Auto-disable CallKit privacy in iOS 11 and later.

Signal/src/ViewControllers/PrivacySettingsTableViewController.m

@@ -1,5 +1,5 @@
 //
-//  Copyright (c) 2017 Open Whisper Systems. All rights reserved.
+//  Copyright (c) 2018 Open Whisper Systems. All rights reserved.
 //
 
 #import "PrivacySettingsTableViewController.h"
@@ -89,7 +89,7 @@ NS_ASSUME_NONNULL_BEGIN
                                                             isOn:[Environment.preferences isCallKitEnabled]
                                                           target:weakSelf
                                                         selector:@selector(didToggleEnableCallKitSwitch:)]];
-        if (Environment.preferences.isCallKitEnabled) {
+        if (Environment.preferences.isCallKitEnabled && !Environment.preferences.isCallKitPrivacyAutoDisabled) {
             [callKitSection
                 addItem:[OWSTableItem switchItemWithText:NSLocalizedString(@"SETTINGS_PRIVACY_CALLKIT_PRIVACY_TITLE",
                                                              @"Label for 'CallKit privacy' preference")

Signal/src/call/Speakerbox/CallKitCallUIAdaptee.swift

@@ -50,6 +50,10 @@ final class CallKitCallUIAdaptee: NSObject, CallUIAdaptee, CXProviderDelegate {
         // default iOS ringtone OR the custom ringtone associated with this user's
         // system contact, if possible (iOS 11 or later).
 
+        if #available(iOS 11.0, *) {
+            providerConfiguration.includesCallsInRecents = false
+        }
+
         return providerConfiguration
     }
 

SignalMessaging/utils/OWSPreferences.h

@@ -68,6 +68,7 @@ extern NSString *const OWSPreferencesKeyEnableDebugLog;
 - (void)setIsCallKitPrivacyEnabled:(BOOL)flag;
 // Returns YES IFF isCallKitPrivacyEnabled has been set by user.
 - (BOOL)isCallKitPrivacySet;
+- (BOOL)isCallKitPrivacyAutoDisabled;
 
 #pragma mark direct call connectivity (non-TURN)
 

SignalMessaging/utils/OWSPreferences.m

@@ -190,10 +190,36 @@ NSString *const OWSPreferencesKey_IsReadyForAppExtensions = @"isReadyForAppExten
     return preference != nil;
 }
 
+- (BOOL)isCallKitPrivacyAutoDisabled
+{
+    // In iOS 10.2.1, Apple fixed a bug wherein call history was backed up to iCloud.
+    //
+    // See: https://support.apple.com/en-us/HT207482
+    //
+    // In iOS 11, Apple introduced a property CXProviderConfiguration.includesCallsInRecents
+    // that allows us to prevent Signal calls made with CallKit from showing up in the device's
+    // call history.
+    //
+    // Therefore in versions of iOS after 11, we have no need of call privacy.
+    if (SYSTEM_VERSION_GREATER_THAN_OR_EQUAL_TO(11, 0)) {
+        return YES;
+    } else {
+        return NO;
+    }
+}
+
 - (BOOL)isCallKitPrivacyEnabled
 {
-    NSNumber *preference = [self tryGetValueForKey:OWSPreferencesKeyCallKitPrivacyEnabled];
-    return preference ? [preference boolValue] : YES;
+    if ([self isCallKitPrivacyAutoDisabled]) {
+        return NO;
+    }
+    NSNumber *_Nullable preference = [self tryGetValueForKey:OWSPreferencesKeyCallKitPrivacyEnabled];
+    if (preference) {
+        return [preference boolValue];
+    } else {
+        // Private by default.
+        return YES;
+    }
 }
 
 - (void)setIsCallKitPrivacyEnabled:(BOOL)flag