JavaScript: Deal with (un-)escaping on captured variables.

Max Schaefer · Max Schaefer · commit 8c133ff61d87 · 2019-10-30T14:46:50.000Z
diff --git a/javascript/ql/src/Security/CWE-116/DoubleEscaping.ql b/javascript/ql/src/Security/CWE-116/DoubleEscaping.ql
@@ -46,7 +46,12 @@ string getStringValue(RegExpLiteral rl) {
  */
 DataFlow::Node getASimplePredecessor(DataFlow::Node nd) {
   result = nd.getAPredecessor() and
-  not nd.(DataFlow::SsaDefinitionNode).getSsaVariable().getDefinition() instanceof SsaPhiNode
+  not exists(SsaDefinition ssa |
+    ssa = nd.(DataFlow::SsaDefinitionNode).getSsaVariable().getDefinition()
+  |
+    ssa instanceof SsaPhiNode or
+    ssa instanceof SsaVariableCapture
+  )
 }
 
 /**
diff --git a/javascript/ql/test/query-tests/Security/CWE-116/DoubleEscaping/tst.js b/javascript/ql/test/query-tests/Security/CWE-116/DoubleEscaping/tst.js
@@ -123,3 +123,10 @@ function roundtrip(s) {
 function badRoundtrip(s) {
   return s.replace(/\\\\/g, "\\").replace(/\\/g, "\\\\");
 }
+
+function testWithCapturedVar(x) {
+  var captured = x;
+  (function() {
+    captured = captured.replace(/\\/g, "\\\\");
+  })();
+}
