Python: Add override helpers to Value classes

RasmusWL · RasmusWL · commit 15bc4cd09026 · 2019-12-20T15:05:49.000+01:00
diff --git a/python/ql/src/semmle/python/objects/ObjectAPI.qll b/python/ql/src/semmle/python/objects/ObjectAPI.qll
@@ -105,6 +105,18 @@ class Value extends TObject {
         or
         this instanceof AbsentModuleAttributeObjectInternal
     }
+
+    /** Whether this overrides v. In this context, "overrides" means that this object
+     *  is a named attribute of a some class C and `v` is a named attribute of another
+     *  class S, both attributes having the same name, and S is a super class of C.
+     */
+    predicate overrides(Value v) {
+        exists(ClassValue my_class, ClassValue other_class, string name |
+            my_class.declaredAttribute(name) = this and
+            other_class.declaredAttribute(name) = v and
+            my_class.getABaseType+() = other_class
+        )
+    }
 }
 
 /** Class representing modules in the Python program
@@ -461,6 +473,14 @@ abstract class FunctionValue extends CallableValue {
 
     /** Gets the maximum number of parameters that can be correctly passed to this function */
     abstract int maxParameters();
+
+    predicate isOverridingMethod() {
+        exists(Value f | this.overrides(f))
+    }
+
+    predicate isOverriddenMethod() {
+        exists(Value f | f.overrides(this))
+    }
 }
 
 /** Class representing Python functions */
diff --git a/python/ql/test/library-tests/overrides/FunctionOverrides.expected b/python/ql/test/library-tests/overrides/FunctionOverrides.expected
@@ -0,0 +1,9 @@
+| test.py:3:5:3:20 | Function Wat.upper | overriding | not overridden |
+| test.py:6:1:6:26 | Function outside_func | not overriding | overridden |
+| test.py:11:11:11:29 | Function Base.lambda | not overriding | overridden |
+| test.py:13:24:13:36 | Function Base.lambda | not overriding | not overridden |
+| test.py:17:5:17:21 | Function Base.normal | not overriding | overridden |
+| test.py:28:5:28:21 | Function Sub2.foo | overriding | overridden |
+| test.py:31:5:31:24 | Function Sub2.tricky | overriding | not overridden |
+| test.py:36:5:36:21 | Function Sub2Sub.foo | overriding | not overridden |
+| test.py:39:5:39:18 | Function Sub2Sub.baz | overriding | not overridden |
diff --git a/python/ql/test/library-tests/overrides/FunctionOverrides.ql b/python/ql/test/library-tests/overrides/FunctionOverrides.ql
@@ -0,0 +1,7 @@
+import python
+
+from PythonFunctionValue f, string overriding, string overridden
+where
+    (if f.isOverridingMethod() then overriding = "overriding" else overriding = "not overriding") and
+    (if f.isOverriddenMethod() then overridden = "overridden" else overridden = "not overridden")
+select f, overriding, overridden
diff --git a/python/ql/test/library-tests/overrides/test.py b/python/ql/test/library-tests/overrides/test.py
@@ -0,0 +1,53 @@
+class Wat(str):
+
+    def upper(self):
+        return self.lower()
+
+def outside_func(self, x):
+    print(x)
+
+class Base(object):
+
+    foo = lambda self, x: x+1
+
+    bar = staticmethod(lambda x: x+1)
+
+    baz = 123
+
+    def normal(self):
+        pass
+
+    tricky = outside_func
+
+class Sub(Base):
+
+    normal = False
+
+class Sub2(Base):
+
+    def foo(self, y):
+        return y * 100
+
+    def tricky(self, x):
+        print('nice!', x)
+
+class Sub2Sub(Sub2):
+
+    def foo(self, z):
+        return z / 123
+
+    def baz(self):
+        print('python is a bit crazy sometimes')
+
+
+ws = Wat('asdf')
+print(ws.upper(), len(ws))
+
+b = Base()
+print(b.foo(1))
+print(b.bar(10))
+
+
+ss = SubSub()
+print(ss.foo(1))
+ss.baz()
