Improve labeled hash helpers

lhash/labeledhash.go

@@ -175,16 +175,38 @@ func (lh *LabeledHash) EqualRaw(otherDigest []byte) bool {
 	return subtle.ConstantTimeCompare(lh.digest, otherDigest) == 1
 }
 
-// MatchesString returns true if the digest of the given string matches the hash.
-func (lh *LabeledHash) MatchesString(s string) bool {
-	return lh.MatchesData([]byte(s))
+// Matches returns true if the digest of the given data matches the hash.
+func (lh *LabeledHash) Matches(data []byte) bool {
+	return lh.Equal(Digest(lh.alg, data))
 }
 
 // MatchesData returns true if the digest of the given data matches the hash.
+// DEPRECATED: Use Matches instead.
 func (lh *LabeledHash) MatchesData(data []byte) bool {
-	hasher := lh.alg.new()
-	_, _ = hasher.Write(data) // never returns an error
-	defer hasher.Reset()      // internal state may leak data if kept in memory
+	return lh.Equal(Digest(lh.alg, data))
+}
+
+// MatchesString returns true if the digest of the given string matches the hash.
+func (lh *LabeledHash) MatchesString(s string) bool {
+	return lh.Matches([]byte(s))
+}
+
+// MatchesFile returns true if the digest of the given file matches the hash.
+func (lh *LabeledHash) MatchesFile(pathToFile string) (bool, error) {
+	fileHash, err := DigestFile(lh.alg, pathToFile)
+	if err != nil {
+		return false, err
+	}
+
+	return lh.Equal(fileHash), nil
+}
+
+// MatchesReader returns true if the digest of the given reader matches the hash.
+func (lh *LabeledHash) MatchesReader(reader io.Reader) (bool, error) {
+	readerHash, err := DigestFromReader(lh.alg, reader)
+	if err != nil {
+		return false, err
+	}
 
-	return subtle.ConstantTimeCompare(lh.digest, hasher.Sum(nil)) == 1
+	return lh.Equal(readerHash), nil
 }

lhash/labeledhash_test.go

@@ -42,13 +42,13 @@ func testAlgorithm(t *testing.T, alg Algorithm, emptyHex, foxHex string) {
 	}
 
 	// test matching with serialized/loaded labeled hash
-	if !lh.MatchesData(testFoxData) {
+	if !lh.Matches(testFoxData) {
 		t.Errorf("alg %d: failed to match reference", alg)
 	}
 	if !lh.MatchesString(testFox) {
 		t.Errorf("alg %d: failed to match reference", alg)
 	}
-	if lh.MatchesData(noMatchData) {
+	if lh.Matches(noMatchData) {
 		t.Errorf("alg %d: failed to non-match garbage", alg)
 	}
 	if lh.MatchesString(noMatch) {
@@ -99,13 +99,13 @@ func testFormat(t *testing.T, alg Algorithm, lhs, loaded *LabeledHash) {
 	}
 
 	// Test matching.
-	if !loaded.MatchesData(testFoxData) {
+	if !loaded.Matches(testFoxData) {
 		t.Errorf("alg %d: failed to match reference", alg)
 	}
 	if !loaded.MatchesString(testFox) {
 		t.Errorf("alg %d: failed to match reference", alg)
 	}
-	if loaded.MatchesData(noMatchData) {
+	if loaded.Matches(noMatchData) {
 		t.Errorf("alg %d: failed to non-match garbage", alg)
 	}
 	if loaded.MatchesString(noMatch) {