mirror of
https://github.com/curl/curl.git
synced 2025-02-17 14:59:45 +08:00
DISTRO-DILEMMA: removed
Out of date and not kept accurate. It was sort of a problem of the past anyway.
This commit is contained in:
Daniel Stenberg
parent
ca20ca54b2
commit
ea2c959db4
@ -1,176 +0,0 @@
|
||||
Date: February 11, 2007
|
||||
Author: Daniel Stenberg <daniel@haxx.se>
|
||||
URL: http://curl.haxx.se/legal/distro-dilemma.html
|
||||
|
||||
Condition
|
||||
|
||||
This document is written to describe the situation as it is right now.
|
||||
libcurl 7.16.1 is currently the latest version available. Things may of
|
||||
course change in the future.
|
||||
|
||||
This document reflects my view and understanding of these things. Please tell
|
||||
me where and how you think I'm wrong, and I'll try to correct my mistakes.
|
||||
|
||||
Background
|
||||
|
||||
The Free Software Foundation has deemed the Original BSD license[1] to be
|
||||
"incompatible"[2] with GPL[3]. I'd rather say it is the other way around, but
|
||||
the point is the same: if you distribute a binary version of a GPL program,
|
||||
it MUST NOT be linked with any Original BSD-licensed parts or libraries.
|
||||
Doing so will violate the GPL license. For a long time, very many GPL
|
||||
licensed programs have avoided this license mess by adding an exception[8] to
|
||||
their license. And many others have just closed their eyes for this problem.
|
||||
|
||||
libcurl is MIT-style[4] licensed - how on earth did this dilemma fall onto
|
||||
our plates?
|
||||
|
||||
libcurl is only a little library. libcurl can be built to use OpenSSL for its
|
||||
SSL/TLS capabilities. OpenSSL is basically Original BSD licensed[5].
|
||||
|
||||
If libcurl built to use OpenSSL is used by a GPL-licensed application and you
|
||||
decide to distribute a binary version of it (Linux distros - for example -
|
||||
tend to), you have a clash. GPL vs Original BSD.
|
||||
|
||||
This dilemma is not libcurl-specific nor is it specific to any particular
|
||||
Linux distro. (This article mentions and refers to Debian several times, but
|
||||
only because Debian seems to be the only Linux distro to have faced this
|
||||
issue yet since no other distro is shipping libcurl built with two SSL
|
||||
libraries.)
|
||||
|
||||
Part of the Operating System
|
||||
|
||||
This would not be a problem if the used lib would be considered part of the
|
||||
underlying operating system, as then the GPL license has an exception
|
||||
clause[6] that allows applications to use such libs without having to be
|
||||
allowed to distribute it or its sources. Possibly some distros will claim
|
||||
that OpenSSL is part of their operating system.
|
||||
|
||||
Debian does however not take this stance and has officially(?) claimed that
|
||||
OpenSSL is not a required part of the Debian operating system
|
||||
|
||||
Some people claim that this paragraph cannot be exploited this way by a Linux
|
||||
distro, but I am not a lawyer and that is a discussion left outside of this
|
||||
document.
|
||||
|
||||
GnuTLS
|
||||
|
||||
Since May 2005 libcurl can get built to use GnuTLS instead of OpenSSL. GnuTLS
|
||||
is an LGPL[7] licensed library that offers a matching set of features as
|
||||
OpenSSL does. Now, you can build and distribute an TLS/SSL capable libcurl
|
||||
without including any Original BSD licensed code.
|
||||
|
||||
I believe Debian is the first (only?) distro that provides libcurl/GnuTLS
|
||||
packages.
|
||||
|
||||
yassl
|
||||
|
||||
libcurl can get also get built to use yassl for the TLS/SSL layer. yassl is a
|
||||
GPL[3] licensed library.
|
||||
|
||||
|
||||
GnuTLS vs OpenSSL vs yassl
|
||||
|
||||
While these three libraries offer similar features, they are not equal.
|
||||
libcurl does not (yet) offer a standardized stable ABI if you decide to
|
||||
switch from using libcurl-openssl to libcurl-gnutls or vice-versa. The GnuTLS
|
||||
and yassl support is very recent in libcurl and it has not been tested nor
|
||||
used very extensively, while the OpenSSL equivalent code has been used and
|
||||
thus matured since 1999.
|
||||
|
||||
GnuTLS
|
||||
- LGPL licensed
|
||||
- supports SRP
|
||||
- lacks SSLv2 support
|
||||
- lacks MD2 support (used by at least some CA certs)
|
||||
- lacks the crypto functions libcurl uses for NTLM
|
||||
|
||||
OpenSSL
|
||||
- Original BSD licensed
|
||||
- lacks SRP
|
||||
- supports SSLv2
|
||||
- older and more widely used
|
||||
- provides crypto functions libcurl uses for NTLM
|
||||
- libcurl can do non-blocking connects with it in 7.15.4 and later
|
||||
|
||||
yassl
|
||||
- GPL licensed
|
||||
- much untested and unproven in the real work by (lib)curl users so we don't
|
||||
know a lot about restrictions or benefits from using this
|
||||
|
||||
The Better License, Original BSD, GPL or LGPL?
|
||||
|
||||
It isn't obvious or without debate to any objective interested party that
|
||||
either of these licenses are the "better" or even the "preferred" one in a
|
||||
generic situation.
