Remove duplicated code by using our generic ledger js package to hand…

…le error response function and improve FVK type definition

fix subarray offset

src/app.ts

@@ -14,7 +14,15 @@
  *  See the License for the specific language governing permissions and
  *  limitations under the License.
  ******************************************************************************* */
-import BaseApp, { BIP32Path, ConstructorParams, LedgerError, PAYLOAD_TYPE, Transport, processErrorResponse } from '@zondax/ledger-js'
+import BaseApp, {
+  BIP32Path,
+  ConstructorParams,
+  LedgerError,
+  PAYLOAD_TYPE,
+  Transport,
+  processErrorResponse,
+  processResponse,
+} from '@zondax/ledger-js'
 
 import { DEFAULT_PATH, P2_VALUES, PREHASH_LEN, RANDOMIZER_LEN, SIGRSLEN } from './consts'
 import { processGetAddrResponse, processGetFvkResponse } from './helper'
@@ -53,7 +61,8 @@ export class PenumbraApp extends BaseApp {
     try {
       const responseBuffer = await this.transport.send(this.CLA, this.INS.GET_ADDR, this.P1_VALUES.ONLY_RETRIEVE, P2_VALUES.DEFAULT, data)
 
-      const response = processGetAddrResponse(responseBuffer)
+      const payload = processResponse(responseBuffer)
+      const response = processGetAddrResponse(payload)
 
       return {
         address: response.address,
@@ -75,7 +84,8 @@ export class PenumbraApp extends BaseApp {
         data
       )
 
-      const response = processGetAddrResponse(responseBuffer)
+      const payload = processResponse(responseBuffer)
+      const response = processGetAddrResponse(payload)
 
       return {
         address: response.address,
@@ -92,11 +102,10 @@ export class PenumbraApp extends BaseApp {
     try {
       const responseBuffer = await this.transport.send(this.CLA, this.INS.FVK, this.P1_VALUES.ONLY_RETRIEVE, P2_VALUES.DEFAULT, data)
 
-      const response = processGetFvkResponse(responseBuffer)
+      const payload = processResponse(responseBuffer)
+      const response = processGetFvkResponse(payload)
 
-      return {
-        fvk: response.fvk,
-      } as ResponseFvk
+      return response
     } catch (e) {
       throw processErrorResponse(e)
     }

src/consts.ts

@@ -7,7 +7,11 @@ export const P2_VALUES = {
 
 export const PKLEN = 65
 export const ADDRLEN = 80
-export const FVKLEN = 64
+// Verification key length
+export const AK_LEN = 32
+// Nullifier key length
+export const NK_LEN = 32
+export const FVKLEN = AK_LEN + NK_LEN
 export const SIGRSLEN = 64
 export const PREHASH_LEN = 32
 export const RANDOMIZER_LEN = 12

src/helper.ts

@@ -1,26 +1,25 @@
-import { ADDRLEN, FVKLEN } from "./consts";
-import { ResponseAddress, ResponseFvk } from "./types";
+import { ResponsePayload } from '@zondax/ledger-js/dist/payload'
 
-export function processGetAddrResponse(response: Buffer): ResponseAddress {
-  const errorCodeData = response.subarray(-2);
-  const returnCode = errorCodeData[0] * 256 + errorCodeData[1];
+import { ADDRLEN, AK_LEN, FVKLEN, NK_LEN } from './consts'
+import { ResponseAddress, ResponseFvk } from './types'
 
-  const address = Buffer.from(response.subarray(0, ADDRLEN));
-  response = response.subarray(ADDRLEN);
+export function processGetAddrResponse(response: ResponsePayload): ResponseAddress {
+  const address = response.readBytes(ADDRLEN)
 
   return {
     address,
-  };
+  }
 }
 
-export function processGetFvkResponse(response: Buffer): ResponseFvk {
-  const errorCodeData = response.subarray(-2);
-  const returnCode = errorCodeData[0] * 256 + errorCodeData[1];
+export function processGetFvkResponse(response: ResponsePayload): ResponseFvk {
+  const keys = response.readBytes(FVKLEN)
 
-  const fvk = Buffer.from(response.subarray(0, FVKLEN));
-  response = response.subarray(FVKLEN);
+  // Extract ak and nullifier_key
+  const ak = Buffer.from(keys.subarray(0, AK_LEN))
+  const nk = Buffer.from(keys.subarray(32, FVKLEN))
 
   return {
-    fvk,
-  };
+    ak,
+    nk,
+  }
 }

src/types.ts

@@ -1,25 +1,31 @@
-import { INSGeneric } from "@zondax/ledger-js";
+import { INSGeneric } from '@zondax/ledger-js'
 
 export interface PenumbraIns extends INSGeneric {
-  GET_VERSION: 0x00;
-  GET_ADDR: 0x01;
-  SIGN: 0x02;
-  FVK: 0x03;
+  GET_VERSION: 0x00
+  GET_ADDR: 0x01
+  SIGN: 0x02
+  FVK: 0x03
 }
 
 export interface AddressIndex {
-  account: number;
-  randomizer?: Buffer;
+  account: number
+  randomizer?: Buffer
 }
 
 export interface ResponseAddress {
-  address?: Buffer;
+  address?: Buffer
 }
 
+// The full viewing key consists of two components:
+//
+//     - ak
+//     - nk
+//
 export interface ResponseFvk {
-  fvk?: Buffer;
+  ak: Buffer
+  nk: Buffer
 }
 
 export interface ResponseSign {
-  signature: Buffer;
+  signature: Buffer
 }