Added summary flow for StringFromCharCode

Author: Napalys

javascript/ql/lib/semmle/javascript/internal/flow_summaries/Strings.qll

@@ -99,3 +99,19 @@ class StringSplitHashOrQuestionMark extends SummarizedCallable {
     )
   }
 }
+
+class StringFromCharCode extends SummarizedCallable {
+  StringFromCharCode() { this = "String#fromCharCode" }
+
+  override DataFlow::CallNode getACall() {
+    result = DataFlow::globalVarRef("String").getAPropertyRead("fromCharCode").getACall()
+  }
+
+  override predicate propagatesFlow(string input, string output, boolean preservesValue) {
+    preservesValue = true and
+    (
+      input = "Argument[0..]" and
+      output = "ReturnValue"
+    )
+  }
+}

javascript/ql/test/library-tests/TaintTracking/BasicTaintTracking.expected

@@ -40,6 +40,7 @@ legacyDataFlowDifference
 | typed-arrays.js:2:13:2:20 | source() | typed-arrays.js:11:10:11:12 | arr | only flow with NEW data flow library |
 | typed-arrays.js:2:13:2:20 | source() | typed-arrays.js:15:10:15:10 | z | only flow with NEW data flow library |
 | typed-arrays.js:2:13:2:20 | source() | typed-arrays.js:18:10:18:12 | sub | only flow with NEW data flow library |
+| typed-arrays.js:2:13:2:20 | source() | typed-arrays.js:42:10:42:30 | typedAr ... ring(y) | only flow with NEW data flow library |
 | typed-arrays.js:2:13:2:20 | source() | typed-arrays.js:48:10:48:12 | str | only flow with NEW data flow library |
 | typed-arrays.js:2:13:2:20 | source() | typed-arrays.js:52:10:52:13 | str2 | only flow with NEW data flow library |
 | use-use-after-implicit-read.js:7:17:7:24 | source() | use-use-after-implicit-read.js:15:10:15:10 | x | only flow with NEW data flow library |
@@ -51,7 +52,6 @@ consistencyIssue
 | typed-arrays.js:28 | expected an alert, but found none | NOT OK -- Should be flagged but it is not. | Consistency |
 | typed-arrays.js:32 | expected an alert, but found none | NOT OK -- Should be flagged but it is not. | Consistency |
 | typed-arrays.js:36 | expected an alert, but found none | NOT OK -- Should be flagged but it is not. | Consistency |
-| typed-arrays.js:42 | expected an alert, but found none | NOT OK -- Should be flagged but it is not. | Consistency |
 flow
 | access-path-sanitizer.js:2:18:2:25 | source() | access-path-sanitizer.js:4:8:4:12 | obj.x |
 | addexpr.js:4:10:4:17 | source() | addexpr.js:7:8:7:8 | x |
@@ -342,6 +342,7 @@ flow
 | typed-arrays.js:2:13:2:20 | source() | typed-arrays.js:11:10:11:12 | arr |
 | typed-arrays.js:2:13:2:20 | source() | typed-arrays.js:15:10:15:10 | z |
 | typed-arrays.js:2:13:2:20 | source() | typed-arrays.js:18:10:18:12 | sub |
+| typed-arrays.js:2:13:2:20 | source() | typed-arrays.js:42:10:42:30 | typedAr ... ring(y) |
 | typed-arrays.js:2:13:2:20 | source() | typed-arrays.js:48:10:48:12 | str |
 | typed-arrays.js:2:13:2:20 | source() | typed-arrays.js:52:10:52:13 | str2 |
 | use-use-after-implicit-read.js:7:17:7:24 | source() | use-use-after-implicit-read.js:8:10:8:17 | captured |

javascript/ql/test/library-tests/TaintTracking/typed-arrays.js

@@ -39,7 +39,7 @@ function test() {
         return function (a) { return String.fromCharCode.apply(null, a); };
     })();
 
-    sink(typedArrayToString(y)); // NOT OK -- Should be flagged but it is not.
+    sink(typedArrayToString(y)); // NOT OK
 
     let str = '';
     for (let i = 0; i < y.length; i++)