Merge pull request #18131 from paldepind/rust-field-flow

Rust: Data flow through tuple and struct fields

Author: paldepind

rust/ql/lib/codeql/rust/dataflow/internal/DataFlowImpl.qll

@@ -252,10 +252,10 @@ module Node {
    * Nodes corresponding to AST elements, for example `ExprNode`, usually refer
    * to the value before the update.
    */
-  final class PostUpdateNode extends Node, TArgumentPostUpdateNode {
+  final class PostUpdateNode extends Node, TExprPostUpdateNode {
     private ExprCfgNode n;
 
-    PostUpdateNode() { this = TArgumentPostUpdateNode(n) }
+    PostUpdateNode() { this = TExprPostUpdateNode(n) }
 
     /** Gets the node before the state update. */
     Node getPreUpdateNode() { result = TExprNode(n) }
@@ -264,7 +264,7 @@ module Node {
 
     final override Location getLocation() { result = n.getLocation() }
 
-    final override string toString() { result = n.toString() }
+    final override string toString() { result = "[post] " + n.toString() }
   }
 
   final class CastNode = NaNode;
@@ -286,6 +286,9 @@ module SsaFlow {
     or
     result.(SsaFlow::ExprNode).getExpr() = n.asExpr()
     or
+    result.(SsaFlow::ExprPostUpdateNode).getExpr() =
+      n.(Node::PostUpdateNode).getPreUpdateNode().asExpr()
+    or
     n = toParameterNode(result.(SsaFlow::ParameterNode).getParameter())
   }
 
@@ -449,6 +452,54 @@ private class VariantFieldContent extends VariantContent, TVariantFieldContent {
   }
 }
 
+/** A canonical path pointing to a struct. */
+private class StructCanonicalPath extends MkStructCanonicalPath {
+  CrateOriginOption crate;
+  string path;
+
+  StructCanonicalPath() { this = MkStructCanonicalPath(crate, path) }
+
+  /** Gets the underlying struct. */
+  Struct getStruct() { hasExtendedCanonicalPath(result, crate, path) }
+
+  string toString() { result = this.getStruct().getName().getText() }
+
+  Location getLocation() { result = this.getStruct().getLocation() }
+}
+
+/** Content stored in a field on a struct. */
+private class StructFieldContent extends Content, TStructFieldContent {
+  private StructCanonicalPath s;
+  private string field_;
+
+  StructFieldContent() { this = TStructFieldContent(s, field_) }
+
+  StructCanonicalPath getStructCanonicalPath(string field) { result = s and field = field_ }
+
+  override string toString() { result = s.toString() + "." + field_.toString() }
+}
+
+/**
+ * Content stored at a position in a tuple.
+ *
+ * NOTE: Unlike `struct`s and `enum`s tuples are structural and not nominal,
+ * hence we don't store a canonical path for them.
+ */
+private class TuplePositionContent extends Content, TTuplePositionContent {
+  private int pos;
+
+  TuplePositionContent() { this = TTuplePositionContent(pos) }
+
+  int getPosition() { result = pos }
+
+  override string toString() { result = "tuple." + pos.toString() }
+}
+
+/** Holds if `access` indexes a tuple at an index corresponding to `c`. */
+private predicate fieldTuplePositionContent(FieldExprCfgNode access, TuplePositionContent c) {
+  access.getNameRef().getText().toInt() = c.getPosition()
+}
+
 /** A value that represents a set of `Content`s. */
 abstract class ContentSet extends TContentSet {
   /** Gets a textual representation of this element. */
@@ -597,6 +648,14 @@ module RustDataFlow implements InputSig<Location> {
    */
   predicate jumpStep(Node node1, Node node2) { none() }
 
+  /** Holds if path `p` resolves to struct `s`. */
+  private predicate pathResolveToStructCanonicalPath(Path p, StructCanonicalPath s) {
+    exists(CrateOriginOption crate, string path |
+      resolveExtendedCanonicalPath(p, crate, path) and
+      s = MkStructCanonicalPath(crate, path)
+    )
+  }
+
   /** Holds if path `p` resolves to variant `v`. */
   private predicate pathResolveToVariantCanonicalPath(Path p, VariantCanonicalPath v) {
     exists(CrateOriginOption crate, string path |
@@ -625,6 +684,12 @@ module RustDataFlow implements InputSig<Location> {
     pathResolveToVariantCanonicalPath(p.getPath(), v)
   }
 
+  /** Holds if `p` destructs a struct `s`. */
+  pragma[nomagic]
+  private predicate structDestruction(RecordPat p, StructCanonicalPath s) {
+    pathResolveToStructCanonicalPath(p.getPath(), s)
+  }
+
   /**
    * Holds if data can flow from `node1` to `node2` via a read of `c`.  Thus,
    * `node1` references an object with a content `c.getAReadContent()` whose
@@ -641,10 +706,24 @@ module RustDataFlow implements InputSig<Location> {
       or
       exists(RecordPatCfgNode pat, string field |
         pat = node1.asPat() and
-        recordVariantDestruction(pat.getPat(),
-          c.(VariantFieldContent).getVariantCanonicalPath(field)) and
+        (
+          // Pattern destructs a struct-like variant.
+          recordVariantDestruction(pat.getPat(),
+            c.(VariantFieldContent).getVariantCanonicalPath(field))
+          or
+          // Pattern destructs a struct.
+          structDestruction(pat.getPat(), c.(StructFieldContent).getStructCanonicalPath(field))
+        ) and
         node2.asPat() = pat.getFieldPat(field)
       )
+      or
+      exists(FieldExprCfgNode access |
+        // Read of a tuple entry
+        fieldTuplePositionContent(access, c) and
+        // TODO: Handle read of a struct field.
+        node1.asExpr() = access.getExpr() and
+        node2.asExpr() = access
+      )
     )
   }
 
