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_unwrap(SVCAUTH *auth, XDR *xdrs, xdrproc_t xdr_func, caddr_t xdr_ptr)
{
	struct svc_rpc_gss_data	*gd;

	log_debug("in svcauth_gss_unwrap()");

	gd = SVCAUTH_PRIVATE(auth);

	if (!gd->established || gd->sec.svc == RPCSEC_GSS_SVC_NONE) {
		return ((*xdr_func)(xdrs, xdr_ptr));
	}
	return (xdr_rpc_gss_data(xdrs, xdr_func, xdr_ptr,
				 gd->ctx, gd->sec.qop,
				 gd->sec.svc, gd->seq));
}

svcauth_gss_unwrap(SVCAUTH *auth, XDR *xdrs, xdrproc_t xdr_func, caddr_t xdr_ptr)
{
	struct svc_rpc_gss_data	*gd;

	log_debug("in svcauth_gss_unwrap()");

	gd = SVCAUTH_PRIVATE(auth);

	if (!gd->established || gd->sec.svc == RPCSEC_GSS_SVC_NONE) {
		return ((*xdr_func)(xdrs, xdr_ptr));
	}
	return (xdr_rpc_gss_data(xdrs, xdr_func, xdr_ptr,
				 gd->ctx, gd->sec.qop,
				 gd->sec.svc, gd->seq));
}
