OPENSSL_CONFIG(3) | Library Functions Manual | OPENSSL_CONFIG(3)

# NAME

`OPENSSL_config`, `OPENSSL_no_config` — simple crypto and ssl library configuration

# SYNOPSIS

library “libcrypto”
`#include <openssl/conf.h>`

void
`OPENSSL_config`(const char *appname);

void
`OPENSSL_no_config`(void);

# DESCRIPTION

`OPENSSL_config`() initializes the crypto library and calls CONF_modules_load_file(3) with the standard configuration file and the given appname. If appname is `NULL`, then the default name openssl_conf is used. Any errors are ignored. Further calls to `OPENSSL_config`() have no effect.

`OPENSSL_no_config`() suppresses the loading of the standard configuration file, so that any future calls to `OPENSSL_config`() or to OPENSSL_init_crypto(3) will ensure the library is initialized but no configuration file will be loaded.

Calling these functions is optional. All required initialization of the crypto libraries happens automatically when needed.

To use a non-standard configuration file, refer to CONF_modules_load_file(3).

Internally, `OPENSSL_config`() calls OPENSSL_init_crypto(3).

If an application is compiled with the preprocessor symbol `OPENSSL_LOAD_CONF` defined, OpenSSL_add_all_algorithms(3) automatically calls `OPENSSL_config`().

Applications should free up configuration at application closedown by calling CONF_modules_free(3).

# FILES

/etc/ssl/openssl.cnf
  standard configuration file

# SEE ALSO

CONF_modules_free(3), CONF_modules_load_file(3), crypto(3), OPENSSL_VERSION_NUMBER(3), openssl.cnf(5), x509v3.cnf(5)

# HISTORY

`OPENSSL_config`() and `OPENSSL_no_config`() first appeared in OpenSSL 0.9.7 and have been available since OpenBSD 3.2.

June 9, 2025 | Debian