Access map key

[jason-invision]

How would I access the key used when reading an element of a map?

For example,

id := vars["id"]

If I traced the dataflow to vars how would I output "id"?

[smowton]

Have you tried looking for a DataFlow::ElementReadNode that reads(base, element)? Here the base would be vars which it sounds like you already have a node for, and element would be "id", so element.getStringValue() would extract the constant.

[jason-invision]

When I use DataFlow::ReadNode I get results, but when I switch to DataFlow::ElementReadNode I don't.

For example,

from DataFlow::ReadNode node, MapType mapType
where node.getType() = mapType
select node

vs.

from DataFlow::ElementReadNode node, MapType mapType
where node.getType() = mapType
select node

[jason-invision]

This also doesn't return any results

from DataFlow::ReadNode node, MapType mapType, DataFlow::Node index
where node.getType() = mapType
and node.readsElement(node, index)
select node, index

[jason-invision]

Looks like the solution is this:

from DataFlow::ElementReadNode node, MapType mapType
where node.getBase().getType() = mapType
select node, node.getIndex(), node.getIndex().getStringValue()