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CONF_MODULES_LOAD_FILE(3) Library Functions Manual CONF_MODULES_LOAD_FILE(3)

CONF_modules_load_file, CONF_modules_load — OpenSSL configuration functions

#include <openssl/conf.h>

int
CONF_modules_load_file(const char *filename, const char *appname, unsigned long flags);

int
CONF_modules_load(const CONF *cnf, const char *appname, unsigned long flags);

The function () configures OpenSSL using the file filename in openssl.cnf(5) format and the application name appname. If filename is NULL, the standard OpenSSL configuration file /etc/ssl/openssl.cnf is used. If appname is NULL, the standard OpenSSL application name "openssl_conf" is used. The behaviour can be customized using flags.

() is identical to CONF_modules_load_file() except it reads configuration information from cnf.

The following flags are currently recognized:

Ignore errors returned by individual configuration modules. By default, the first module error is considered fatal and no further modules are loaded.
Do not add any error information. By default, all module errors add error information to the error queue.
Disable loading of configuration modules from DSOs.
Let () ignore missing configuration files. By default, a missing configuration file returns an error.
CONF_MFLAGS_DEFAULT_SECTION
If appname is not NULL but does not exist, fall back to the default section "openssl_conf".

By using () with appropriate flags, an application can customise application configuration to best suit its needs. In some cases the use of a configuration file is optional and its absence is not an error: in this case CONF_MFLAGS_IGNORE_MISSING_FILE would be set.

Errors during configuration may also be handled differently by different applications. For example in some cases an error may simply print out a warning message and the application may continue. In other cases an application might consider a configuration file error fatal and exit immediately.

Applications can use the () function if they wish to load a configuration file themselves and have finer control over how errors are treated.

These functions return 1 for success and zero or a negative value for failure. If module errors are not ignored, the return code will reflect the return value of the failing module (this will always be zero or negative).

/etc/ssl/openssl.cnf
standard configuration file

Load a configuration file and print out any errors and exit (missing file considered fatal):

if (CONF_modules_load_file(NULL, NULL, 0) <= 0) {
	fprintf(stderr, "FATAL: error loading configuration file\n");
	ERR_print_errors_fp(stderr);
	exit(1);
}

Load default configuration file using the section indicated by "myapp", tolerate missing files, but exit on other errors:

if (CONF_modules_load_file(NULL, "myapp",
    CONF_MFLAGS_IGNORE_MISSING_FILE) <= 0) {
	fprintf(stderr, "FATAL: error loading configuration file\n");
	ERR_print_errors_fp(stderr);
	exit(1);
}

Load custom configuration file and section, only print warnings on error, missing configuration file ignored:

if (CONF_modules_load_file("/something/app.cnf", "myapp",
    CONF_MFLAGS_IGNORE_MISSING_FILE) <= 0) {
	fprintf(stderr, "WARNING: error loading configuration file\n");
	ERR_print_errors_fp(stderr);
}

Load and parse configuration file manually, custom error handling:

FILE	*fp;
CONF	*cnf = NULL;
long	 eline;

fp = fopen("/somepath/app.cnf", "r");
if (fp == NULL) {
	fprintf(stderr, "Error opening configuration file\n");
	/* Other missing configuration file behaviour */
} else {
	cnf = NCONF_new(NULL);
	if (NCONF_load_fp(cnf, fp, &eline) == 0) {
		fprintf(stderr, "Error on line %ld of configuration file\n",
		    eline);
		ERR_print_errors_fp(stderr);
		/* Other malformed configuration file behaviour */
	} else if (CONF_modules_load(cnf, "appname", 0) <= 0) {
		fprintf(stderr, "Error configuring application\n");
		ERR_print_errors_fp(stderr);
		/* Other configuration error behaviour */
	}
	fclose(fp);
	NCONF_free(cnf);
}

CONF_modules_free(3), ERR(3), OPENSSL_config(3), OPENSSL_init_crypto(3)

CONF_modules_load_file() and CONF_modules_load() first appeared in OpenSSL 0.9.7 and have been available since OpenBSD 3.2.

March 20, 2019 DragonFly-5.6.1