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