[Nix-dev] Authenticating binary substitutes

[Ludovic Courtès]

Lluís Batlle i Rossell <viric at viric.name> skribis:

> On Wed, May 22, 2013 at 05:12:20PM +0200, Ludovic Courtès wrote:
>> Hello,
>> 
>> Currently the “binary cache” substituter relies on DNS to authenticate
>> downloaded binaries: anything coming from, say, hydra.nixos.org is
>> considered authentic, because hydra.nixos.org is listed in the
>> ‘trusted-binary-cache’ list.
>> 
>> This is obviously subject to person-in-the-middle attacks: one could
>> connect over Wifi to somebody else’s network, which happens to redirect
>> hydra.nixos.org to evil.example.com, and end up downloading evil binaries.
>> 
>> I was thinking of a simple extension to solve that:
>> 
>>   1a. The /nix-cache-info file would contain an (optional)
>>      ‘OpenPGPFingerprint’ field, to announce the fingerprint of the
>>      OpenPGP key used to sign Nars.
>> 
>>   1b. In addition to, or alternatively, a /nix-signing-key file would be
>>       served, containing the OpenPGP key used to sign Nars.
>> 
>>   2.  In addition to serving, say,
>>       /nar/zwpx7d0sv36fi4xpwqx2dak0axx5nji8-gmp-5.1.1, the server would
>>       also serve /nar/zwpx7d0sv36fi4xpwqx2dak0axx5nji8-gmp-5.1.1.sig, an
>>       OpenPGP binary signature of the uncompressed Nar.
>> 
>> WDYT?  Could this be implemented in Hydra?
>
> I add myself to the request.

Thanks.  ;-)

> The /nix-cache-info or /nix-signing-key files should be requested
> only once and stored in the local system, unless the user deletes them. If they
> are fetched at every run, we are doomed again.

Sure.  They’re only needed when you get introduced to a server anyway.

Ludo’.