@@ -660,30 +739,55 @@ module RustDataFlow implements InputSig<Location> {
     pathResolveToVariantCanonicalPath(re.getPath(), v)
   }
 
+  /** Holds if `re` constructs a struct value of type `s`. */
+  pragma[nomagic]
+  private predicate structConstruction(RecordExpr re, StructCanonicalPath s) {
+    pathResolveToStructCanonicalPath(re.getPath(), s)
+  }
+
+  private predicate tupleAssignment(Node node1, Node node2, TuplePositionContent c) {
+    exists(AssignmentExprCfgNode assignment, FieldExprCfgNode access |
+      assignment.getLhs() = access and
+      fieldTuplePositionContent(access, c) and
+      node1.asExpr() = assignment.getRhs() and
+      node2.asExpr() = access.getExpr()
+    )
+  }
+
   /**
    * Holds if data can flow from `node1` to `node2` via a store into `c`.  Thus,
    * `node2` references an object with a content `c.getAStoreContent()` that
    * contains the value of `node1`.
    */
   predicate storeStep(Node node1, ContentSet cs, Node node2) {
     exists(Content c | c = cs.(SingletonContentSet).getContent() |
-      node2.asExpr() =
-        any(CallExprCfgNode call, int pos |
-          tupleVariantConstruction(call.getCallExpr(),
-            c.(VariantPositionContent).getVariantCanonicalPath(pos)) and
-          node1.asExpr() = call.getArgument(pos)
-        |
-          call
-        )
+      exists(CallExprCfgNode call, int pos |
+        tupleVariantConstruction(call.getCallExpr(),
+          c.(VariantPositionContent).getVariantCanonicalPath(pos)) and
+        node1.asExpr() = call.getArgument(pos) and
+        node2.asExpr() = call
+      )
       or
-      node2.asExpr() =
-        any(RecordExprCfgNode re, string field |
+      exists(RecordExprCfgNode re, string field |
+        (
+          // Expression is for a struct-like enum variant.
           recordVariantConstruction(re.getRecordExpr(),
-            c.(VariantFieldContent).getVariantCanonicalPath(field)) and
-          node1.asExpr() = re.getFieldExpr(field)
-        |
-          re
-        )
+            c.(VariantFieldContent).getVariantCanonicalPath(field))
+          or
+          // Expression is for a struct.
+          structConstruction(re.getRecordExpr(),
+            c.(StructFieldContent).getStructCanonicalPath(field))
+        ) and
+        node1.asExpr() = re.getFieldExpr(field) and
+        node2.asExpr() = re
+      )
+      or
+      exists(TupleExprCfgNode tuple |
+        node1.asExpr() = tuple.getField(c.(TuplePositionContent).getPosition()) and
+        node2.asExpr() = tuple
+      )
+      or
+      tupleAssignment(node1, node2.(PostUpdateNode).getPreUpdateNode(), c)
     )
   }
 
@@ -692,7 +796,9 @@ module RustDataFlow implements InputSig<Location> {
    * any value stored inside `f` is cleared at the pre-update node associated with `x`
    * in `x.f = newValue`.
    */
-  predicate clearsContent(Node n, ContentSet c) { none() }
+  predicate clearsContent(Node n, ContentSet cs) {
+    tupleAssignment(_, n, cs.(SingletonContentSet).getContent())
+  }
 
   /**
    * Holds if the value that is being tracked is expected to be stored inside content `c`
@@ -762,7 +868,9 @@ private module Cached {
     TExprNode(ExprCfgNode n) or
     TParameterNode(ParamBaseCfgNode p) or
     TPatNode(PatCfgNode p) or
-    TArgumentPostUpdateNode(ExprCfgNode e) { isArgumentForCall(e, _, _) } or
+    TExprPostUpdateNode(ExprCfgNode e) {
+      isArgumentForCall(e, _, _) or e = any(FieldExprCfgNode access).getExpr()
+    } or
     TSsaNode(SsaImpl::DataFlowIntegration::SsaNode node)
 
   cached
@@ -800,6 +908,12 @@ private module Cached {
       name = ["Ok", "Err"]
     }
 
+  cached
+  newtype TStructCanonicalPath =
+    MkStructCanonicalPath(CrateOriginOption crate, string path) {
+      exists(Struct s | hasExtendedCanonicalPath(s, crate, path))
+    }
+
   cached
   newtype TContent =
     TVariantPositionContent(VariantCanonicalPath v, int pos) {
@@ -815,6 +929,16 @@ private module Cached {
     } or
     TVariantFieldContent(VariantCanonicalPath v, string field) {
       field = v.getVariant().getFieldList().(RecordFieldList).getAField().getName().getText()
+    } or
+    TTuplePositionContent(int pos) {
+      pos in [0 .. max([
+                any(TuplePat pat).getNumberOfFields(),
+                any(FieldExpr access).getNameRef().getText().toInt()
+              ]
+          )]
+    } or
+    TStructFieldContent(StructCanonicalPath s, string field) {
+      field = s.getStruct().getFieldList().(RecordFieldList).getAField().getName().getText()
     }
 
   cached