--- a/modules/ssl/ssl_engine_init.c	2021/06/29 09:30:24	1891137
+++ b/modules/ssl/ssl_engine_init.c	2021/06/29 11:24:17	1891138
@@ -1378,6 +1378,22 @@
 #endif
 }
 
+/* SSL_CTX_use_PrivateKey_file() can fail either because the private
+ * key was encrypted, or due to a mismatch between an already-loaded
+ * cert and the key - a common misconfiguration - from calling
+ * X509_check_private_key().  This macro is passed the last error code
+ * off the OpenSSL stack and evaluates to true only for the first
+ * case.  With OpenSSL < 3 the second case is identifiable by the
+ * function code, but function codes are not used from 3.0. */
+#if OPENSSL_VERSION_NUMBER < 0x30000000L
+#define CHECK_PRIVKEY_ERROR(ec) (ERR_GET_FUNC(ec) != X509_F_X509_CHECK_PRIVATE_KEY)
+#else
+#define CHECK_PRIVKEY_ERROR(ec) (ERR_GET_LIB != ERR_LIB_X509            \
+                                 || (ERR_GET_REASON(ec) != X509_R_KEY_TYPE_MISMATCH \
+                                     && ERR_GET_REASON(ec) != X509_R_KEY_VALUES_MISMATCH \
+                                     && ERR_GET_REASON(ec) != X509_R_UNKNOWN_KEY_TYPE))
+#endif
+
 static apr_status_t ssl_init_server_certs(server_rec *s,
                                           apr_pool_t *p,
                                           apr_pool_t *ptemp,