126 lines · cpp
1//=== CastToStructChecker.cpp ----------------------------------*- 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-exception6//7//===----------------------------------------------------------------------===//8//9// This files defines CastToStructChecker, a builtin checker that checks for10// cast from non-struct pointer to struct pointer and widening struct data cast.11// This check corresponds to CWE-588.12//13//===----------------------------------------------------------------------===//14 15#include "clang/AST/DynamicRecursiveASTVisitor.h"16#include "clang/StaticAnalyzer/Checkers/BuiltinCheckerRegistration.h"17#include "clang/StaticAnalyzer/Core/BugReporter/BugType.h"18#include "clang/StaticAnalyzer/Core/Checker.h"19#include "clang/StaticAnalyzer/Core/CheckerManager.h"20#include "clang/StaticAnalyzer/Core/PathSensitive/CheckerContext.h"21 22using namespace clang;23using namespace ento;24 25namespace {26class CastToStructVisitor : public DynamicRecursiveASTVisitor {27 BugReporter &BR;28 const CheckerBase *Checker;29 AnalysisDeclContext *AC;30 31public:32 explicit CastToStructVisitor(BugReporter &B, const CheckerBase *Checker,33 AnalysisDeclContext *A)34 : BR(B), Checker(Checker), AC(A) {}35 bool VisitCastExpr(CastExpr *CE) override;36};37}38 39bool CastToStructVisitor::VisitCastExpr(CastExpr *CE) {40 const Expr *E = CE->getSubExpr();41 ASTContext &Ctx = AC->getASTContext();42 QualType OrigTy = Ctx.getCanonicalType(E->getType());43 QualType ToTy = Ctx.getCanonicalType(CE->getType());44 45 const PointerType *OrigPTy = dyn_cast<PointerType>(OrigTy.getTypePtr());46 const PointerType *ToPTy = dyn_cast<PointerType>(ToTy.getTypePtr());47 48 if (!ToPTy || !OrigPTy)49 return true;50 51 QualType OrigPointeeTy = OrigPTy->getPointeeType();52 QualType ToPointeeTy = ToPTy->getPointeeType();53 54 if (!ToPointeeTy->isStructureOrClassType())55 return true;56 57 // We allow cast from void*.58 if (OrigPointeeTy->isVoidType())59 return true;60 61 // Now the cast-to-type is struct pointer, the original type is not void*.62 if (!OrigPointeeTy->isRecordType()) {63 SourceRange Sr[1] = {CE->getSourceRange()};64 PathDiagnosticLocation Loc(CE, BR.getSourceManager(), AC);65 BR.EmitBasicReport(66 AC->getDecl(), Checker, "Cast from non-struct type to struct type",67 categories::LogicError, "Casting a non-structure type to a structure "68 "type and accessing a field can lead to memory "69 "access errors or data corruption.",70 Loc, Sr);71 } else {72 // Don't warn when size of data is unknown.73 const auto *U = dyn_cast<UnaryOperator>(E);74 if (!U || U->getOpcode() != UO_AddrOf)75 return true;76 77 // Don't warn for references78 const ValueDecl *VD = nullptr;79 if (const auto *SE = dyn_cast<DeclRefExpr>(U->getSubExpr()))80 VD = SE->getDecl();81 else if (const auto *SE = dyn_cast<MemberExpr>(U->getSubExpr()))82 VD = SE->getMemberDecl();83 if (!VD || VD->getType()->isReferenceType())84 return true;85 86 if (ToPointeeTy->isIncompleteType() ||87 OrigPointeeTy->isIncompleteType())88 return true;89 90 // Warn when there is widening cast.91 unsigned ToWidth = Ctx.getTypeInfo(ToPointeeTy).Width;92 unsigned OrigWidth = Ctx.getTypeInfo(OrigPointeeTy).Width;93 if (ToWidth <= OrigWidth)94 return true;95 96 PathDiagnosticLocation Loc(CE, BR.getSourceManager(), AC);97 BR.EmitBasicReport(AC->getDecl(), Checker, "Widening cast to struct type",98 categories::LogicError,99 "Casting data to a larger structure type and accessing "100 "a field can lead to memory access errors or data "101 "corruption.",102 Loc, CE->getSourceRange());103 }104 105 return true;106}107 108namespace {109class CastToStructChecker : public Checker<check::ASTCodeBody> {110public:111 void checkASTCodeBody(const Decl *D, AnalysisManager &Mgr,112 BugReporter &BR) const {113 CastToStructVisitor Visitor(BR, this, Mgr.getAnalysisDeclContext(D));114 Visitor.TraverseDecl(const_cast<Decl *>(D));115 }116};117} // end anonymous namespace118 119void ento::registerCastToStructChecker(CheckerManager &mgr) {120 mgr.registerChecker<CastToStructChecker>();121}122 123bool ento::shouldRegisterCastToStructChecker(const CheckerManager &mgr) {124 return true;125}126