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.

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 2015-2019 The OpenSSL Project Authors. All Rights Reserved.

Licensed under the OpenSSL license (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

2021-08-24 1.1.1l