implement Clone for SHA[256,384,512]

(cherry picked from commit 0b09d53)

hash.go

@@ -231,6 +231,34 @@ func (h *evpHash) sum(out []byte) {
 	runtime.KeepAlive(h)
 }
 
+// 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() (*evpHash, error) {
+	ctx := C.go_openssl_EVP_MD_CTX_new()
+	if ctx == nil {
+		return nil, newOpenSSLError("EVP_MD_CTX_new")
+	}
+	if C.go_openssl_EVP_MD_CTX_copy_ex(ctx, h.ctx) != 1 {
+		C.go_openssl_EVP_MD_CTX_free(ctx)
+		return nil, newOpenSSLError("EVP_MD_CTX_copy_ex")
+	}
+	ctx2 := C.go_openssl_EVP_MD_CTX_new()
+	if ctx2 == nil {
+		C.go_openssl_EVP_MD_CTX_free(ctx)
+		return nil, newOpenSSLError("EVP_MD_CTX_new")
+	}
+	cloned := &evpHash{
+		ctx:          ctx,
+		ctx2:         ctx2,
+		size:         h.size,
+		blockSize:    h.blockSize,
+		marshallable: h.marshallable,
+	}
+	runtime.SetFinalizer(cloned, (*evpHash).finalize)
+	return cloned, nil
+}
+
 var testNotMarshalable bool // Used in tests.
 
 // hashState returns a pointer to the internal hash structure.
@@ -576,6 +604,17 @@ func (h *sha256Hash) UnmarshalBinary(b []byte) error {
 	return nil
 }
 
+// Clone returns a new [hash.Hash] 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 *sha256Hash) Clone() (hash.Hash, error) {
+	c, err := h.clone()
+	if err != nil {
+		return nil, err
+	}
+	return &sha256Hash{evpHash: c}, nil
+}
+
 // NewSHA384 returns a new SHA384 hash.
 func NewSHA384() hash.Hash {
 	return &sha384Hash{
@@ -588,6 +627,17 @@ type sha384Hash struct {
 	out [384 / 8]byte
 }
 
+// Clone returns a new [hash.Hash] 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 *sha384Hash) Clone() (hash.Hash, error) {
+	c, err := h.clone()
+	if err != nil {
+		return nil, err
+	}
+	return &sha384Hash{evpHash: c}, nil
+}
+
 func (h *sha384Hash) Sum(in []byte) []byte {
 	h.sum(h.out[:])
 	return append(in, h.out[:]...)
@@ -731,6 +781,17 @@ func (h *sha512Hash) UnmarshalBinary(b []byte) error {
 	return nil
 }
 
+// Clone returns a new [hash.Hash] 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 *sha512Hash) Clone() (hash.Hash, error) {
+	c, err := h.clone()
+	if err != nil {
+		return nil, err
+	}
+	return &sha512Hash{evpHash: c}, nil
+}
+
 // NewSHA3_224 returns a new SHA3-224 hash.
 func NewSHA3_224() hash.Hash {
 	return &sha3_224Hash{

hash_test.go

@@ -60,6 +60,38 @@ func TestHashNotMarshalable(t *testing.T) {
 	}
 }
 
+func TestHash_Clone(t *testing.T) {
+	msg := []byte("testing")
+	for _, ch := range []crypto.Hash{crypto.SHA256, crypto.SHA384, crypto.SHA512} {
+		ch := ch
+		t.Run(ch.String(), func(t *testing.T) {
+			t.Parallel()
+			if !openssl.SupportsHash(ch) {
+				t.Skip("skipping: not supported")
+			}
+			h := cryptoToHash(ch)()
+			if _, ok := h.(encoding.BinaryMarshaler); !ok {
+				t.Skip("skipping: 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)
+			}
+			h.Write(msg)
+			h2.Write(msg)
+			if actual, actual2 := h.Sum(nil), h2.Sum(nil); !bytes.Equal(actual, actual2) {
+				t.Errorf("%s(%q) = 0x%x != cloned 0x%x", ch.String(), msg, actual, actual2)
+			}
+		})
+	}
+}
+
 func TestHash(t *testing.T) {
 	msg := []byte("testing")
 	var tests = []struct {

shims.h

@@ -198,6 +198,7 @@ DEFINEFUNC(int, RAND_bytes, (unsigned char *arg0, int arg1), (arg0, arg1)) \
 DEFINEFUNC_RENAMED_1_1(GO_EVP_MD_CTX_PTR, EVP_MD_CTX_new, EVP_MD_CTX_create, (void), ()) \
 DEFINEFUNC_RENAMED_1_1(void, EVP_MD_CTX_free, EVP_MD_CTX_destroy, (GO_EVP_MD_CTX_PTR ctx), (ctx)) \
 DEFINEFUNC(int, EVP_MD_CTX_copy, (GO_EVP_MD_CTX_PTR out, const GO_EVP_MD_CTX_PTR in), (out, in)) \
+DEFINEFUNC(int, EVP_MD_CTX_copy_ex, (GO_EVP_MD_CTX_PTR out, const GO_EVP_MD_CTX_PTR in), (out, in)) \
 DEFINEFUNC(int, EVP_Digest, (const void *data, size_t count, unsigned char *md, unsigned int *size, const GO_EVP_MD_PTR type, GO_ENGINE_PTR impl), (data, count, md, size, type, impl)) \
 DEFINEFUNC(int, EVP_DigestInit_ex, (GO_EVP_MD_CTX_PTR ctx, const GO_EVP_MD_PTR type, GO_ENGINE_PTR impl), (ctx, type, impl)) \
 DEFINEFUNC(int, EVP_DigestInit, (GO_EVP_MD_CTX_PTR ctx, const GO_EVP_MD_PTR type), (ctx, type)) \