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(5) 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.
OPENSSL_no_config()
disables configuration. If called before
OPENSSL_config(), no configuration takes place.
It is
strongly
recommended that
all new
applications call
OPENSSL_config()
or the more sophisticated functions such as
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.
It is also possible to automatically call
OPENSSL_config()
when an application calls
OpenSSL_add_all_algorithms(3) 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 ASN.1 OBJECT and ENGINE configuration can be performed.
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 which 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(3).
RETURN VALUES
Neither OPENSSL_config() nor
OPENSSL_no_config() return a value.
FILES
- /etc/ssl/openssl.cnf
- standard configuration file
SEE ALSO
HISTORY
OPENSSL_config() and
OPENSSL_no_config() first appeared in OpenSSL
0.9.7.
CAVEATS
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_modules_load(3) directly.