I'm not sure how important the bulk-create issue is either, but I
thought I'd bring up the file creation as a related place where a
malicious user could consume lots of resources quickly. Seems like if
we're going to try to address one then we need to try to address the
other?
Rob
On Jun 25, 2009, at 11:04 AM, Walter Ligon wrote:
up until now it has been the user's prerogative to create files with
as many dfiles as he wants - I assume a user is limited to some max
by the configuration (is he?) but that could be large - so he could
allocate 100 dfiles and only use 2 (if he only uses 1 the stuffing
will come into play). I'm open to discussion of how to deal with
that in terms of interface and such. If we need that we can work on
a way to do it.
Over the last year I've found David & Nick to be very thorough in
trying to design so that users can only do what they are supposed to
do. It may be that it really isn't that bid a deal if users can
allocate extra object - as long as they can't link anything to
them. I fully suspect that we can improve beyond the basic level of
security we are working on now and we can discuss that. What I'm
saying is I'm not sure how important this bulk-create issue really
is - but there are ways to deal with it.
Walt
Rob Ross wrote:
On Jun 25, 2009, at 9:45 AM, Nicholas Mills wrote:
Rob -
You're absolutely correct. The capabilities are trusted and can
only come from servers. If a client gets a hold of one it's
assumed that some server determined the client had a need for the
capability. Servers are able to create capabilities for themselves
that allow them to do anything.
Everyone -
Right now I haven't had a need to differentiate between client and
server requests. However, in the case of batch create I'd really
like to prevent a client from having access to this capability.
For the moment the only client state machine to use batch create
is sys-symlink, and even then the state machine only creates one
handle.
Walt suggested perhaps limiting clients to a single create by use
of some sort of differentiator in the capability. This would avoid
the need to change how PVFS is working today, but means you'd have
to do a little parameter checking; how awkward would that be? Seems
to me you might want to similarly be restricting the *types* of
objects that a client could create, if you're going to try to
minimize the potential damage from this particular call. Since
clients would only be using this to create a symlink object (if I
understand the earlier discussion correctly), you could limit
clients to only creating symlink objects and only one at a time.
Otherwise a client might be able to use this facility to create a
metadata object, populate it with something that makes it look like
it should have permission to access the associated datafiles, and
then point at some datafiles it would like to access? I dunno the
bigger picture, so I don't know if you have already handled this
possibility in some other way...
Ok, so all that leads me to agree that you don't ideally want
clients to be given permission to use this operation :).
Above all I want everyone to know that I'm very open to
suggestion. Of course I realize that in the future new client
state machines could make use of the batch create request. But for
now, at least, only the servers have a legitimate need for this
request.
Now that I'm looking at this, why aren't you equally worried about
a user using the new create request and specifying some
ridiculously large num_dfiles_req? Doesn't that have the same
problem with respect to resource consumption?
Rob
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