Fix HMAC validation for Banking webhooks

src/__mocks__/notification/accountHolderCreated.json

@@ -0,0 +1,61 @@
+{
+    "data": {
+      "balancePlatform": "YOUR_BALANCE_PLATFORM",
+      "accountHolder": {
+        "contactDetails": {
+          "email": "test@adyen.com",
+          "phone": {
+            "number": "0612345678",
+            "type": "mobile"
+          },
+          "address": {
+            "houseNumberOrName": "23",
+            "city": "Amsterdam",
+            "country": "NL",
+            "postalCode": "12345",
+            "street": "Main Street 1"
+          }
+        },
+        "description": "Shelly Eller",
+        "legalEntityId": "LE00000000000000000001",
+        "reference": "YOUR_REFERENCE-2412C",
+        "capabilities": {
+          "issueCard": {
+            "enabled": true,
+            "requested": true,
+            "allowed": false,
+            "verificationStatus": "pending"
+          },
+          "receiveFromTransferInstrument": {
+            "enabled": true,
+            "requested": true,
+            "allowed": false,
+            "verificationStatus": "pending"
+          },
+          "sendToTransferInstrument": {
+            "enabled": true,
+            "requested": true,
+            "allowed": false,
+            "verificationStatus": "pending"
+          },
+          "sendToBalanceAccount": {
+            "enabled": true,
+            "requested": true,
+            "allowed": false,
+            "verificationStatus": "pending"
+          },
+          "receiveFromBalanceAccount": {
+            "enabled": true,
+            "requested": true,
+            "allowed": false,
+            "verificationStatus": "pending"
+          }
+        },
+        "id": "AH00000000000000000001",
+        "status": "active"
+      }
+    },
+    "environment": "test",
+    "timestamp": "2024-12-15T15:42:03+01:00",
+    "type": "balancePlatform.accountHolder.created"
+  }

src/__tests__/hmacValidator.spec.ts

@@ -2,6 +2,7 @@ import HmacValidator from "../utils/hmacValidator";
 import {NotificationItem, NotificationRequestItem } from "../typings/notification/models";
 import { ApiConstants } from "../constants/apiConstants";
 import NotificationRequestService from "../notification/notificationRequest";
+import { readFileSync } from "fs";
 
 const key = "DFB1EB5485895CFA84146406857104ABB4CBCABDC8AAF103A624C8F6A3EAAB00";
 const expectedSign = "ZNBPtI+oDyyRrLyD1XirkKnQgIAlFc07Vj27TeHsDRE=";
@@ -127,4 +128,21 @@ describe("HMAC Validator", function (): void {
         notification.notificationItems![0].additionalData![ApiConstants.HMAC_SIGNATURE] = "notValidSign";
         expect(hmacValidator.validateHMAC(notification.notificationItems![0], key)).toBeFalsy();
     });
+
+    it("should calculate Banking webhook correctly", function (): void {
+        const data = readFileSync("./src/__mocks__/notification/accountHolderCreated.json", "utf8"); 
+        const encrypted = hmacValidator.calculateHmac(data, "11223344D785FBAE710E7F943F307971BB61B21281C98C9129B3D4018A57B2EB");
+
+        expect(encrypted).toEqual("UVBzHbDayhfT1XgaRGAkuKvxwoxrLoVCBdfi3WZU8lI=");
+    });
+
+    it("should validate Banking webhook correctly", function (): void {
+        const hmacKey = "11223344D785FBAE710E7F943F307971BB61B21281C98C9129B3D4018A57B2EB";
+        const hmacSignature = "UVBzHbDayhfT1XgaRGAkuKvxwoxrLoVCBdfi3WZU8lI=";
+        const data = readFileSync("./src/__mocks__/notification/accountHolderCreated.json", "utf8");
+        const isValid = hmacValidator.validateHMACSignature(hmacKey, hmacSignature, data);
+
+        expect(isValid).toBeTruthy;
+    });
+
 });

src/utils/hmacValidator.ts

@@ -27,12 +27,26 @@ class HmacValidator {
     public static HMAC_SHA256_ALGORITHM = "sha256";
     public static DATA_SEPARATOR = ":";
 
+    /**
+     * Calculate HMAC signature of the payload data
+     * @param data payload as String or as NotificationRequestItem
+     * @param key HMAC key
+     * @returns HMAC signature
+     */
     public calculateHmac(data: string | NotificationRequestItem, key: string): string {
         const dataString = typeof data !== "string" ? this.getDataToSign(data) : data;
         const rawKey = Buffer.from(key, "hex");
         return createHmac(HmacValidator.HMAC_SHA256_ALGORITHM, rawKey).update(dataString, "utf8").digest("base64");
     }
 
+    /**
+     * @deprecated use Use validateHMACSignature with correct parameter order instead
+     * Validate HMAC signature for Banking webhooks
+     * @param hmacKey 
+     * @param hmacSign 
+     * @param notification 
+     * @returns 
+     */
     public validateBankingHMAC(hmacKey: string, hmacSign: string, notification: string): boolean {
         const expectedSign = createHmac(HmacValidator.HMAC_SHA256_ALGORITHM, Buffer.from(hmacSign, "hex")).update(notification, "utf8").digest("base64");
         if(hmacKey?.length === expectedSign.length) {
@@ -44,6 +58,30 @@ class HmacValidator {
         return false;
     }
 
+    /**
+     * Validate HMAC signature for Banking/Management webhooks
+     * @param hmacKey HMAC key
+     * @param hmacSignature HMAC signature to validate 
+     * @param data webhook payload (as string)
+     * @returns true when HMAC signature is valid
+     */
+    public validateHMACSignature(hmacKey: string, hmacSignature: string, data: string): boolean {
+        const expectedSign = createHmac(HmacValidator.HMAC_SHA256_ALGORITHM, Buffer.from(hmacKey, "hex")).update(data, "utf8").digest("base64");
+        if(hmacSignature?.length === expectedSign.length) {
+            return timingSafeEqual(
+                Buffer.from(expectedSign, "base64"),
+                Buffer.from(hmacSignature, "base64")
+            );
+        }
+        return false;
+    }
+
+    /**
+     * Validate HMAC signature for Payment webhooks
+     * @param notificationRequestItem webhook payload (as NotificationRequestItem object)
+     * @param key HMAC key
+     * @returns true when HMAC signature is valid
+     */
     public validateHMAC(notificationRequestItem: NotificationRequestItem, key: string): boolean {
         if (notificationRequestItem.additionalData?.[ApiConstants.HMAC_SIGNATURE]) {
             const expectedSign = this.calculateHmac(notificationRequestItem, key);
@@ -55,7 +93,6 @@ class HmacValidator {
                 );
             }
             return false;
-
         }
         throw Error(`Missing ${ApiConstants.HMAC_SIGNATURE}`);
     }
@@ -64,6 +101,11 @@ class HmacValidator {
         return !Object.values(item).every((value): boolean => typeof value === "string");
     }
 
+    /**
+     * extract fields to be used to calculate the HMAC signature
+     * @param notificationRequestItem webhook payload
+     * @returns data to sign (as string)
+     */
     public getDataToSign(notificationRequestItem: DataToSign): string {
         if (this.isNotificationRequestItem(notificationRequestItem)) {
             const signedDataList = [];