16 Mar 2011 dkg   » (Master)

CryptLib and the OpenSSL License

I spent part of today looking at packaging Peter Gutmann's CryptLib for debian. My conclusion: it may not be worth my time.

One of the main reasons i wanted to package it for debian is because i would like to see more OpenPGP-compliant free software available to debian users and developers, particularly if the code is GPL-compatible.

Cryptlib makes it quite clear that it intends to be GPL-compatible:

cryptlib is distributed under a dual license that allows free, open-source use under a GPL-compatible license and closed-source use under a standard commercial license.
However, a significant portion of the cryptlib codebase (particularly within the bn/ and crypt/ directories) appears to derive directly from OpenSSL, and it retains Eric Young's copyright and licensing. This licensing retains the so-called "advertising clause" that is generally acknowledged to be deliberately incompatible with the GPL. (A common counterargument for this incompatibility is that OpenSSL should be considered a "System Library" for GPL'ed tools that link against it; whether or not you believe this for tools linked against OpenSSL, this counterargument clearly does not hold for a project that embeds and ships OpenSSL code directly, as CryptLib does)

This does not mean that CryptLib is not free software (it is!), nor does it mean that you cannot link it against GPL'ed code (you can!). However, you probably can't distribute the results of linking CryptLib against any GPL'ed code, because the GPL is incompatible with the OpenSSL license.

The un-distributability of derived GPL-covered works makes the CryptLib package much less appealing to me, since i want to be able to write distributable code that links against useful libraries, and many of the libaries i care about happen to be under the GPL.

I also note that Peter Gutmann and CryptLib Security Software (apparently some sort of company set up to distribute CryptLib) may be in violation of Eric Young's License, which states:

 * 3. All advertising materials mentioning features or use of this software
 *    must display the following acknowledgement:
 *    "This product includes cryptographic software written by
 *     Eric Young (eay@cryptsoft.com)"
 *    The word 'cryptographic' can be left out if the rouines from the library
 *    being used are not cryptographic related :-).
A Google search for Eric Young's name on cryptlib.com yields no hits. I do find his name on page 340 of the Cryptlib manual, but that hardly seems like it covers "All advertising materials mentioning features or use of this software". I suppose it's also possible that CryptLib has negotiated an alternate license with Eric Young that I simply don't know about.

In summary: i think CryptLib could go into debian, but its incorporation of OpenSSL-licensed code makes it less useful than i was hoping it would be.

I have a few other concerns about the package after looking it over in more detail. I suspect these are fixable one way or another, but i haven't sorted them out yet. I'm not sure i'll spend the time to do so based on the licensing issues i sorted out above.

But in case anyone feels inspired, the other concerns i see are:

embedded code copies
In addition to embedded (and slightly-modified) copies of bn/ and crypt/ from OpenSSL, CryptLib contains an embedded copy of zlib. Debian has good reasons for wanting to avoid embedded code copies. I've got it CryptLib building against the system copy of zlib, but the bits copied from OpenSSL seem to be more heavily patched, which might complicate relying on the system version.
executable stack
lintian reports shlib-with-executable-stack for the library after it is built. I don't fully understand what this means or how to fix it, but i suspect it derives from the following set of object files that also have an executable stack:
0 dkg@pip:~/src/cryptlib/cryptlib$ for foo in $(find . -iname '*.o'); do
>  if ! readelf -S "$foo" | grep -q .note.GNU-stack ; then
>   echo "$foo"
>  fi
> done
0 dkg@pip:~/src/cryptlib/cryptlib$ 
They probably all need to be fixed, unless there's a good reason for them to be that way (in which case they need to be documented).
non-PIC code
lintian reports shlib-with-non-pic-code on the library after it is built. I don't fully understand what this means, or how to resolve it cleanly, but i imagine this is just a question of sorting out the details.
Anyone interested in using my packaging attempts as a jumping off point can start with:
git clone git://lair.fifthhorseman.net/~dkg/cryptlib
Oh, and please correct me about anything in this post; I'd be especially happy to hear that my analysis of the licensing issues above is wrong :)

Tags: cryptlib, gpl, licensing, openssl

Syndicated 2011-03-16 04:40:00 from Weblogs for dkg

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