send null message when syncing verification state

// FREEBIE

src/Devices/OWSVerificationStateSyncMessage.h

@@ -19,6 +19,8 @@ NS_ASSUME_NONNULL_BEGIN
 // This is a clunky name, but we want to differentiate it from `recipientIdentifier` inherited from `TSOutgoingMessage`
 @property (nonatomic, readonly) NSString *verificationForRecipientId;
 
+@property (nonatomic, readonly) size_t paddingBytesLength;
+
 @end
 
 NS_ASSUME_NONNULL_END

src/Devices/OWSVerificationStateSyncMessage.m

@@ -68,6 +68,9 @@ NS_ASSUME_NONNULL_BEGIN
     _verificationState = verificationState;
     _identityKey = identityKey;
     _verificationForRecipientId = verificationForRecipientId;
+    
+    // Add 1-512 bytes of random padding bytes.
+    _paddingBytesLength = arc4random_uniform(512) + 1;
 
     return self;
 }
@@ -110,11 +113,10 @@ NS_ASSUME_NONNULL_BEGIN
                 return OWSSignalServiceProtosVerifiedStateUnverified;
         }
     }();
-
-    // Add 1-512 bytes of random padding bytes.
-    size_t paddingLengthBytes = arc4random_uniform(512) + 1;
-    syncMessageBuilder.padding = [Cryptography generateRandomBytes:paddingLengthBytes];
-
+    
+    OWSAssert(self.paddingBytesLength != 0);
+    syncMessageBuilder.padding = [Cryptography generateRandomBytes:self.paddingBytesLength];
+    
     return [syncMessageBuilder build];
 }
 

src/Messages/Interactions/TSOutgoingMessage.m

@@ -455,8 +455,6 @@ NSString *const kTSOutgoingMessageSentRecipientAll = @"kTSOutgoingMessageSentRec
     return [[self dataMessageBuilder] build];
 }
 
-// For legacy message this is a serialized DataMessage.
-// For modern messages, e.g. Sync and Call messages, this is a serialized Contact
 - (NSData *)buildPlainTextData
 {
     OWSSignalServiceProtosContentBuilder *contentBuilder = [OWSSignalServiceProtosContentBuilder new];

src/Messages/OWSIdentityManager.h

@@ -47,7 +47,7 @@ extern const NSUInteger kIdentityKeyLength;
 - (nullable OWSRecipientIdentity *)untrustedIdentityForSendingToRecipientId:(NSString *)recipientId;
 
 // Will try to send a sync message with all verification states.
-- (void)syncAllVerificationStates;
+//- (void)syncAllVerificationStates;
 
 - (void)processIncomingSyncMessage:(OWSSignalServiceProtosVerified *)verified;
 

src/Messages/OWSIdentityManager.m

@@ -7,6 +7,7 @@
 #import "NotificationsProtocol.h"
 #import "OWSMessageSender.h"
 #import "OWSRecipientIdentity.h"
+#import "OWSOutgoingNullMessage.h"
 #import "OWSVerificationStateChangeMessage.h"
 #import "OWSVerificationStateSyncMessage.h"
 #import "TSAccountManager.h"
@@ -550,6 +551,20 @@ NSString *const kNSNotificationName_IdentityStateDidChange = @"kNSNotificationNa
     OWSAssert(message.verificationForRecipientId.length > 0);
     OWSAssert([NSThread isMainThread]);
 
+    TSContactThread *contactThread = [TSContactThread getOrCreateThreadWithContactId:message.verificationForRecipientId];
+    
+    // Send null message to appear as though we're sending a normal message to cover the sync messsage sent
+    // subsequently
+    OWSOutgoingNullMessage *nullMessage = [[OWSOutgoingNullMessage alloc] initWithContactThread:contactThread
+                                                                   verificationStateSyncMessage:message];
+    [self.messageSender sendMessage:nullMessage
+                            success:^{
+                                DDLogInfo(@"%@ Successfully sent verification state NullMessage", self.tag);
+                            }
+                            failure:^(NSError * _Nonnull error) {
+                                DDLogError(@"%@ Failed to send verification state NullMessage with error: %@", self.tag, error);
+                            }];
+    
     [self.messageSender sendMessage:message
         success:^{
             DDLogInfo(@"%@ Successfully sent verification state sync message", self.tag);

