Re: squeeze update of prosody?

[Sergei Golovan <sgolovan@nes.ru>]

Hi Antoine,

On Sat, Jan 30, 2016 at 9:45 PM, Antoine Beaupré
<anarcat@orangeseeds.org> wrote:
>
> It looks, however, that there's a bit missing in the patch... Upstream
> seems to have made *two* patches to solve the issue. It looks like you
> backported this:
>
> https://github.com/bjc/prosody/commit/8708def4f55e61acdd5b2c762d420ab40da0d015

This is a patch which works for 0.9.10 and earlier (moreover, it won't
work directly with 0.7.0 in squeeze because the code is actually in
another file - core/s2smanager.lua and not plugins/mod_dialback.lua)

>
> but there's also:
>
> https://github.com/bjc/prosody/commit/c9ce85a5d7575f9c55ce85b45db812f3e8392b07

This is the same patch but suitable for the master branch. Since 0.7.0
don't have an option named "dialback_secret" in module dialback, one
doesn't have to backport it.

>
> It looks like there's some initialisation of the dialback_secret
> variable missing... Upstream master currently has:
>
> local dialback_secret = sha256_hash(module:get_option_string("dialback_secret", uuid_gen()), true);
>
> ... which i think is missing from the resulting patch.

It shouldn't go to the 0.7.0.

>
> I am also unclear as to the source of the second patch, regarding the
> RNG seeding. It sure looks like we do not seed it anymore:
>
> +-function seed(x)
> +-      urandom:write(x);
> +-      urandom:flush();
> ++function seed()
> + end
>
> That looks wrong, no? Is that a patch upstream? I see that 0.9.1 uses
> the lua "random" module instead of the above:

util.random is a new module which appears in 0.9.10. It can be seen here:
http://hg.prosody.im/trunk/file/43328166dcf1/util/random.lua
You can see that it's using /dev/urandom just the way the patch does.
And the patch is a non-intrusive adaptation of this new module to the
old code.

The patch fixes a regression caused by a previous one
(0008-CVE-2016-1232-weak-PRNG-for-dialback-on-S2S.patch) which
someone has already ported to 0.7.0 currently in squeeze-lts. The
problem is that if /dev/urandom is readonly then prosody stops
working. So, the solution is to drop seeding at all because
/dev/urandom is already sufficiently random.

>
> https://github.com/bjc/prosody/blob/master/util/uuid.lua
>
> Yet your patch says the source is "upstream"... could you clarify where
> it comes from or the rationale for this fix?

See above.

Cheers!
-- 
Sergei Golovan