Authentifier les utilisateurs avec WebView

// The class talking to Javascript should inherit:
class PasskeyWebListener(
  private val activity: Activity,
  private val coroutineScope: CoroutineScope,
  private val credentialManagerHandler: CredentialManagerHandler
) : WebViewCompat.WebMessageListener {
  /** havePendingRequest is true if there is an outstanding WebAuthn request.
  There is only ever one request outstanding at a time. */
  private var havePendingRequest = false

  /** pendingRequestIsDoomed is true if the WebView has navigated since
  starting a request. The FIDO module cannot be canceled, but the response
  will never be delivered in this case. */
  private var pendingRequestIsDoomed = false

  /** replyChannel is the port that the page is listening for a response on.
  It is valid if havePendingRequest is true. */
  private var replyChannel: ReplyChannel? = null

  /**
   * Called by the page during a WebAuthn request.
   *
   * @param view Creates the WebView.
   * @param message The message sent from the client using injected JavaScript.
   * @param sourceOrigin The origin of the HTTPS request. Should not be null.
   * @param isMainFrame Should be set to true. Embedded frames are not
  supported.
   * @param replyProxy Passed in by JavaScript. Allows replying when wrapped in
  the Channel.
   * @return The message response.
   */
  @UiThread
  override fun onPostMessage(
    view: WebView,
    message: WebMessageCompat,
    sourceOrigin: Uri,
    isMainFrame: Boolean,
    replyProxy: JavaScriptReplyProxy,
  ) {
    val messageData = message.data ?: return
    onRequest(
      messageData,
      sourceOrigin,
      isMainFrame,
      JavaScriptReplyChannel(replyProxy)
    )
  }

  private fun onRequest(
    msg: String,
    sourceOrigin: Uri,
    isMainFrame: Boolean,
    reply: ReplyChannel,
  ) {
    msg?.let {
      val jsonObj = JSONObject(msg);
      val type = jsonObj.getString(TYPE_KEY)
      val message = jsonObj.getString(REQUEST_KEY)

      if (havePendingRequest) {
        postErrorMessage(reply, "The request already in progress", type)
        return
      }

      replyChannel = reply
      if (!isMainFrame) {
        reportFailure("Requests from subframes are not supported", type)
        return
      }
      val originScheme = sourceOrigin.scheme
      if (originScheme == null || originScheme.lowercase() != "https") {
        reportFailure("WebAuthn not permitted for current URL", type)
        return
      }

      // Verify that origin belongs to your website,
      // it's because the unknown origin may gain credential info.
      // if (isUnknownOrigin(originScheme)) {
      // return
      // }

      havePendingRequest = true
      pendingRequestIsDoomed = false

      // Use a temporary "replyCurrent" variable to send the data back, while
      // resetting the main "replyChannel" variable to null so it’s ready for
      // the next request.
      val replyCurrent = replyChannel
      if (replyCurrent == null) {
        Log.i(TAG, "The reply channel was null, cannot continue")
        return;
      }

      when (type) {
        CREATE_UNIQUE_KEY ->
          this.coroutineScope.launch {
            handleCreateFlow(credentialManagerHandler, message, replyCurrent)
          }

        GET_UNIQUE_KEY -> this.coroutineScope.launch {
          handleGetFlow(credentialManagerHandler, message, replyCurrent)
        }

        else -> Log.i(TAG, "Incorrect request json")
      }
    }
  }

  private suspend fun handleCreateFlow(
    credentialManagerHandler: CredentialManagerHandler,
    message: String,
    reply: ReplyChannel,
  ) {
    try {
      havePendingRequest = false
      pendingRequestIsDoomed = false
      val response = credentialManagerHandler.createPasskey(message)
      val successArray = ArrayList<Any>();
      successArray.add("success");
      successArray.add(JSONObject(response.registrationResponseJson));
      successArray.add(CREATE_UNIQUE_KEY);
      reply.send(JSONArray(successArray).toString())
      replyChannel = null // setting initial replyChannel for the next request
    } catch (e: CreateCredentialException) {
      reportFailure(
        "Error: ${e.errorMessage} w type: ${e.type} w obj: $e",
        CREATE_UNIQUE_KEY
      )
    } catch (t: Throwable) {
      reportFailure("Error: ${t.message}", CREATE_UNIQUE_KEY)
    }
  }

