1 //== BoolAssignmentChecker.cpp - Boolean assignment checker -----*- C++ -*--==//
2 //
3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
4 // See https://llvm.org/LICENSE.txt for license information.
5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
6 //
7 //===----------------------------------------------------------------------===//
8 //
9 // This defines BoolAssignmentChecker, a builtin check in ExprEngine that
10 // performs checks for assignment of non-Boolean values to Boolean variables.
11 //
12 //===----------------------------------------------------------------------===//
13 
14 #include "clang/StaticAnalyzer/Checkers/BuiltinCheckerRegistration.h"
15 #include "clang/StaticAnalyzer/Checkers/Taint.h"
16 #include "clang/StaticAnalyzer/Core/BugReporter/BugType.h"
17 #include "clang/StaticAnalyzer/Core/Checker.h"
18 #include "clang/StaticAnalyzer/Core/CheckerManager.h"
19 #include "clang/StaticAnalyzer/Core/PathSensitive/CheckerContext.h"
20 #include <optional>
21 
22 using namespace clang;
23 using namespace ento;
24 
25 namespace {
26   class BoolAssignmentChecker : public Checker< check::Bind > {
27     mutable std::unique_ptr<BugType> BT;
28     void emitReport(ProgramStateRef state, CheckerContext &C,
29                     bool IsTainted = false) const;
30 
31   public:
32     void checkBind(SVal loc, SVal val, const Stmt *S, CheckerContext &C) const;
33   };
34 } // end anonymous namespace
35 
36 void BoolAssignmentChecker::emitReport(ProgramStateRef state, CheckerContext &C,
37                                        bool IsTainted) const {
38   if (ExplodedNode *N = C.generateNonFatalErrorNode(state)) {
39     if (!BT)
40       BT.reset(new BugType(this, "Assignment of a non-Boolean value"));
41 
42     StringRef Msg = IsTainted ? "Might assign a tainted non-Boolean value"
43                               : "Assignment of a non-Boolean value";
44     C.emitReport(std::make_unique<PathSensitiveBugReport>(*BT, Msg, N));
45   }
46 }
47 
48 static bool isBooleanType(QualType Ty) {
49   if (Ty->isBooleanType()) // C++ or C99
50     return true;
51 
52   if (const TypedefType *TT = Ty->getAs<TypedefType>())
53     return TT->getDecl()->getName() == "BOOL"   || // Objective-C
54            TT->getDecl()->getName() == "_Bool"  || // stdbool.h < C99
55            TT->getDecl()->getName() == "Boolean";  // MacTypes.h
56 
57   return false;
58 }
59 
60 void BoolAssignmentChecker::checkBind(SVal loc, SVal val, const Stmt *S,
61                                       CheckerContext &C) const {
62 
63   // We are only interested in stores into Booleans.
64   const TypedValueRegion *TR =
65     dyn_cast_or_null<TypedValueRegion>(loc.getAsRegion());
66 
67   if (!TR)
68     return;
69 
70   QualType valTy = TR->getValueType();
71 
72   if (!isBooleanType(valTy))
73     return;
74 
75   // Get the value of the right-hand side.  We only care about values
76   // that are defined (UnknownVals and UndefinedVals are handled by other
77   // checkers).
78   std::optional<NonLoc> NV = val.getAs<NonLoc>();
79   if (!NV)
80     return;
81 
82   // Check if the assigned value meets our criteria for correctness.  It must
83   // be a value that is either 0 or 1.  One way to check this is to see if
84   // the value is possibly < 0 (for a negative value) or greater than 1.
85   ProgramStateRef state = C.getState();
86   SValBuilder &svalBuilder = C.getSValBuilder();
87   BasicValueFactory &BVF = svalBuilder.getBasicValueFactory();
88   ConstraintManager &CM = C.getConstraintManager();
89 
90   llvm::APSInt Zero = BVF.getValue(0, valTy);
91   llvm::APSInt One = BVF.getValue(1, valTy);
92 
93   ProgramStateRef StIn, StOut;
94   std::tie(StIn, StOut) = CM.assumeInclusiveRangeDual(state, *NV, Zero, One);
95 
96   if (!StIn)
97     emitReport(StOut, C);
98   if (StIn && StOut && taint::isTainted(state, *NV))
99     emitReport(StOut, C, /*IsTainted=*/true);
100 }
101 
102 void ento::registerBoolAssignmentChecker(CheckerManager &mgr) {
103     mgr.registerChecker<BoolAssignmentChecker>();
104 }
105 
106 bool ento::shouldRegisterBoolAssignmentChecker(const CheckerManager &mgr) {
107   return true;
108 }
109