Python: Model stdin thread-model

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

@@ -12,6 +12,9 @@ extensions:
       - ['sys', 'Member[argv]', 'commandargs']
       - ['sys', 'Member[orig_argv]', 'commandargs']
 
+      - ['sys', 'Member[stdin]', 'stdin']
+      - ['builtins', 'Member[input].ReturnValue', 'stdin']
+
       # 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']
   - addsTo:
@@ -20,5 +23,3 @@ extensions:
     data:
       - ['argparse.ArgumentParser', 'Member[parse_args,parse_known_args]', 'Argument[0,args:]', 'ReturnValue', 'taint']
       # note: taint of attribute lookups is handled in QL
-
-      # TODO: input / read from stdin

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

@@ -5009,6 +5009,19 @@ module StdlibPrivate {
       nodeTo.(DataFlow::AttrRead).getObject() = nodeFrom
     }
   }
+
+  // ---------------------------------------------------------------------------
+  // sys
+  // ---------------------------------------------------------------------------
+  /**
+   * An access of `sys.stdin`/`sys.stdout`/`sys.stderr`, to get additional FileLike
+   * modeling.
+   */
+  private class SysStandardStreams extends Stdlib::FileLikeObject::InstanceSource, DataFlow::Node {
+    SysStandardStreams() {
+      this = API::moduleImport("sys").getMember(["stdin", "stdout", "stderr"]).asSource()
+    }
+  }
 }
 
 // ---------------------------------------------------------------------------

python/ql/test/library-tests/frameworks/stdlib/threat_models.py

@@ -44,8 +44,8 @@ ensure_not_tainted(fake_args.foo) # $ SPURIOUS: tainted
 ########################################
 
 ensure_tainted(
-    sys.stdin.readline(), # $ MISSING: tainted threatModelSource
-    input(), # $ MISSING: tainted threatModelSource
+    sys.stdin.readline(), # $ tainted threatModelSource[stdin]=sys.stdin
+    input(), # $ tainted threatModelSource[stdin]=input()
 )
 
 ########################################