Since the flag would be in the SecurityEvaluator you could conceivably have soft in one place and hard in another.
Does the above conversation mean that we should look at soft errors from Writes? (e.g. not report an error if the user is not permitted) And do we then consider soft errors for Updates separately? The only place an update occurs is in the Model code, this is explained in the notes about the difference between SecuredModel and Model on a SecuredGraph. For now I think we should do the soft read error flag and leave the rest for when it is requested. Claude On Tue, Mar 2, 2021 at 3:11 PM Rob Vesse <[email protected]> wrote: > Updates and soft mode is an interesting conundrum > > In my $dayjob system update operations are all resource centric i.e. you > are either creating a new resource or overwriting an existing one. So for > update we do use hard errors for non-permissible updates because it still > doesn't let you infer any data. There's no update operations in our system > that are conditional/calculated as in the SPARQL Update case. Aside, most > of the resources in this system are owned by a specific user and by default > you can only write to your own "space" within the system. If you try to > write to another users "space" the error is same whether that other user > exists or not because your default permissions are minimal. About the only > obvious side channel I can think of in our system is that you can infer the > existence of another user if the other user has modified their permissions > from the system defaults. > > Whereas here we're talking about much more fine grained permissions. And > I think what you are alluding to here is that SPARQL is trickier because > you can do INSERT {} WHERE {} or DELETE {} WHERE {} (and of course the > combined form). A clever user could perhaps craft an update that takes > advantage of soft errors in the WHERE {} clause. > > There's definitely a contention here between where the authentication > (AuthC) and authorization (AuthZ) pieces happen complicated by the fact you > need to solve both the in-memory case and the HTTP case. It may be that > different machinery is needed in different places. > > Rob > > On 02/03/2021, 11:53, "Andy Seaborne" <[email protected]> wrote: > > > On 02/03/2021 10:04, Rob Vesse wrote: > > No I like that approach > > > > In a system we're building currently in $dayjob we do much the same > thing. If a user doesn't have permission to see the data it just looks to > that user like that data does not exist so they get null, empty/truncated > lists, false etc. From an information security perspective soft errors are > actually more secure because they don't provide side channels. With a hard > error users can explicitly distinguish between data that isn't there and > data that is there but to which they don’t have access i.e. a clever user > can infer the existence of data under a hard error setup. With soft errors > the two cases are indistinguishable. > > > > Jena 4 is an opportunity to make breaking changes so even if you > make the soft vs hard error behaviour configurable I would suggest making > the default be soft error and document the change as part of whatever Jena > 3 -> 4 migration guide we end up writing. Then people who are using the > permissions modules and upgrading would be forced to understand the change, > the reasoning behind it and make a decision about how to migrate based on > their own use cases. If you leave the default as-is those users could > carry on none the wiser without realising they are missing out on potential > security benefits. > > > > Rob > > jena-fuseki-access might be interesting for that. > > For TDB, it puts in a filter right in at the bottom as the quads come > off the database itself, filtering by NodeId of the graph. Works for > defaultUnionGraph as well. > > TIM could do the same but doesn't. > > It could filter on anything in the quad but per graph was the > requirement. > > Authentication is part of the HTTP request cycle. > It's for SPARQL operations and hooks into the operation processors. > > The core dataset and QueryExecution work is not Fuseki dependent. > > For other datasets, it builds a view datasets that only have the > graphs > the request has access to. That makes it work with defaultUnionGraph > across a mix of graphs. Filtering quads is harder for a mixes dataset > - > have to put back a quads view, filter and undo that work which at the > low level looked expensive and it wasn't the primary requirement for > the > work. > > Having it Fuseki means that application code isn't in the same JVM as > the security mechanisms. > > I agree that soft/view mode is safer. > > Does your work include controlling update in soft mode? I think that > can > get into information leakage situations. > > Andy > > > > > > On 01/03/2021, 22:44, "Claude Warren" <[email protected]> wrote: > > > > I started looking at the read permissions on graphs issue that > was raised > > today. > > > > It seems to me that if we change the functioning of > graph.find() then we > > need to change graph.contains() and graph.size() accordingly. > > > > This led me to look at the Model based classes, and there we > find a number > > of iterators, lists of properties, hasX() methods, etc. All of > which > > currently throw the ReadDeniedException. > > > > Changing these methods will change the default operation in the > wild. > > Something that is OK for v4 but in v3 I think it should stay > the same. > > > > So I am thinking that it might make sense to specify > HardReadErrors (the > > current throw the exception we have now) or SoftReadErrors > (return empty > > iterators, false for hasX() and so on). At first I thought of > putting this > > in a context, but it could be added to the SecurityEvaluator. > Since the > > SecurityEvaluator is an interface I would add it with a default > of > > HardReadErrors and allow implementations to override that. > > > > I think this might be the best way forward, though there will > be a lot of > > change in the permissions code base. Does anyone see an issue > with this > > approach or a better approach? > > > > Claude > > > > > > > > -- > > I like: Like Like - The likeliest place on the web > > <http://like-like.xenei.com> > > LinkedIn: http://www.linkedin.com/in/claudewarren > > > > > > > > > > > > > -- I like: Like Like - The likeliest place on the web <http://like-like.xenei.com> LinkedIn: http://www.linkedin.com/in/claudewarren
