R4R: Fix merkle proof verification (#122)

* Fix merkle proof verification

* existence iavl proof and iavl absence proof

* make lcd test with proof verification

client/context/context.go

@@ -26,7 +26,8 @@ import (
 const ctxAccStoreName = "acc"
 
 var (
-	verifier tmlite.Verifier
+	verifier     tmlite.Verifier
+	verifierHome string
 )
 
 // CLIContext implements a typical CLI context created in SDK modules for
@@ -46,6 +47,7 @@ type CLIContext struct {
 	JSON          bool
 	PrintResponse bool
 	Verifier      tmlite.Verifier
+	VerifierHome  string
 	DryRun        bool
 	GenerateOnly  bool
 	fromAddress   types.AccAddress
@@ -67,8 +69,9 @@ func NewCLIContext() CLIContext {
 	fromAddress, fromName := fromFields(from)
 
 	// We need to use a single verifier for all contexts
-	if verifier == nil {
+	if verifier == nil || verifierHome != viper.GetString(cli.HomeFlag) {
 		verifier = createVerifier()
+		verifierHome = viper.GetString(cli.HomeFlag)
 	}
 
 	return CLIContext{

client/context/query.go

@@ -220,9 +220,17 @@ func (ctx CLIContext) verifyProof(queryPath string, resp abci.ResponseQuery) err
 	kp = kp.AppendKey([]byte(storeName), merkle.KeyEncodingURL)
 	kp = kp.AppendKey(resp.Key, merkle.KeyEncodingURL)
 
+	if resp.Value == nil {
+		err = prt.VerifyAbsence(resp.Proof, commit.Header.AppHash, kp.String())
+		if err != nil {
+			return errors.Wrap(err, "failed to prove merkle absence proof")
+		}
+		return nil
+	}
+
 	err = prt.VerifyValue(resp.Proof, commit.Header.AppHash, kp.String(), resp.Value)
 	if err != nil {
-		return errors.Wrap(err, "failed to prove merkle proof")
+		return errors.Wrap(err, "failed to prove merkle existence proof")
 	}
 
 	return nil

client/lcd/test_helpers.go

@@ -264,8 +264,7 @@ func InitializeTestLCD(
 	// XXX: Need to set this so LCD knows the tendermint node address!
 	viper.Set(client.FlagNode, config.RPC.ListenAddress)
 	viper.Set(client.FlagChainID, genDoc.ChainID)
-	// TODO Set to false once the upstream Tendermint proof verification issue is fixed.
-	viper.Set(client.FlagTrustNode, true)
+	viper.Set(client.FlagTrustNode, false)
 	dir, err := ioutil.TempDir("", "lcd_test")
 	require.NoError(t, err)
 	viper.Set(cli.HomeFlag, dir)

store/iavlstore.go

@@ -204,8 +204,21 @@ func (st *IavlStore) Query(req abci.RequestQuery) (res abci.ResponseQuery) {
 				res.Log = err.Error()
 				break
 			}
-			res.Value = value
-			res.Proof = &merkle.Proof{Ops: []merkle.ProofOp{iavl.NewIAVLValueOp(key, proof).ProofOp()}}
+			if proof == nil {
+				// Proof == nil implies that the store is empty.
+				if value != nil {
+					panic("unexpected value for an empty proof")
+				}
+			}
+			if value != nil {
+				// value was found
+				res.Value = value
+				res.Proof = &merkle.Proof{Ops: []merkle.ProofOp{iavl.NewIAVLValueOp(key, proof).ProofOp()}}
+			} else {
+				// value wasn't found
+				res.Value = nil
+				res.Proof = &merkle.Proof{Ops: []merkle.ProofOp{iavl.NewIAVLAbsenceOp(key, proof).ProofOp()}}
+			}
 		} else {
 			_, res.Value = tree.GetVersioned(key, res.Height)
 		}