fix padding calculation

// FREEBIE

src/Devices/OWSVerificationStateSyncMessage.h

@@ -17,6 +17,7 @@ NS_ASSUME_NONNULL_BEGIN
 @property (nonatomic, readonly) NSString *verificationForRecipientId;
 
 @property (nonatomic, readonly) size_t paddingBytesLength;
+@property (nonatomic, readonly) size_t unpaddedVerifiedLength;
 
 @end
 

src/Devices/OWSVerificationStateSyncMessage.m

@@ -26,9 +26,9 @@ NS_ASSUME_NONNULL_BEGIN
                               identityKey:(NSData *)identityKey
                verificationForRecipientId:(NSString *)verificationForRecipientId
 {
-
     OWSAssert(identityKey.length == kIdentityKeyLength);
     OWSAssert(verificationForRecipientId.length > 0);
+
     // we only sync user's marking as un/verified. Never sync the conflicted state, the sibling device
     // will figure that out on it's own.
     OWSAssert(verificationState != OWSVerificationStateNoLongerVerified);
@@ -51,6 +51,13 @@ NS_ASSUME_NONNULL_BEGIN
 
 - (OWSSignalServiceProtosSyncMessageBuilder *)syncMessageBuilder
 {
+    OWSAssert(self.identityKey.length == kIdentityKeyLength);
+    OWSAssert(self.verificationForRecipientId.length > 0);
+
+    // we only sync user's marking as un/verified. Never sync the conflicted state, the sibling device
+    // will figure that out on it's own.
+    OWSAssert(self.verificationState != OWSVerificationStateNoLongerVerified);
+
     OWSSignalServiceProtosSyncMessageBuilder *syncMessageBuilder = [OWSSignalServiceProtosSyncMessageBuilder new];
 
     OWSSignalServiceProtosVerifiedBuilder *verifiedBuilder = [OWSSignalServiceProtosVerifiedBuilder new];
@@ -66,6 +73,23 @@ NS_ASSUME_NONNULL_BEGIN
     return syncMessageBuilder;
 }
 
+- (size_t)unpaddedVerifiedLength
+{
+    OWSAssert(self.identityKey.length == kIdentityKeyLength);
+    OWSAssert(self.verificationForRecipientId.length > 0);
+
+    // we only sync user's marking as un/verified. Never sync the conflicted state, the sibling device
+    // will figure that out on it's own.
+    OWSAssert(self.verificationState != OWSVerificationStateNoLongerVerified);
+
+    OWSSignalServiceProtosVerifiedBuilder *verifiedBuilder = [OWSSignalServiceProtosVerifiedBuilder new];
+    verifiedBuilder.destination = self.verificationForRecipientId;
+    verifiedBuilder.identityKey = self.identityKey;
+    verifiedBuilder.state = OWSVerificationStateToProtoState(self.verificationState);
+
+    return [verifiedBuilder build].data.length;
+}
+
 @end
 
 NS_ASSUME_NONNULL_END

src/Messages/OWSOutgoingNullMessage.m

@@ -40,9 +40,11 @@ NS_ASSUME_NONNULL_BEGIN
     OWSSignalServiceProtosContentBuilder *contentBuilder = [OWSSignalServiceProtosContentBuilder new];
     OWSSignalServiceProtosNullMessageBuilder *nullMessageBuilder = [OWSSignalServiceProtosNullMessageBuilder new];
 
-    NSUInteger contentLength = self.verificationStateSyncMessage.buildPlainTextData.length;
-    contentLength -= self.verificationStateSyncMessage.paddingBytesLength;
-    
+    NSUInteger contentLength = self.verificationStateSyncMessage.unpaddedVerifiedLength;
+
+    OWSAssert(self.verificationStateSyncMessage.paddingBytesLength > 0);
+    contentLength += self.verificationStateSyncMessage.paddingBytesLength;
+
     OWSAssert(contentLength > 0)
     
     nullMessageBuilder.padding = [Cryptography generateRandomBytes:contentLength];