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
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