C++: Use isSource in queries. These were the only queries that restrict the source after dataflow terminates.

Author: MathiasVP

cpp/ql/src/Security/CWE/CWE-079/CgiXss.ql

@@ -29,6 +29,8 @@ class QueryString extends EnvironmentRead {
 }
 
 class Configuration extends TaintTrackingConfiguration {
+  override predicate isSource(Expr source) { source instanceof QueryString }
+
   override predicate isSink(Element tainted) {
     exists(PrintStdoutCall call | call.getAnArgument() = tainted)
   }

cpp/ql/src/Security/CWE/CWE-313/CleartextSqliteDatabase.ql

@@ -34,6 +34,10 @@ predicate sqlite_encryption_used() {
 }
 
 class Configuration extends TaintTrackingConfiguration {
+  override predicate isSource(Expr source) {
+    super.isSource(source) and source instanceof SensitiveExpr
+  }
+
   override predicate isSink(Element taintedArg) {
     exists(SqliteFunctionCall sqliteCall |
       taintedArg = sqliteCall.getASource() and