Ruby: Add query for debugging regexp flow

Author: hvitved

ruby/ql/lib/codeql/ruby/Regexp.qll

@@ -7,11 +7,10 @@
 
 import regexp.RegExpTreeView // re-export
 private import regexp.internal.ParseRegExp
-private import codeql.ruby.ast.Literal as AST
+private import regexp.internal.RegExpConfiguration
+private import codeql.ruby.ast.Literal as Ast
 private import codeql.ruby.DataFlow
-private import codeql.ruby.controlflow.CfgNodes
 private import codeql.ruby.ApiGraphs
-private import codeql.ruby.dataflow.internal.tainttrackingforlibraries.TaintTrackingImpl
 
 /**
  * Provides utility predicates related to regular expressions.
@@ -47,7 +46,7 @@ abstract class RegExpPatternSource extends DataFlow::Node {
  * A regular expression literal, viewed as the pattern source for itself.
  */
 private class RegExpLiteralPatternSource extends RegExpPatternSource {
-  private AST::RegExpLiteral astNode;
+  private Ast::RegExpLiteral astNode;
 
   RegExpLiteralPatternSource() { astNode = this.asExpr().getExpr() }
 
@@ -70,7 +69,7 @@ private class StringRegExpPatternSource extends RegExpPatternSource {
   override RegExpTerm getRegExpTerm() { result.getRegExp() = this.asExpr().getExpr() }
 }
 
-private class RegExpLiteralRegExp extends RegExp, AST::RegExpLiteral {
+private class RegExpLiteralRegExp extends RegExp, Ast::RegExpLiteral {
   override predicate isDotAll() { this.hasMultilineFlag() }
 
   override predicate isIgnoreCase() { this.hasCaseInsensitiveFlag() }
@@ -115,32 +114,7 @@ class StdLibRegExpInterpretation extends RegExpInterpretation::Range {
       mce.getMethodName() = ["match", "match?"] and
       this = mce.getArgument(0) and
       // exclude https://ruby-doc.org/core-2.4.0/Regexp.html#method-i-match
-      not mce.getReceiver().asExpr().getExpr() instanceof AST::RegExpLiteral
-    )
-  }
-}
-
-private class RegExpConfiguration extends Configuration {
-  RegExpConfiguration() { this = "RegExpConfiguration" }
-
-  override predicate isSource(DataFlow::Node source) {
-    source.asExpr() =
-      any(ExprCfgNode e |
-        e.getConstantValue().isString(_) and
-        not e instanceof ExprNodes::VariableReadAccessCfgNode and
-        not e instanceof ExprNodes::ConstantReadAccessCfgNode
-      )
-  }
-
-  override predicate isSink(DataFlow::Node sink) { sink instanceof RegExpInterpretation::Range }
-
-  override predicate isSanitizer(DataFlow::Node node) {
-    // stop flow if `node` is receiver of
-    // https://ruby-doc.org/core-2.4.0/String.html#method-i-match
-    exists(DataFlow::CallNode mce |
-      mce.getMethodName() = ["match", "match?"] and
-      node = mce.getReceiver() and
-      mce.getArgument(0).asExpr().getExpr() instanceof AST::RegExpLiteral
+      not mce.getReceiver().asExpr().getExpr() instanceof Ast::RegExpLiteral
     )
   }
 }

ruby/ql/lib/codeql/ruby/regexp/internal/DebugRegExpConfiguration.ql

@@ -0,0 +1,12 @@
+/**
+ * @description Used to debug the discovery of regexp literals.
+ * @kind path-problem
+ */
+
+import RegExpConfiguration
+import codeql.ruby.dataflow.internal.DataFlowImplForLibraries
+import PathGraph
+
+from RegExpConfiguration c, PathNode source, PathNode sink
+where c.hasFlowPath(source, sink)
+select source.getNode(), source, sink, source.toString()

ruby/ql/lib/codeql/ruby/regexp/internal/RegExpConfiguration.qll

@@ -0,0 +1,30 @@
+private import codeql.ruby.Regexp
+private import codeql.ruby.ast.Literal as Ast
+private import codeql.ruby.DataFlow
+private import codeql.ruby.controlflow.CfgNodes
+private import codeql.ruby.dataflow.internal.tainttrackingforlibraries.TaintTrackingImpl
+
+class RegExpConfiguration extends Configuration {
+  RegExpConfiguration() { this = "RegExpConfiguration" }
+
+  override predicate isSource(DataFlow::Node source) {
+    source.asExpr() =
+      any(ExprCfgNode e |
+        e.getConstantValue().isString(_) and
+        not e instanceof ExprNodes::VariableReadAccessCfgNode and
+        not e instanceof ExprNodes::ConstantReadAccessCfgNode
+      )
+  }
+
+  override predicate isSink(DataFlow::Node sink) { sink instanceof RegExpInterpretation::Range }
+
+  override predicate isSanitizer(DataFlow::Node node) {
+    // stop flow if `node` is receiver of
+    // https://ruby-doc.org/core-2.4.0/String.html#method-i-match
+    exists(DataFlow::CallNode mce |
+      mce.getMethodName() = ["match", "match?"] and
+      node = mce.getReceiver() and
+      mce.getArgument(0).asExpr().getExpr() instanceof Ast::RegExpLiteral
+    )
+  }
+}