bug#25094: Add comments to archive keys and acls

[ludo@gnu.org (Ludovic Courtès)]

Leo Famulari <leo@famulari.name> skribis:

> On Fri, Dec 02, 2016 at 06:38:12PM +0100, Hartmut Goebel wrote:
>> Hi,
>> 
>> the keys for authenticating an archive currently do not hold any
>> comment. This makes it hard to track acls and remove certain keys if
>> required.
>
> Indeed, this makes key management a little harder than it needs to be.

Agreed.  The crux of the problem is that libgcrypt’s canonical sexp
parser does not recognize comments.
<http://people.csail.mit.edu/rivest/Sexp.txt> does not specify comments,
which may be the reason, but other implementations of canonical sexps
(such as lsh and Nettle) do recognize them, so we should just get
libgcrypt to follow suit.

>> Please implement some way to add and change the comment on keys in
>> /etc/guix/ and in /etc/guix/acl.
>> 
>> Proposed usage when generating the key:
>>   guix archive --generate-key=… --comment "store.example.com"
>> 
>> Proposed usage when importing the key and overwriting any existing comment
>> 
>>   guix archive --authorize --comment "store.example.com"
>> 
>> For now, since we have no commands for key management, these would be
>> enough IMO. Existing commenty an easily be changed in the file, so for
>> now we do not need a tool for this.
>
> I think that the comment should either be signed somehow, or the field
> name should be "untrusted-comment".

I think it’s no different than the optional comment in OpenSSH public
keys, and it should be clear that it’s free from and untrusted by
definition (the sexp syntax at least makes it clear that it’s a comment,
as opposed to the OpenSSH public key format).

Ludo’.