CONF_MODULES_LOAD_FILE(3)

NAME
CONF_get1_default_config_file, CONF_modules_load_file_ex, CONF_modules_load_file, CONF_modules_load - OpenSSL configuration functions

SYNOPSIS
 #include <openssl/conf.h>

 char *CONF_get1_default_config_file(void);
 int CONF_modules_load_file_ex(OSSL_LIB_CTX *libctx, const char *filename,
                               const char *appname, unsigned long flags);
 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);

DESCRIPTION
The function CONF_get1_default_config_file() determines the default configuration file pathname as follows. If the OPENSSL_CONF environment variable is set its value is returned. Else the function returns the path obtained using X509_get_default_cert_area(3) with the filename "openssl.cnf" appended. The caller is responsible for freeing any string returned.

The function CONF_modules_load_file_ex() configures OpenSSL using library context libctx file filename and application name appname. If filename is NULL the standard OpenSSL configuration file is used as determined by calling CONF_get1_default_config_file(). If appname is NULL the standard OpenSSL application name openssl_conf is used. The behaviour can be customized using flags. Note that error handling can be customised via the configuration file's default section config_diagnostics parameter as described in config(5).

CONF_modules_load_file() is the same as CONF_modules_load_file_ex() but has a NULL library context. The global (NULL) library context is typically initialised just once at application startup. Library initialisation is typically implicit, but explicit initialisation is also supported by calling OPENSSL_init_crypto(3) or OPENSSL_init_ssl(3), sufficiently early in the main program, before implicit OpenSSL library initialisation has taken place as a side-effect of other OpenSSL function calls.

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

NOTES
The following flags are currently recognized:

If CONF_MFLAGS_IGNORE_ERRORS is 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 CONF_MFLAGS_SILENT is set no error information is added.

If CONF_MFLAGS_IGNORE_RETURN_CODES is set the function unconditionally returns success. This is used by default in OPENSSL_init_crypto(3) to ignore any errors in the default system-wide configuration file, as having all OpenSSL applications fail to start when there are potentially minor issues in the file is too risky. Applications calling CONF_modules_load_file_ex explicitly should not generally set this flag.

If CONF_MFLAGS_NO_DSO is set configuration module loading from DSOs is disabled.

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.

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

By using CONF_modules_load_file_ex() 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 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.

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).

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

 if (CONF_modules_load_file_ex(libctx, 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_ex(NULL, 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_ex(NULL, "/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_ex(libctx, 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);
 }

BUGS
In OpenSSL 3.x the CONF_modules_load_file_ex() and CONF_modules_load_file() functions affect some shared global state other than the specified library context. Therefore, even if used with a freshly created library context, the function is not thread safe, and should not be used except as part of early application initialisation. The SSL_CTX_config(3) and SSL_config(3) functions can be used to perform late customisation of SSL contexts and connection handles. Here late means that the chosen section's settings are applied in addition to any initial settings from the ssl module's system_default section that are used during initial construction of the SSL context. This sort of fine-tuning does not involve a separate configuration file or library context.

SEE ALSO
config(5), OPENSSL_config(3), NCONF_new_ex(3)

COPYRIGHT
Copyright 2004-2022 The OpenSSL Project Authors. All Rights Reserved.

Licensed under the Apache License 2.0 (the "License"). You may not use this file except in compliance with the License. You can obtain a copy in the file LICENSE in the source distribution or at <https://www.openssl.org/source/license.html>.