Re: [Keyrings] Re: [PATCH 01/04] Add multi-precision-integer maths library

[Adrian Bunk <bunk@stusta.de>]

On Sat, Jan 28, 2006 at 02:17:49AM -0500, Kyle Moffett wrote:
> On Jan 27, 2006, at 19:22, Adrian Bunk wrote:
> >On Fri, Jan 27, 2006 at 09:41:58PM +0100, David Härdeman wrote:
> >>The in-kernel key management also protects the key against many of  
> >>the different ways in which a user-space daemon could be attacked  
> >>(ptrace, swap-out, coredump, etc).
> >
> >If an attacker has enough privileges for attacking the daemon, he  
> >should usually also have enough privileges for attacking the kernel.
> 
> Not necessarily.  If the daemon runs as the "backup" user or similar,  
> access to it does not imply root.  We want to make an efficient way  
> to allow the _use_ of keys without implying access to the key data.   
> For example, one item under consideration is a "key handle" that  
> could be cloned, however if you revoke a given handle, all of its  
> cloned handles (and their clones), will be automatically revoked as  
> well.  This would make it possible to pass a key to a program without  
> risking the key to compromise of that program.  Say I pass my SSL key  
> to Mozilla.  With this and some of the other new security features  
> (One of the code-isolation ones I think?), you could allow Mozilla to  
> use SSL websites without risking compromise of the SSL keys because  
> of a browser security hole.


I still haven't gotten the point which part of this is technically 
impossible to implement in userspace.


> On Jan 27, 2006, at 22:45, Trond Myklebust wrote:
> >On Fri, 2006-01-27 at 18:35 -0500, Kyle Moffett wrote:
> >
> >>No, the point is not to put the backup daemon into the kernel, but  
> >>to provide a way for the backup daemon and my user process to  
> >>communicate DSA key details without completely giving the backup  
> >>daemon my key.  I may not entirely trust the backup daemon not to  
> >>get compromised, but with support for the kernel keyring system,  
> >>compromising the backup daemon would only compromise the backed up  
> >>files, not the private keys and other secure data.
> >
> >This sort of thing is implemented routinely in user space by means  
> >of proxy  tickets/certificates/credentials. What makes them  
> >insufficient for this use?
> 
> The problem is that there is no standard way to store/use the keys.   
> I can put my key in an ssh-agent to handle SSH, but that doesn't let  
> me securely auth mozilla.  To do that, I need to explore how mozilla  
> configs work.  And there are similar problems with context for  
> Kerberos, OpenAFS, encrypted filesystems, etc.  You need to have a  
> common standardized way to pass the secure information around.  This  
> provides that interface.


"There's currently no standard" doesn't sound like a compelling reason 
why a standard should be implemented in the kernel instead of userspace.


> Cheers,
> Kyle Moffett

cu
Adrian

-- 

       "Is there not promise of rain?" Ling Tan asked suddenly out
        of the darkness. There had been need of rain for many days.
       "Only a promise," Lao Er said.
                                       Pearl S. Buck - Dragon Seed