(***************************************************************************** * Copyright (c) 2005-2010 ETH Zurich, Switzerland * 2008-2015 Achim D. Brucker, Germany * 2009-2016 Université Paris-Sud, France * 2015-2016 The University of Sheffield, UK * * All rights reserved. * * Redistribution and use in source and binary forms, with or without * modification, are permitted provided that the following conditions are * met: * * * Redistributions of source code must retain the above copyright * notice, this list of conditions and the following disclaimer. * * * Redistributions in binary form must reproduce the above * copyright notice, this list of conditions and the following * disclaimer in the documentation and/or other materials provided * with the distribution. * * * Neither the name of the copyright holders nor the names of its * contributors may be used to endorse or promote products derived * from this software without specific prior written permission. * * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. *****************************************************************************) subsection ‹Policy Core› theory PolicyCore imports NetworkCore UPF.UPF begin text‹A policy is seen as a partial mapping from packet to packet out.› type_synonym ('α, 'β) FWPolicy = "('α, 'β) packet ↦ unit" text‹ When combining several rules, the firewall is supposed to apply the first matching one. In our setting this means the first rule which maps the packet in question to ‹Some (packet out)›. This is exactly what happens when using the map-add operator (‹rule1 ++ rule2›). The only difference is that the rules must be given in reverse order. › text‹ The constant ‹p_accept› is ‹True› iff the policy accepts the packet. › definition p_accept :: "('α, 'β) packet ⇒ ('α, 'β) FWPolicy ⇒ bool" where "p_accept p pol = (pol p = ⌊allow ()⌋)" end