Merge pull request github#17566 from yoff/python/dict-can-take-multiple-args

Python: All dict constructor args are relevant

Author: yoff

python/ql/lib/semmle/python/dataflow/new/internal/DataFlowDispatch.qll

@@ -368,14 +368,13 @@ abstract class DataFlowFunction extends DataFlowCallable, TFunction {
   int positionalOffset() { result = 0 }
 
   override ParameterNode getParameter(ParameterPosition ppos) {
+    // Do not handle lower bound positions (such as `[1..]`) here
+    // they are handled by parameter matching and would create
+    // inconsistencies here as multiple parameters could match such a position.
     exists(int index | ppos.isPositional(index) |
       result.getParameter() = func.getArg(index + this.positionalOffset())
     )
     or
-    exists(int index1, int index2 | ppos.isPositionalLowerBound(index1) and index2 >= index1 |
-      result.getParameter() = func.getArg(index2 + this.positionalOffset())
-    )
-    or
     exists(string name | ppos.isKeyword(name) | result.getParameter() = func.getArgByName(name))
     or
     // `*args`

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

@@ -4235,7 +4235,11 @@ module StdlibPrivate {
   // ---------------------------------------------------------------------------
   // Flow summaries for functions contructing containers
   // ---------------------------------------------------------------------------
-  /** A flow summary for `dict`. */
+  /**
+   * A flow summary for `dict`.
+   *
+   * see https://docs.python.org/3/library/stdtypes.html#dict
+   */
   class DictSummary extends SummarizedCallable {
     DictSummary() { this = "builtins.dict" }
 
@@ -4246,18 +4250,23 @@ module StdlibPrivate {
     }
 
     override predicate propagatesFlow(string input, string output, boolean preservesValue) {
+      // The positional argument contains a mapping.
+      // TODO: Add the list-of-pairs version
+      // TODO: these values can be overwritten by keyword arguments
       exists(DataFlow::DictionaryElementContent dc, string key | key = dc.getKey() |
         input = "Argument[0].DictionaryElement[" + key + "]" and
         output = "ReturnValue.DictionaryElement[" + key + "]" and
         preservesValue = true
       )
       or
+      // The keyword arguments are added to the dictionary.
       exists(DataFlow::DictionaryElementContent dc, string key | key = dc.getKey() |
         input = "Argument[" + key + ":]" and
         output = "ReturnValue.DictionaryElement[" + key + "]" and
         preservesValue = true
       )
       or
+      // Imprecise content in any argument ends up on the container itself.
       input = "Argument[0]" and
       output = "ReturnValue" and
       preservesValue = false

python/ql/test/library-tests/dataflow/coverage/test_builtins.py

@@ -142,6 +142,14 @@ def test_dict_from_dict():
     SINK(d2["k"]) #$ flow="SOURCE, l:-2 -> d2['k']"
     SINK_F(d2["k1"])
 
+@expects(4)
+def test_dict_from_multiple_args():
+    d = dict([("k", SOURCE), ("k1", NONSOURCE)], k2 = SOURCE, k3 = NONSOURCE)
+    SINK(d["k"]) #$ MISSING: flow="SOURCE, l:-1 -> d['k']"
+    SINK_F(d["k1"])
+    SINK(d["k2"]) #$ flow="SOURCE, l:-3 -> d['k2']"
+    SINK_F(d["k3"])
+
 ## Container methods
 
 ### List