arbo: CheckProof now returns nil or error instead of (bool, error)

Author: altergui

api/censuses.go

@@ -945,15 +945,15 @@ func (a *API) censusVerifyHandler(msg *apirest.APIdata, ctx *httprouter.HTTPCont
 		}
 	}
 
-	valid, err := ref.Tree().VerifyProof(leafKey, cdata.Value, cdata.CensusProof, cdata.CensusRoot)
-	if err != nil {
+	if err := ref.Tree().VerifyProof(leafKey, cdata.Value, cdata.CensusProof, cdata.CensusRoot); err != nil {
+		if strings.Contains(err.Error(), "calculated vs expected root mismatch") {
+			return ctx.Send(nil, apirest.HTTPstatusBadRequest)
+		}
 		return ErrCensusProofVerificationFailed.WithErr(err)
 	}
-	if !valid {
-		return ctx.Send(nil, apirest.HTTPstatusBadRequest)
-	}
+
 	response := Census{
-		Valid: valid,
+		Valid: true,
 	}
 	var data []byte
 	if data, err = json.Marshal(&response); err != nil {

censustree/censustree.go

@@ -162,12 +162,12 @@ func (t *Tree) Get(key []byte) ([]byte, error) {
 // VerifyProof verifies a census proof.
 // If the census is indexed key can be nil (value provides the key already).
 // If root is nil the last merkle root is used for verify.
-func (t *Tree) VerifyProof(key, value, proof, root []byte) (bool, error) {
+func (t *Tree) VerifyProof(key, value, proof, root []byte) error {
 	var err error
 	if root == nil {
 		root, err = t.Root()
 		if err != nil {
-			return false, fmt.Errorf("cannot get tree root: %w", err)
+			return fmt.Errorf("cannot get tree root: %w", err)
 		}
 	}
 	// If the provided key is longer than the defined maximum length truncate it
@@ -176,7 +176,10 @@ func (t *Tree) VerifyProof(key, value, proof, root []byte) (bool, error) {
 	if len(leafKey) > DefaultMaxKeyLen {
 		leafKey = leafKey[:DefaultMaxKeyLen]
 	}
-	return t.tree.VerifyProof(leafKey, value, proof, root)
+	if err := t.tree.VerifyProof(leafKey, value, proof, root); err != nil {
+		return err
+	}
+	return nil
 }
 
 // GenProof generates a census proof for the provided key.

censustree/censustree_test.go

@@ -110,9 +110,8 @@ func TestWeightedProof(t *testing.T) {
 	root, err := censusTree.Root()
 	qt.Assert(t, err, qt.IsNil)
 
-	verified, err := censusTree.VerifyProof(userKey, value, siblings, root)
+	err = censusTree.VerifyProof(userKey, value, siblings, root)
 	qt.Assert(t, err, qt.IsNil)
-	qt.Assert(t, verified, qt.IsTrue)
 }
 
 func TestGetCensusWeight(t *testing.T) {

tree/arbo/addbatch_test.go

@@ -998,27 +998,23 @@ func TestAddKeysWithEmptyValues(t *testing.T) {
 	// check with empty array
 	root, err := tree.Root()
 	c.Assert(err, qt.IsNil)
-	verif, err := CheckProof(tree.hashFunction, keys[9], []byte{}, root, siblings)
+	err = CheckProof(tree.hashFunction, keys[9], []byte{}, root, siblings)
 	c.Assert(err, qt.IsNil)
-	c.Check(verif, qt.IsTrue)
 
 	// check with array with only 1 zero
-	verif, err = CheckProof(tree.hashFunction, keys[9], []byte{0}, root, siblings)
+	err = CheckProof(tree.hashFunction, keys[9], []byte{0}, root, siblings)
 	c.Assert(err, qt.IsNil)
-	c.Check(verif, qt.IsTrue)
 
 	// check with array with 32 zeroes
 	e32 := []byte{
 		0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
 		0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
 	}
 	c.Assert(len(e32), qt.Equals, 32)
-	verif, err = CheckProof(tree.hashFunction, keys[9], e32, root, siblings)
+	err = CheckProof(tree.hashFunction, keys[9], e32, root, siblings)
 	c.Assert(err, qt.IsNil)
-	c.Check(verif, qt.IsTrue)
 
 	// check with array with value!=0 returns false at verification
-	verif, err = CheckProof(tree.hashFunction, keys[9], []byte{0, 1}, root, siblings)
-	c.Assert(err, qt.IsNil)
-	c.Check(verif, qt.IsFalse)
+	err = CheckProof(tree.hashFunction, keys[9], []byte{0, 1}, root, siblings)
+	c.Assert(err, qt.ErrorMatches, "calculated vs expected root mismatch")
 }

tree/arbo/proof.go

@@ -159,18 +159,19 @@ func bytesToBitmap(b []byte) []bool {
 
 // CheckProof verifies the given proof. The proof verification depends on the
 // HashFunction passed as parameter.
-func CheckProof(hashFunc HashFunction, k, v, root, packedSiblings []byte) (bool, error) {
+// Returns nil if the proof is valid, or an error otherwise.
+func CheckProof(hashFunc HashFunction, k, v, root, packedSiblings []byte) error {
 	siblings, err := UnpackSiblings(hashFunc, packedSiblings)
 	if err != nil {
-		return false, err
+		return err
 	}
 
