Backport x509_up_ref (#4029)

* pytest 3.3.0 has an issue with parametrized null bytes again (#4026)

* add X509_up_ref (#4028)

setup.py

@@ -45,7 +45,7 @@
     setup_requirements.append("cffi>=1.7")
 
 test_requirements = [
-    "pytest>=3.2.1",
+    "pytest>=3.2.1,!=3.3.0",
     "pretend",
     "iso8601",
     "pytz",

src/_cffi_src/openssl/x509.py

@@ -83,6 +83,7 @@
 void X509_free(X509 *);
 X509 *X509_dup(X509 *);
 int X509_cmp(const X509 *, const X509 *);
+int X509_up_ref(X509 *);
 
 int X509_print_ex(BIO *, X509 *, unsigned long, unsigned long);
 
@@ -382,6 +383,10 @@
    opaquing. */
 #if CRYPTOGRAPHY_OPENSSL_LESS_THAN_110
 
+int X509_up_ref(X509 *x) {
+   return CRYPTO_add(&x->references, 1, CRYPTO_LOCK_X509);
+}
+
 const X509_ALGOR *X509_get0_tbs_sigalg(const X509 *x)
 {
     return x->cert_info->signature;