hash: implement Clone() and speed up NewShaX

Author: gdams

xcrypto/hash.go

@@ -92,6 +92,20 @@ func SHA512(p []byte) (sum [64]byte) {
 	return
 }
 
+// cloneHash is an interface that defines a Clone method.
+//
+// hash.CloneHash will probably be added in Go 1.25, see https://golang.org/issue/69521,
+// but we need it now.
+type cloneHash interface {
+	hash.Hash
+	// Clone returns a separate Hash instance with the same state as h.
+	Clone() hash.Hash
+}
+
+var _ hash.Hash = (*evpHash)(nil)
+var _ cloneHash = (*evpHash)(nil)
+
+// evpHash implements generic hash methods.
 type evpHash struct {
 	ctx unsafe.Pointer
 	// ctx2 is used in evpHash.sum to avoid changing
@@ -107,12 +121,7 @@ type evpHash struct {
 }
 
 func newEvpHash(init func(ctx unsafe.Pointer) C.int, update func(ctx unsafe.Pointer, data []byte) C.int, final func(ctx unsafe.Pointer, digest []byte) C.int, ctxSize, blockSize, size int) *evpHash {
-	ctx := C.malloc(C.size_t(ctxSize))
-	ctx2 := C.malloc(C.size_t(ctxSize))
-	init(ctx)
 	h := &evpHash{
-		ctx:       ctx,
-		ctx2:      ctx2,
 		init:      init,
 		update:    update,
 		final:     final,
@@ -125,8 +134,24 @@ func newEvpHash(init func(ctx unsafe.Pointer) C.int, update func(ctx unsafe.Poin
 }
 
 func (h *evpHash) finalize() {
-	C.free(h.ctx)
-	C.free(h.ctx2)
+	if h.ctx != nil {
+		C.free(h.ctx)
+	}
+	if h.ctx2 != nil {
+		C.free(h.ctx2)
+	}
+}
+
+func (h *evpHash) initialize() {
+	if h.ctx == nil {
+		h.ctx = C.malloc(C.size_t(h.ctxSize))
+		h.ctx2 = C.malloc(C.size_t(h.ctxSize))
+		if h.init(h.ctx) != 1 {
+			C.free(h.ctx)
+			C.free(h.ctx2)
+			panic("commoncrypto: initialization failed")
+		}
+	}
 }
 
 func (h *evpHash) Reset() {
@@ -137,6 +162,7 @@ func (h *evpHash) Reset() {
 }
 
 func (h *evpHash) Write(p []byte) (int, error) {
+	h.initialize()
 	if len(p) > 0 {
 		// Use a local variable to prevent the compiler from misinterpreting the pointer
 		data := p
@@ -149,6 +175,7 @@ func (h *evpHash) Write(p []byte) (int, error) {
 }
 
 func (h *evpHash) WriteString(s string) (int, error) {
+	h.initialize()
 	if len(s) > 0 {
 		data := []byte(s)
 		if h.update(h.ctx, data) != 1 {
@@ -160,6 +187,7 @@ func (h *evpHash) WriteString(s string) (int, error) {
 }
 
 func (h *evpHash) WriteByte(c byte) error {
+	h.initialize()
 	if h.update(h.ctx, []byte{c}) != 1 {
 		return errors.New("commoncrypto: Update function failed")
 	}
@@ -175,12 +203,35 @@ func (h *evpHash) BlockSize() int {
 }
 
 func (h *evpHash) Sum(b []byte) []byte {
+	h.initialize()
 	digest := make([]byte, h.size)
 	C.memcpy(h.ctx2, h.ctx, C.size_t(h.ctxSize))
 	h.final(h.ctx2, digest)
 	return append(b, digest...)
 }
 
+// Clone returns a new evpHash object that is a deep clone of itself.
+// The duplicate object contains all state and data contained in the
+// original object at the point of duplication.
+func (h *evpHash) Clone() hash.Hash {
+	h.initialize()
+	cloned := &evpHash{
+		init:      h.init,
+		update:    h.update,
+		final:     h.final,
+		blockSize: h.blockSize,
+		size:      h.size,
+		ctxSize:   h.ctxSize,
+	}
+	cloned.ctx = C.malloc(C.size_t(h.ctxSize))
+	cloned.ctx2 = C.malloc(C.size_t(h.ctxSize))
+	C.memcpy(cloned.ctx, h.ctx, C.size_t(h.ctxSize))
+	C.memcpy(cloned.ctx2, h.ctx2, C.size_t(h.ctxSize))
+	runtime.SetFinalizer(cloned, (*evpHash).finalize)
+	runtime.KeepAlive(h)
+	return cloned
+}
+
 type md4Hash struct {
 	*evpHash
 }

xcrypto/hash_test.go

@@ -199,19 +199,13 @@ func TestHash_Clone(t *testing.T) {
 				t.Skip("not supported")
 			}
 			h := cryptoToHash(ch)()
-			if _, ok := h.(encoding.BinaryMarshaler); !ok {
-				t.Skip("not supported")
-			}
 			_, err := h.Write(msg)
 			if err != nil {
 				t.Fatal(err)
 			}
 			// We don't define an interface for the Clone method to avoid other
 			// packages from depending on it. Use type assertion to call it.
-			h2, err := h.(interface{ Clone() (hash.Hash, error) }).Clone()
-			if err != nil {
-				t.Fatal(err)
-			}
+			h2 := h.(interface{ Clone() hash.Hash }).Clone()
 			h.Write(msg)
 			h2.Write(msg)
 			if actual, actual2 := h.Sum(nil), h2.Sum(nil); !bytes.Equal(actual, actual2) {
@@ -494,6 +488,13 @@ func BenchmarkSHA256(b *testing.B) {
 	}
 }
 
+func BenchmarkNewSHA256(b *testing.B) {
+	b.ReportAllocs()
+	for i := 0; i < b.N; i++ {
+		xcrypto.NewSHA256()
+	}
+}
+
 // stubHash is a hash.Hash implementation that does nothing.
 type stubHash struct{}