3 files changed, 10 insertions, 0 deletions
diff --git a/src/cryptography/hazmat/backends/openssl/backend.py b/src/cryptography/hazmat/backends/openssl/backend.py
index de653032..27d5e353 100644
--- a/src/cryptography/hazmat/backends/openssl/backend.py
+++ b/src/cryptography/hazmat/backends/openssl/backend.py
@@ -320,6 +320,7 @@ class Backend(object):
         )
 
     def _bn_to_int(self, bn):
+        assert bn != self._ffi.NULL
         if six.PY3:
             # Python 3 has constant time from_bytes, so use that.
 
@@ -346,6 +347,7 @@ class Backend(object):
         ownership of the object). Be sure to register it for GC if it will
         be discarded after use.
         """
+        assert bn is None or bn != self._ffi.NULL
 
         if bn is None:
             bn = self._ffi.NULL
diff --git a/src/cryptography/hazmat/bindings/openssl/dh.py b/src/cryptography/hazmat/bindings/openssl/dh.py
index 3c15bd35..b66e7196 100644
--- a/src/cryptography/hazmat/bindings/openssl/dh.py
+++ b/src/cryptography/hazmat/bindings/openssl/dh.py
@@ -18,6 +18,9 @@ typedef struct dh_st {
     BIGNUM *priv_key;
     /* Public DH value g^x */
     BIGNUM *pub_key;
+    /* X9.42/RFC 2631 */
+    BIGNUM *q;
+    BIGNUM *j;
     ...;
 } DH;
 """
diff --git a/src/cryptography/hazmat/bindings/openssl/err.py b/src/cryptography/hazmat/bindings/openssl/err.py
index ec393c1b..0ee19c9e 100644
--- a/src/cryptography/hazmat/bindings/openssl/err.py
+++ b/src/cryptography/hazmat/bindings/openssl/err.py
@@ -21,6 +21,7 @@ struct ERR_string_data_st {
 };
 typedef struct ERR_string_data_st ERR_STRING_DATA;
 
+static const int ERR_LIB_DH;
 static const int ERR_LIB_EVP;
 static const int ERR_LIB_EC;
 static const int ERR_LIB_PEM;
@@ -95,6 +96,10 @@ static const int ASN1_R_UNSUPPORTED_TYPE;
 static const int ASN1_R_WRONG_TAG;
 static const int ASN1_R_WRONG_TYPE;
 
+static const int DH_F_COMPUTE_KEY;
+
+static const int DH_R_INVALID_PUBKEY;
+
 static const int EVP_F_AES_INIT_KEY;
 static const int EVP_F_D2I_PKEY;
 static const int EVP_F_DSA_PKEY2PKCS8;