secnet - flexible VPN software
==============================

secnet is
  Copyright 1995-2003 Stephen Early <steve@greenend.org.uk>
  Copyright 2002-2023 Ian Jackson <ijackson@chiark.greenend.org.uk>
  Copyright 1991      Massachusetts Institute of Technology
  Copyright 1998      Ross Anderson, Eli Biham, Lars Knudsen
  Copyright 1993      Colin Plumb
  Copyright 1998      James H. Brown, Steve Reid
  Copyright 1998      Miquel van Smoorenburg, Ian Murdock
  Copyright 2000      Vincent Rijmen, Antoon Bosselaers, Paulo Barreto
  Copyright 2001      Joey Hess
  Copyright 2000-2006 Joachim Henkea
  Copyright 2012-2016 Adrien Béraud
  Copyright 2015      Guillaume Jacquenot
  Copyright 2016      SunDwarf aka eyesismine
  Copyright 2001      Saul Kravitz
  Copyright 2004      Fabrice Bellard
  Copyright 2002      Guido Draheim
  Copyright 2005-2010 Free Software Foundation, Inc.
  Copyright 1995-2001 Jonathan Amery
  Copyright 1995-2003 Peter Benie
  Copyright 2011      Richard Kettlewell
  Copyright 2012      Matthew Vernon
  Copyright 2013-2019 Mark Wooding
  Copyright 1995-2013 Simon Tatham
  Copyright 2012,2013 "Omnifarious" and "btel" on Stackoverflow


GPLv3+
======

secnet is distributed under the terms of the GNU General Public
License, version 3 or later.

secnet is distributed in the hope that it will be useful, but WITHOUT
ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
for more details.

The file COPYING in the source tree contains a copy of the GNU GPL v3.
A copy of this licence can be found on Debian systems (and
derivatives) in /usr/share/common-licenses/GPL-3.

Some files contain a notice with the abbreviated form:
  SPDX-License-Identifier: GPL-3.0-or-later
As is conventional, this should be read as a licence grant.

Some included libraries contain CC-BY-SA 4.0 code, which is not
necessarily compatibile with future GPL versions, so the effective
licence for a built and distributed secnet package is GPLv3 only.


Contributing
============

Contributions to secnet are accepted based on the git commit
Signed-off-by convention, by which the contributors' certify their
contributions according to the Developer Certificate of Origin version
1.1 - see the file DEVELOPER-CERTIFICATE.

In accordance with the Developer Certificate of Origin, if you make a
contribution to one of the incorporated works with a more liberal
licence, you will be taken to have made your contribution under that
more liberal licence.

If you create a new file please be sure to add an appropriate licence
header.  In the main parts of secnet this should be something like:
 * This file is part of secnet.
 * See LICENCE and CREDITS for full list of copyright holders.
 * SPDX-License-Identifier: GPL-3.0-or-later
 * There is NO WARRANTY.


Incorporated works
==================

Some of the source code has more liberal licences, all of which are
GPLv3-compatible, and potentially GPLv3+-compatible.

These portions can be used, distributed, and modified, separately,
under the more liberal licence.  But when they are used or distributed
as part of secnet, the GPL applies to the combination.


ac_prog_cc_no_writeable_strings.m4
-----------------------------------

This is a version of ax_cflags_no_writable_strings.m4 which is
now in the Autoconf Archive, where it has this permission notice:

  Copyright (c) 2008 Guido U. Draheim <guidod@gmx.de>

  This program is free software; you can redistribute it and/or modify it
  under the terms of the GNU General Public License as published by the
  Free Software Foundation; either version 3 of the License, or (at your
  option) any later version.

  This program is distributed in the hope that it will be useful, but
  WITHOUT ANY WARRANTY; without even the implied warranty of
  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General
  Public License for more details.

  You should have received a copy of the GNU General Public License along
  with this program. If not, see <https://www.gnu.org/licenses/>.

  As a special exception, the respective Autoconf Macro's copyright owner
  gives unlimited permission to copy, distribute and modify the configure
  scripts that are the output of Autoconf when processing the Macro. You
  need not follow the terms of the GNU General Public License when using
  or distributing such scripts, even though portions of the text of the
  Macro appear in them. The GNU General Public License (GPL) does govern
  all other use of the material that constitutes the Autoconf Macro.

  This special exception to the GPL applies to versions of the Autoconf
  Macro released by the Autoconf Archive. When you make and distribute a
  modified version of the Autoconf Macro, you may extend this special
  exception to the GPL to apply to your modified version as well.


argparseactionnoyes.py
----------------------

  Copyright 2012 "Omnifarious" (a user on StackOverFlow)
  Copyright 2013 "btel" (a user on StackOverFlow)

  https://stackoverflow.com/questions/9234258/in-python-argparse-is-it-possible-to-have-paired-no-something-something-arg/20422915#20422915

  CC-BY-SA 4.0
  https://creativecommons.org/licenses/by-sa/4.0/legalcode
  by virtue of
  https://stackoverflow.com/legal/terms-of-service#licensing
  which says everything is CC-BY-SA and has a link to v4.0
  (And which is therefore compatible with secnet's GPLv3)

  all retrieved 4.11.2019 and rechecked 12.11.2022


aes.[ch]
--------

Copyright 2000 Vincent Rijmen, Antoon Bosselaers, Paulo Barreto
Copyright 2004 Fabrice Bellard
Copyright 2013 Ian Jackson

Original licence:

  This code is hereby placed in the public domain.

