Add mass assignment query

ruby/ql/lib/codeql/ruby/security/MassAssignmentQuery.qll

@@ -0,0 +1,100 @@
+/**
+ * Provides a taint tracking configuration for reasoning about insecure mass assignment.
+ */
+
+private import codeql.ruby.AST
+private import codeql.ruby.DataFlow
+private import codeql.ruby.TaintTracking
+private import codeql.ruby.dataflow.RemoteFlowSources
+
+/** Provides default sources and sinks for the mass assignment query. */
+module MassAssignment {
+  /**
+   * A data flow source for user input used for mass assignment.
+   */
+  abstract class Source extends DataFlow::Node { }
+
+  /**
+   * A data flow sink for user input used for mass assignment.
+   */
+  abstract class Sink extends DataFlow::Node { }
+
+  /**
+   * A call that permits arbitrary parameters to be used for mass assignment.
+   */
+  abstract class MassPermit extends DataFlow::Node {
+    /** Gets the argument for the parameters to be permitted */
+    abstract DataFlow::Node getParamsArgument();
+
+    /** Gets the result node of the permitted parameters. */
+    abstract DataFlow::Node getPermittedParamsResult();
+  }
+
+  private class RemoteSource extends Source instanceof RemoteFlowSource { }
+
+  private class CreateSink extends Sink {
+    CreateSink() {
+      this.asExpr().getExpr().(MethodCall).getMethodName() = ["create", "new", "update"]
+    }
+  }
+
+  private class PermitCall extends MassPermit instanceof DataFlow::CallNode {
+    PermitCall() {
+      this.asExpr().getExpr().(MethodCall).getMethodName() = ["permit!", "to_unsafe_h"]
+    }
+
+    override DataFlow::Node getParamsArgument() { result = this.(DataFlow::CallNode).getReceiver() }
+
+    override DataFlow::Node getPermittedParamsResult() { result = this }
+  }
+}
+
+private module FlowState {
+  private newtype TState =
+    TUnpermitted() or
+    TPermitted()
+
+  /** A flow state used to distinguish whether arbitrary user parameters have been permitted to be used for mass assignment. */
+  class State extends TState {
+    string toString() {
+      this = TUnpermitted() and result = "unpermitted"
+      or
+      this = TPermitted() and result = "permitted"
+    }
+  }
+
+  /** A flow state used for user parameters for which arbitrary parameters have not been permitted to use for mass assignment. */
+  class Unpermitted extends State, TUnpermitted { }
+
+  /** A flow state used for user parameters for which arbitrary parameters have been permitted to use for mass assignment. */
+  class Permitted extends State, TPermitted { }
+}
+
+/** A flow configuration for reasoning about insecure mass assignment. */
+private module Config implements DataFlow::StateConfigSig {
+  class FlowState = FlowState::State;
+
+  predicate isSource(DataFlow::Node node, FlowState state) {
+    node instanceof MassAssignment::Source and
+    state instanceof FlowState::Unpermitted
+  }
+
+  predicate isSink(DataFlow::Node node, FlowState state) {
+    node instanceof MassAssignment::Sink and
+    state instanceof FlowState::Permitted
+  }
+
+  predicate isAdditionalFlowStep(
+    DataFlow::Node node1, FlowState state1, DataFlow::Node node2, FlowState state2
+  ) {
+    exists(MassAssignment::MassPermit permit |
+      node1 = permit.getParamsArgument() and
+      state1 instanceof FlowState::Unpermitted and
+      node2 = permit.getPermittedParamsResult() and
+      state2 instanceof FlowState::Permitted
+    )
+  }
+}
+
+/** Taint tracking for reasoning about user input used for mass assignment. */
+module MassAssignmentFlow = TaintTracking::GlobalWithState<Config>;

ruby/ql/src/queries/security/cwe-915/MassAssignment.ql

@@ -0,0 +1,18 @@
+/**
+ * @name Insecure Mass Assignment
+ * @description Using mass assignment with user-controlled keys allows unintended parameters to be set.
+ * @kind path-problem
+ * @problem.severity error
+ * @security-severity 7.5
+ * @precision high
+ * @id ruby/insecure-mass-assignment
+ * @tags security
+ *       external/cwe/cwe-915
+ */
+
+import codeql.ruby.security.MassAssignmentQuery
+import MassAssignmentFlow::PathGraph
+
+from MassAssignmentFlow::PathNode source, MassAssignmentFlow::PathNode sink
+where MassAssignmentFlow::flowPath(source, sink)
+select sink.getNode(), source, sink, "mass assignment"