--- cryptography-2.2.2/src/_cffi_src/openssl/src/osrandom_engine.c	2018-03-27 15:12:05.000000000 +0100
+++ cryptography-2.2.2-patch/src/_cffi_src/openssl/src/osrandom_engine.c	2018-06-02 05:21:49.000000000 +0100
@@ -205,14 +205,10 @@
 #if !defined(__APPLE__)
     getentropy_works = CRYPTOGRAPHY_OSRANDOM_GETENTROPY_WORKS;
 #else
-    if (&getentropy != NULL) {
-        getentropy_works = CRYPTOGRAPHY_OSRANDOM_GETENTROPY_WORKS;
-    } else {
-        getentropy_works = CRYPTOGRAPHY_OSRANDOM_GETENTROPY_FALLBACK;
-        int fd = dev_urandom_fd();
-        if (fd < 0) {
-            return 0;
-        }
+    getentropy_works = CRYPTOGRAPHY_OSRANDOM_GETENTROPY_FALLBACK;
+    int fd = dev_urandom_fd();
+    if (fd < 0) {
+        return 0;
     }
 #endif
     return 1;
@@ -228,22 +224,7 @@
         return dev_urandom_read(buffer, size);
 #endif
     case CRYPTOGRAPHY_OSRANDOM_GETENTROPY_WORKS:
-        while (size > 0) {
-            /* OpenBSD and macOS restrict maximum buffer size to 256. */
-            len = size > 256 ? 256 : (size_t)size;
-            res = getentropy(buffer, len);
-            if (res < 0) {
-                ERR_Cryptography_OSRandom_error(
-                    CRYPTOGRAPHY_OSRANDOM_F_RAND_BYTES,
-                    CRYPTOGRAPHY_OSRANDOM_R_GETENTROPY_FAILED,
-                    __FILE__, __LINE__
-                );
-                return 0;
-            }
-            buffer += len;
-            size -= len;
-        }
-        return 1;
+        return 0;
     }
     __builtin_unreachable();
 }