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JS: Rephrase flowsTo to avoid redundant SourceNode::Range check

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This commit is contained in:
Asger Feldthaus
2020-04-19 10:28:24 +01:00
parent 243dea706e
commit bccc27f1e7
1 changed files with 19 additions and 5 deletions
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24
javascript/ql/src/semmle/javascript/dataflow/Sources.qll
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@@ -39,11 +39,7 @@ class SourceNode extends DataFlow::Node {
* Holds if this node flows into `sink` in zero or more local (that is,
* intra-procedural) steps.
*/
cached
predicate flowsTo(DataFlow::Node sink) {
sink = this or
flowsTo(sink.getAPredecessor())
}
predicate flowsTo(DataFlow::Node sink) { hasLocalSource(sink, this) }
/**
* Holds if this node flows into `sink` in zero or more local (that is,
@@ -195,6 +191,24 @@ class SourceNode extends DataFlow::Node {
}
}
/**
* Holds if `source` is a `SourceNode` that can reach `sink` via local flow steps.
*
* The slightly backwards parametering ordering is to force correct indexing.
*/
cached
private predicate hasLocalSource(DataFlow::Node sink, DataFlow::Node source) {
// Declaring `source` to be a `SourceNode` currently causes a redundant check in the
// recursive case, so instead we check it explicitly here.
source = sink and
source instanceof DataFlow::SourceNode
or
exists(DataFlow::Node mid |
hasLocalSource(mid, source) and
DataFlow::localFlowStep(mid, sink)
)
}
module SourceNode {
/**
* A data flow node that should be considered a source node.