Ruby: Rework call-context sensitivity logic

Author: hvitved

ruby/ql/lib/codeql/ruby/dataflow/internal/DataFlowDispatch.qll

@@ -975,42 +975,35 @@ private DataFlow::Node trackSingletonMethodOnInstance(MethodBase method, string
   result = trackSingletonMethodOnInstance(method, name, TypeTracker::end())
 }
 
-/** Same as `isInstance`, but includes local must-flow through SSA definitions. */
-private predicate isInstanceLocalMustFlow(DataFlow::Node n, Module tp, boolean exact) {
-  isInstance(n, tp, exact)
-  or
-  exists(DataFlow::Node mid | isInstanceLocalMustFlow(mid, tp, exact) |
-    n.asExpr() = mid.(SsaDefinitionNode).getDefinition().getARead()
-    or
-    n.(SsaDefinitionNode).getDefinition().(Ssa::WriteDefinition).assigns(mid.asExpr())
-  )
-}
-
 /**
  * Holds if `ctx` targets `encl`, which is the enclosing callable of `call`, the receiver
  * of `call` is a parameter access, where the corresponding argument of `ctx` is `arg`.
  *
- * `name` is the name of the method being called by `call`.
+ * `name` is the name of the method being called by `call`, `source` is a
+ * `LocalSourceNode` that flows to `arg`, and `paramDef` is the SSA definition for the
+ * parameter that is the receiver of `call`.
  */
 pragma[nomagic]
-private predicate argFlowsToReceiver(
-  RelevantCall ctx, ArgumentNode arg, RelevantCall call, Callable encl, string name
+private predicate argMustFlowToReceiver(
+  RelevantCall ctx, DataFlow::LocalSourceNode source, ArgumentNode arg, SsaDefinitionNode paramDef,
+  RelevantCall call, Callable encl, string name
 ) {
-  exists(
-    ParameterNodeImpl p, SsaDefinitionNode ssaNode, ParameterPosition ppos, ArgumentPosition apos
-  |
+  exists(ParameterNodeImpl p, ParameterPosition ppos, ArgumentPosition apos |
     // the receiver of `call` references `p`
-    LocalFlow::localFlowSsaParamInput(p, ssaNode) and
-    flowsToMethodCallReceiver(pragma[only_bind_into](call), pragma[only_bind_into](ssaNode),
-      pragma[only_bind_into](name)) and
+    exists(DataFlow::Node receiver |
+      LocalFlow::localFlowSsaParamInput(p, paramDef) and
+      methodCall(pragma[only_bind_into](call), receiver, pragma[only_bind_into](name)) and
+      receiver.asExpr() = paramDef.getDefinition().getARead()
+    ) and
     // `p` is a parameter of `encl`,
     encl = call.getScope() and
     p.isParameterOf(TCfgScope(encl), ppos) and
     // `ctx` targets `encl`
     getTarget(ctx) = encl and
     // `arg` is the argument for `p` in the call `ctx`
     arg.sourceArgumentOf(ctx, apos) and
-    parameterMatch(ppos, apos)
+    parameterMatch(ppos, apos) and
+    source.flowsTo(arg)
   )
 }
 
@@ -1027,20 +1020,11 @@ private predicate mayBenefitFromCallContextInstance(
   RelevantCall ctx, RelevantCall call, ArgumentNode arg, Callable encl, Module tp, boolean exact,
   string name
 ) {
-  argFlowsToReceiver(ctx, pragma[only_bind_into](arg), call, encl, pragma[only_bind_into](name)) and
-  // `arg` has a relevant instance type
-  isInstanceLocalMustFlow(arg, tp, exact) and
-  exists(lookupMethod(tp, pragma[only_bind_into](name)))
-}
-
-/** Same as `resolveConstantReadAccess`, but includes local must-flow through SSA definitions. */
-private predicate resolveConstantReadAccessMustFlow(DataFlow::Node n, Module tp) {
-  tp = resolveConstantReadAccess(n.asExpr().getExpr())
-  or
-  exists(DataFlow::Node mid | resolveConstantReadAccessMustFlow(mid, tp) |
-    n.asExpr() = mid.(SsaDefinitionNode).getDefinition().getARead()
-    or
-    n.(SsaDefinitionNode).getDefinition().(Ssa::WriteDefinition).assigns(mid.asExpr())
+  exists(DataFlow::LocalSourceNode source |
+    argMustFlowToReceiver(ctx, pragma[only_bind_into](source), arg, _, call, encl,
+      pragma[only_bind_into](name)) and
+    source = trackInstance(tp, exact) and
+    exists(lookupMethod(tp, pragma[only_bind_into](name)))
   )
 }
 
