Refactor source node classes to use SourceNode superclass

Refactor the existing flowsource classes to use the `SourceNode` class
to specify which threat model they support.

Author: egregius313

csharp/ql/lib/semmle/code/csharp/security/dataflow/flowsources/Local.qll

@@ -5,11 +5,14 @@
 import csharp
 private import semmle.code.csharp.frameworks.system.windows.Forms
 private import semmle.code.csharp.dataflow.internal.ExternalFlow
+private import semmle.code.csharp.security.dataflow.flowsources.SourceNode
 
 /** A data flow source of local data. */
-abstract class LocalFlowSource extends DataFlow::Node {
+abstract class LocalFlowSource extends SourceNode {
   /** Gets a string that describes the type of this local flow source. */
   abstract string getSourceType();
+
+  override string getThreatModel() { result = "local" }
 }
 
 private class ExternalLocalFlowSource extends LocalFlowSource {

csharp/ql/lib/semmle/code/csharp/security/dataflow/flowsources/Remote.qll

@@ -13,11 +13,14 @@ private import semmle.code.csharp.frameworks.WCF
 private import semmle.code.csharp.frameworks.microsoft.Owin
 private import semmle.code.csharp.frameworks.microsoft.AspNetCore
 private import semmle.code.csharp.dataflow.internal.ExternalFlow
+private import semmle.code.csharp.security.dataflow.flowsources.SourceNode
 
 /** A data flow source of remote user input. */
-abstract class RemoteFlowSource extends DataFlow::Node {
+abstract class RemoteFlowSource extends SourceNode {
   /** Gets a string that describes the type of this remote flow source. */
   abstract string getSourceType();
+
+  override string getThreatModel() { result = "remote" }
 }
 
 /**

csharp/ql/lib/semmle/code/csharp/security/dataflow/flowsources/Stored.qll

@@ -9,15 +9,22 @@ private import semmle.code.csharp.frameworks.system.data.Entity
 private import semmle.code.csharp.frameworks.EntityFramework
 private import semmle.code.csharp.frameworks.NHibernate
 private import semmle.code.csharp.frameworks.Sql
+private import semmle.code.csharp.security.dataflow.flowsources.SourceNode
 
 /** A data flow source of stored user input. */
-abstract class StoredFlowSource extends DataFlow::Node { }
+abstract class StoredFlowSource extends SourceNode {
+  override string getThreatModel() { result = "local" }
+}
+
+abstract class DatabaseInputSource extends StoredFlowSource {
+  override string getThreatModel() { result = "database" }
+}
 
 /**
  * An expression that has a type of `DbRawSqlQuery`, representing the result of an Entity Framework
  * SqlQuery.
  */
-class DbRawSqlStoredFlowSource extends StoredFlowSource {
+class DbRawSqlStoredFlowSource extends DatabaseInputSource {
   DbRawSqlStoredFlowSource() {
     this.asExpr().getType() instanceof SystemDataEntityInfrastructure::DbRawSqlQuery
   }
@@ -27,30 +34,30 @@ class DbRawSqlStoredFlowSource extends StoredFlowSource {
  * An expression that has a type of `DbDataReader` or a sub-class, representing the result of a
  * data command.
  */
-class DbDataReaderStoredFlowSource extends StoredFlowSource {
+class DbDataReaderStoredFlowSource extends DatabaseInputSource {
   DbDataReaderStoredFlowSource() {
     this.asExpr().getType() = any(SystemDataCommon::DbDataReader dataReader).getASubType*()
   }
 }
 
 /** An expression that accesses a method of `DbDataReader` or a sub-class. */
-class DbDataReaderMethodStoredFlowSource extends StoredFlowSource {
+class DbDataReaderMethodStoredFlowSource extends DatabaseInputSource {
   DbDataReaderMethodStoredFlowSource() {
     this.asExpr().(MethodCall).getTarget().getDeclaringType() =
       any(SystemDataCommon::DbDataReader dataReader).getASubType*()
   }
 }
 
 /** An expression that accesses a property of `DbDataReader` or a sub-class. */
-class DbDataReaderPropertyStoredFlowSource extends StoredFlowSource {
+class DbDataReaderPropertyStoredFlowSource extends DatabaseInputSource {
   DbDataReaderPropertyStoredFlowSource() {
     this.asExpr().(PropertyAccess).getTarget().getDeclaringType() =
       any(SystemDataCommon::DbDataReader dataReader).getASubType*()
   }
 }
 
 /** A read of a mapped property. */
-class ORMMappedProperty extends StoredFlowSource {
+class ORMMappedProperty extends DatabaseInputSource {
   ORMMappedProperty() {
     this instanceof EntityFramework::StoredFlowSource or
     this instanceof NHibernate::StoredFlowSource
@@ -60,4 +67,6 @@ class ORMMappedProperty extends StoredFlowSource {
 /** A file stream source is considered a stored flow source. */
 class FileStreamStoredFlowSource extends StoredFlowSource {
   FileStreamStoredFlowSource() { sourceNode(this, "file") }
+
+  override string getThreatModel() { result = "file" }
 }