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<BuiltinBug> 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
emitReport(ProgramStateRef state,CheckerContext & C,bool IsTainted) const36 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 BuiltinBug(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
isBooleanType(QualType Ty)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
checkBind(SVal loc,SVal val,const Stmt * S,CheckerContext & C) const60 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
registerBoolAssignmentChecker(CheckerManager & mgr)102 void ento::registerBoolAssignmentChecker(CheckerManager &mgr) {
103 mgr.registerChecker<BoolAssignmentChecker>();
104 }
105
shouldRegisterBoolAssignmentChecker(const CheckerManager & mgr)106 bool ento::shouldRegisterBoolAssignmentChecker(const CheckerManager &mgr) {
107 return true;
108 }
109