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