[linux-cifs-client] security and trusted extended attributes into the -mm kernel

[Dave Kleikamp]

I'm copying the SELinux mailing list, as I don't know very much about
it.

On Mon, 2004-12-06 at 17:56 -0600, Steven French wrote:
> 
> > jfs adds security and trusted extended attributes into the -mm
> kernel 
> 
> I see the corresponding patch
> (http://jfs.bkbits.net:8080/linux-2.5/gnupatch@41ae4315obsBp8r9Y0EzmG870QJhFA) on bitkeeper.   
> Do you have some additional context explaining this and what they are
> for beyond the minimal info in man 5 attr?  

The security xattrs are to support SELinux.  I don't honestly know who
uses the trusted xattrs, but if other file systems have them, there is
no reason not to add them to jfs.

> It sounds like something I need to do add to the cifs client too (and
> probably something smbd needs to be aware of) but ... the "security."
> and "trusted." namespace certainly would have different security
> considerations than the user. category which is the only one which I
> map to OS/2 EAs on the wire for Samba.

The security attributes are unique in that the file system does not do
any permission checks, but relies on the security module for that.
Trusted attributes rely on the CAP_SYS_ADMIN capability.

>    I don't really want to overuse the EA call for other namespace if
> it opens a security issue (namespace prefix "os2." and "user." are
> stripped off by the client and sent to the Samba server as EAs).
> This is tricky because the ACL model which Samba knows about has a
> concept of who is granted permission in ACEs for modifying EAs and
> modifying the ACL but not sure how authorization for these two would
> be handled from the point of view of the server side ACL 
> 
> Perhaps the best approach is to make another minor CIFS POSIX
> extension (a one-off of current set extended attributes) to handle
> these two namespaces - at least based on my read of man attr(5) and
> the security implications of these two. 
> 
> Opinions? 

Questions for the SELinux list:  Can SELinux play nicely with cifs?
Should cifs support security.* xattrs?

> Steve French
> Senior Software Engineer
> Linux Technology Center - IBM Austin
> phone: 512-838-2294
> email: sfrench at-sign us dot ibm dot co> 
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Shaggy
-- 
David Kleikamp
IBM Linux Technology Center