Discard GroupInfoRequest from unknown group

// FREEBIE

Signal/src/ViewControllers/DebugUI/DebugUIMessages.m

@@ -8,10 +8,12 @@
 #import "SecurityUtils.h"
 #import "Signal-Swift.h"
 #import "ThreadUtil.h"
+#import <25519/Randomness.h>
 #import <AFNetworking/AFNetworking.h>
 #import <AxolotlKit/PreKeyBundle.h>
 #import <SignalServiceKit/OWSDisappearingConfigurationUpdateInfoMessage.h>
 #import <SignalServiceKit/OWSDisappearingMessagesConfiguration.h>
+#import <SignalServiceKit/OWSSyncGroupsRequestMessage.h>
 #import <SignalServiceKit/OWSVerificationStateChangeMessage.h>
 #import <SignalServiceKit/TSCall.h>
 #import <SignalServiceKit/TSInvalidIdentityKeyReceivingErrorMessage.h>
@@ -184,6 +186,21 @@ NS_ASSUME_NONNULL_BEGIN
                         actionBlock:^{
                             [DebugUIMessages sendTextAndSystemMessages:1000 thread:thread];
                         }],
+        [OWSTableItem
+            itemWithTitle:@"Request Bogus group info"
+              actionBlock:^{
+                  DDLogInfo(@"%@ Requesting bogus group info for thread: %@", self.tag, thread);
+                  OWSSyncGroupsRequestMessage *syncGroupsRequestMessage =
+                      [[OWSSyncGroupsRequestMessage alloc] initWithThread:thread
+                                                                  groupId:[Randomness generateRandomBytes:16]];
+                  [[Environment getCurrent].messageSender sendMessage:syncGroupsRequestMessage
+                      success:^{
+                          DDLogWarn(@"%@ Successfully sent Request Group Info message.", self.tag);
+                      }
+                      failure:^(NSError *error) {
+                          DDLogError(@"%@ Failed to send Request Group Info message with error: %@", self.tag, error);
+                      }];
+              }],
     ] mutableCopy];
     if ([thread isKindOfClass:[TSContactThread class]]) {
         TSContactThread *contactThread = (TSContactThread *)thread;

SignalServiceKit/src/Messages/TSMessagesManager.m

@@ -510,16 +510,23 @@ NS_ASSUME_NONNULL_BEGIN
     OWSAssert([NSThread isMainThread]);
 
     if (dataMessage.hasGroup) {
-        __block BOOL ignoreMessage = NO;
+        __block BOOL unknownGroup = NO;
         [self.dbConnection readWithBlock:^(YapDatabaseReadTransaction *transaction) {
             TSGroupModel *emptyModelToFillOutId =
                 [[TSGroupModel alloc] initWithTitle:nil memberIds:nil image:nil groupId:dataMessage.group.id];
             TSGroupThread *gThread = [TSGroupThread threadWithGroupModel:emptyModelToFillOutId transaction:transaction];
             if (gThread == nil && dataMessage.group.type != OWSSignalServiceProtosGroupContextTypeUpdate) {
-                ignoreMessage = YES;
+                unknownGroup = YES;
             }
         }];
-        if (ignoreMessage) {
+        if (unknownGroup) {
+            if (dataMessage.group.type == OWSSignalServiceProtosGroupContextTypeRequestInfo) {
+                DDLogInfo(@"%@ Ignoring group info request for group I don't know about from: %@",
+                    self.tag,
+                    incomingEnvelope.source);
+                return;
+            }
+
             // FIXME: https://github.com/WhisperSystems/Signal-iOS/issues/1340
             DDLogInfo(@"%@ Received message from group that I left or don't know about from: %@.",
                 self.tag,