don't sanitize calls through substring calls that just remove the start

Author: erik-krogh

javascript/ql/lib/semmle/javascript/security/regexp/PolynomialReDoSCustomizations.qll

@@ -90,7 +90,8 @@ module PolynomialReDoS {
         isCharClassLike(root)
       )
       or
-      this.(DataFlow::MethodCallNode).getMethodName() = StringOps::substringMethodName()
+      this.(DataFlow::MethodCallNode).getMethodName() = StringOps::substringMethodName() and
+      not this.(DataFlow::MethodCallNode).getNumArgument() = 1 // with one argument it just slices off the beginning
     }
   }
 

javascript/ql/test/query-tests/Security/CWE-400/ReDoS/PolynomialReDoS.expected

@@ -32,6 +32,11 @@ nodes
 | lib/lib.js:41:32:41:35 | name |
 | lib/lib.js:42:17:42:20 | name |
 | lib/lib.js:42:17:42:20 | name |
+| lib/lib.js:44:5:44:25 | name |
+| lib/lib.js:44:12:44:15 | name |
+| lib/lib.js:44:12:44:25 | name.substr(1) |
+| lib/lib.js:45:17:45:20 | name |
+| lib/lib.js:45:17:45:20 | name |
 | lib/moduleLib/moduleLib.js:1:28:1:31 | name |
 | lib/moduleLib/moduleLib.js:1:28:1:31 | name |
 | lib/moduleLib/moduleLib.js:2:13:2:16 | name |
@@ -257,6 +262,12 @@ edges
 | lib/lib.js:41:32:41:35 | name | lib/lib.js:42:17:42:20 | name |
 | lib/lib.js:41:32:41:35 | name | lib/lib.js:42:17:42:20 | name |
 | lib/lib.js:41:32:41:35 | name | lib/lib.js:42:17:42:20 | name |
+| lib/lib.js:41:32:41:35 | name | lib/lib.js:44:12:44:15 | name |
+| lib/lib.js:41:32:41:35 | name | lib/lib.js:44:12:44:15 | name |
+| lib/lib.js:44:5:44:25 | name | lib/lib.js:45:17:45:20 | name |
+| lib/lib.js:44:5:44:25 | name | lib/lib.js:45:17:45:20 | name |
+| lib/lib.js:44:12:44:15 | name | lib/lib.js:44:12:44:25 | name.substr(1) |
+| lib/lib.js:44:12:44:25 | name.substr(1) | lib/lib.js:44:5:44:25 | name |
 | lib/moduleLib/moduleLib.js:1:28:1:31 | name | lib/moduleLib/moduleLib.js:2:13:2:16 | name |
 | lib/moduleLib/moduleLib.js:1:28:1:31 | name | lib/moduleLib/moduleLib.js:2:13:2:16 | name |
 | lib/moduleLib/moduleLib.js:1:28:1:31 | name | lib/moduleLib/moduleLib.js:2:13:2:16 | name |
@@ -449,6 +460,7 @@ edges
 | lib/lib.js:8:2:8:17 | /f*g/.test(name) | lib/lib.js:7:19:7:22 | name | lib/lib.js:8:13:8:16 | name | This $@ that depends on $@ may run slow on strings with many repetitions of 'f'. | lib/lib.js:8:3:8:4 | f* | regular expression | lib/lib.js:7:19:7:22 | name | library input |
 | lib/lib.js:36:2:36:17 | /f*g/.test(name) | lib/lib.js:32:32:32:40 | arguments | lib/lib.js:36:13:36:16 | name | This $@ that depends on $@ may run slow on strings with many repetitions of 'f'. | lib/lib.js:36:3:36:4 | f* | regular expression | lib/lib.js:32:32:32:40 | arguments | library input |
 | lib/lib.js:42:17:42:33 | name.match(/f*g/) | lib/lib.js:41:32:41:35 | name | lib/lib.js:42:17:42:20 | name | This $@ that depends on $@ may run slow on strings with many repetitions of 'f'. | lib/lib.js:42:29:42:30 | f* | regular expression | lib/lib.js:41:32:41:35 | name | library input |
+| lib/lib.js:45:17:45:33 | name.match(/f*g/) | lib/lib.js:41:32:41:35 | name | lib/lib.js:45:17:45:20 | name | This $@ that depends on $@ may run slow on strings with many repetitions of 'f'. | lib/lib.js:45:29:45:30 | f* | regular expression | lib/lib.js:41:32:41:35 | name | library input |
 | lib/moduleLib/moduleLib.js:2:2:2:17 | /a*b/.test(name) | lib/moduleLib/moduleLib.js:1:28:1:31 | name | lib/moduleLib/moduleLib.js:2:13:2:16 | name | This $@ that depends on $@ may run slow on strings with many repetitions of 'a'. | lib/moduleLib/moduleLib.js:2:3:2:4 | a* | regular expression | lib/moduleLib/moduleLib.js:1:28:1:31 | name | library input |
 | lib/otherLib/js/src/index.js:2:2:2:17 | /a*b/.test(name) | lib/otherLib/js/src/index.js:1:28:1:31 | name | lib/otherLib/js/src/index.js:2:13:2:16 | name | This $@ that depends on $@ may run slow on strings with many repetitions of 'a'. | lib/otherLib/js/src/index.js:2:3:2:4 | a* | regular expression | lib/otherLib/js/src/index.js:1:28:1:31 | name | library input |
 | lib/snapdragon.js:7:15:7:32 | this.match(/aa*$/) | lib/snapdragon.js:3:34:3:38 | input | lib/snapdragon.js:7:15:7:18 | this | This $@ that depends on $@ may run slow on strings starting with 'a' and with many repetitions of 'a'. | lib/snapdragon.js:7:28:7:29 | a* | regular expression | lib/snapdragon.js:3:34:3:38 | input | library input |

javascript/ql/test/query-tests/Security/CWE-400/ReDoS/lib/lib.js

@@ -42,5 +42,5 @@ module.exports.foo = function (name) {
     var data1 = name.match(/f*g/); // NOT OK
 
     name = name.substr(1);
-    var data2 = name.match(/f*g/); // NOT OK - but not flagged
+    var data2 = name.match(/f*g/); // NOT OK
 }