SSL_config(3ssl)

SSL_config3ssl

Configure ssl_ctx or ssl structure

Part of SSL_CTX_config(3ssl).

Usage

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

Overview

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.

Releases

6 releases since Debian 9 (Stretch); the text changed 5 times.

  1. 9
  2. 10
  3. 11
  4. 12
  5. 13
  6. Arch

History

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

From openssl 3.6.5-1 in Arch Linux 2026-11-01. Parsed by carta from the page's man source.