Cryptography and SSL/TLS Toolkit



SSL_CTX_config, SSL_config - configure SSL_CTX or SSL structure


#include <openssl/ssl.h>

int SSL_CTX_config(SSL_CTX *ctx, const char *name);
int SSL_config(SSL *s, const char *name);


The functions SSL_CTX_config() and SSL_config() configure an SSL_CTX or SSL structure using the configuration name.

By calling SSL_CTX_config() or SSL_config() an application can perform many complex tasks based on the contents of the configuration file: greatly simplifying application configuration code. A degree of future proofing can also be achieved: an application can support configuration features in newer versions of OpenSSL automatically.

A configuration file must have been previously loaded, for example using CONF_modules_load_file(). See config(5) for details of the configuration file syntax.


SSL_CTX_config() and SSL_config() return 1 for success or 0 if an error occurred.


If the file "config.cnf" contains the following:

testapp = test_sect

# list of configuration modules

ssl_conf = ssl_sect

server = server_section

RSA.Certificate = server-rsa.pem
ECDSA.Certificate = server-ecdsa.pem
Ciphers = ALL:!RC4

An application could call:

if (CONF_modules_load_file("config.cnf", "testapp", 0) <= 0) {
    fprintf(stderr, "Error processing config file\n");
    goto err;

ctx = SSL_CTX_new(TLS_server_method());

if (SSL_CTX_config(ctx, "server") == 0) {
    fprintf(stderr, "Error configuring server.\n");
    goto err;

In this example two certificates and the cipher list are configured without the need for any additional application code.


ssl(7), config(5), SSL_CONF_cmd(3), CONF_modules_load_file(3)


The SSL_CTX_config() and SSL_config() functions were added in OpenSSL 1.1.0.

Copyright 2015-2020 The OpenSSL Project Authors. All Rights Reserved.

Licensed under the Apache License 2.0 (the "License"). You may not use this file except in compliance with the License. You can obtain a copy in the file LICENSE in the source distribution or at