[zeromq-dev] TLS (openssl) for ZeroMQ

Luca Boccassi luca.boccassi at gmail.com
Tue Dec 25 21:13:42 CET 2018


On Tue, 2018-12-25 at 21:05 +0100, 林宝龙 wrote:
> I suggested to use curve directly, but as a hole system, they didn't
> want
> to have two key management system, TLS was there which was used by
> other
> node. And another reason they gave to me is the curve was not been
> used so
> much by big companies compare to TLS, even it's simple than TLS.
> Further
> more the running environment has already had OpenSSL installed, use
> openssl
> can lower the security libraries maintenance.

First of all curve was created by expert cryptographers, and it's
extensively used, so it's not really a problem. The crypto primitives
are provides by libsodium, which again is a very high quality library
and used by many, many applications and libraries, and will most likely
be already installed everywhere.

Regarding key management, are you aware that there's the ZAP protocol?
You can use it to implement the key management scheme you prefer,
programmatically. For example, you could map 1:1 from SSL keys to curve
keys internally.

> About the license problem, as you explained to me, it is a big
> problem, I
> saw there is an issue which was registered 2 years ago to change the
> libzmq's license, but it is not coming to end. I'll check with my
> colleagues how to make the license issue gone?  Come back to you when
> I
> have more information.

Again - you *cannot* make the license issue go away. We have been
trying to relicense to MPL2 for years, it will take years to finish, if
ever. This is not something that can be worked around or "hacked". It's
a legal issue.

> Best regards,
> Baolong
> 
> On Tue, 25 Dec 2018, 12:31 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
> > > > 
> > > 
> > > _______________________________________________
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> > 
> > --
> > 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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