[zeromq-dev] TLS (openssl) for ZeroMQ

Luca Boccassi luca.boccassi at gmail.com
Tue Dec 25 21:15:37 CET 2018


On Tue, 2018-12-25 at 11:47 -0500, Steven McCoy wrote:
> A common workaround is to dynamically pull in OpenSSL at
> runtime.  Have a
> context option that specifies the OpenSSL “.so” or “.dll” path and
> cache
> the required API inside a struct or similar.

Sorry but that's not a legal solution, but rather a way to try and be
"clever" and waltz around the precise wording of the licenses. A lawyer
could very well convince a judge that that still counts as a single
unit of compilation and as distributions. We cannot take chances like
that - we don't have any lawyers "working" here, it's a community
driven project.

> On Tue, Dec 25, 2018 at 6:30 Luca Boccassi <luca.boccassi at gmail.com>
> wrote:
> 
> > On Tue, 2018-12-25 at 00:53 +0100, 林宝龙 wrote:
> > > The problem of first option we met is that OpenSSL provides a lot
> > > configurable things, for example, trust group, external
> > > verification
> > > callback, etc. We must add more options to sockopt to have such
> > > things
> > > configurable. For the callback functions, if we continue using
> > > setsockopt,
> > > we need to cast function pointer to void pointer and vice versa,
> > > looks not
> > > good.
> > 
> > As mentioned, there is really no alternative to continue supporting
> > bindings. Also, exposing a third party API/ABI again would mean
> > that
> > the users would need to start worrying about OpenSSL's API/ABI
> > changes,
> > and keep them in sync with the internal usage of the library. That
> > would not be maintainable.
> > 
> > So it looks like there are both legal and implementation problems.
> > So
> > let's take a step back: why is the current
> > encryption/authentication
> > support via CURVE and GSSAPI not sufficient? What is lacking that
> > you
> > need in your application?
> > 
> > > About the licence issue, I'm not familiar with those licenses,
> > > and I
> > > have
> > > asked someone inside my company, got the answer that I can use
> > > OpenSSL in
> > > libzmq with an exception, I don't know how. He said that we will
> > > share the
> > > code out in the end, but can't contribute back to libzmq
> > > directly.
> > > Does it
> > > same as what you concern? Do you have more information that we
> > > must
> > > stop
> > > using OpenSSL inside libzmq?
> > 
> > Yes an exception is needed as I said, but not just from you: from
> > every
> > single copyright holder of libzmq, of which there are many. That's
> > because adding an exception to the license is a change in license,
> > and
> > cannot legally be done unilaterally.
> > 
> > Note that this is not only a problem for contributing code back,
> > but
> > also for your application. You cannot distribute those changes to
> > anybody without a license change, which means you cannot give your
> > application to anybody without breaching the terms of the license,
> > and
> > thus copyright law.
> > 
> > > On Mon, 24 Dec 2018, 23:42 Luca Boccassi <luca.boccassi at gmail.com
> > > wrote:
> > > 
> > > > On Mon, 24 Dec 2018, 23:03 林宝龙 <lbl52001 at gmail.com wrote:
> > > > 
> > > > > Hi,
> > > > > 
> > > > > We are adding TLS support for ZeroMQ(based on 4.2.5). Product
> > > > > reason, we
> > > > > choosed OpenSSL as TLS library.
> > > > > 
> > > > > Ask community for suggestions, which solution below is
> > > > > better?
> > > > > 1. Use TLS public certification, private key, etc as socket
> > > > > option (set
> > > > > through setsockopt), ZeroMQ manages the OpenSSL context,
> > > > > one  OpenSSL
> > > > > context per socket_base_t object.
> > > > > 2. Use OpenSSL context as socket option(set through
> > > > > setsockopt),
> > > > > external
> > > > > application should provide the OpenSSL context, with public
> > > > > certification,
> > > > > private key, etc. set in context level, all ssl connections
> > > > > share
> > > > > the same
> > > > > configuration as the input OpenSSL context.
> > > > > 
> > > > > At beginning we choosed the first solution, like curve, use
> > > > > public
> > > > > certification, private key as the socket option. But later
> > > > > on, we
> > > > > found the
> > > > > second solution that use external OpenSSL context can make
> > > > > the
> > > > > ZeroMQ code
> > > > > simpler, and more flexible, external application can
> > > > > configure
> > > > > the OpenSSL
> > > > > context without change the ZeroMQ socket options.
> > > > > 
> > > > > Welcome your comments.
> > > > > 
> > > > > Best regards,
> > > > > Baolong
> > > > > 
> > > > 
> > > > The first option would be better, exposing third party API and
> > > > ABI
> > > > would
> > > > be a nightmare, especially for bindings. O
> > > > 
> > > > But the most important issue is that the Openssl license is not
> > > > compatible
> > > > with libzmq, which is licensed under the lgpl3, so I'm afraid
> > > > such
> > > > combination will not be legally distributable. At least not
> > > > without
> > > > a
> > > > relicensing effort to add an exception - we are already trying
> > > > that
> > > > to
> > > > change to mpl2 and are nowhere near done unfortunately.
> > > > 
> > > > > _______________________________________________
> > > > 
> > > > zeromq-dev mailing list
> > > > zeromq-dev at lists.zeromq.org
> > > > https://lists.zeromq.org/mailman/listinfo/zeromq-dev
> > > > 
> > > 
> > > _______________________________________________
> > > zeromq-dev mailing list
> > > zeromq-dev at lists.zeromq.org
> > > https://lists.zeromq.org/mailman/listinfo/zeromq-dev
> > 
> > --
> > Kind regards,
> > Luca Boccassi_______________________________________________
> > zeromq-dev mailing list
> > zeromq-dev at lists.zeromq.org
> > https://lists.zeromq.org/mailman/listinfo/zeromq-dev
> > 
> 
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-- 
Kind regards,
Luca Boccassi
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