Revert "Chaff Requests Implementation (iOS) (#891)" (#905)

This reverts commit 6d7dc48.

Author: Matt Buckley

ios/AppDelegate.m

@@ -55,7 +55,6 @@ - (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(
 
   [ExposureManager createSharedInstance];
   [[ExposureManager shared] registerExposureDetectionBackgroundTask];
-  [[ExposureManager shared] registerChaffBackgroundTask];
   [[ExposureManager shared] registerDeleteOldExposuresBackgroundTask];
 
   [RNSplashScreen showSplash:@"LaunchScreen" inRootView:rootView];

ios/BT/ExposureManager.swift

@@ -36,13 +36,12 @@ enum ENAPIVersion { case V1, V2 }
 
 @objc(ExposureManager)
 /**
- This class wrapps [ENManager](https://developer.apple.com/documentation/exposurenotification/enmanager) and acts like a controller and entry point of the different flows
+ This class wraps [ENManager](https://developer.apple.com/documentation/exposurenotification/enmanager) and acts like a controller and entry point of the different flows
  */
 
 final class ExposureManager: NSObject {
 
-  private static let backgroundTaskIdentifier = "\(Bundle.main.bundleIdentifier!).exposure-notification"
-  private static let chaffBackgroundTaskIdentifier = "\(Bundle.main.bundleIdentifier!).chaff"
+  private static let exposureDetectionBackgroundTaskIdentifier = "\(Bundle.main.bundleIdentifier!).exposure-notification"
   private static let deleteOldExposuresBackgroundTaskIdentifier = "\(Bundle.main.bundleIdentifier!).delete-old-exposures"
 
   @objc private(set) static var shared: ExposureManager?
@@ -86,20 +85,13 @@ final class ExposureManager: NSObject {
         self?.activateSuccess()
       }
     }
-    // Schedule background tasks if needed whenever EN authorization status changes
+    // Schedule background task if needed whenever EN authorization status changes
     notificationCenter.addObserver(
       self,
       selector: #selector(scheduleExposureDetectionBackgroundTaskIfNeeded),
       name: .ExposureNotificationStatusDidChange,
       object: nil
     )
-
-    notificationCenter.addObserver(
-      self,
-      selector: #selector(scheduleChaffBackgroundTaskIfNeeded),
-      name: .ChaffRequestTriggered,
-      object: nil
-    )
   }
 
   deinit {
@@ -216,12 +208,6 @@ final class ExposureManager: NSObject {
     }, callback: callback)
   }
 
-  @objc func fetchChaffKeys(callback: @escaping (ExposureKeysDictionaryArray?, ExposureManagerError?) -> Void) {
-    getDiagnosisKeys(transform: { (keys) -> ExposureKeysDictionaryArray in
-      (keys ?? []).map { $0.chaffRepresentation }
-    }, callback: callback)
-  }
-
 
   // MARK: == Exposure Detection ==
 
@@ -230,7 +216,7 @@ final class ExposureManager: NSObject {
     All launch handlers must be registered before application finishes launching
    */
   @objc func registerExposureDetectionBackgroundTask() {
-    bgTaskScheduler.register(forTaskWithIdentifier: ExposureManager.backgroundTaskIdentifier,
+    bgTaskScheduler.register(forTaskWithIdentifier: ExposureManager.exposureDetectionBackgroundTaskIdentifier,
                              using: .main) { [weak self] task in
       guard let strongSelf = self else { return }
       // Notify the user if bluetooth is off
@@ -256,27 +242,7 @@ final class ExposureManager: NSObject {
       self?.scheduleExposureDetectionBackgroundTaskIfNeeded()
     }
   }
-
-  /**
-   Registers the background task of sending chaff requests
-   All launch handlers must be registered before application finishes launching
-   */
-  @objc func registerChaffBackgroundTask() {
-    bgTaskScheduler.register(forTaskWithIdentifier: ExposureManager.chaffBackgroundTaskIdentifier,
-                             using: .main) { [weak self] task in
-
-      // Perform the chaff request
-      let currentHour = Calendar.current.dateComponents([.hour], from: Date()).hour ?? 0
-
-      if (currentHour > 8 && currentHour < 19) {
-        self?.performChaffRequest()
-      }
-
-      // Schedule the next background task
-      self?.scheduleChaffBackgroundTaskIfNeeded()
-    }
-  }
-
+  
   /**
    Registers the background task of deleting exposures > 14 days old
    from the local database
@@ -294,18 +260,7 @@ final class ExposureManager: NSObject {
 
