Convert os.stdin model to MaD

Author: owen-mc

go/ql/lib/ext/os.model.yml

@@ -53,6 +53,7 @@ extensions:
       - ["os", "", False, "Open", "", "", "ReturnValue[0]", "file", "manual"]
       - ["os", "", False, "OpenFile", "", "", "ReturnValue[0]", "file", "manual"]
       - ["os", "", False, "ReadFile", "", "", "ReturnValue[0]", "file", "manual"]
+      - ["os", "", False, "Stdin", "", "", "", "stdin", "manual"]
       - ["os", "", False, "UserCacheDir", "", "", "ReturnValue[0]", "environment", "manual"]
       - ["os", "", False, "UserConfigDir", "", "", "ReturnValue[0]", "environment", "manual"]
       - ["os", "", False, "UserHomeDir", "", "", "ReturnValue[0]", "environment", "manual"]

go/ql/lib/semmle/go/frameworks/stdlib/Os.qll

@@ -43,12 +43,4 @@ module Os {
       input = inp and output = outp
     }
   }
-
-  private class Stdin extends SourceNode {
-    Stdin() {
-      exists(Variable osStdin | osStdin.hasQualifiedName("os", "Stdin") | this = osStdin.getARead())
-    }
-
-    override string getThreatModel() { result = "stdin" }
-  }
 }