[DIFF-INFORMED] Rust: AccessAfterLifetime

Author: d10c

rust/ql/src/queries/security/CWE-825/AccessAfterLifetime.ql

@@ -28,25 +28,40 @@ module AccessAfterLifetimeConfig implements DataFlow::ConfigSig {
   predicate isSink(DataFlow::Node node) { node instanceof AccessAfterLifetime::Sink }
 
   predicate isBarrier(DataFlow::Node barrier) { barrier instanceof AccessAfterLifetime::Barrier }
+
+  predicate observeDiffInformedIncrementalMode() { any() }
+
+  Location getASelectedSourceLocation(DataFlow::Node source) {
+    exists(Variable target, DataFlow::Node sink | result = target.getLocation() |
+      isSink(sink) and
+      narrowDereferenceAfterLifetime(source, sink, target)
+    )
+  }
 }
 
 module AccessAfterLifetimeFlow = TaintTracking::Global<AccessAfterLifetimeConfig>;
 
+pragma[inline]
+predicate narrowDereferenceAfterLifetime(DataFlow::Node source, DataFlow::Node sink, Variable target) {
+  // check that the dereference is outside the lifetime of the target
+  AccessAfterLifetime::dereferenceAfterLifetime(source, sink, target) and
+  // include only results inside `unsafe` blocks, as other results tend to be false positives
+  (
+    sink.asExpr().getExpr().getEnclosingBlock*().isUnsafe() or
+    sink.asExpr().getExpr().getEnclosingCallable().(Function).isUnsafe()
+  ) and
+  // exclude cases with sources / sinks in macros, since these results are difficult to interpret
+  not source.asExpr().getExpr().isFromMacroExpansion() and
+  not sink.asExpr().getExpr().isFromMacroExpansion()
+}
+
 from
   AccessAfterLifetimeFlow::PathNode sourceNode, AccessAfterLifetimeFlow::PathNode sinkNode,
   Variable target
 where
   // flow from a pointer or reference to the dereference
   AccessAfterLifetimeFlow::flowPath(sourceNode, sinkNode) and
   // check that the dereference is outside the lifetime of the target
-  AccessAfterLifetime::dereferenceAfterLifetime(sourceNode.getNode(), sinkNode.getNode(), target) and
-  // include only results inside `unsafe` blocks, as other results tend to be false positives
-  (
-    sinkNode.getNode().asExpr().getExpr().getEnclosingBlock*().isUnsafe() or
-    sinkNode.getNode().asExpr().getExpr().getEnclosingCallable().(Function).isUnsafe()
-  ) and
-  // exclude cases with sources / sinks in macros, since these results are difficult to interpret
-  not sourceNode.getNode().asExpr().getExpr().isFromMacroExpansion() and
-  not sinkNode.getNode().asExpr().getExpr().isFromMacroExpansion()
+  narrowDereferenceAfterLifetime(sourceNode.getNode(), sinkNode.getNode(), target)
 select sinkNode.getNode(), sourceNode, sinkNode,
   "Access of a pointer to $@ after its lifetime has ended.", target, target.toString()