Add a test for private key size zero

Author: xin-tsla

src/crypto/rsa/pkcs1v15_test.go

@@ -213,6 +213,19 @@ func TestSignPKCS1v15(t *testing.T) {
 }
 }
 
+func TestSignPKCS1v15WithPrivateKeySizeZero(t *testing.T) {
+h := sha1.New()
+h.Write([]byte("key"))
+digest := h.Sum(nil)
+_, err := SignPKCS1v15(nil, &PrivateKey{}, crypto.SHA1, digest)
+if err == nil {
+t.Error("expected error but got nil")
+}
+if err != nil && err.Error() != "crypto/rsa: private key size zero" {
+t.Errorf("unexpected error: %v", err)
+}
+}
+
 func TestVerifyPKCS1v15(t *testing.T) {
 for i, test := range signPKCS1v15Tests {
 h := sha1.New()