session-ios/SignalServiceKit/src/Messages/OWSOutgoingNullMessage.m

97 lines
3.2 KiB
Objective-C

//
// Copyright (c) 2018 Open Whisper Systems. All rights reserved.
//
#import "OWSOutgoingNullMessage.h"
#import "OWSVerificationStateSyncMessage.h"
#import "TSContactThread.h"
#import <SignalCoreKit/Cryptography.h>
#import <SignalCoreKit/NSDate+OWS.h>
#import <SignalServiceKit/SignalServiceKit-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
{
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];
if (!self) {
return self;
}
_verificationStateSyncMessage = verificationStateSyncMessage;
return self;
}
#pragma mark - override TSOutgoingMessage
- (nullable NSData *)buildPlainTextData:(SignalRecipient *)recipient
{
SSKProtoNullMessageBuilder *nullMessageBuilder = [SSKProtoNullMessage builder];
NSUInteger 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;
OWSAssertDebug(contentLength > 0);
nullMessageBuilder.padding = [Cryptography generateRandomBytes:contentLength];
NSError *error;
SSKProtoNullMessage *_Nullable nullMessage = [nullMessageBuilder buildAndReturnError:&error];
if (error || !nullMessage) {
OWSFailDebug(@"could not build protobuf: %@", error);
return nil;
}
SSKProtoContentBuilder *contentBuilder = [SSKProtoContent builder];
contentBuilder.nullMessage = nullMessage;
NSData *_Nullable contentData = [contentBuilder buildSerializedDataAndReturnError:&error];
if (error || !contentData) {
OWSFailDebug(@"could not serialize protobuf: %@", error);
return nil;
}
return contentData;
}
- (BOOL)shouldSyncTranscript
{
return NO;
}
- (BOOL)shouldBeSaved
{
return NO;
}
@end
NS_ASSUME_NONNULL_END