fix FP related to inverted character classes choosing a char that was not matched by the char class

erik-krogh · erik-krogh · commit 97acf1fd87fa · 2020-11-17T17:34:43.000+01:00
diff --git a/javascript/ql/src/Performance/ReDoS.ql b/javascript/ql/src/Performance/ReDoS.ql
@@ -222,7 +222,7 @@ abstract class CharacterClass extends InputSymbol {
   /**
    * Gets a character matched by this character class.
    */
-  string choose() { result = getARelevantChar() }
+  string choose() { result = getARelevantChar() and matches(result) }
 }
 
 /**
diff --git a/javascript/ql/test/query-tests/Performance/ReDoS/tst.js b/javascript/ql/test/query-tests/Performance/ReDoS/tst.js
@@ -258,3 +258,6 @@ var bad57 = /^([^>a]+)*(>|$)/;
 
 // NOT GOOD
 var bad58 = /(\n\s*)+$/;
+
+// GOOD
+var good26 = /([^\\\]]+)*/

Original file line number	Diff line number	Diff line change
`@@ -222,7 +222,7 @@ abstract class CharacterClass extends InputSymbol {`
`222`	`222`	`/**`
`223`	`223`	`* Gets a character matched by this character class.`
`224`	`224`	`*/`
`225`		`- string choose() { result = getARelevantChar() }`
	`225`	`+ string choose() { result = getARelevantChar() and matches(result) }`
`226`	`226`	`}`
`227`	`227`
`228`	`228`	`/**`