src/Messages/OWSOutgoingNullMessage.h

@@ -0,0 +1,19 @@
+//
+//  Copyright (c) 2017 Open Whisper Systems. All rights reserved.
+//
+
+#import "TSOutgoingMessage.h"
+
+NS_ASSUME_NONNULL_BEGIN
+
+@class OWSVerificationStateSyncMessage;
+@class TSContactThread;
+
+@interface OWSOutgoingNullMessage : TSOutgoingMessage
+
+- (instancetype)initWithContactThread:(TSContactThread *)contactThread
+         verificationStateSyncMessage:(OWSVerificationStateSyncMessage *)verificationStateSyncMessage;
+
+@end
+
+NS_ASSUME_NONNULL_END

src/Messages/OWSOutgoingNullMessage.m

@@ -0,0 +1,67 @@
+//
+//  Copyright (c) 2017 Open Whisper Systems. All rights reserved.
+//
+
+#import "OWSOutgoingNullMessage.h"
+#import "OWSSignalServiceProtos.pb.h"
+#import "Cryptography.h"
+#import "OWSVerificationStateSyncMessage.h"
+#import "NSDate+millisecondTimeStamp.h"
+#import "TSContactThread.h"
+
+NS_ASSUME_NONNULL_BEGIN
+
+@interface OWSOutgoingNullMessage ()
+
+@property (nonatomic, readonly) OWSVerificationStateSyncMessage *verificationStateSyncMessage;
+
+@end
+
+@implementation OWSOutgoingNullMessage
+
+- (instancetype)initWithContactThread:(TSContactThread *)contactThread
+         verificationStateSyncMessage:(OWSVerificationStateSyncMessage *)verificationStateSyncMessage
+{
+    self = [super initWithTimestamp:[NSDate ows_millisecondTimeStamp]
+                           inThread:contactThread];
+    if (!self) {
+        return self;
+    }
+    
+    _verificationStateSyncMessage = verificationStateSyncMessage;
+    
+    return self;
+}
+
+#pragma mark - override TSOutgoingMessage
+
+- (NSData *)buildPlainTextData
+{
+    OWSSignalServiceProtosContentBuilder *contentBuilder = [OWSSignalServiceProtosContentBuilder new];
+    OWSSignalServiceProtosNullMessageBuilder *nullMessageBuilder = [OWSSignalServiceProtosNullMessageBuilder new];
+
+    // TODO padding size.
+    NSUInteger contentLength = self.verificationStateSyncMessage.buildPlainTextData.length;
+    contentLength -= self.verificationStateSyncMessage.paddingBytesLength;
+    
+    OWSAssert(contentLength > 0)
+    
+    // Add 1-512 bytes of random padding bytes.
+    contentLength += arc4random_uniform(512) + 1;
+    
+    nullMessageBuilder.padding = [Cryptography generateRandomBytes:contentLength];
+    
+    contentBuilder.nullMessage = [nullMessageBuilder build];
+    
+    return [contentBuilder build].data;
+}
+
+- (void)saveWithTransaction:(YapDatabaseReadWriteTransaction *)transaction
+{
+    // No-op as we don't want to actually display this as an outgoing message in our thread.
+    return;
+}
+
+@end
+
+NS_ASSUME_NONNULL_END

src/Messages/TSMessagesManager.m

@@ -171,6 +171,8 @@ NS_ASSUME_NONNULL_BEGIN
         return [NSString stringWithFormat:@"<DataMessage: %@ />", [self descriptionForDataMessage:content.dataMessage]];
     } else if (content.hasCallMessage) {
         return [NSString stringWithFormat:@"<CallMessage: %@ />", content.callMessage];
+    } else if (content.hasNullMessage) {
+        return [NSString stringWithFormat:@"<NullMessage: %@ />", content.nullMessage];
     } else {
         OWSAssert(NO);
         return @"UnknownContent";