refactor: [SIW-1176] Change decoded assertion format on iOS

backend/src/index.ts

@@ -85,11 +85,13 @@
  * The server then verifies the assertion using the stored public key.
  * The server also verifies the signCount and stores the new signCount.
  */
 app.post(`/assertion/verify`, (req, res) => {
   try {
-    const { hardwareKeyTag, assertion } = req.body;
+    const { hardwareKeyTag } = req.body;
 
-    if (hardwareKeyTag === undefined || assertion === undefined) {
+    console.log(req.body);
+
+    if (hardwareKeyTag === undefined) {
       throw new Error('Invalid authentication');
     }
 
@@ -102,7 +104,8 @@
     }
 
     const result = verifyAssertion({
-      assertion: Buffer.from(assertion, 'base64').toString('utf-8'),
+      signature: req.body.signature,
+      authenticatorData: req.body.authenticatorData,
       payload: req.body.payload,
       publicKey: attestation.publicKey,
       bundleIdentifier: BUNDLE_IDENTIFIER,

backend/src/verifyAssertion.ts

@@ -1,7 +1,8 @@
 import { createHash, createVerify } from 'crypto';
 
 export type VerifyAssertionParams = {
-  assertion: string;
+  signature: string;
+  authenticatorData: string;
   payload: Buffer;
   publicKey: string;
   bundleIdentifier: string;
@@ -16,7 +17,8 @@ export type VerifyAssertionParams = {
  */
 const verifyAssertion = (params: VerifyAssertionParams) => {
   const {
-    assertion,
+    signature,
+    authenticatorData,
     payload,
     publicKey,
     bundleIdentifier,
@@ -32,8 +34,12 @@ const verifyAssertion = (params: VerifyAssertionParams) => {
     throw new Error('teamIdentifier is required');
   }
 
-  if (!assertion) {
-    throw new Error('assertion is required');
+  if (!signature) {
+    throw new Error('signature is required');
+  }
+
+  if (!authenticatorData) {
+    throw new Error('authenticatorData is required');
   }
 
   if (!payload) {
@@ -44,11 +50,8 @@ const verifyAssertion = (params: VerifyAssertionParams) => {
     throw new Error('publicKey is required');
   }
 
-  // 1. Get signature and authenticator data from the assertion.
-  const { signature, authenticatorData } = JSON.parse(assertion);
-
-  const sign = Buffer.from(signature);
-  const authData = Buffer.from(authenticatorData);
+  const sign = Buffer.from(signature, 'base64');
+  const authData = Buffer.from(authenticatorData, 'base64');
   // 2. Compute the SHA256 hash of the client data, and store it as clientDataHash.
   const clientDataHash = createHash('sha256').update(payload).digest();
 

example/src/IosApp.tsx

@@ -111,11 +111,13 @@ export default function App() {
     if (assertion) {
       // decode CBOR assertion on native side (iOS only)
       const decodedAssertion = await decodeAssertion(assertion);
+      console.log(decodedAssertion);
       // verify attestation on the server with POST
       // and body of challenge, attestation and keyId
       const result = await postRequest('assertion/verify', {
         challenge: challenge,
-        assertion: decodedAssertion,
+        signature: decodedAssertion.signature,
+        authenticatorData: decodedAssertion.authenticatorData,
         hardwareKeyTag: hardwareKeyTag,
         payload: JSON.stringify({ challenge: challenge, jwk: jwk }),
       });

ios/IoReactNativeIntegrity.swift

@@ -7,11 +7,6 @@ import SwiftCBOR
 class IoReactNativeIntegrity: NSObject {
   private typealias ME = ModuleException
 
-  struct DecodedData: Codable {
-    var signature: [UInt8]
-    var authenticatorData: [UInt8]
-  }
-
   enum CBORDecodingError: Error {
     case invalidFormat(String)
   }
@@ -46,12 +41,13 @@ class IoReactNativeIntegrity: NSObject {
             case let .byteString(authenticatorDataBytes)? = map["authenticatorData"] else {
         throw CBORDecodingError.invalidFormat("Expected signature and authenticatorData in the CBOR map")
       }
-
-      let decodedData = DecodedData(signature: signatureBytes, authenticatorData: authenticatorDataBytes)
 
-      let jsonData = try JSONEncoder().encode(decodedData)
+      let decodedData: [String:String]  = [
+        "signature": Data(signatureBytes).base64EncodedString(),
+        "authenticatorData": Data(authenticatorDataBytes).base64EncodedString()
+      ]
 
-      resolve(jsonData.base64EncodedString())
+      resolve(decodedData)
     } catch {
       ME.decodingAssertionFailed.reject(reject: reject, ("error", error.localizedDescription))
     }

src/index.tsx

@@ -159,7 +159,9 @@ export function generateHardwareSignatureWithAssertion(
  * @param assertion - the CBOR assertion to be decoded
  * @returns - a promise that resolves to a string.
  */
-export function decodeAssertion(assertion: string): Promise<string> {
+export function decodeAssertion(
+  assertion: string
+): Promise<{ signature: string; authenticatorData: string }> {
   return IoReactNativeIntegrity.decodeAssertion(assertion);
 }