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OPENSSL_config(3)
NAME
OPENSSL_config, OPENSSL_no_config - simple OpenSSL configuration functions
SYNOPSIS
#include <openssl/conf.h>
void OPENSSL_config(const char *config_name); void OPENSSL_no_config(void);
DESCRIPTION
OPENSSL_config() configures OpenSSL using the standard openssl.cnf
configuration file name using config_name. If config_name is NULL then the default name openssl_conf will be used. Any errors are ignored. Further calls to
OPENSSL_config() will have no effect. The configuration file
format is documented in the conf(5) manual page.
OPENSSL_no_config() disables configuration. If called before
OPENSSL_config() no configuration takes place.
NOTES
It is strongly recommended that all new applications call OPENSSL_config() or the more
sophisticated functions such as CONF_modules_load() during
initialization (that is before starting any threads). By doing this an
application does not need to keep track of all configuration options and
some new functionality can be supported automatically.
It is also possible to automatically call OPENSSL_config()
when an application calls OPENSSL_add_all_algorithms() by
compiling an application with the preprocessor symbol OPENSSL_LOAD_CONF #define'd. In this way configuration can be added without source changes.
The environment variable OPENSSL_CONF can be set to specify the location of the configuration file. Currently ASN1 OBJECTs and ENGINE configuration can be performed future versions of OpenSSL will add new configuration options.
There are several reasons why calling the OpenSSL configuration routines is
advisable. For example new ENGINE functionality was added to OpenSSL 0.9.7.
In OpenSSL 0.9.7 control functions can be supported by ENGINEs, this can be
used (among other things) to load dynamic ENGINEs from shared libraries
(DSOs). However very few applications currently support the control
interface and so very few can load and use dynamic ENGINEs. Equally in
future more sophisticated ENGINEs will require certain control operations
to customize them. If an application calls OPENSSL_config() it
doesn't need to know or care about ENGINE control operations because they
can be performed by editing a configuration file.
Applications should free up configuration at application closedown by
calling CONF_modules_free().
RESTRICTIONS
The OPENSSL_config() function is designed to be a very simple
``call it and forget it'' function. As a result its behaviour is somewhat
limited. It ignores all errors silently and it can only load from the
standard configuration file location for example.
It is however much better than nothing. Applications which need finer control over their
configuration functionality should use the configuration functions such as
CONF_load_modules() directly.
RETURN VALUES
Neither OPENSSL_config() nor OPENSSL_no_config()
return a value.
SEE ALSO
conf(5), CONF_load_modules_file(3), CONF_modules_free(3),CONF_modules_free(3)
HISTORY
OPENSSL_config() and OPENSSL_no_config() first
appeared in OpenSSL 0.9.7
