[3.8] bpo-40515: Require OPENSSL_THREADS (GH-19953) (GH-20119)

Author: tiran

Misc/NEWS.d/next/Library/2020-05-06-13-51-19.bpo-40515.TUCvYB.rst

@@ -0,0 +1,3 @@
+The :mod:`ssl` and :mod:`hashlib` modules now actively check that OpenSSL is
+build with thread support. Python 3.7.0 made thread support mandatory and no
+longer works safely with a no-thread builds.

Modules/_hashopenssl.c

@@ -26,6 +26,10 @@
 #include <openssl/objects.h>
 #include "openssl/err.h"
 
+#ifndef OPENSSL_THREADS
+#  error "OPENSSL_THREADS is not defined, Python requires thread-safe OpenSSL"
+#endif
+
 #if (OPENSSL_VERSION_NUMBER < 0x10100000L) || defined(LIBRESSL_VERSION_NUMBER)
 /* OpenSSL < 1.1.0 */
 #define EVP_MD_CTX_new EVP_MD_CTX_create

Modules/_ssl.c

@@ -75,6 +75,10 @@ static PySocketModule_APIObject PySocketModule;
 #  endif
 #endif
 
+#ifndef OPENSSL_THREADS
+#  error "OPENSSL_THREADS is not defined, Python requires thread-safe OpenSSL"
+#endif
+
 /* SSL error object */
 static PyObject *PySSLErrorObject;
 static PyObject *PySSLCertVerificationErrorObject;
@@ -6008,7 +6012,7 @@ PyInit__ssl(void)
     if (!_setup_ssl_threads()) {
         return NULL;
     }
-#elif OPENSSL_VERSION_1_1 && defined(OPENSSL_THREADS)
+#elif OPENSSL_VERSION_1_1
     /* OpenSSL 1.1.0 builtin thread support is enabled */
     _ssl_locks_count++;
 #endif