session-ios/SignalUtilitiesKit/OWSOutgoingNullMessage.m

108 lines
3.6 KiB
Objective-C

//
// Copyright (c) 2019 Open Whisper Systems. All rights reserved.
//
#import "OWSOutgoingNullMessage.h"
#import "OWSVerificationStateSyncMessage.h"
#import "TSContactThread.h"
#import <SessionProtocolKit/Cryptography.h>
#import <SessionProtocolKit/NSDate+OWS.h>
#import <SignalUtilitiesKit/SignalUtilitiesKit-Swift.h>
NS_ASSUME_NONNULL_BEGIN
@interface OWSOutgoingNullMessage ()
@property (nonatomic, readonly) OWSVerificationStateSyncMessage *verificationStateSyncMessage;
@end
#pragma mark -
@implementation OWSOutgoingNullMessage
- (instancetype)initWithContactThread:(TSContactThread *)contactThread
verificationStateSyncMessage:(OWSVerificationStateSyncMessage *)verificationStateSyncMessage
{
// MJK TODO - remove senderTimestamp
self = [super initOutgoingMessageWithTimestamp:[NSDate ows_millisecondTimeStamp]
inThread:contactThread
messageBody:nil
attachmentIds:[NSMutableArray new]
expiresInSeconds:0
expireStartedAt:0
isVoiceMessage:NO
groupMetaMessage:TSGroupMetaMessageUnspecified
quotedMessage:nil
contactShare:nil
linkPreview:nil];
if (!self) {
return self;
}
_verificationStateSyncMessage = verificationStateSyncMessage;
return self;
}
#pragma mark - override TSOutgoingMessage
- (nullable NSData *)buildPlainTextData:(SignalRecipient *)recipient
{
SSKProtoNullMessageBuilder *nullMessageBuilder = [SSKProtoNullMessage builder];
NSUInteger contentLength;
if (self.verificationStateSyncMessage != nil) {
contentLength = self.verificationStateSyncMessage.unpaddedVerifiedLength;
OWSAssertDebug(self.verificationStateSyncMessage.paddingBytesLength > 0);
// We add the same amount of padding in the VerificationStateSync message and it's coresponding NullMessage so that
// the sync message is indistinguishable from an outgoing Sent transcript corresponding to the NullMessage. We pad
// the NullMessage so as to obscure it's content. The sync message (like all sync messages) will be *additionally*
// padded by the superclass while being sent. The end result is we send a NullMessage of a non-distinct size, and a
// verification sync which is ~1-512 bytes larger then that.
contentLength += self.verificationStateSyncMessage.paddingBytesLength;
} else {
contentLength = arc4random_uniform(512);
}
OWSAssertDebug(contentLength > 0);
nullMessageBuilder.padding = [Cryptography generateRandomBytes:contentLength];
NSError *error;
SSKProtoNullMessage *_Nullable nullMessage = [nullMessageBuilder buildAndReturnError:&error];
if (error != nil || nullMessage == nil) {
OWSFailDebug(@"Couldn't build protobuf due to error: %@.", error);
return nil;
}
SSKProtoContentBuilder *contentBuilder = [SSKProtoContent builder];
contentBuilder.nullMessage = nullMessage;
NSData *_Nullable contentData = [contentBuilder buildSerializedDataAndReturnError:&error];
if (error != nil || contentData == nil) {
OWSFailDebug(@"Couldn't serialize protobuf due to error: %@.", error);
return nil;
}
return contentData;
}
- (uint)ttl { return (uint)[LKTTLUtilities getTTLFor:LKMessageTypeEphemeral]; }
- (BOOL)shouldSyncTranscript
{
return NO;
}
- (BOOL)shouldBeSaved
{
return NO;
}
@end
NS_ASSUME_NONNULL_END