Fix gssrpc data leakage [CVE-2014-9423]

[MITKRB5-SA-2015-001] In svcauth_gss_accept_sec_context(), do not copy
bytes from the union context into the handle field we send to the
client.  We do not use this handle field, so just supply a fixed
string of "xxxx".

In gss_union_ctx_id_struct, remove the unused "interposer" field which
was causing part of the union context to remain uninitialized.

ticket: 8058 (new)
target_version: 1.13.1
tags: pullup
svcauth_gss_release_cred(void)
{
	OM_uint32	maj_stat, min_stat;

	log_debug("in svcauth_gss_release_cred()");

	maj_stat = gss_release_cred(&min_stat, &svcauth_gss_creds);

	if (maj_stat != GSS_S_COMPLETE) {
		log_status("gss_release_cred", maj_stat, min_stat);
		return (FALSE);
	}

	svcauth_gss_creds = NULL;

	return (TRUE);
}

svcauth_gss_release_cred(void)
{
	OM_uint32	maj_stat, min_stat;

	log_debug("in svcauth_gss_release_cred()");

	maj_stat = gss_release_cred(&min_stat, &svcauth_gss_creds);

	if (maj_stat != GSS_S_COMPLETE) {
		log_status("gss_release_cred", maj_stat, min_stat);
		return (FALSE);
	}

	svcauth_gss_creds = NULL;

	return (TRUE);
}
