Python: Model file threat-model

python/ql/lib/semmle/python/frameworks/Stdlib.model.yml

@@ -17,6 +17,8 @@ extensions:
 
       # if no argument is given, the default is to use sys.argv[1:]
       - ['argparse.ArgumentParser', 'Member[parse_args,parse_known_args].WithArity[0].ReturnValue', 'commandargs']
+
+      - ['os', 'Member[read].ReturnValue', 'file']
   - addsTo:
       pack: codeql/python-all
       extensible: summaryModel

python/ql/lib/semmle/python/frameworks/Stdlib.qll

@@ -1499,13 +1499,17 @@ module StdlibPrivate {
    * See https://docs.python.org/3/library/functions.html#open
    */
   private class OpenCall extends FileSystemAccess::Range, Stdlib::FileLikeObject::InstanceSource,
-    DataFlow::CallCfgNode
+    ThreatModelSource::Range, DataFlow::CallCfgNode
   {
     OpenCall() { this = getOpenFunctionRef().getACall() }
 
     override DataFlow::Node getAPathArgument() {
       result in [this.getArg(0), this.getArgByName("file")]
     }
+
+    override string getThreatModel() { result = "file" }
+
+    override string getSourceType() { result = "open()" }
   }
 
   /**