handle previous registration by raising RuntimeError

2 files changed, 3 insertions, 5 deletions

diff --git a/src/cryptography/hazmat/bindings/openssl/binding.py b/src/cryptography/hazmat/bindings/openssl/binding.py
index 727522a3..be9904a2 100644
--- a/src/cryptography/hazmat/bindings/openssl/binding.py
+++ b/src/cryptography/hazmat/bindings/openssl/binding.py
@@ -46,8 +46,7 @@ def _register_osrandom_engine():
     assert lib.ERR_peek_error() == 0
     looked_up_engine = lib.ENGINE_by_id(_osrandom_engine_id)
     if looked_up_engine != ffi.NULL:
-        assert lib.ERR_peek_error() == 0
-        return 2
+        raise RuntimeError("osrandom engine already registered")
 
     lib.ERR_clear_error()
 
@@ -64,7 +63,6 @@ def _register_osrandom_engine():
     finally:
         result = lib.ENGINE_free(engine)
         assert result == 1
-    return 1
 
 
 class Binding(object):
diff --git a/tests/hazmat/bindings/test_openssl.py b/tests/hazmat/bindings/test_openssl.py
index fe78b0ba..75a8e3f1 100644
--- a/tests/hazmat/bindings/test_openssl.py
+++ b/tests/hazmat/bindings/test_openssl.py
@@ -89,8 +89,8 @@ class TestOpenSSL(object):
 
     def test_add_engine_more_than_once(self):
         b = Binding()
-        res = b._register_osrandom_engine()
-        assert res == 2
+        with pytest.raises(RuntimeError):
+            b._register_osrandom_engine()
 
     def test_ssl_ctx_options(self):
         # Test that we're properly handling 32-bit unsigned on all platforms.