engine: disable OpenSSL::Engine on OpenSSL 3.0

The entire ENGINE API is deprecated in OpenSSL 3.0 in favor of the new
"Provider" concept.

OpenSSL::Engine will not be defined when compiled with OpenSSL 3.0.
We would need a way to interact with providers from Ruby programs, but
since the concept is completely different from the ENGINE API, it will
not be through the current OpenSSL::Engine interface.

Author: rhenium

ext/openssl/openssl_missing.c

@@ -10,9 +10,6 @@
 #include RUBY_EXTCONF_H
 
 #include <string.h> /* memcpy() */
-#if !defined(OPENSSL_NO_ENGINE)
-# include <openssl/engine.h>
-#endif
 #include <openssl/x509_vfy.h>
 
 #include "openssl_missing.h"

ext/openssl/ossl.h

@@ -18,6 +18,7 @@
 #include <ruby/io.h>
 #include <ruby/thread.h>
 #include <openssl/opensslv.h>
+
 #include <openssl/err.h>
 #include <openssl/asn1.h>
 #include <openssl/x509v3.h>
@@ -30,9 +31,6 @@
   #include <openssl/ts.h>
 #endif
 #include <openssl/crypto.h>
-#if !defined(OPENSSL_NO_ENGINE)
-#  include <openssl/engine.h>
-#endif
 #if !defined(OPENSSL_NO_OCSP)
 #  include <openssl/ocsp.h>
 #endif
@@ -54,6 +52,10 @@
       (LIBRESSL_VERSION_NUMBER >= (maj << 28) | (min << 20) | (pat << 12))
 #endif
 
+#if !defined(OPENSSL_NO_ENGINE) && !OSSL_OPENSSL_PREREQ(3, 0, 0)
+# define OSSL_USE_ENGINE
+#endif
+
 /*
  * Common Module
  */

ext/openssl/ossl_engine.c

@@ -9,7 +9,8 @@
  */
 #include "ossl.h"
 
-#if !defined(OPENSSL_NO_ENGINE)
+#ifdef OSSL_USE_ENGINE
+# include <openssl/engine.h>
 
 #define NewEngine(klass) \
     TypedData_Wrap_Struct((klass), &ossl_engine_type, 0)

ext/openssl/ossl_pkey.c

@@ -9,6 +9,10 @@
  */
 #include "ossl.h"
 
+#ifdef OSSL_USE_ENGINE
+# include <openssl/engine.h>
+#endif
+
 /*
  * Classes
  */