   @objc func scheduleExposureDetectionBackgroundTaskIfNeeded() {
     guard manager.exposureNotificationStatus == .active else { return }
-    let taskRequest = BGProcessingTaskRequest(identifier: ExposureManager.backgroundTaskIdentifier)
-    taskRequest.requiresNetworkConnectivity = true
-    do {
-      try bgTaskScheduler.submit(taskRequest)
-    } catch {
-      print("Unable to schedule background task: \(error)")
-    }
-  }
-
-  @objc func scheduleChaffBackgroundTaskIfNeeded() {
-    guard manager.exposureNotificationStatus == .active else { return }
-    let taskRequest = BGProcessingTaskRequest(identifier: ExposureManager.chaffBackgroundTaskIdentifier)
+    let taskRequest = BGProcessingTaskRequest(identifier: ExposureManager.exposureDetectionBackgroundTaskIdentifier)
     taskRequest.requiresNetworkConnectivity = true
     do {
       try bgTaskScheduler.submit(taskRequest)
@@ -661,18 +616,6 @@ private extension ExposureManager {
     ))
   }
 
-  func performChaffRequest() {
-    fetchChaffKeys { [weak self] (keyArray, error) in
-      if error != nil {
-        print("error: \(error.debugDescription)")
-      }
-      self?.notificationCenter.post(Notification(
-        name: .ChaffRequestTriggered,
-        object: keyArray
-      ))
-    }
-  }
-
   func getDiagnosisKeys<T>(transform: @escaping ([ENTemporaryExposureKey]?) -> T,
                            callback: @escaping (T?, ExposureManagerError?) -> Void) {
     manager.getDiagnosisKeys { (keys, error) in

ios/BT/Extensions/Exposure Notifications/ENTemporaryExposureKey+Extensions.swift

@@ -19,15 +19,6 @@ extension ENTemporaryExposureKey {
     ]
   }
 
-  var chaffRepresentation : [String: Any] {
-    return [
-      "key": keyData.base64EncodedString().shuffled(),
-      "rollingPeriod": rollingPeriod,
-      "rollingStartNumber": rollingStartNumber,
-      "transmissionRisk": transmissionRiskLevel
-    ]
-  }
-
   static func rollingStartNumber(_ date: Date) -> UInt32 {
     UInt32(Int(date.timeIntervalSince1970 / (24 * 60 * 60)) * Constants.intervalsPerRollingPeriod)
   }

ios/BT/Extensions/Foundation/Notification+Extensions.swift

@@ -7,7 +7,6 @@ extension Notification.Name {
   public static let HMACKeyDidChange = Notification.Name(rawValue: "BTSecureStorageHMACKeyDidChange")
   public static let revisionTokenDidChange = Notification.Name(rawValue: "onRevisionTokenDidChange")
   public static let ExposuresDidChange = Notification.Name(rawValue: "onExposureRecordUpdated")
-  public static let ChaffRequestTriggered = Notification.Name(rawValue: "onChaffRequestTriggered")
   public static let ExposureNotificationStatusDidChange = Notification.Name(rawValue: "onEnabledStatusUpdated")
   public static let remainingDailyFileProcessingCapacityDidChange = Notification.Name(rawValue: "remainingDailyFileProcessingCapacityDidChange")
   public static let UrlOfMostRecentlyDetectedKeyFileDidChange = Notification.Name(rawValue: "UrlOfMostRecentlyDetectedKeyFileDidChange")

ios/BT/bridge/ExposureEventEmitter.m

@@ -2,7 +2,6 @@
 #import <React/RCTEventEmitter.h>
 
 // Notification/Event Names
-NSString *const onChaffRequestTriggered = @"onChaffRequestTriggered";
 NSString *const onEnabledStatusUpdated = @"onEnabledStatusUpdated";
 NSString *const onExposuresChanged = @"onExposureRecordUpdated";
 
