From d0f4c2f823b2562a512fd7dc6672ed3669cba3f4 Mon Sep 17 00:00:00 2001
From: Robert Marsh <rdmarsh@semmle.com>
Date: Mon, 8 Aug 2022 14:30:55 -0400
Subject: [PATCH] C++: product flow prototype

---
 .../semmle/code/cpp/dataflow/ProductFlow.qll  | 111 ++++++++++++++++++
 1 file changed, 111 insertions(+)
 create mode 100644 cpp/ql/lib/experimental/semmle/code/cpp/dataflow/ProductFlow.qll

diff --git a/cpp/ql/lib/experimental/semmle/code/cpp/dataflow/ProductFlow.qll b/cpp/ql/lib/experimental/semmle/code/cpp/dataflow/ProductFlow.qll
new file mode 100644
index 00000000000..07f6203f910
--- /dev/null
+++ b/cpp/ql/lib/experimental/semmle/code/cpp/dataflow/ProductFlow.qll
@@ -0,0 +1,111 @@
+import semmle.code.cpp.ir.dataflow.DataFlow
+import semmle.code.cpp.ir.dataflow.DataFlow2
+
+module ProductFlow {
+  abstract class Configuration extends string {
+    bindingset[this]
+    Configuration() { any() }
+
+    /**
+     * Holds if `(source1, source2)` is a relevant data flow source.
+     *
+     * `source1` and `source2` must belong to the same callable.
+     */
+    abstract predicate isSourcePair(DataFlow::Node source1, DataFlow::Node source2);
+
+    /**
+     * Holds if `(sink1, sink2)` is a relevant data flow sink.
+     *
+     * `sink1` and `sink2` must belong to the same callable.
+     */
+    abstract predicate isSinkPair(DataFlow::Node sink1, DataFlow::Node sink2);
+
+    predicate hasFlowPath(
+      DataFlow::PathNode source1, DataFlow2::PathNode source2, DataFlow::PathNode sink1,
+      DataFlow2::PathNode sink2
+    ) {
+      isSourcePair(source1.getNode(), source2.getNode()) and
+      isSinkPair(sink1.getNode(), sink2.getNode()) and
+      reachablePair(this, source1, source2, sink1, sink2)
+    }
+  }
+
+  class Conf1 extends DataFlow::Configuration {
+    Conf1() { this = "Conf1" }
+
+    override predicate isSource(DataFlow::Node source) {
+      exists(Configuration conf | conf.isSourcePair(source, _))
+    }
+
+    override predicate isSink(DataFlow::Node sink) {
+      exists(Configuration conf | conf.isSinkPair(sink, _))
+    }
+  }
+
+  class Conf2 extends DataFlow2::Configuration {
+    Conf2() { this = "Conf2" }
+
+    override predicate isSource(DataFlow::Node source) {
+      exists(Configuration conf | conf.isSourcePair(_, source))
+    }
+
+    override predicate isSink(DataFlow::Node sink) {
+      exists(Configuration conf | conf.isSinkPair(_, sink))
+    }
+  }
+
+  predicate reachablePair1(
+    Configuration conf, DataFlow::PathNode source1, DataFlow2::PathNode source2,
+    DataFlow::PathNode node1, DataFlow2::PathNode node2
+  ) {
+    reachablePair(conf, source1, source2, node1, node2)
+    or
+    exists(DataFlow::PathNode mid1 |
+      reachablePair1(conf, source1, source2, mid1, node2) and
+      mid1.getASuccessor() = node1 and
+      mid1.getNode().getFunction() = node1.getNode().getFunction()
+    )
+  }
+
+  predicate reachablePair2(
+    Configuration conf, DataFlow::PathNode source1, DataFlow2::PathNode source2,
+    DataFlow::PathNode node1, DataFlow2::PathNode node2
+  ) {
+    reachablePair1(conf, source1, source2, node1, node2) // TODO: restrict more
+    or
+    exists(DataFlow2::PathNode mid2 |
+      reachablePair2(conf, source1, source2, node1, mid2) and
+      mid2.getASuccessor() = node2 and
+      mid2.getNode().getFunction() = node2.getNode().getFunction()
+    )
+  }
+
+  predicate interprocStep(
+    Configuration conf, DataFlow::PathNode source1, DataFlow2::PathNode source2,
+    DataFlow::PathNode node1, DataFlow2::PathNode node2
+  ) {
+    exists(DataFlow::PathNode mid1, DataFlow2::PathNode mid2, Function funcMid, Function func |
+      reachablePair2(conf, source1, source2, mid1, mid2) and
+      mid1.getASuccessor() = node1 and
+      mid2.getASuccessor() = node2 and
+      mid1.getNode().getFunction() = funcMid and // TODO: recursive function weirdness?
+      mid2.getNode().getFunction() = funcMid and
+      node1.getNode().getFunction() = func and
+      node2.getNode().getFunction() = func and
+      funcMid != func
+    )
+  }
+
+  predicate reachablePair(
+    Configuration conf, DataFlow::PathNode source1, DataFlow2::PathNode source2,
+    DataFlow::PathNode node1, DataFlow2::PathNode node2
+  ) {
+    conf.isSourcePair(node1.getNode(), node2.getNode()) and
+    node1.isSource() and
+    node2.isSource() and
+    source1 = node1 and
+    source2 = node2
+    or
+    interprocStep(conf, source1, source2, node1, node2)
+  }
+}