blockchain: refactor verification out of process udata

Take out verification from process udata as we were performing
verification and modification in the same function. Separating these out
make it possible to keep the utreexo state in case signature
verification fails.

blockchain/chain.go

@@ -1068,9 +1068,16 @@ func (b *BlockChain) reorganizeChain(detachNodes, attachNodes *list.List) error
 				return err
 			}
 		} else {
-			// Check that the block txOuts are valid by checking the utreexo proof and
-			// extra data and then update the accumulator.
-			err := b.utreexoView.ProcessUData(block, b.bestChain, block.MsgBlock().UData)
+			err := b.utreexoView.VerifyUData(block, b.bestChain, block.MsgBlock().UData)
+			if err != nil {
+				return fmt.Errorf("reorganizeChain fail while attaching "+
+					"block %s. Error: %v", block.Hash().String(), err)
+			}
+			err = b.utreexoView.ProcessUData(block, b.bestChain, block.MsgBlock().UData)
+			if err != nil {
+				return fmt.Errorf("reorganizeChain fail while attaching "+
+					"block %s. Error: %v", block.Hash().String(), err)
+			}
 			if err != nil {
 				return fmt.Errorf("reorganizeChain fail while attaching "+
 					"block %s. Error: %v", block.Hash().String(), err)
@@ -1329,7 +1336,14 @@ func (b *BlockChain) verifyReorganizationValidity(detachNodes, attachNodes *list
 			} else {
 				// Check that the block txOuts are valid by checking the utreexo proof and
 				// extra data and then update the accumulator.
-				err := utreexoView.ProcessUData(block, b.bestChain, block.MsgBlock().UData)
+				err := utreexoView.VerifyUData(block, b.bestChain, block.MsgBlock().UData)
+				if err != nil {
+					return nil, nil, nil,
+						fmt.Errorf("verifyReorganizationValidity fail "+
+							"while attaching block %s. Error %v",
+							block.Hash().String(), err)
+				}
+				err = utreexoView.ProcessUData(block, b.bestChain, block.MsgBlock().UData)
 				if err != nil {
 					return nil, nil, nil,
 						fmt.Errorf("verifyReorganizationValidity fail "+
@@ -1369,6 +1383,15 @@ func (b *BlockChain) verifyReorganizationValidity(detachNodes, attachNodes *list
 			}
 			return nil, nil, nil, err
 		}
+		if utreexoView != nil {
+			err = utreexoView.ProcessUData(block, b.bestChain, block.MsgBlock().UData)
+			if err != nil {
+				return nil, nil, nil,
+					fmt.Errorf("verifyReorganizationValidity fail "+
+						"while attaching block %s. Error %v",
+						block.Hash().String(), err)
+			}
+		}
 		b.index.SetStatusFlags(n, statusValid)
 	}
 
@@ -1445,16 +1468,22 @@ func (b *BlockChain) connectBestChain(node *blockNode, block *btcutil.Block, fla
 		if b.utreexoView != nil {
 			if fastAdd {
 				// Check that the block txOuts are valid by checking the utreexo proof and
-				// extra data and then update the accumulator.
-				err := b.utreexoView.ProcessUData(block, b.bestChain, block.MsgBlock().UData)
+				// the leaf data.
+				err := b.utreexoView.VerifyUData(block, b.bestChain, block.MsgBlock().UData)
 				if err != nil {
 					return false, fmt.Errorf("connectBestChain fail on block %s. "+
 						"Error: %v", block.Hash().String(), err)
 				}
 			}
+			// Update the accumulator.
+			err := b.utreexoView.ProcessUData(block, b.bestChain, block.MsgBlock().UData)
+			if err != nil {
+				return false, fmt.Errorf("connectBestChain fail on block %s. "+
+					"Error: %v", block.Hash().String(), err)
+			}
 			view := NewUtxoViewpoint()
 			view.SetBestHash(parentHash)
-			err := view.BlockToUtxoView(block)
+			err = view.BlockToUtxoView(block)
 			if err != nil {
 				return false, err
 			}

blockchain/utreexoviewpoint.go

@@ -46,8 +46,7 @@ func (uview *UtreexoViewpoint) CopyWithRoots() *UtreexoViewpoint {
 	return newUview
 }
 