|
||||
|
||||
Instead, I think we should accept the fact that the SSL/TLS libraries and
|
||||
their different licenses will fit different applications and their authors
|
||||
differently depending on the applications' licenses and their general usage
|
||||
pattern (considering how GPL and LGPL libraries for example can be burdensome
|
||||
for embedded systems usage).
|
||||
|
||||
In Debian land, there seems to be a common opinion that LGPL is "maximally
|
||||
compatible" with apps while Original BSD is not. Like this:
|
||||
|
||||
https://lists.debian.org/debian-devel/2005/09/msg01417.html
|
||||
|
||||
More SSL Libraries
|
||||
|
||||
In libcurl, there's no stopping us here. There are more Open Source/Free
|
||||
SSL/TLS libraries out there and we would very much like to support them as
|
||||
well, to offer application authors an even wider scope of choice.
|
||||
|
||||
Application Angle of this Problem
|
||||
|
||||
libcurl is built to use one SSL/TLS library. It uses a single fixed name (by
|
||||
default) on the built/created lib file, and applications are built/linked to
|
||||
use that single lib. Replacing one libcurl instance with another one that
|
||||
uses the other SSL/TLS library might break one or more applications (due to
|
||||
ABI differences and/or different feature set). You want your application to
|
||||
use the libcurl it was built for.
|
||||
|
||||
Project cURL Angle of this Problem
|
||||
|
||||
We distribute libcurl and everyone may build libcurl with either library at
|
||||
their choice. This problem is not directly a problem of ours. It merely
|
||||
affects users - GPL application authors only - of our lib as it comes
|
||||
included and delivered on some distros.
|
||||
|
||||
libcurl has different ABI when built with different SSL/TLS libraries due to
|
||||
these reasons:
|
||||
|
||||
1. No one has worked on fixing this. The mutex/lock callbacks should be set
|
||||
with a generic libcurl function that should use the proper underlying
|
||||
functions.
|
||||
|
||||
2. The CURLOPT_SSL_CTX_FUNCTION option is not possible to "emulate" on GnuTLS
|
||||
but simply requires OpenSSL.
|
||||
|
||||
3. There might be some other subtle differences just because nobody has yet
|
||||
tried to make a fixed ABI like this.
|
||||
|
||||
Distro Angle of this Problem
|
||||
|
||||
To my knowledge there is only one distro that ships libcurl built with either
|
||||
OpenSSL or GnuTLS.
|
||||
|
||||
Debian Linux is now (since mid September 2005) providing two different
|
||||
libcurl packages, one for libcurl built with OpenSSL and one built with
|
||||
GnuTLS. They use different .so names and can this both be installed in a
|
||||
single system simultaneously. This has been said to be a transitional system
|
||||
not desired to keep in the long run.
|
||||
|
||||
Footnotes
|
||||
|
||||
[1] = http://www.xfree86.org/3.3.6/COPYRIGHT2.html#6
|
||||
[2] = https://www.gnu.org/philosophy/bsd.html
|
||||
[3] = https://www.gnu.org/licenses/gpl.html
|
||||
[4] = http://curl.haxx.se/docs/copyright.html
|
||||
[5] = https://www.openssl.org/source/license.html
|
||||
[6] = https://www.gnu.org/licenses/gpl.html end of section 3
|
||||
[7] = https://www.gnu.org/licenses/lgpl.html
|
||||
[8] = https://en.wikipedia.org/wiki/OpenSSL_exception
|
||||
|
||||
Feedback/Updates provided by
|
||||
|
||||
Eric Cooper
|
||||
@ -33,12 +33,12 @@ SUBDIRS = examples libcurl
|
||||
|
||||
CLEANFILES = $(GENHTMLPAGES) $(PDFPAGES)
|
||||
|
||||
EXTRA_DIST = MANUAL BUGS CONTRIBUTE FAQ FEATURES INTERNALS SSLCERTS \
|
||||
README.win32 RESOURCES TODO TheArtOfHttpScripting THANKS VERSIONS \
|
||||
KNOWN_BUGS BINDINGS $(man_MANS) $(HTMLPAGES) HISTORY INSTALL \
|
||||
$(PDFPAGES) LICENSE-MIXING README.netware DISTRO-DILEMMA INSTALL.devcpp \
|
||||
MAIL-ETIQUETTE HTTP-COOKIES SECURITY RELEASE-PROCEDURE \
|
||||
SSL-PROBLEMS HTTP2.md ROADMAP.md CODE_OF_CONDUCT.md
|
||||
EXTRA_DIST = MANUAL BUGS CONTRIBUTE FAQ FEATURES INTERNALS SSLCERTS \
|
||||
README.win32 RESOURCES TODO TheArtOfHttpScripting THANKS VERSIONS \
|
||||
KNOWN_BUGS BINDINGS $(man_MANS) $(HTMLPAGES) HISTORY INSTALL \
|
||||
$(PDFPAGES) LICENSE-MIXING README.netware INSTALL.devcpp \
|
||||
MAIL-ETIQUETTE HTTP-COOKIES SECURITY RELEASE-PROCEDURE SSL-PROBLEMS \
|
||||
HTTP2.md ROADMAP.md CODE_OF_CONDUCT.md
|
||||
|
||||
MAN2HTML= roffit < $< >$@
|
||||
|
||||
|
||||
Loading…
Reference in New Issue
Block a user