@@ -32,7 +31,6 @@ - (instancetype)init
   return @[
     onExposuresChanged,
     onEnabledStatusUpdated,
-    onChaffRequestTriggered
   ];
 }
 

ios/COVIDSafePathsTests/ExposureManagerUnitTests.swift

@@ -289,18 +289,14 @@ class ExposureManagerUnitTests: XCTestCase {
     let activateExpectation = self.expectation(description: "Activate gets called")
     let invalidateExpectation = self.expectation(description: "Invalidate gets called")
 
-    let registerExposureNotificationsStatusNotificationExpectation = self.expectation(description: "Registers for authorization changes")
-    let registerChaffRequestNotificationExpectation = self.expectation(description: "Registers for chaff request notifications")
-
+    let registerNotificationExpectation = self.expectation(description: "Registers for authorization changes")
+    
     let setExposureNotificationEnabledTrueExpectation = self.expectation(description: "When activated, if disabled, request to enable exposure notifications")
 
     let notificationCenterMock = NotificationCenterMock()
     notificationCenterMock.addObserverHandler = { (_, _, name, _) in
       if name == Notification.Name.ExposureNotificationStatusDidChange {
-        registerExposureNotificationsStatusNotificationExpectation.fulfill()
-      }
-      if name == Notification.Name.ChaffRequestTriggered {
-        registerChaffRequestNotificationExpectation.fulfill()
+        registerNotificationExpectation.fulfill()
       }
     }
 
@@ -327,8 +323,7 @@ class ExposureManagerUnitTests: XCTestCase {
                         notificationCenter: notificationCenterMock)
     wait(for: [activateExpectation,
                invalidateExpectation,
-               registerExposureNotificationsStatusNotificationExpectation,
-               registerChaffRequestNotificationExpectation,
+               registerNotificationExpectation,
                setExposureNotificationEnabledTrueExpectation], timeout: 1)
   }
 
@@ -497,7 +492,7 @@ class ExposureManagerUnitTests: XCTestCase {
     wait(for: [addNotificatiionRequestExpectation, removeNotificationsExpectation], timeout: 0)
   }
 
-  func testRegisterExposureDetectionBackgroundTask() {
+  func testregisterExposureDetectionBackgroundTask() {
     let registerExpectation = self.expectation(description: "A background task with the given identifier is registered")
     let bgSchedulerMock = BGTaskSchedulerMock()
     bgSchedulerMock.registerHandler = { identifier, launchHanlder in
@@ -509,7 +504,7 @@ class ExposureManagerUnitTests: XCTestCase {
     wait(for: [registerExpectation], timeout: 0)
   }
 
-  func testSubmitExposureDetectionBackgroundTask() {
+  func testSubmitBackgroundTask() {
     let mockEnManager = ENManagerMock()
     mockEnManager.exposureNotificationStatusHandler = {
       return .active
@@ -525,34 +520,6 @@ class ExposureManagerUnitTests: XCTestCase {
     wait(for: [submitExpectation], timeout: 0)
   }
 
-  func testRegisterChaffBackgroundTask() {
-    let registerExpectation = self.expectation(description: "A background task with the given identifier is registered")
-    let bgSchedulerMock = BGTaskSchedulerMock()
-    bgSchedulerMock.registerHandler = { identifier, launchHanlder in
-      registerExpectation.fulfill()
-      return true
-    }
-    let exposureManager = ExposureManager(backgroundTaskScheduler: bgSchedulerMock)
-    exposureManager.registerChaffBackgroundTask()
-    wait(for: [registerExpectation], timeout: 0)
-  }
-
-  func testSubmitChaffBackgroundTask() {
-    let mockEnManager = ENManagerMock()
-    mockEnManager.exposureNotificationStatusHandler = {
-      return .active
-    }
-    let submitExpectation = self.expectation(description: "A background task request is submitted")
-    let bgSchedulerMock = BGTaskSchedulerMock()
-    bgSchedulerMock.submitHandler = { taskRequest in
-      submitExpectation.fulfill()
-    }
-    let exposureManager = ExposureManager(exposureNotificationManager: mockEnManager,
-                                          backgroundTaskScheduler: bgSchedulerMock)
-    exposureManager.scheduleChaffBackgroundTaskIfNeeded()
-    wait(for: [submitExpectation], timeout: 0)
-  }
-
   func testRegisterDeleteOldExposuresBackgroundTask() {
     let registerExpectation = self.expectation(description: "A background task with the given identifier is registered")
     let bgSchedulerMock = BGTaskSchedulerMock()

src/AffectedUserFlow/verificationAPI.ts

@@ -49,20 +49,15 @@ interface VerifiedCodeResponse {
 
 export const postCode = async (
   code: string,
-  isChaffRequest = false,
 ): Promise<NetworkResponse<CodeVerificationSuccess, CodeVerificationError>> => {
   const data = {
     code,
   }
 
