Ensure EC private keys retain leading zeros

[oweals/openssl.git] / doc / crypto / CONF_modules_load_file.pod

diff --git a/doc/crypto/CONF_modules_load_file.pod b/doc/crypto/CONF_modules_load_file.pod
index 9965d69bf2ecc7a71e8e7cbaa250089441e5bf6f..cc0b537b8ea56ee859eaf15fa1561377c8521bef 100644 (file)
--- a/doc/crypto/CONF_modules_load_file.pod
+++ b/doc/crypto/CONF_modules_load_file.pod
@@ -9,9 +9,9 @@
  #include <openssl/conf.h>
 
  int CONF_modules_load_file(const char *filename, const char *appname,
-                          unsigned long flags);
+                                       unsigned long flags);
  int CONF_modules_load(const CONF *cnf, const char *appname,
-                     unsigned long flags);
+                              unsigned long flags);
 
 =head1 DESCRIPTION
 
@@ -22,7 +22,7 @@ NULL the standard OpenSSL application name B<openssl_conf> is used.
 The behaviour can be cutomized using B<flags>.
 
 CONF_modules_load() is idential to CONF_modules_load_file() except it
-read configuration information from B<cnf>. 
+reads configuration information from B<cnf>.
 
 =head1 NOTES
 
@@ -30,7 +30,7 @@ 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 loads.
+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.
@@ -42,7 +42,84 @@ 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.
 
-=head1 RETURN VALUE
+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
@@ -51,7 +128,7 @@ return value of the failing module (this will always be zero or negative).
 =head1 SEE ALSO
 
 L<conf(5)|conf(5)>, L<OPENSSL_config(3)|OPENSSL_config(3)>,
-L<CONF_free(3), CONF_free(3)>, L<err(3),err(3)>
+L<CONF_free(3)|CONF_free(3)>, L<err(3)|err(3)>
 
 =head1 HISTORY