CastToStructChecker.cpp
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//=== 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 || !OrigPTy)
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_AddrOf)
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())
return true;
if (ToPointeeTy->isIncompleteType() ||
OrigPointeeTy->isIncompleteType())
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 LangOptions &LO) {
return true;
}