Update CSR tests and implementation

- Use keyword arguments for x509.BasicConstraints in tests (missed in
  b790edbdc8fb9a026353d6fb99994326197705c7).
- Place X509_request garbage collection under assertion.
- Assert that X509 extensions created are not null.
- Don't copy the extensions list in CertificateSigningBuilder.
  They're never appended to, so copying isn't necessary.
- Use RSA key fixtures instead of generating new ones on each test run

2 files changed, 3 insertions, 2 deletions

diff --git a/src/cryptography/hazmat/backends/openssl/backend.py b/src/cryptography/hazmat/backends/openssl/backend.py
index 1861d182..406117b9 100644
--- a/src/cryptography/hazmat/backends/openssl/backend.py
+++ b/src/cryptography/hazmat/backends/openssl/backend.py
@@ -817,8 +817,8 @@ class Backend(object):
 
         # Create an empty request.
         x509_req = self._lib.X509_REQ_new()
-        x509_req = self._ffi.gc(x509_req, self._lib.X509_REQ_free)
         assert x509_req != self._ffi.NULL
+        x509_req = self._ffi.gc(x509_req, self._lib.X509_REQ_free)
 
         # Set x509 version.
         res = self._lib.X509_REQ_set_version(x509_req, x509.Version.v1.value)
@@ -839,6 +839,7 @@ class Backend(object):
 
         # Add extensions.
         extensions = self._lib.sk_X509_EXTENSION_new_null()
+        assert extensions != self._ffi.NULL
         extensions = self._ffi.gc(
             extensions,
             self._lib.sk_X509_EXTENSION_free,
diff --git a/src/cryptography/x509.py b/src/cryptography/x509.py
index ab4f3c7e..7e1e34e2 100644
--- a/src/cryptography/x509.py
+++ b/src/cryptography/x509.py
@@ -1450,7 +1450,7 @@ class CertificateSigningRequestBuilder(object):
         Creates an empty X.509 certificate request (v1).
         """
         self._subject_name = subject_name
-        self._extensions = extensions[:]
+        self._extensions = extensions
 
     def subject_name(self, name):
         """