openssl/doc/crypto/CONF_modules_load_file.pod

=pod

=head1 NAME

 CONF_modules_load_file, CONF_modules_load - OpenSSL configuration functions

=head1 SYNOPSIS

 #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);

=head1 DESCRIPTION

The function CONF_modules_load_file() configures OpenSSL using file
B<filename> and application name B<appname>. If B<filename> is NULL
the standard OpenSSL configuration file is used. If B<appname> is
NULL the standard OpenSSL application name B<openssl_conf> is used.
The behaviour can be customized using B<flags>.

CONF_modules_load() is identical to CONF_modules_load_file() except it
reads configuration information from B<cnf>.

=head1 NOTES

The following B<flags> are currently recognized:

B<CONF_MFLAGS_IGNORE_ERRORS> if set errors returned by individual
configuration modules are ignored. If not set the first module error is
considered fatal and no further modules are loaded.

Normally any modules errors will add error information to the error queue. If
B<CONF_MFLAGS_SILENT> is set no error information is added.

If B<CONF_MFLAGS_NO_DSO> is set configuration module loading from DSOs is
disabled.

B<CONF_MFLAGS_IGNORE_MISSING_FILE> if set will make CONF_load_modules_file()
ignore missing configuration files. Normally a missing configuration file
return an error.

B<CONF_MFLAGS_DEFAULT_SECTION> if set and B<appname> is not NULL will use the
default section pointed to by B<openssl_conf> if B<appname> does not exist.

Applications should call these functions after loading builtin modules using
OPENSSL_load_builtin_modules(), any ENGINEs for example using
ENGINE_load_builtin_engines(), any algorithms for example
OPENSSL_add_all_algorithms() and (if the application uses libssl)
SSL_library_init().

By using CONF_modules_load_file() 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 B<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 continue. In other cases an application might
consider a configuration file error as fatal and exit immediately.

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

=head1 EXAMPLES

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);
  }

=head1 RETURN VALUES

These functions return 1 for success and a zero or 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).

=head1 SEE ALSO

L<conf(5)>, L<OPENSSL_config(3)>,
L<CONF_free(3)>, L<err(3)>

=cut