//=== CastToStructChecker.cpp ----------------------------------*- C++ -*--===//

//

// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.

// See https://llvm.org/LICENSE.txt for license information.

// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception

//

//===----------------------------------------------------------------------===//

//

// This files defines CastToStructChecker, a builtin checker that checks for

// cast from non-struct pointer to struct pointer and widening struct data cast.

// This check corresponds to CWE-588.

//

//===----------------------------------------------------------------------===//

#include "clang/StaticAnalyzer/Checkers/BuiltinCheckerRegistration.h"

#include "clang/AST/RecursiveASTVisitor.h"

#include "clang/StaticAnalyzer/Core/BugReporter/BugType.h"

#include "clang/StaticAnalyzer/Core/Checker.h"

#include "clang/StaticAnalyzer/Core/CheckerManager.h"

#include "clang/StaticAnalyzer/Core/PathSensitive/CheckerContext.h"

using namespace clang;

using namespace ento;

namespace {

class CastToStructVisitor : public RecursiveASTVisitor<CastToStructVisitor> {

  BugReporter &BR;

  const CheckerBase *Checker;

  AnalysisDeclContext *AC;

public:

  explicit CastToStructVisitor(BugReporter &B, const CheckerBase *Checker,

                               AnalysisDeclContext *A)

      : BR(B), Checker(Checker), AC(A) {}

  bool VisitCastExpr(const CastExpr *CE);

};

}

bool CastToStructVisitor::VisitCastExpr(const CastExpr *CE) {

  const Expr *E = CE->getSubExpr();

  ASTContext &Ctx = AC->getASTContext();

  QualType OrigTy = Ctx.getCanonicalType(E->getType());

  QualType ToTy = Ctx.getCanonicalType(CE->getType());

  const PointerType *OrigPTy = dyn_cast<PointerType>(OrigTy.getTypePtr());

  const PointerType *ToPTy = dyn_cast<PointerType>(ToTy.getTypePtr());

  if (!ToPTy || 
!OrigPTy3.89k
)

    return true;

  QualType OrigPointeeTy = OrigPTy->getPointeeType();

  QualType ToPointeeTy = ToPTy->getPointeeType();

  if (!ToPointeeTy->isStructureOrClassType())

    return true;

  // We allow cast from void*.

  if (OrigPointeeTy->isVoidType())

    return true;

  // Now the cast-to-type is struct pointer, the original type is not void*.

  if (!OrigPointeeTy->isRecordType()) {

    SourceRange Sr[1] = {CE->getSourceRange()};

    PathDiagnosticLocation Loc(CE, BR.getSourceManager(), AC);

    BR.EmitBasicReport(

        AC->getDecl(), Checker, "Cast from non-struct type to struct type",

        categories::LogicError, "Casting a non-structure type to a structure "

                                "type and accessing a field can lead to memory "

                                "access errors or data corruption.",

        Loc, Sr);

  } else {

    // Don't warn when size of data is unknown.

    const auto *U = dyn_cast<UnaryOperator>(E);

    if (!U || 
U->getOpcode() != UO_AddrOf30
)

      return true;

    // Don't warn for references

    const ValueDecl *VD = nullptr;

    if (const auto *SE = dyn_cast<DeclRefExpr>(U->getSubExpr()))

      VD = SE->getDecl();

    else if (const auto *SE = dyn_cast<MemberExpr>(U->getSubExpr()))

      VD = SE->getMemberDecl();

    if (!VD || 
VD->getType()->isReferenceType()25
)

      return true;

    if (ToPointeeTy->isIncompleteType() ||

        
OrigPointeeTy->isIncompleteType()21
)

      return true;

    // Warn when there is widening cast.

    unsigned ToWidth = Ctx.getTypeInfo(ToPointeeTy).Width;

    unsigned OrigWidth = Ctx.getTypeInfo(OrigPointeeTy).Width;

    if (ToWidth <= OrigWidth)

      return true;

    PathDiagnosticLocation Loc(CE, BR.getSourceManager(), AC);

    BR.EmitBasicReport(AC->getDecl(), Checker, "Widening cast to struct type",

                       categories::LogicError,

                       "Casting data to a larger structure type and accessing "

                       "a field can lead to memory access errors or data "

                       "corruption.",

                       Loc, CE->getSourceRange());

  }

  return true;

}

namespace {

class CastToStructChecker : public Checker<check::ASTCodeBody> {

public:

  void checkASTCodeBody(const Decl *D, AnalysisManager &Mgr,

                        BugReporter &BR) const {

    CastToStructVisitor Visitor(BR, this, Mgr.getAnalysisDeclContext(D));

    Visitor.TraverseDecl(const_cast<Decl *>(D));

  }

};

} // end anonymous namespace

void ento::registerCastToStructChecker(CheckerManager &mgr) {

  mgr.registerChecker<CastToStructChecker>();

}

bool ento::shouldRegisterCastToStructChecker(const CheckerManager &mgr) {

  return true;

}