If an engine comes up explicitely, it must also come down explicitely

In apps/apps.c, one can set up an engine with setup_engine().
However, we freed the structural reference immediately, which means
that for engines that don't already have a structural reference
somewhere else (because it's a built in engine), we end up returning
an invalid reference.

Instead, the function release_engine() is added, and called at the end
of the routines that call setup_engine().

Reviewed-by: Rich Salz <rsalz@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/1643)

1 files changed, 9 insertions, 3 deletions

diff --git a/apps/apps.c b/apps/apps.c
index 68f2f2710a..05e1c2d009 100644
--- a/apps/apps.c
+++ b/apps/apps.c
@@ -1280,14 +1280,20 @@ ENGINE *setup_engine(const char *engine, int debug)
         }
 
         BIO_printf(bio_err, "engine \"%s\" set.\n", ENGINE_get_id(e));
-
-        /* Free our "structural" reference. */
-        ENGINE_free(e);
     }
     return e;
 }
 #endif
 
+void release_engine(ENGINE *e)
+{
+#ifndef OPENSSL_NO_ENGINE
+    if (e != NULL)
+        /* Free our "structural" reference. */
+        ENGINE_free(e);
+#endif
+}
+
 static unsigned long index_serial_hash(const OPENSSL_CSTRING *a)
 {
     const char *n;