SSL_CTX_config(3)

SSL_CTX_config(3) | OpenSSL | SSL_CTX_config(3)

# NAME

SSL_CTX_config, SSL_config - configure SSL_CTX or SSL structure

# SYNOPSIS

     #include <openssl/ssl.h>
     int SSL_CTX_config(SSL_CTX *ctx, const char *name);
     int SSL_config(SSL *s, const char *name);

# DESCRIPTION

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.

# RETURN VALUES

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

# EXAMPLES

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

     testapp = test_sect
     [test_sect]
     # list of configuration modules
     ssl_conf = ssl_sect
     [ssl_sect]
     server = server_section
     [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.

# SEE ALSO

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

# HISTORY

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

# COPYRIGHT

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 <https://www.openssl.org/source/license.html>.

2025-07-01 | 3.5.1