.\"	$OpenBSD: OPENSSL_config.3,v 1.2 2016/11/06 15:52:50 jmc Exp $
.\"
.Dd $Mdocdate: November 6 2016 $
.Dt OPENSSL_CONFIG 3
.Os
.Sh NAME
.Nm OPENSSL_config ,
.Nm OPENSSL_no_config
.Nd simple OpenSSL configuration functions
.Sh SYNOPSIS
.In openssl/conf.h
.Ft void
.Fo OPENSSL_config
.Fa "const char *config_name"
.Fc
.Ft void
.Fn OPENSSL_no_config void
.Sh DESCRIPTION
.Fn OPENSSL_config
configures OpenSSL using the standard
.Pa openssl.cnf
configuration file name using
.Fa config_name .
If
.Fa config_name
is
.Dv NULL
then the default name
.Sy openssl_conf
will be used.
Any errors are ignored.
Further calls to
.Fn OPENSSL_config
will have no effect.
.Pp
.Fn OPENSSL_no_config
disables configuration.
If called before
.Fn OPENSSL_config ,
no configuration takes place.
.Pp
It is
.Sy strongly
recommended that
.Sy all
new applications call
.Fn OPENSSL_config
or the more sophisticated functions such as
.Xr CONF_modules_load 3
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.
.Pp
It is also possible to automatically call
.Fn OPENSSL_config
when an application calls
.Xr OPENSSL_add_all_algorithms 3
by compiling an application with the preprocessor symbol
.Dv OPENSSL_LOAD_CONF
#define'd.
In this way configuration can be added without source changes.
.Pp
The environment variable
.Ev OPENSSL_CONF
can be set to specify the location of the configuration file.
.Pp
Currently ASN1 OBJECT and ENGINE configuration can be performed.
.Pp
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
.Fn OPENSSL_config
it doesn't need to know or care about ENGINE control operations because
they can be performed by editing a configuration file.
.Pp
Applications should free up configuration at application closedown by
calling
.Xr CONF_modules_free 3 .
.Sh RETURN VALUES
Neither
.Fn OPENSSL_config
nor
.Fn OPENSSL_no_config
return a value.
.Sh SEE ALSO
.Xr CONF_modules_free 3 ,
.Xr CONF_modules_load 3
.Sh HISTORY
.Fn OPENSSL_config
and
.Fn OPENSSL_no_config
first appeared in OpenSSL 0.9.7.
.Sh CAVEATS
The
.Fn 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.
.Pp
It is however
.Sy much
better than nothing.
Applications which need finer control over their configuration
functionality should use the configuration functions such as
.Xr CONF_load_modules 3
directly.