@@ -1057,10 +1041,12 @@ private predicate mayBenefitFromCallContextSingleton(
   RelevantCall ctx, RelevantCall call, ArgumentNode arg, Callable encl, Module tp, boolean exact,
   string name
 ) {
-  argFlowsToReceiver(ctx, pragma[only_bind_into](arg), call, encl, pragma[only_bind_into](name)) and
-  // `arg` has a relevant module type
-  (
-    resolveConstantReadAccessMustFlow(arg, tp) and
+  exists(DataFlow::LocalSourceNode source |
+    argMustFlowToReceiver(ctx, pragma[only_bind_into](source), pragma[only_bind_into](arg), _, call,
+      encl, pragma[only_bind_into](name)) and
+    exists(lookupSingletonMethod(tp, pragma[only_bind_into](name), exact))
+  |
+    source = trackModuleAccess(tp) and
     exact = true
     or
     exists(SelfVariable self | arg.asExpr().getExpr() = self.getAnAccess() |
@@ -1073,8 +1059,7 @@ private predicate mayBenefitFromCallContextSingleton(
         exact = false
       )
     )
-  ) and
-  exists(lookupSingletonMethod(tp, pragma[only_bind_into](name), exact))
+  )
 }
 
 /**
@@ -1101,7 +1086,7 @@ DataFlowCallable viableImplInCallContext(DataFlowCall call, DataFlowCall ctx) {
     exists(RelevantCall call0, Callable res |
       call0 = call.asCall() and
       res = result.asCallable() and
-      res = getTarget(call0) and // make sure to not include e.g. private methods
+      result = viableSourceCallable(call) and // make sure to not include e.g. private methods
       exists(Module m, boolean exact, string name |
         mayBenefitFromCallContextInstance(ctx.asCall(), pragma[only_bind_into](call0), _, _,
           pragma[only_bind_into](m), exact, pragma[only_bind_into](name)) and
@@ -1113,18 +1098,22 @@ DataFlowCallable viableImplInCallContext(DataFlowCall call, DataFlowCall ctx) {
       )
     )
     or
-    // `ctx` cannot provide a type bound
-    exists(RelevantCall call0, RelevantCall ctx0, ArgumentNode arg, string name |
+    // `ctx` cannot provide a type bound, and the receiver of the call is `self`;
+    // in this case, still apply an open-world assumption
+    exists(
+      RelevantCall call0, RelevantCall ctx0, ArgumentNode arg, SsaSelfDefinitionNode self,
+      string name
+    |
       call0 = call.asCall() and
       ctx0 = ctx.asCall() and
-      argFlowsToReceiver(ctx0, arg, call0, _, name) and
+      argMustFlowToReceiver(ctx0, _, arg, self, call0, _, name) and
       not mayBenefitFromCallContextInstance(ctx0, call0, arg, _, _, _, name) and
       not mayBenefitFromCallContextSingleton(ctx0, call0, arg, _, _, _, name) and
       result = viableSourceCallable(call)
     )
     or
     // library calls should always be able to resolve
-    argFlowsToReceiver(ctx.asCall(), _, call.asCall(), _, _) and
+    argMustFlowToReceiver(ctx.asCall(), _, _, _, call.asCall(), _, _) and
     result = viableLibraryCallable(call)
   )
 }