  companion object {
    /** INTERFACE_NAME is the name of the MessagePort that must be injected into pages. */
    const val INTERFACE_NAME = "__webauthn_interface__"
    const val TYPE_KEY = "type"
    const val REQUEST_KEY = "request"
    const val CREATE_UNIQUE_KEY = "create"
    const val GET_UNIQUE_KEY = "get"
    /** INJECTED_VAL is the minified version of the JavaScript code described at this class
     * heading. The non minified form is found at credmanweb/javascript/encode.js.*/
    const val INJECTED_VAL = """
            var __webauthn_interface__,__webauthn_hooks__;!function(e){console.log("In the hook."),__webauthn_interface__.addEventListener("message",function e(n){var r=JSON.parse(n.data),t=r[2];"get"===t?o(r):"create"===t?u(r):console.log("Incorrect response format for reply")});var n=null,r=null,t=null,a=null;function o(e){if(null!==n&&null!==t){if("success"!=e[0]){var r=t;n=null,t=null,r(new DOMException(e[1],"NotAllowedError"));return}var a=i(e[1]),o=n;n=null,t=null,o(a)}}function l(e){var n=e.length%4;return Uint8Array.from(atob(e.replace(/-/g,"+").replace(/_/g,"/").padEnd(e.length+(0===n?0:4-n),"=")),function(e){return e.charCodeAt(0)}).buffer}function s(e){return btoa(Array.from(new Uint8Array(e),function(e){return String.fromCharCode(e)}).join("")).replace(/\+/g,"-").replace(/\//g,"_").replace(/=+${'$'}/,"")}function u(e){if(null===r||null===a){console.log("Here: "+r+" and reject: "+a);return}if(console.log("Output back: "+e),"success"!=e[0]){var n=a;r=null,a=null,n(new DOMException(e[1],"NotAllowedError"));return}var t=i(e[1]),o=r;r=null,a=null,o(t)}function i(e){return console.log("Here is the response from credential manager: "+e),e.rawId=l(e.rawId),e.response.clientDataJSON=l(e.response.clientDataJSON),e.response.hasOwnProperty("attestationObject")&&(e.response.attestationObject=l(e.response.attestationObject)),e.response.hasOwnProperty("authenticatorData")&&(e.response.authenticatorData=l(e.response.authenticatorData)),e.response.hasOwnProperty("signature")&&(e.response.signature=l(e.response.signature)),e.response.hasOwnProperty("userHandle")&&(e.response.userHandle=l(e.response.userHandle)),e.getClientExtensionResults=function e(){return{}},e}e.create=function n(t){if(!("publicKey"in t))return e.originalCreateFunction(t);var o=new Promise(function(e,n){r=e,a=n}),l=t.publicKey;if(l.hasOwnProperty("challenge")){var u=s(l.challenge);l.challenge=u}if(l.hasOwnProperty("user")&&l.user.hasOwnProperty("id")){var i=s(l.user.id);l.user.id=i}var c=JSON.stringify({type:"create",request:l});return __webauthn_interface__.postMessage(c),o},e.get=function r(a){if(!("publicKey"in a))return e.originalGetFunction(a);var o=new Promise(function(e,r){n=e,t=r}),l=a.publicKey;if(l.hasOwnProperty("challenge")){var u=s(l.challenge);l.challenge=u}var i=JSON.stringify({type:"get",request:l});return __webauthn_interface__.postMessage(i),o},e.onReplyGet=o,e.CM_base64url_decode=l,e.CM_base64url_encode=s,e.onReplyCreate=u}(__webauthn_hooks__||(__webauthn_hooks__={})),__webauthn_hooks__.originalGetFunction=navigator.credentials.get,__webauthn_hooks__.originalCreateFunction=navigator.credentials.create,navigator.credentials.get=__webauthn_hooks__.get,navigator.credentials.create=__webauthn_hooks__.create,window.PublicKeyCredential=function(){},window.PublicKeyCredential.isUserVerifyingPlatformAuthenticatorAvailable=function(){return Promise.resolve(!1)};
        """
  }
PasskeyWebListener.kt

// The setup for the reply channel allows communication with JavaScript.
private class JavaScriptReplyChannel(private val reply: JavaScriptReplyProxy) :
  ReplyChannel {
  override fun send(message: String?) {
    try {
      reply.postMessage(message!!)
    } catch (t: Throwable) {
      Log.i(TAG, "Reply failure due to: " + t.message);
    }
  }
}

// ReplyChannel is the interface where replies to the embedded site are
// sent. This allows for testing since AndroidX bans mocking its objects.
interface ReplyChannel {
  fun send(message: String?)
}
PasskeyWebListener.kt

val credentialManagerHandler = CredentialManagerHandler(this)

setContent {
  val coroutineScope = rememberCoroutineScope()
  AndroidView(factory = {
    WebView(it).apply {
      settings.javaScriptEnabled = true

      // Test URL:
      val url = "https://passkeys-codelab.glitch.me/"
      val listenerSupported = WebViewFeature.isFeatureSupported(
        WebViewFeature.WEB_MESSAGE_LISTENER
      )
      if (listenerSupported) {
        // Inject local JavaScript that calls Credential Manager.
        hookWebAuthnWithListener(
          this, this@WebViewMainActivity,
          coroutineScope, credentialManagerHandler
        )
      } else {
        // Fallback routine for unsupported API levels.
      }
      loadUrl(url)
    }
  }
  )
}
WebViewMainActivity.kt

val passkeyWebListener = PasskeyWebListener(activity, coroutineScope, credentialManagerHandler)

val webViewClient = object : WebViewClient() {
  override fun onPageStarted(view: WebView?, url: String?, favicon: Bitmap?) {
    super.onPageStarted(view, url, favicon)
    webView.evaluateJavascript(PasskeyWebListener.INJECTED_VAL, null)
  }
}

webView.webViewClient = webViewClient
WebViewMainActivity.kt

val rules = setOf("*")
if (WebViewFeature.isFeatureSupported(WebViewFeature.WEB_MESSAGE_LISTENER)) {
  WebViewCompat.addWebMessageListener(webView, PasskeyWebListener.INTERFACE_NAME,
    rules, passkeyWebListener)
}
WebViewMainActivity.kt