  THIS SOFTWARE IS PROVIDED BY THE AUTHORS ''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 AUTHORS 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.


base91-c/
---------

  Copyright (c) 2000-2006 Joachim Henke

  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 Joachim Henke nor the names of his
      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.


base91-python/
---------------

  Copyright (c) 2012 Adrien Beraud
  Copyright (c) 2015 Guillaume Jacquenot

  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 Adrien Beraud, Wisdom Vibes Pte. Ltd., 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.


configure
---------

This is autogenerated from various other inputs, including FSF code in
utotools, regarding which the FSF say this:

  Copyright (C) 1992-1996, 1998-2012 Free Software Foundation, Inc.

  This configure script is free software; the Free Software Foundation
  gives unlimited permission to copy, distribute and modify it.

However, in fact, the script is GPLv3+ because it contains pieces
derived from secnet's aclocal.m4, etc.


debian/
-------

debian/init is from an original init script example by Miquel van
Smoorenburg and Ian Murdock.  Modified by Richard Kettlewell.

debian/rules was once from an example from Joey Hess and is now
(after most of it was deleted) probably entirely the work of Ian
Jackson.

The remainder of debian/ is by the authors of Secnet (with possible
future changes made by Debian contributors).


install-sh
----------

Copyright 1991 by the Massachusetts Institute of Technology

  Permission to use, copy, modify, distribute, and sell this software
  and its documentation for any purpose is hereby granted without fee,
  provided that the above copyright notice appear in all copies and
  that both that copyright notice and this permission notice appear in
  supporting documentation, and that the name of M.I.T. not be used in
  advertising or publicity pertaining to distribution of the software
  without specific, written prior permission.  M.I.T. makes no
  representations about the suitability of this software for any
  purpose.  It is provided "as is" without express or implied
  warranty.


md5.[ch]
--------

Authored by Colin Plumb in 1993.  Public domain statement:

  This code implements the MD5 message-digest algorithm.
  The algorithm is due to Ron Rivest.  This code was
  written by Colin Plumb in 1993, no copyright is claimed.
  This code is in the public domain; do with it what you wish.

I interpet this as a blanket permision.


serpent.c, serpentsboxes.h
---------------------------

Authored by Ross Anderson, Eli Biham, Lars Knudsen.

Quoting the Serpent web page:

  Serpent is now completely in the public domain, and we impose no
  restrictions on its use. This was announced on the 21st August at
  the First AES Candidate Conference.  The optimised implementations
  in the submission package are now under the General Public License
  (GPL), although some comments in the code still say otherwise. You
  are welcome to use Serpent for any application.  If you do use it,
  we would appreciate it if you would let us know!

https://www.cl.cam.ac.uk/~rja14/serpent.html

I have indeed corresponded with Ross Anderson about the use of Serpent
in secnet, and have updated the source comments to reflect the licence
upgrade.


sha1.c
------

Authored by Steve Reid and modified by James H. Brown,
Saul Kravitz, and Ian Jackson.

  100% Public Domain

I interpet this as a blanket permision.


sha512.[ch]
-----------

  Copyright (C) 2005, 2006, 2008, 2009, 2010 Free Software Foundation, Inc.

  This program is free software: you can redistribute it and/or modify
  it under the terms of the GNU General Public License as published by
  the Free Software Foundation, either version 3 of the License, or
  (at your option) any later version.

  This program is distributed in the hope that it will be useful,
  but WITHOUT ANY WARRANTY; without even the implied warranty of
  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  GNU General Public License for more details.

  Written by David Madore, considerably copypasting from
  Scott G. Miller's sha1.c


subdirmk/
---------

Copyright 2019-2020 Ian Jackson
Copyright 2019 Mark Wooding

    subdirmk and its example is free software; you can redistribute it
    and/or modify it under the terms of the GNU Library General Public
    License as published by the Free Software Foundation; either
    version 2 of the License, or (at your option) any later version.

    This is distributed in the hope that it will be useful, but
    WITHOUT ANY WARRANTY; without even the implied warranty of
    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
    Library General Public License for more details.

    You should have received a copy of the GNU Library General Public
    License along with this library as the file LGPL-2.
    If not, see https://www.gnu.org/.

    A copy of this licence can be found on Debian systems (and
    derivatives) in /usr/share/common-licenses/LGPL-3.



u64.h
-----

  uint64_t-like operations that work even on hosts lacking uint64_t

  Copyright (C) 2006, 2009, 2010 Free Software Foundation, Inc.

  This program is free software: you can redistribute it and/or modify
  it under the terms of the GNU General Public License as published by
  the Free Software Foundation, either version 3 of the License, or
  (at your option) any later version.

  This program is distributed in the hope that it will be useful,
  but WITHOUT ANY WARRANTY; without even the implied warranty of
  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  GNU General Public License for more details.

  Written by Paul Eggert.