 	keyPath := make([]byte, int(math.Ceil(float64(len(siblings))/float64(8))))
 	copy(keyPath, k)
 
 	key, _, err := newLeafValue(hashFunc, k, v)
 	if err != nil {
-		return false, err
+		return err
 	}
 
 	path := getPath(len(siblings), keyPath)
@@ -181,8 +182,11 @@ func CheckProof(hashFunc HashFunction, k, v, root, packedSiblings []byte) (bool,
 			key, _, err = newIntermediate(hashFunc, key, sibling)
 		}
 		if err != nil {
-			return false, err
+			return err
 		}
 	}
-	return bytes.Equal(key, root), nil
+	if !bytes.Equal(key, root) {
+		return fmt.Errorf("calculated vs expected root mismatch")
+	}
+	return nil
 }

tree/arbo/tree_test.go

@@ -539,9 +539,8 @@ func TestGenProofAndVerify(t *testing.T) {
 
 	root, err := tree.Root()
 	c.Assert(err, qt.IsNil)
-	verif, err := CheckProof(tree.hashFunction, k, v, root, siblings)
+	err = CheckProof(tree.hashFunction, k, v, root, siblings)
 	c.Assert(err, qt.IsNil)
-	c.Check(verif, qt.IsTrue)
 }
 
 func TestDumpAndImportDump(t *testing.T) {
@@ -933,16 +932,14 @@ func TestKeyLen(t *testing.T) {
 
 	root, err := tree.Root()
 	c.Assert(err, qt.IsNil)
-	verif, err := CheckProof(tree.HashFunction(), kAux, vAux, root, packedSiblings)
+	err = CheckProof(tree.HashFunction(), kAux, vAux, root, packedSiblings)
 	c.Assert(err, qt.IsNil)
-	c.Assert(verif, qt.IsTrue)
 
 	// use a similar key but with one zero, expect that CheckProof fails on
 	// the verification
 	kAux = append(kAux, 0)
-	verif, err = CheckProof(tree.HashFunction(), kAux, vAux, root, packedSiblings)
-	c.Assert(err, qt.IsNil)
-	c.Assert(verif, qt.IsFalse)
+	err = CheckProof(tree.HashFunction(), kAux, vAux, root, packedSiblings)
+	c.Assert(err, qt.ErrorMatches, "calculated vs expected root mismatch")
 }
 
 func TestKeyLenBiggerThan32(t *testing.T) {

tree/tree.go

@@ -229,13 +229,13 @@ func (t *Tree) GenProof(rTx db.Reader, key []byte) ([]byte, []byte, error) {
 
 // VerifyProof checks the proof for the given key, value and root, using the
 // passed hash function
-func VerifyProof(hashFunc arbo.HashFunction, key, value, proof, root []byte) (bool, error) {
+func VerifyProof(hashFunc arbo.HashFunction, key, value, proof, root []byte) error {
 	return arbo.CheckProof(hashFunc, key, value, root, proof)
 }
 
 // VerifyProof checks the proof for the given key, value and root, using the
 // hash function of the Tree
-func (t *Tree) VerifyProof(key, value, proof, root []byte) (bool, error) {
+func (t *Tree) VerifyProof(key, value, proof, root []byte) error {
 	return VerifyProof(t.tree.HashFunction(), key, value, proof, root)
 }
 

tree/tree_test.go

@@ -84,9 +84,8 @@ func TestGenProof(t *testing.T) {
 	root, err := tree.Root(wTx)
 	qt.Assert(t, err, qt.IsNil)
 
-	verif, err := tree.VerifyProof(k, v, proof, root)
+	err = tree.VerifyProof(k, v, proof, root)
 	qt.Assert(t, err, qt.IsNil)
-	qt.Assert(t, verif, qt.IsTrue)
 
 	err = wTx.Commit()
 	qt.Assert(t, err, qt.IsNil)

vochain/transaction/proofs/arboproof/arboproof.go

@@ -52,8 +52,8 @@ func (*ProofVerifierArbo) Verify(process *models.Process, envelope *models.VoteE
 				key = key[:censustree.DefaultMaxKeyLen]
 			}
 		}
-		valid, err := tree.VerifyProof(hashFunc, key, p.AvailableWeight, p.Siblings, process.CensusRoot)
-		if !valid || err != nil {
+
+		if err := tree.VerifyProof(hashFunc, key, p.AvailableWeight, p.Siblings, process.CensusRoot); err != nil {
 			return false, nil, err
 		}
 		// Legacy: support p.LeafWeight == nil, assume then value=1

vochain/vote_test.go

@@ -46,9 +46,8 @@ func testCreateKeysAndBuildWeightedZkCensus(t *testing.T, size int, weight *big.
 		_, proof, err := tr.GenProof(k.Address().Bytes())
 		qt.Check(t, err, qt.IsNil)
 		proofs = append(proofs, proof)
-		valid, err := tr.VerifyProof(k.Address().Bytes(), encWeight, proof, root)
+		err = tr.VerifyProof(k.Address().Bytes(), encWeight, proof, root)
 		qt.Check(t, err, qt.IsNil)
-		qt.Check(t, valid, qt.IsTrue)
 	}
 	return keys, root, proofs
 }