Why are system-namespaces not copied?

L A Walsh rsync at tlinx.org
Fri Oct 12 22:41:03 UTC 2018

On 9/18/2018 7:44 AM, Frank Steiner via rsync wrote:
> Hi,
> the man page states
>     For systems that support extended-attribute namespaces, a  copy  being
>     done  by a super-user copies all namespaces except system.*.
> That's the reason why NFAv4 ACLs are not copied as they are in the
> system.nfs4_acl (or system.nfs4acl) namespace.
> Why are those namespaces excluded?
> Not being able rsync ACLs von NFSv4 is a major drawback now that
> NFsv4 becomes standard oder v3 and ACLs are getting more widely used.
	Because they are storing them in the security (sometimes also
called system) section and not the 'root' section (at least on XFS).
The linux kernel disallows you reading ex-attrs with the Security

	I don't particularly like it for the same reasons you don't.
It takes patching a linux kernel to enable them being copied.  I've
done it but more as proof of theory.  Problem comes in when you restore
attribute to a secure namespace.  Are those attrs really secure when you
take them "off the system".  If not, you could modify them, then if
they are copied to a target, you could use modified attrs to 
give yourself root capabilities.

	So...have to solve that before it can be safely allowed.
NeverTheLess, it's still a potential hole to allow copying of such 
security attrs. Unless you want to change the way security attrs are
stored to use 4k-long signing strings to ensure non-tampering, I don't
see how you can do it...and doing that would be adding 4k to each 

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