GNU bug report logs - #34125
Installation script needs to be secured with a gpg signature

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Message #13 received at 34125-done <at> debbugs.gnu.org (full text, mbox):

From: Björn Höfling <bjoern.hoefling <at> bjoernhoefling.de>
To: Ricardo Wurmus <rekado <at> elephly.net>
Cc: 34125-done <at> debbugs.gnu.org, Laura Lazzati <laura.lazzati.15 <at> gmail.com>
Subject: Re: bug#34125: Installation script needs to be secured with a gpg
 signature
Date: Fri, 25 Jan 2019 22:25:47 +0100

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On Tue, 22 Jan 2019 08:18:09 +0100
Ricardo Wurmus <rekado <at> elephly.net> wrote:

> Hi Björn,
> 
> > I was looking at the installation video from Laura (not yet public)
> > and wondered about that:
> >
> > We just download the installation script:
> >
> > $ wget https://.../guix-install.sh
> >
> > Then we go on directly executing that script.
> >
> > Shouldn't that be save-garded by a PGP-signature too?  
> 
> I don’t know.
> 
> > Because if it is not, the user could be tricked into a script that
> > downloads a "bad" Guix installation tarball.  
> 
> To avoid having the user tricked we use HTTPS.  At least the users
> will know that this file comes from the official project website.
> 
> A user who is tricked into downloading a script from a malicious site
> could just as well download a matching signature from somewhere else,
> so the script body itself should be signed.  We can’t sign the whole
> file because the first line must be the shebang — unless we forgo the
> shebang and the “chmod +x” instruction and ask people to execute it
> with “sudo bash guix-install.sh”.  “gpg --clear-sign” adds a block of
> text before and after the file, which would be a syntax error in a
> shell script.
> 
> We are probably stuck with having a separate signature file.  I don’t
> know if it’s worth doing when HTTPS is used to fetch the script from
> an authoritative source.
> 

OK, agreed. Let's close this.

Björn

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