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