OPENSSL_CONFIG(3) OpenSSL OPENSSL_CONFIG(3)NAME
OPENSSL_config, OPENSSL_no_config - simple OpenSSL confi-
guration functions
SYNOPSIS
#include <openssl/conf.h>
void OPENSSL_config(const char *config_name);
void OPENSSL_no_config(void);
DESCRIPTIONOPENSSL_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 per-
formed future versions of OpenSSL will add new configuration
options.
There are several reasons why calling the OpenSSL configura-
tion routines is advisable. For example new ENGINE func-
tionality was added to OpenSSL 0.9.7. In OpenSSL 0.9.7 con-
trol 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
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OPENSSL_CONFIG(3) OpenSSL OPENSSL_CONFIG(3)
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 sim-
ple "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 configura-
tion 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 ALSOconf(5), CONF_load_modules_file(3),
CONF_modules_free(3),CONF_modules_free(3)HISTORYOPENSSL_config() and OPENSSL_no_config() first appeared in
OpenSSL 0.9.7
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