This is a bit of a bandaid to cover issues with the push() method on next/router being
treated as an array push, which causes it to flow into other taint sources.
With the capture library we sometimes bails out of handling certain functions for scalability reasons.
This means we have a notion of "captured but imprecisely-tracked" variables and 'this'. In these cases we go back to propagating flow from a post-update node to the local source.
Such that we can reuse the existing modeling, but have it globally
applied as a threat-model as well.
I Basically just moved the modeling. One important aspect is that this
changes is that the previously query-specific `argsParseStep` is now a
globally applied taint-step. This seems reasonable, if someone applied
the argument parsing to any user-controlled string, it seems correct to
propagate that taint for _any_ query.
Integration with RemoteFlowSource is not straightforward, so postponing
that for later
Naming in other languages:
- `SourceNode` (for QL only modeling)
- `ThreatModelFlowSource` (for active sources from QL or data-extensions)
However, since we use `LocalSourceNode` in Python, and `SourceNode` in
JS (for local source nodes), it seems a bit confusing to follow the same
naming convention as other languages, and instead I came up with new names.
We need these to return the dominator instead of declaring it in the parameter list, so that we can use it directly to fulfill part of the signature for the SSA library.
We can't rewrite it with an inline predicate since the SSA module calls with a transitive closure '*', which does not permit inline predicates.
TaintedUrlSuffix is currently only used in TaintTracking configs meaning it is already propagated
by taint steps. The inclusion of these taint steps here however meant that implicit reads could appear prior to any of these steps.
This was is problematic for PropRead steps as an expression like x[0] could spuriously read from array element 1 via the path:
x [element 1]
x [empty access path] (after implicit read)
x[0] (taint step through PropRead)
Array.prototype.shift only returns the first array element.
The mutation of Argument[this] is not yet modelled, and is better handled when we have use-use flow.
