krb5_get_error_message() and krb5_free_error_message() functions

[Russ Allbery]

vir vir <vitrou2004 at yahoo.com> writes:

> Thank you for your response.
> I am using krb5 earlier then 1.4 that provided by the Linux OS.
> Can you please  recommend what are the best functions to use instead?

If you want maximum portability, you have to do something like this (see
http://www.eyrie.org/~eagle/software/rra-c-util/ for the complete context
and corresponding M4 macros).  However, for more situations, falling back
on com_err if the new functions aren't available will work.  (You lose
with native AIX Kerberos, but you may or may not care.)

/* Figure out what header files to include for error reporting. */
#if !defined(HAVE_KRB5_GET_ERROR_MESSAGE) && !defined(HAVE_KRB5_GET_ERR_TEXT)
# if !defined(HAVE_KRB5_GET_ERROR_STRING)
#  if defined(HAVE_IBM_SVC_KRB5_SVC_H)
#   include <ibm_svc/krb5_svc.h>
#  elif defined(HAVE_ET_COM_ERR_H)
#   include <et/com_err.h>
#  else
#   include <com_err.h>
#  endif
# endif
#endif

/* Used for unused parameters to silence gcc warnings. */
#define UNUSED __attribute__((__unused__))

/*
 * This string is returned for unknown error messages.  We use a static
 * variable so that we can be sure not to free it.
 */
static const char error_unknown[] = "unknown error";


#ifndef HAVE_KRB5_GET_ERROR_MESSAGE
/*
 * Given a Kerberos error code, return the corresponding error.  Prefer the
 * Kerberos interface if available since it will provide context-specific
 * error information, whereas the error_message() call will only provide a
 * fixed message.
 */
const char *
krb5_get_error_message(krb5_context ctx UNUSED, krb5_error_code code UNUSED)
{
    const char *msg = NULL;

# if defined(HAVE_KRB5_GET_ERROR_STRING)
    msg = krb5_get_error_string(ctx);
# elif defined(HAVE_KRB5_GET_ERR_TEXT)
    msg = krb5_get_err_text(ctx, code);
# elif defined(HAVE_KRB5_SVC_GET_MSG)
    krb5_svc_get_msg(code, (char **) &msg);
# else
    msg = error_message(code);
# endif
    if (msg == NULL)
        return error_unknown;
    else
        return msg;
}
#endif /* !HAVE_KRB5_GET_ERROR_MESSAGE */


#ifndef HAVE_KRB5_FREE_ERROR_MESSAGE
/*
 * Free an error string if necessary.  If we returned a static string, make
 * sure we don't free it.
 *
 * This code assumes that the set of implementations that have
 * krb5_free_error_message is a subset of those with krb5_get_error_message.
 * If this assumption ever breaks, we may call the wrong free function.
 */
void
krb5_free_error_message(krb5_context ctx UNUSED, const char *msg)
{
    if (msg == error_unknown)
        return;
# if defined(HAVE_KRB5_GET_ERROR_STRING)
    krb5_free_error_string(ctx, (char *) msg);
# elif defined(HAVE_KRB5_SVC_GET_MSG)
    krb5_free_string(ctx, (char *) msg);
# endif
}
#endif /* !HAVE_KRB5_FREE_ERROR_MESSAGE */

-- 
Russ Allbery (rra at stanford.edu)             <http://www.eyrie.org/~eagle/>