add missing extensions documentation to CertificateSigningRequest
diff --git a/docs/x509/reference.rst b/docs/x509/reference.rst
index 9179468..4d164dc 100644
--- a/docs/x509/reference.rst
+++ b/docs/x509/reference.rst
@@ -431,6 +431,25 @@
>>> isinstance(csr.signature_hash_algorithm, hashes.SHA1)
True
+ .. attribute:: extensions
+
+ :type: :class:`Extensions`
+
+ The extensions encoded in the certificate signing request.
+
+ :raises cryptography.x509.DuplicateExtension: If more than one
+ extension of the same type is found within the certificate siging request.
+
+ :raises cryptography.x509.UnsupportedExtension: If the certificate siging request
+ contains an extension that is not supported.
+
+ :raises cryptography.x509.UnsupportedGeneralNameType: If an extension
+ contains a general name that is not supported.
+
+ :raises UnicodeError: If an extension contains IDNA encoding that is
+ invalid or not compliant with IDNA 2008.
+
+
.. method:: public_bytes(encoding)
.. versionadded:: 1.0