Patch for unix extensions

John Newbigin jn at
Wed Jan 1 22:18:00 GMT 2003

jra at wrote:
> On Tue, Dec 31, 2002 at 10:36:33AM +0100, Simo Sorce wrote:
>> Jeremy, in case of unix extensions, shouldn't we pass the symlink
>> as is and not resolve it?
> Yes we do - if the client uses the UNIX extensions to readlink. The
> problem is a UNIX extension client could set a symlink on the server
> (which in a UNIX <--> UNIX scenario would never be resolved on the
> server, but read and resolved on the clients filesystem) and then do
> a normal SMB open call on it to escape the restrictions of exporting
> only a small part of the servers filesystem.
This is not always a problem.  There might be cases where users must be
restricted to a specific shared directory, but in the case of UNIX
extensions, the users probably* have shell access to the server anyway.
  Using samba they still have the same user restrictions as shell access
so there is no greater security risk if they access a file remotly than
if they do localy.

By making this an option, the default level of security is suitable for
a restricted server but can be relaxed if need be.  The name of this
option could be changed and perhaps other semantics associated with it
(what exactly is a wide link?) but I don't think it creates any
security problems.


*probably is a bit of a generalisation.  In the case of sharing home 
directories it is possible.  What other writable directories are going 
to be shared?  Are symlinks required in those directories?

>> I think a proper unix-like file system should be able to return
>> links.
> It can. I just can't trust the client to do this.
> Jeremy.

Information Technology Innovation Group
Swinburne University. Melbourne, Australia

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