add support for Certificate signature and tbs_certificate
diff --git a/docs/x509/reference.rst b/docs/x509/reference.rst
index f056a72..bac48ab 100644
--- a/docs/x509/reference.rst
+++ b/docs/x509/reference.rst
@@ -382,6 +382,26 @@
<Extension(oid=<ObjectIdentifier(oid=2.5.29.32, name=certificatePolicies)>, critical=False, value=<CertificatePolicies([<PolicyInformation(policy_identifier=<ObjectIdentifier(oid=2.16.840.1.101.3.2.1.48.1, name=Unknown OID)>, policy_qualifiers=None)>])>)>
<Extension(oid=<ObjectIdentifier(oid=2.5.29.19, name=basicConstraints)>, critical=True, value=<BasicConstraints(ca=True, path_length=None)>)>
+ .. attribute:: signature
+
+ .. versionadded:: 1.2
+
+ :type: bytes
+
+ The bytes of the certificate's signature.
+
+ .. attribute:: tbs_certificate
+
+ .. versionadded:: 1.2
+
+ :type: bytes
+
+ The DER encoded bytes payload (as defined by :rfc:`5280`) that is hashed
+ and then signed by the private key of the certificate's issuer. This
+ data may be used to validate a signature, but use extreme caution as
+ certificate validation is a complex problem that involves much more
+ than just signature checks.
+
.. method:: public_bytes(encoding)
.. versionadded:: 1.0