JS: Share more code with Ruby

javascript/ql/lib/semmle/javascript/security/IncompleteMultiCharacterSanitization.qll

@@ -157,3 +157,46 @@ private predicate isCommonWordMatcher(RegExpTerm t) {
         .getValue() = "w"
   )
 }
+
+/**
+ * Holds if `replace` has a pattern argument containing a regular expression
+ * `dangerous` which matches a dangerous string beginning with `prefix`, in an
+ * attempt to avoid a vulnerability of kind `kind`.
+ */
+predicate isResult(
+  StringSubstitutionCall replace, EmptyReplaceRegExpTerm dangerous, string prefix, string kind
+) {
+  exists(EmptyReplaceRegExpTerm regexp |
+    replace = regexp.getCall() and
+    dangerous.getRootTerm() = regexp and
+    // skip leading optional elements
+    not dangerous.isNullable() and
+    // only warn about the longest match
+    prefix = max(string m | matchesDangerousPrefix(dangerous, m, kind) | m order by m.length(), m) and
+    // only warn once per kind
+    not exists(EmptyReplaceRegExpTerm other |
+      other = dangerous.getAChild+() or other = dangerous.getPredecessor+()
+    |
+      matchesDangerousPrefix(other, _, kind) and
+      not other.isNullable()
+    ) and
+    // avoid anchored terms
+    not exists(RegExpAnchor a | regexp = a.getRootTerm()) and
+    // Don't flag replace operations that are called repeatedly in a loop, as they can actually work correctly.
+    not replace.flowsTo(replace.getReceiver+())
+  )
+}
+
+/**
+ * Holds if `replace` has a pattern argument containing a regular expression
+ * `dangerous` which matches a dangerous string beginning with `prefix`. `msg`
+ * is the alert we report.
+ */
+query predicate problems(
+  StringSubstitutionCall replace, string msg, EmptyReplaceRegExpTerm dangerous, string prefix
+) {
+  exists(string kind |
+    isResult(replace, dangerous, prefix, kind) and
+    msg = "This string may still contain $@, which may cause a " + kind + " vulnerability."
+  )
+}

javascript/ql/lib/semmle/javascript/security/IncompleteMultiCharacterSanitizationSpecific.qll

@@ -5,6 +5,8 @@
 import javascript
 import semmle.javascript.security.performance.ReDoSUtil as ReDoSUtil
 
+class StringSubstitutionCall = StringReplaceCall;
+
 /**
  * A regexp term that matches substrings that should be replaced with the empty string.
  */
@@ -15,4 +17,9 @@ class EmptyReplaceRegExpTerm extends RegExpTerm {
       this = replace.getRegExp().getRoot().getAChild*()
     )
   }
+
+  /**
+   * Get the substitution call that uses this regexp term.
+   */
+  StringSubstitutionCall getCall() { this = result.getRegExp().getRoot() }
 }

javascript/ql/src/Security/CWE-116/IncompleteMultiCharacterSanitization.ql

@@ -13,29 +13,4 @@
  *       external/cwe/cwe-116
  */
 
-import javascript
+import semmle.javascript.security.IncompleteMultiCharacterSanitization
-private import semmle.javascript.security.IncompleteMultiCharacterSanitization
-
-from
-  StringReplaceCall replace, EmptyReplaceRegExpTerm regexp, EmptyReplaceRegExpTerm dangerous,
-  string prefix, string kind
-where
-  regexp = replace.getRegExp().getRoot() and
-  dangerous.getRootTerm() = regexp and
-  // skip leading optional elements
-  not dangerous.isNullable() and
-  // only warn about the longest match (presumably the most descriptive)
-  prefix = max(string m | matchesDangerousPrefix(dangerous, m, kind) | m order by m.length(), m) and
-  // only warn once per kind
-  not exists(EmptyReplaceRegExpTerm other |
-    other = dangerous.getAChild+() or other = dangerous.getPredecessor+()
-  |
-    matchesDangerousPrefix(other, _, kind) and
-    not other.isNullable()
-  ) and
-  // don't flag replace operations in a loop
-  not replace.getAMethodCall*().flowsTo(replace.getReceiver()) and
-  // avoid anchored terms
-  not exists(RegExpAnchor a | regexp = a.getRootTerm())
-select replace, "This string may still contain $@, which may cause a " + kind + " vulnerability.",
-  dangerous, prefix