add verifyInterceptorPayload method with shared verification logic

lib/scalekit.d.ts

@@ -106,6 +106,26 @@ export default class ScalekitClient {
      * @return {boolean} Returns true if the payload is valid.
      */
     verifyWebhookPayload(secret: string, headers: Record<string, string>, payload: string): boolean;
+    /**
+     * Verify interceptor payload
+     *
+     * @param {string} secret The secret
+     * @param {Record<string, string>} headers The headers
+     * @param {string} payload The payload
+     * @return {boolean} Returns true if the payload is valid.
+     */
+    verifyInterceptorPayload(secret: string, headers: Record<string, string>, payload: string): boolean;
+    /**
+     * Common payload signature verification logic
+     *
+     * @param {string} secret The secret
+     * @param {string} id The webhook/interceptor id
+     * @param {string} timestamp The timestamp
+     * @param {string} signature The signature
+     * @param {string} payload The payload
+     * @return {boolean} Returns true if the payload signature is valid.
+     */
+    private verifyPayloadSignature;
     /**
      * Validates a token and returns its payload if valid.
      * Supports issuer, audience, and scope validation.

package.json

@@ -1,5 +1,5 @@
 {
-  "version": "2.1.4",
+  "version": "2.1.5",
   "name": "@scalekit-sdk/node",
   "description": "Official Scalekit Node SDK",
   "main": "lib/index.js",

src/core.ts

@@ -20,7 +20,7 @@ export default class CoreClient {
   public keys: JWK[] = [];
   public accessToken: string | null = null;
   public axios: Axios;
-  public sdkVersion = `Scalekit-Node/2.1.4`;
+  public sdkVersion = `Scalekit-Node/2.1.5`;
   public apiVersion = "20250830";
   public userAgent = `${this.sdkVersion} Node/${process.version} (${process.platform}; ${os.arch()})`;
   constructor(

src/scalekit.ts

@@ -257,7 +257,37 @@ export default class ScalekitClient {
     const webhookTimestamp = headers['webhook-timestamp'];
     const webhookSignature = headers['webhook-signature'];
 
-    if (!webhookId || !webhookTimestamp || !webhookSignature) {
+    return this.verifyPayloadSignature(secret, webhookId, webhookTimestamp, webhookSignature, payload);
+  }
+
+  /**
+   * Verify interceptor payload
+   * 
+   * @param {string} secret The secret
+   * @param {Record<string, string>} headers The headers
+   * @param {string} payload The payload
+   * @return {boolean} Returns true if the payload is valid.
+   */
+  verifyInterceptorPayload(secret: string, headers: Record<string, string>, payload: string): boolean {
+    const interceptorId = headers['interceptor-id'];
+    const interceptorTimestamp = headers['interceptor-timestamp'];
+    const interceptorSignature = headers['interceptor-signature'];
+
+    return this.verifyPayloadSignature(secret, interceptorId, interceptorTimestamp, interceptorSignature, payload);
+  }
+
+  /**
+   * Common payload signature verification logic
+   * 
+   * @param {string} secret The secret
+   * @param {string} id The webhook/interceptor id
+   * @param {string} timestamp The timestamp
+   * @param {string} signature The signature
+   * @param {string} payload The payload
+   * @return {boolean} Returns true if the payload signature is valid.
+   */
+  private verifyPayloadSignature(secret: string, id: string, timestamp: string, signature: string, payload: string): boolean {
+    if (!id || !timestamp || !signature) {
       throw new WebhookVerificationError("Missing required headers");
     }
 
@@ -267,18 +297,18 @@ export default class ScalekitClient {
     }
 
     try {
-      const timestamp = this.verifyTimestamp(webhookTimestamp);
-      const data = `${webhookId}.${Math.floor(timestamp.getTime() / 1000)}.${payload}`;
+      const timestampDate = this.verifyTimestamp(timestamp);
+      const data = `${id}.${Math.floor(timestampDate.getTime() / 1000)}.${payload}`;
       const secretBytes = Buffer.from(secretParts[1], 'base64');
       const computedSignature = this.computeSignature(secretBytes, data);
-      const receivedSignatures = webhookSignature.split(" ");
+      const receivedSignatures = signature.split(" ");
 
       for (const versionedSignature of receivedSignatures) {
-        const [version, signature] = versionedSignature.split(",");
+        const [version, receivedSignature] = versionedSignature.split(",");
         if (version !== WEBHOOK_SIGNATURE_VERSION) {
           continue;
         }
-        if (crypto.timingSafeEqual(Buffer.from(signature, 'base64'), Buffer.from(computedSignature, 'base64'))) {
+        if (crypto.timingSafeEqual(Buffer.from(receivedSignature, 'base64'), Buffer.from(computedSignature, 'base64'))) {
           return true;
         }
       }