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 const BugType BT{this, "Assignment of a non-Boolean value"};
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 StringRef Msg = IsTainted ? "Might assign a tainted non-Boolean value"
40 : "Assignment of a non-Boolean value";
41 C.emitReport(std::make_unique<PathSensitiveBugReport>(BT, Msg, N));
42 }
43 }
44
isBooleanType(QualType Ty)45 static bool isBooleanType(QualType Ty) {
46 if (Ty->isBooleanType()) // C++ or C99
47 return true;
48
49 if (const TypedefType *TT = Ty->getAs<TypedefType>())
50 return TT->getDecl()->getName() == "BOOL" || // Objective-C
51 TT->getDecl()->getName() == "_Bool" || // stdbool.h < C99
52 TT->getDecl()->getName() == "Boolean"; // MacTypes.h
53
54 return false;
55 }
56
checkBind(SVal loc,SVal val,const Stmt * S,CheckerContext & C) const57 void BoolAssignmentChecker::checkBind(SVal loc, SVal val, const Stmt *S,
58 CheckerContext &C) const {
59
60 // We are only interested in stores into Booleans.
61 const TypedValueRegion *TR =
62 dyn_cast_or_null<TypedValueRegion>(loc.getAsRegion());
63
64 if (!TR)
65 return;
66
67 QualType valTy = TR->getValueType();
68
69 if (!isBooleanType(valTy))
70 return;
71
72 // Get the value of the right-hand side. We only care about values
73 // that are defined (UnknownVals and UndefinedVals are handled by other
74 // checkers).
75 std::optional<NonLoc> NV = val.getAs<NonLoc>();
76 if (!NV)
77 return;
78
79 // Check if the assigned value meets our criteria for correctness. It must
80 // be a value that is either 0 or 1. One way to check this is to see if
81 // the value is possibly < 0 (for a negative value) or greater than 1.
82 ProgramStateRef state = C.getState();
83 SValBuilder &svalBuilder = C.getSValBuilder();
84 BasicValueFactory &BVF = svalBuilder.getBasicValueFactory();
85 ConstraintManager &CM = C.getConstraintManager();
86
87 llvm::APSInt Zero = BVF.getValue(0, valTy);
88 llvm::APSInt One = BVF.getValue(1, valTy);
89
90 ProgramStateRef StIn, StOut;
91 std::tie(StIn, StOut) = CM.assumeInclusiveRangeDual(state, *NV, Zero, One);
92
93 if (!StIn)
94 emitReport(StOut, C);
95 if (StIn && StOut && taint::isTainted(state, *NV))
96 emitReport(StOut, C, /*IsTainted=*/true);
97 }
98
registerBoolAssignmentChecker(CheckerManager & mgr)99 void ento::registerBoolAssignmentChecker(CheckerManager &mgr) {
100 mgr.registerChecker<BoolAssignmentChecker>();
101 }
102
shouldRegisterBoolAssignmentChecker(const CheckerManager & mgr)103 bool ento::shouldRegisterBoolAssignmentChecker(const CheckerManager &mgr) {
104 return true;
105 }
106