add rsa_padding_supported interface to RSABackend and OpenSSL backend
diff --git a/docs/hazmat/backends/interfaces.rst b/docs/hazmat/backends/interfaces.rst
index ff389cb..e98b9a5 100644
--- a/docs/hazmat/backends/interfaces.rst
+++ b/docs/hazmat/backends/interfaces.rst
@@ -263,6 +263,17 @@
:returns: ``True`` if the specified ``algorithm`` is supported by this
backend, otherwise ``False``.
+ .. method:: rsa_padding_supported(padding)
+
+ Check if the specified ``padding`` is supported by the backend.
+
+ :param padding: An instance of an
+ :class:`~cryptography.hazmat.primitives.interfaces.AsymmetricPadding`
+ provider.
+
+ :returns: ``True`` if the specified ``padding`` is supported by this
+ backend, otherwise ``False``.
+
.. method:: decrypt_rsa(private_key, ciphertext, padding)
:param private_key: An instance of an