Merge pull request #22 from lazyledger/hlib/digest-validation

Remove panic from IntervalDigestFromBytes

namespace/digest.go

@@ -11,16 +11,17 @@ type IntervalDigest struct {
 // IntervalDigestFromBytes is the inverse function to IntervalDigest.Bytes().
 // In other words, it assumes that the passed in digestBytes are of the form
 // d.Min() || d.Max() || d.Hash() for an IntervalDigest d.
-func IntervalDigestFromBytes(nIDLen IDSize, digestBytes []byte) IntervalDigest {
+func IntervalDigestFromBytes(nIDLen IDSize, digestBytes []byte) (IntervalDigest, error) {
 	if len(digestBytes) < int(2*nIDLen) {
-		panic(fmt.Sprintf("invalid digest: %x, expected length >= %v, got: %v",
-			digestBytes, 2*nIDLen, len(digestBytes)))
+		return IntervalDigest{}, fmt.Errorf("invalid digest: %x, expected length >= %v, got: %v",
+			digestBytes, 2*nIDLen, len(digestBytes))
 	}
+
 	return IntervalDigest{
 		min:    digestBytes[:nIDLen],
 		max:    digestBytes[nIDLen : 2*nIDLen],
 		digest: digestBytes[2*nIDLen:],
-	}
+	}, nil
 }
 
 func (d IntervalDigest) Min() ID {

namespace/digest_test.go

@@ -17,10 +17,10 @@ func TestIntervalDigestFromBytesPanic(t *testing.T) {
 	for _, tt := range tests {
 		t.Run(tt.name, func(t *testing.T) {
 			func() {
-				//nolint:errcheck
-				defer func() { recover() }()
-				IntervalDigestFromBytes(tt.nIDLen, tt.digestBytes)
-				t.Errorf("should have panicked")
+				_, err := IntervalDigestFromBytes(tt.nIDLen, tt.digestBytes)
+				if err == nil {
+					t.Errorf("should have errored")
+				}
 			}()
 		})
 	}

nmt.go

@@ -262,7 +262,7 @@ func (n *NamespacedMerkleTree) Push(id namespace.ID, data []byte) error {
 // Return the namespaced Merkle Tree's root together with the
 // min. and max. namespace ID.
 func (n *NamespacedMerkleTree) Root() namespace.IntervalDigest {
-	return namespace.IntervalDigestFromBytes(n.NamespaceSize(), n.computeRoot(0, len(n.leaves)))
+	return mustIntervalDigestFromBytes(n.NamespaceSize(), n.computeRoot(0, len(n.leaves)))
 }
 
 func (n NamespacedMerkleTree) computeRoot(start, end int) []byte {

proof.go

@@ -183,15 +183,15 @@ func (proof Proof) verifyLeafHashes(nth *Hasher, verifyCompleteness bool, nID na
 	if verifyCompleteness {
 		// leftSubtrees contains the subtree roots upto [0, r.Start)
 		for _, subtree := range leftSubtrees {
-			leftSubTreeMax := namespace.IntervalDigestFromBytes(nth.NamespaceSize(), subtree).Max()
+			leftSubTreeMax := mustIntervalDigestFromBytes(nth.NamespaceSize(), subtree).Max()
 			if nID.LessOrEqual(leftSubTreeMax) {
 				return false
 			}
 		}
 		// rightSubtrees only contains the subtrees after [0, r.Start)
 		rightSubtrees := proof.nodes
 		for _, subtree := range rightSubtrees {
-			rightSubTreeMin := namespace.IntervalDigestFromBytes(nth.NamespaceSize(), subtree).Min()
+			rightSubTreeMin := mustIntervalDigestFromBytes(nth.NamespaceSize(), subtree).Min()
 			if rightSubTreeMin.LessOrEqual(nID) {
 				return false
 			}
@@ -220,3 +220,13 @@ func nextSubtreeSize(start, end uint64) int {
 	}
 	return 1 << uint(ideal)
 }
+
+// mustIntervalDigestFromBytes optimistially converts bytes to IntervalDigest or panics
+func mustIntervalDigestFromBytes(idlen namespace.IDSize, bytes []byte) namespace.IntervalDigest {
+	id, err := namespace.IntervalDigestFromBytes(idlen, bytes)
+	if err != nil {
+		panic(err)
+	}
+
+	return id
+}