Subject: bug#56322: Ruby packaging issues

From: Maxime Devos <[email-masked]>
Date: Wed, 24 Aug 2022 20:38:43 +0200

On 24-08-2022 17:24, Remco van 't Veer wrote:
> [...]
>>    * Ruby bundles zlib.
> Can you point out where it is in the source tree?  Looking at the
> sources I can only find a (very beefy) wrapper around zlib which seems
> to implement all kinds of zlib stuff but also depends on the zlib
> library.  I dunno how to determine if this is bundling or not.
>
>    https://github.com/ruby/ruby/blob/master/ext/zlib/zlib.c

I probably confused the wrapper for a local copy of zlib, nevermind.

There's a zlib-1.2.11-mswin.patch though, I wonder what's up with that.

>>    * Ruby contains some things generated by bison or such.
> It seems the generated parse.c file (from parse.y) is included in the
> tarballs as a service to workaround a bootstrap problem; generating the
> parser requires ruby.  See also:
>
>    https://github.com/ruby/ruby/blob/master/common.mk#L910
>
> I don't know how to deal with this properly.  The only thing I can think
> of is compiling in two phases: first with the supplied parse.c and after
> without.  Or try it with mruby as a native-input but that seems to
> require ruby to compile too.

We have a bunch of old rubies packaged, maybe it can be generated with 
one of the old versions? Though possibly the old versions have the same 
problem, I haven't checked.

If not: fully properly generating it might not be possible, but 
something in-between could be an option:

 1. First, use the pre-generated parse.c.
 2. Once ruby is built, regenerate the parse.c, and verify that it is
    the same as the old parse.c (ignoring the timestamp)

> What's to gain by this?

(1) I would assume it is much easier to hide malware in a generated file 
like parse.c than in the real source code (*) (IIRC, the .c code 
generated by bison is much longer than the .y). By generating the 
parse.c, the potential issue is side-stepped; any security reviewers 
wouldn't even have to look at parse.c because the pre-generated parse.c 
isn't used, it's regenerated.

(2) Also: generators like Bison can have bugs, fixed in later versions. 
Now imagine that Bison had, say, a buffer overflow bug, and that 
distro's just used the pre-generated parse.c. Then once a fixed version 
of Bison comes out, we would have to check every package to see if it 
has a pre-generated parser. It would be much less stressful to just 
always generate parsers from source, then once the version of Bison in 
Guix is updated then all packages automatically get the buffer overflow fix.

I don't think my in-between proposal helps much with (1) in case of a 
competent attacker (though it could stop some insufficiently 
sophisticated attacks where the parse.c malware doesn't try to subvert 
the later check), but it still helps with (2) -- it at least detects if 
ruby used an old bison (and hence that a patch might be in order)

Greetings,
Maxime.

(*) Caveat: I don't have any statistics on this.