
        String cleaned = pem.replace("-----BEGIN PRIVATE KEY-----", "")
                .replace("-----END PRIVATE KEY-----", "").replaceAll("\\s+", "");
        byte[] keyBytes = Base64.getDecoder().decode(cleaned);
        java.security.KeyFactory kf = java.security.KeyFactory.getInstance("RSA");
        return kf.generatePrivate(new java.security.spec.PKCS8EncodedKeySpec(keyBytes));
    }
}

The JSON schema enforces required fields before any business logic executes. The envelope decryption uses RSA-OAEP for the symmetric key and AES-GCM for the payload data. This matches industry standards for secure webhook transmission.

Step 4: Correlation ID Logging and Health Check Endpoint

Genesys Cloud includes X-Correlation-Id in every webhook request. You must capture this identifier for audit trails and troubleshooting. Additionally, webhook registration requires a reachable health check endpoint that returns a 200 OK response.

Health Check and Logging Configuration

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.RestController;

@RestController
public class WebhookHealthController {
    private static final Logger logger = LoggerFactory.getLogger(WebhookHealthController.class);

    @GetMapping("/health/webhook")
    public ResponseEntity<HealthStatus> checkHealth() {
        logger.info("Health check invoked for webhook receiver");
        return ResponseEntity.ok(new HealthStatus("healthy", System.currentTimeMillis()));
    }

    public record HealthStatus(String status, long timestamp) {}
}

The health check endpoint must be publicly accessible and return a successful HTTP status code. Genesys Cloud polls this URL during webhook registration and periodically to verify endpoint availability. The correlation ID from Step 2 should be passed to your logging framework using MDC (Mapped Diagnostic Context) for distributed tracing.

Complete Working Example

The following structure combines all components into a runnable Spring Boot application. Place each class in the appropriate package.

// application.properties
server.port=8443
genesys.webhook.secret=${WEBHOOK_SECRET:default-dev-secret}
spring.security.enabled=false

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;

@SpringBootApplication
public class WebhookReceiverApplication {
    public static void main(String[] args) {
        SpringApplication.run(WebhookReceiverApplication.class, args);
    }
}

// RegistrationRunner.java
import org.springframework.boot.CommandLineRunner;
import org.springframework.stereotype.Component;
import com.genesyscloud.platformclient.v2.ApiClient;

@Component
public class RegistrationRunner implements CommandLineRunner {
    @Override
    public void run(String... args) throws Exception {
        ApiClient client = GenesysAuthConfig.getAuthenticatedApiClient();
        String targetUrl = "https://your-domain.com/api/v1/webhooks/genesys";
        String healthUrl = "https://your-domain.com/health/webhook";
        
        // In production, check if webhook exists before creating
        WebhookRegistrar.registerWebhook(client, targetUrl, System.getenv("WEBHOOK_SECRET"));
        System.out.println("Webhook registration complete. Health endpoint: " + healthUrl);
    }
}

Configure your pom.xml with the required dependencies. Run the application with mvn spring-boot:run. The startup sequence acquires an OAuth token, registers the webhook, and starts the Spring Web server. Incoming requests flow through signature verification, timestamp validation, schema validation, decryption, and logging.

Common Errors and Debugging

Error: 401 Unauthorized or Signature Verification Failed

• Cause: The shared secret in your Genesys Cloud webhook configuration does not match the WEBHOOK_SECRET environment variable, or the request body is modified before HMAC computation.
• Fix: Ensure you compute the HMAC over the exact raw bytes received by Spring Boot. Do not parse the body into an object before verification. Verify that the secret contains no trailing whitespace or newline characters.

Error: 403 Forbidden on Webhook Registration

• Cause: The OAuth token lacks the webhooks:write scope, or the client credentials are misconfigured.
• Fix: Navigate to the Genesys Cloud admin console, open the OAuth client configuration, and verify that webhooks:write is selected. Regenerate the token after scope changes.

Error: 429 Too Many Requests

• Cause: The Java SDK or your application exceeds the rate limit for webhook registration or token refresh calls.
• Fix: Implement exponential backoff for retry logic. The SDK does not automatically retry 429 responses. Wrap the registration call in a retry mechanism that respects the Retry-After header.

Error: JSON Schema Validation Failure

• Cause: The Genesys Cloud payload structure changed, or your schema is too restrictive. Genesys occasionally adds optional fields to event payloads.
• Fix: Use "additionalProperties": true in your schema to allow unknown fields. Validate only the required fields and nested objects that your application depends on.

Error: Decryption Failed or Padding Exception

• Cause: The RSA private key format is incorrect, or the IV/key length does not match AES-GCM requirements.
• Fix: Ensure your RSA key uses PKCS#8 format. Verify that the IV is exactly 12 bytes for GCM mode. Base64 decode all encrypted fields before passing them to the cipher.

Official References

• Genesys Cloud Webhooks API Documentation
• Genesys Cloud Java SDK Reference
• HMAC-SHA256 Webhook Signature Guide
• NetworkNT JSON Schema Validator
• Bouncy Castle Cryptography Provider