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|
{% extends "common/base.j2" %}
{% block body_content %}
<div class="container-fluid">
<div class="container text-center">
<h1>{{ _("gnurl / libgnurl") }}</h1>
<p>
{% trans %}
libgnurl is a fork of libcurl, which is mostly for GNUnet but it might
be usable for others, hence we're releasing the code on this website
to the general public. Please read the README for instructions, as you
must supply the correct options to configure to get a proper build of
libgnurl. In addition to the source as a TAR, we also offer the
changes we made against libcurl's Git repository to create
libgnurl. In the following, I will explain the motiviations behind
this fork.
{% endtrans %}
</p>
<h3>{{_("Motivation") }}</h3>
<p>
{% trans %}
cURL supports a bunch of crypto backends. GNUnet requires the use of
GnuTLS, but other variants are used by some distributions. Supporting
other crypto backends would again expose us to a wider array of
security issues, may create licensing issues and most importantly
introduce new bugs as some crypto backends are known to introduce
subtle runtime issues. While it is possible to have two versions of
libcurl installed on the same system, this is error-prone, especially
as if we are linked against the wrong version, the bugs that arise
might be rather subtle.
{% endtrans %}
</p>
<p>
{% trans %}
For GNUnet, we also need a particularly modern version of
GnuTLS. Thus, it would anyway be necessary to recompile cURL for
GNUnet. But what happens if one links cURL against this version of
GnuTLS? Well, first one would install GnuTLS by hand in the
system. Then, we build cURL. cURL will build against it just fine, but
the linker will eventually complain bitterly. The reason is that cURL
also links against a bunch of other system libraries (gssapi, ldap,
ssh2, rtmp, krb5, sasl2, see discussion on obscure protocols above),
which --- as they are part of the distribution --- were linked against
an older version of GnuTLS. As a result, the same binary would be
linked against two different versions of GnuTLS. That is typically a
recipe for disaster. Thus, in order to avoid updating a dozen system
libraries (and having two versions of those installed), it is
necessary to disable all of those cURL features that GNUnet does not
use, and there are many of those. For GNUnet, the more obscure
protocols supported by cURL are close to dead code --- mostly
harmless, but not useful. However, as some application may use one of
those features, distributions are typically forced to enable all of
those features, and thus including security issues that might arise
from that code.
{% endtrans %}
</p>
<p>
{% trans %}
So to use a modern version of GnuTLS, a sane approach is to disable
all of the "optional" features of cURL that drag in system libraries
that link against the older GnuTLS. That works, except that one should
then NEVER install that version of libcurl in say /usr or /usr/local,
as that may break other parts of the system that might depend on these
features that we just disabled. Libtool versioning doesn't help here,
as it is not intended to deal with libraries that have optional
features. Naturally, installing cURL somewhere else is also
problematic, as we now need to be really careful that the linker will
link GNUnet against the right version. Note that none of this can
really be trivially fixed by the cURL developers.
{% endtrans %}
</p>
<h3>{{_("Rename to fix") }}</h3>
<p>
{% trans %}
At this point, developers that don't want to rebuild an entire
distribution from scratch get grumpy. Grumpy developers do silly
things, like forking code to fix it. I called the fork gnurl (to be
pronounced with a grumpy voice and an emphasis on the R) as it is bits
of cURL, a bit more GNUish, for GnuNet, and gnurl can be pronounced to
indicate the grumpy origins.
{% endtrans %}
</p>
<p>
{% trans %}
How does forking fix it? Easy. First, we can get rid of all of the
compatibility issues --- if you use libgnurl, you state that you don't
need anything but HTTP/HTTPS. Those applications that need more,
should stick with the original cURL. Those that do not, can choose to
move to something simpler. As the library gets a new name, we do not
have to worry about tons of packages breaking as soon as one rebuilds
it. So renaming itself and saying that "libgnurl = libcurl with only
HTTP/HTTPS support and GnuTLS" fixes 99% of the problems that darkened
my mood. Note that this pretty much CANNOT be done without a fork, as
renaming is an essential part of the fix. Now, there might be creative
solutions to achieve the same thing within the standard cURL build
system, but I'm not happy to wait for a decade for Daniel to review
the patches. The changes libgnurl makes to curl are miniscule and can
easily be applied again and again whenever libcurl makes a new
release.
{% endtrans %}
</p>
<h3>{{_("Summary") }}</h3>
<p>
{% trans %}
At this point, developers that don't want to rebuild an entire
distribution from scratch get grumpy. Grumpy developers do silly
things, like forking code to fix it. I called the fork gnurl (to be
pronounced with a grumpy voice and an emphasis on the R) as it is bits
of cURL, a bit more GNUish, for GnuNet, and gnurl can be pronounced to
indicate the grumpy origins.
{% endtrans %}
</p>
<h3>{{_("Using libgnurl") }}</h3>
<p>
{% trans %}
Projects that use cURL only for HTTP/HTTPS and that would work
with GnuTLS should be able to switch to libgnurl by changing
"-lcurl" to "-lgnurl". That's it. No changes to the source code
should be required. Continue to read the cURL documentation ---
as libgnurl strives for bug-for-bug compatibility with the
HTTP/HTTPS/GnuTLS subset of cURL. However, we're happy to add
new features relating to this core subset and might be easier to
convince than the cURL developers.
{% endtrans %}
</p>
<p>
{% trans %}
libgnurl and gnurl are not intended to be used as a replacement
for curl for users. Since no conflicts in filenames should occur
you are not expected to remove curl to make use of gnurl and
viceversa.
{% endtrans %}
</p>
</div>
</div>
<div class="container adorn_h3_bracket">
<div class="row">
<div class="col-lg-6">
<h3>{{ _("Source Code") }}</h3>
<p>
{% trans %}
You can get the Gnurl Git repository using:
git clone https://git.taler.net/gnurl.git/
The versions are checked in as signed git tags.
{% endtrans %}
</p>
</div>
<div class="col-lg-6">
<h3>{{ _("Downloads") }}</h3>
<p>
{% trans %}
Releases are published on <a href="https://ftp.gnu.org/gnu/gnunet/">ftp.gnu.org/gnu/gnunet</a>.
gnURL is available from within a variety of distributions and package managers.
To some extent officially supported and maintained is gnURL within GNU Guix, the package manager (available as "gnurl"),
as well as the collaborative Gentoo ebuild collection (<a href="https://overlays.gentoo.org">overlay</a>)
<a href="https://gnunet.org/git/youbroketheinternet-overlay.git/">youbroketheinternet</a>.
{% endtrans %}
</p>
</div>
</div>
<div class="row">
<div class="col-lg-6">
<h3>{{ _("Reporting Bugs") }}</h3>
<p>
{% trans %}
You can report bugs on our bug tracker:
<a href="https://gnunet.org/bugs/">gnunet.org/bugs</a>. Alternatively
you can use our bug mailinglist, but we prefer to track bugs
on the bugtracker.
{% endtrans %}
</p>
</div>
<div class="col-lg-6">
<h3>{{ _("Maintainer and Cryptographic signatures") }}</h3>
<p>
{% trans %}
libgnurl is maintained by Nils Gillmann.
Releases are signed
with the OpenPG Key <b>A88C8ADD129828D7EAC02E52E22F9BBFEE348588</b>,
with the key fingerprint <b>A88C 8ADD 1298 28D7 EAC0 2E52 E22F 9BBF EE34 8588</b>.
{% endtrans %}
</p>
</div>
</div>
</div>
</div> <!-- /container -->
{% endblock body_content %}
|
