I actually didn't explain Capabilities exactly as they can be used in
the extreme. You will see that this can be used also when you have the
inventory server behind closed doors.
A capability URL doesn't need to be a direct web service. It can be an
indirect pointer. So you have the public URL that you give out to the
client, and when that is invoked it finds a capability mapping service
that finally invokes the capability function provider.
I don't think I want to do this right now. So yes, all those URLs should
be configurable.
The bigger issue I'm debating is how all this should look like in the
code. We all know we don't know where to put CAPs :-) I'm hoping this
will finally give it a natural place to be, but I need to think a lot
more. One thing's for sure: CAPs is an LL Viewer thing and as such it
should be under LLxxx. It's very unlikely that other viewers will use
capabilities. (although the more I think about it, the more similarities
I see with OpenID Tokens...)
Melanie wrote:
Well, if FetchInventoryDescendents works better over CAPS, then we
can try using that. Now, that would serve another purpose beyond
your intended trust issue:
Currently, inventory is fetched by the region en-bloc, rather than
being fetched only on demand. There isn't even a function to fetch a
single item by UUID.
Now, here is what I found:
- If an item is given to a user while that user is offline, the user
needs to clear cache to see it
- If an item is given to a user while that user is in another
region, the item will not show until a relog & cache clear
You just supplied a very important bit of information, namely that
the viewer sends SendInventoryDescendents over UDP only after a
cache clear, but over CAPS it's sent all the time.
So, CAPS would seem to be the solution to this issue.
Now, here it goes, again:
There are grids that are set up to have an inventory server that is
inaccessible to the viewer. So, while I'm, of course, not opposed to
your approach of lettign the viewer talk to the inventory server,
that needs to be optional. The inventory server is not secure enough
to be open to the internet! Not for the fledgling commercial
offerings like LCO.
Also, this highlights a new, additional reason to have a function
like "get item by uuid" on the inventory server interface. On
cross-region gives, the region of the receiving agent receives a
message (via IM) containing the item ID. In order to send the bulk
update message that is needed to make the viewer actually see the
item, it needs to first fetch it. This is not an issue if giver and
receiver are in one region, because the item is already in the
region's inventory cache, but if it;s a different region, it doesn't
have that item and currently has no way to request it, short of
reloading that user's complete inventory!
So, maybe, as a side effect, this problem can be solved, since such
a "fetch item to region by UUID" function will be needed for that
scenario, too.
For open grid offerings, I see some added security against regions
corrupting user inventories, for all grids, I see some advantage in
memory consumption, because the full inventory fetch on region entry
is removed by it, and also maybe a chance to make cross-region item
giving work.
The only thing I'm asking is, please make the ex-region CAPS giving
for this optional, e.g. provide a region implementation to proxy it
and allow selection of either a region caps (for trusted regions and
closed grids) and inventory server CAPS (for open grids that have
accessible inventory servers).
Melanie
Diva Canto wrote:
After more poking at the viewer, here's what I found.
FetchInventoryDescendents seems to be working consistently over CAPs, in
fact better than over UDP. When the agent logs in, the client always
invokes that CAP, unlike the message over UDP which only seems to come
after a clear cache. That first FetchInventoryDescendents request is for
getting the 1st-level items just below the Root folder. Whenever you
unfold folders, this CAP is invoked too, and that happens all the time.
In other words, the inventory skeleton is passed in a lazy mode to the
client, and directly from wherever this Capability is being served. Why
is this commented in the code?
Observation #1: we could make the provider of this CAP be the inventory
service, instead of the region. That way, the user can *browse* the
contents of her inventory *safely everywhere* -- even if the region
where she is doesn't have her inventory.
Unfortunately, the goodies sort of stop here. I tried coercing the
viewer to use FetchInventory, CreateInventoryItem,
CreateInventoryFolder, and other inventory manipulation operations, over
CAPs, but the viewer doesn't seem to want to do that. The only ones that
are over CAPs are the ones we already have related to notecards and
scripts. Those can also be split eventually, some of them should go to
the inv server directly, namely: NewFileAgentInventory,
UpdateNotecardAgentInventory, UpdateScriptAgentInventory. There's really
no need to let the regions serve these.
However, even though inventory access doesn't seem to be entirely over
CAPs, not all is lost. What this means is that we can stop regions (the
untrusted ones, at least) from getting the user's inventory in its
entirety while the user still *sees* it. The next problem is *access*.
That is, I can see I have a shape in there, but as soon as I try to wear
it, that fails, because the region where I am doesn't known anything
about it (it doesn't have the assetID, because it doesn't have the
inventory).
We have three options here.
(1) We have the region fetch that inventory item from the user's
inventory, and then send it to the viewer; so the region gets a copy of
the item.
(2) We have the region serve merely as front-end of the request, passing
it to the user's inventory server or home region, and have them send the
actual item to the viewer. (my favorite; in this case, Identity and
Authentication would be established by the viewer's EndPoint, again)
(3) We simply don't serve the item.
In any case, the great thing here is that the region doesn't have the
complete listing of the users' inventory items, but the viewer does.
That is, we avoid that dreadful "Loading...". The region may get
requests for fetching items, and those IDs come from the client. So when
the inv server gets a request to fetch an item, we know that with all
likelihood this request came from the legitimate viewer; the odds of the
region guessing a valid itemID are pretty low.
---
I can already hear Melanie saying that any of this is going to break 57
things related to attachments and scripting :-) That's ok. I'm talking
about crossing boundaries of trust for now, so Hypergrid, OSGrid and
others like that. And there's ways of not breaking attachments and
scripts across region boundaries.
My main objective is to defeat what I've put DNCH doing at the moment --
wiping out people's inventories.
Melanie wrote:
That is what was said. Linden reverted the inventory protocol to UDP
on their servers because of an issue in the viewer that was so
fundamental that it was decided to not be worth fixing.
Whether this is true, I don't know. but it was said.
Melanie
Diva Canto wrote:
Melanie wrote:
Linden turned it off because it's broken in the client. So, we can
try to use it but will hit the same wall, since the client was never
fixed.
Melanie: are you 100% sure about this? This, of course, is critical. The
whole point of my thinking was to access inventory over the consistent
model of CAPs; if that's not working, then everything else is minor.
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