-  const headers = isChaffRequest
-    ? { ...defaultHeaders, "x-chaff": "1" }
-    : defaultHeaders
-
   try {
     const response = (await fetchWithTimeout(verifyUrl, {
       method: "POST",
-      headers: headers,
+      headers: defaultHeaders,
       body: JSON.stringify(data),
     })) as Response
 
@@ -118,22 +113,18 @@ export type TokenVerificationError =
 export const postTokenAndHmac = async (
   token: Token,
   hmacDigest: string,
-  isChaffRequest = false,
 ): Promise<
   NetworkResponse<TokenVerificationSuccess, TokenVerificationError>
 > => {
   const data = {
     token,
     ekeyhmac: hmacDigest,
   }
-  const headers = isChaffRequest
-    ? { ...defaultHeaders, "x-Chaff": "1" }
-    : defaultHeaders
 
   try {
     const response = await fetch(certificateUrl, {
       method: "POST",
-      headers,
+      headers: defaultHeaders,
       body: JSON.stringify(data),
     })
 

src/ExposureContext.tsx

@@ -11,8 +11,6 @@ import { ExposureKey } from "./exposureKey"
 import { ExposureInfo } from "./exposure"
 import { useProductAnalyticsContext } from "./ProductAnalytics/Context"
 import * as NativeModule from "./gaen/nativeModule"
-import { calculateHmac } from "./AffectedUserFlow/hmac"
-import * as API from "./AffectedUserFlow/verificationAPI"
 
 type Posix = number
 
@@ -66,27 +64,6 @@ const ExposureProvider: FunctionComponent = ({ children }) => {
     })
   }, [])
 
-  const sendChaffRequest = useCallback(async () => {
-    const code = Math.random().toString().substring(2, 10)
-    const response = await API.postCode(code, true)
-
-    if (response.kind === "success") {
-      const token = response.body.token
-      const exposureKeys = await NativeModule.fetchChaffKeys()
-      const [hmacDigest] = await calculateHmac(exposureKeys)
-
-      const certResponse = await API.postTokenAndHmac(token, hmacDigest, true)
-
-      if (certResponse.kind === "success") {
-        trackEvent("epi_analytics", "chaff_request_sent")
-      } else {
-        trackEvent("epi_analytics", "chaff_request_failed")
-      }
-    } else {
-      trackEvent("epi_analytics", "chaff_request_failed")
-    }
-  }, [trackEvent])
-
   const refreshExposureInfo = useCallback(async () => {
     const exposureInfo = await NativeModule.getCurrentExposures()
     setExposureInfo(exposureInfo)
@@ -96,26 +73,18 @@ const ExposureProvider: FunctionComponent = ({ children }) => {
   }, [])
 
   useEffect(() => {
-    // Exposures subscription
-    const exposuresSubscription = NativeModule.subscribeToExposureEvents(
+    const subscription = NativeModule.subscribeToExposureEvents(
       (exposureInfo: ExposureInfo) => {
         setExposureInfo(exposureInfo)
         getLastExposureDetectionDate()
       },
     )
     getLastExposureDetectionDate()
 
-    // Chaff subscription
-    const chaffSubscription = NativeModule.subscribeToChaffRequestEvents(() => {
-      sendChaffRequest()
-    })
-    sendChaffRequest()
-
     return () => {
-      exposuresSubscription.remove()
-      chaffSubscription.remove()
+      subscription.remove()
     }
-  }, [getLastExposureDetectionDate, sendChaffRequest])
+  }, [getLastExposureDetectionDate])
 
   useEffect(() => {
     const subscription = NativeModule.subscribeToExposureEvents(() => {