-// ProcessUData checks that the accumulator proof and the utxo data included in the UData
-// passes consensus and then it updates the underlying accumulator.
+// ProcessUData updates the underlying accumulator. It does NOT check if the verification passes.
 func (uview *UtreexoViewpoint) ProcessUData(block *btcutil.Block,
 	bestChain *chainView, ud *wire.UData) error {
 
@@ -57,6 +56,32 @@ func (uview *UtreexoViewpoint) ProcessUData(block *btcutil.Block,
 	if err != nil {
 		return err
 	}
+
+	dels, err := ExtractAccumulatorDels(block, bestChain, ud.RememberIdx)
+	if err != nil {
+		return err
+	}
+
+	// Update the underlying accumulator.
+	updateData, err := uview.Modify(ud, adds, dels)
+	if err != nil {
+		return fmt.Errorf("ProcessUData fail. Error: %v", err)
+	}
+
+	// Add the utreexo data to the block.
+	block.SetUtreexoUpdateData(updateData)
+	block.SetUtreexoAdds(adds)
+
+	return nil
+}
+
+// VerifyUData checks the accumulator proof to ensure that the leaf preimages exist in the
+// accumulator.
+func (uview *UtreexoViewpoint) VerifyUData(block *btcutil.Block,
+	bestChain *chainView, ud *wire.UData) error {
+
+	// Extracts the block into additions and deletions that will be processed.
+	// Adds correspond to newly created UTXOs and dels correspond to STXOs.
 	dels, err := ExtractAccumulatorDels(block, bestChain, ud.RememberIdx)
 	if err != nil {
 		return err
@@ -84,17 +109,13 @@ func (uview *UtreexoViewpoint) ProcessUData(block *btcutil.Block,
 		}
 	}
 
-	// Update the underlying accumulator.
-	updateData, err := uview.Modify(ud, adds, dels)
-	if err != nil {
-		return fmt.Errorf("ProcessUData fail. Error: %v", err)
+	// TODO we should be verifying here but aren't as the accumulator.Verify
+	// function expects a complete proof.
+	if uview.proofInterval != 1 {
+		return nil
 	}
 
-	// Add the utreexo data to the block.
-	block.SetUtreexoUpdateData(updateData)
-	block.SetUtreexoAdds(adds)
-
-	return nil
+	return uview.accumulator.Verify(dels, ud.AccProof, false)
 }
 
 // AddProof first checks that the utreexo proofs are valid. If it is valid,
@@ -124,7 +145,7 @@ func (uview *UtreexoViewpoint) Modify(ud *wire.UData,
 	var err error
 	var updateData utreexo.UpdateData
 	if uview.proofInterval == 1 {
-		err = uview.accumulator.Verify(dels, ud.AccProof, true)
+		err = uview.accumulator.Ingest(dels, ud.AccProof)
 		if err != nil {
 			return nil, err
 		}

blockchain/validate.go

@@ -1075,7 +1075,7 @@ func (b *BlockChain) checkConnectBlock(node *blockNode, block *btcutil.Block,
 	// If utreexo accumulators are enabled, then check that the accumulator
 	// proof is ok.  Then convert the msgBlock.UData into UtxoViewpoint.
 	if utreexoView != nil {
-		err := utreexoView.ProcessUData(block, b.bestChain, block.MsgBlock().UData)
+		err := utreexoView.VerifyUData(block, b.bestChain, block.MsgBlock().UData)
 		if err != nil {
 			return fmt.Errorf("checkConnectBlock fail. error: %v", err)
 		}