Only reply to group info requester.

// FREEBIE

src/Messages/Interactions/TSOutgoingMessage.h

@@ -94,6 +94,9 @@ typedef NS_ENUM(NSInteger, TSGroupMetaMessage) {
 
 @property (atomic, readonly) TSGroupMetaMessage groupMetaMessage;
 
+// If set, this group message should only be sent to a single recipient.
+@property (atomic, readonly) NSString *singleGroupRecipient;
+
 /**
  * Whether the message should be serialized as a modern aka Content, or the old style legacy message.
  * Sync and Call messsages must be sent as Content, but other old style DataMessage payloads should be
@@ -168,6 +171,8 @@ typedef NS_ENUM(NSInteger, TSGroupMetaMessage) {
 - (void)updateWithWasDeliveredWithTransaction:(YapDatabaseReadWriteTransaction *)transaction;
 - (void)updateWithWasDelivered;
 - (void)updateWithWasSentAndDelivered;
+- (void)updateWithSingleGroupRecipient:(NSString *)singleGroupRecipient
+                           transaction:(YapDatabaseReadWriteTransaction *)transaction;
 
 #pragma mark - Sent Recipients
 

src/Messages/Interactions/TSOutgoingMessage.m

@@ -22,6 +22,7 @@ NSString *const kTSOutgoingMessageSentRecipientAll = @"kTSOutgoingMessageSentRec
 @property (atomic) NSString *customMessage;
 @property (atomic) NSString *mostRecentFailureText;
 @property (atomic) BOOL wasDelivered;
+@property (atomic) NSString *singleGroupRecipient;
 
 // For outgoing, non-legacy group messages sent from this client, this
 // contains the list of recipients to whom the message has been sent.
@@ -321,6 +322,18 @@ NSString *const kTSOutgoingMessageSentRecipientAll = @"kTSOutgoingMessageSentRec
     }];
 }
 
+- (void)updateWithSingleGroupRecipient:(NSString *)singleGroupRecipient
+                           transaction:(YapDatabaseReadWriteTransaction *)transaction
+{
+    OWSAssert(transaction);
+    OWSAssert(singleGroupRecipient.length > 0);
+
+    [self applyChangeToSelfAndLatestOutgoingMessage:transaction
+                                        changeBlock:^(TSOutgoingMessage *message) {
+                                            [message setSingleGroupRecipient:singleGroupRecipient];
+                                        }];
+}
+
 #pragma mark - Sent Recipients
 
 - (NSArray<NSString *> *)sentRecipients

src/Messages/OWSMessageSender.m

@@ -735,11 +735,18 @@ NSString *const OWSMessageSenderRateLimitedException = @"RateLimitedException";
     NSMutableArray<TOCFuture *> *futures = [NSMutableArray array];
 
     for (SignalRecipient *recipient in recipients) {
+        NSString *recipientId = recipient.recipientId;
+
         // We don't need to send the message to ourselves...
-        if ([recipient.uniqueId isEqualToString:[TSStorageManager localNumber]]) {
+        if ([recipientId isEqualToString:[TSStorageManager localNumber]]) {
+            continue;
+        }
+        // We don't need to sent the message to all group members if
+        // it has a "single group recipient".
+        if (message.singleGroupRecipient && ![message.singleGroupRecipient isEqualToString:recipientId]) {
             continue;
         }
-        if ([message wasSentToRecipient:recipient.uniqueId]) {
+        if ([message wasSentToRecipient:recipientId]) {
             // Skip recipients we have already sent this message to (on an
             // earlier retry, perhaps).
             DDLogInfo(@"%@ Skipping group message recipient; already sent: %@", self.tag, recipient.uniqueId);

src/Messages/TSMessagesManager.m

@@ -775,7 +775,8 @@ NS_ASSUME_NONNULL_BEGIN
     }
 }
 
-- (void)handleGroupInfoRequest:(OWSSignalServiceProtosDataMessage *)dataMessage
+- (void)handleGroupInfoRequest:(OWSSignalServiceProtosEnvelope *)envelope
+                   dataMessage:(OWSSignalServiceProtosDataMessage *)dataMessage
 {
     OWSAssert([NSThread isMainThread]);
     OWSAssert(dataMessage.group.type == OWSSignalServiceProtosGroupContextTypeRequestInfo);
@@ -786,7 +787,7 @@ NS_ASSUME_NONNULL_BEGIN
         return;
     }
 
-    DDLogInfo(@"%@ Received 'Request Group Info' message for group: %@", self.tag, groupId);
+    DDLogInfo(@"%@ Received 'Request Group Info' message for group: %@ from: %@", self.tag, groupId, envelope.source);
 
     [self.dbConnection readWriteWithBlock:^(YapDatabaseReadWriteTransaction *transaction) {
         TSGroupModel *emptyModelToFillOutId =
@@ -803,6 +804,8 @@ NS_ASSUME_NONNULL_BEGIN
                                                                          inThread:gThread
                                                                  groupMetaMessage:TSGroupMessageUpdate];
         [message updateWithCustomMessage:updateGroupInfo transaction:transaction];
+        // Only send this group update to the requester.
+        [message updateWithSingleGroupRecipient:envelope.source transaction:transaction];
 
         dispatch_async(dispatch_get_main_queue(), ^{
             [self sendGroupUpdateForThread:gThread message:message];
@@ -827,7 +830,7 @@ NS_ASSUME_NONNULL_BEGIN
     NSString *localNumber = [TSAccountManager localNumber];
 
     if (dataMessage.group.type == OWSSignalServiceProtosGroupContextTypeRequestInfo) {
-        [self handleGroupInfoRequest:dataMessage];
+        [self handleGroupInfoRequest:envelope dataMessage:dataMessage];
         return nil;
     }