[clamav-users] Database updated over unencrypted connection?

Paul Kosinski clamav-users at iment.com
Wed Mar 20 20:49:17 EDT 2019

My comments were mainly concerning CVD *validation*, not HTTPS.

Debian updates (for example) are delivered via plain HTTP, but they are
validated using standard GPG tools. Firefox (ESR) updates are handled
similarly (up to SHA512 hash, validated using GPG). I have more
confidence in standard GPG tools than ClamAV's current one-off scheme.

In any case, transporting ClamAV's CVD files over HTTPS secures the
transport, but doesn't necessarily validate the content: a rogue source
could perhaps deliver fake CVDs over HTTPS (perhaps via some form of
DNS hijacking, such as MITM DNS). GPG-equivalent signing would help
defend against this.

If only HTTPS is used, then at least ClamAV should check the server
certificate: e.g. against a built-in list. (Can libcurl do this?)

But ... some organizations MITM all external HTTPS these days. I think
that would cause server certificate checking to fail. (And again make
fake CVDs a possibility.)

On Mon, 18 Mar 2019 02:09:33 +0000
"Joel Esler (jesler)" <jesler at cisco.com> wrote:

> As Micah said, when we roll out the new version of freshclam that
> supports https, this will be a done deal.   Technically, https on the
> cdn is available now.  Freshclam just doesn’t know how to use it.  We
> want people to freshclam. As the way it functions does so in a way
> that reduces load on the mirrors and allows us to plan and predict
> how updating will work.  Not something we can do if people are using
> wget or curl to download the entire main, daily, safebrowsing, and
> bytecode cvd’s every second (looking at you, person in Japan). 
> It’s not a question of if we are going to do it.  It’s not even a
> question of when.  We know we are and we know when.  There are only
> so many hours in the day, and we haven’t gotten to this one yet.
> This debate, while interesting is essentially pointless.  We’re going
> to do it.  
> Sent from my  iPhone
> > On Mar 17, 2019, at 21:25, Paul Kosinski via clamav-users
> > <clamav-users at lists.clamav.net> wrote:
> > 
> > Looking at the PiperMail thread about how ClamAV verifies CVD
> > signatures, I see two things that concern me.
> > 
> > First, it says it uses "an implementation of RSA inspired by
> > http://www.erikyyy.de/yyyRSA/". How well has this implementation
> > been vetted? I'm not a crypto expert (by any means), but people
> > like Bruce Schneier stress that doing crypto right is difficult,
> > and that there are many possibilities for subtle errors that cause
> > the encryption to be weak. Witness the non-random seed that turned
> > up in Debian a few years ago, or the recent Elliptic Curve
> > "scandal".
> > 
> > Second, if the decryption key is baked in to ClamAV, what protocol
> > is there to update it in case the encryption key is compromised? I
> > presume it would require a ClamAV software update, but such an
> > update would be critical, and the current out-of-date notice
> > wouldn't cut it. In fact the fake CVD might even lie about the need
> > for a software update.
> > 
> > I'm not saying that HTTPS would answer these questions, but perhaps
> > a more robust security model would be desirable.

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