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126 lines
4.4 KiB
126 lines
4.4 KiB
//=== CastToStructChecker.cpp ----------------------------------*- C++ -*--===//
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//
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// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
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// See https://llvm.org/LICENSE.txt for license information.
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// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
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//
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//===----------------------------------------------------------------------===//
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//
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// This files defines CastToStructChecker, a builtin checker that checks for
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// cast from non-struct pointer to struct pointer and widening struct data cast.
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// This check corresponds to CWE-588.
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//
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//===----------------------------------------------------------------------===//
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#include "clang/StaticAnalyzer/Checkers/BuiltinCheckerRegistration.h"
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#include "clang/AST/RecursiveASTVisitor.h"
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#include "clang/StaticAnalyzer/Core/BugReporter/BugType.h"
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#include "clang/StaticAnalyzer/Core/Checker.h"
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#include "clang/StaticAnalyzer/Core/CheckerManager.h"
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#include "clang/StaticAnalyzer/Core/PathSensitive/CheckerContext.h"
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using namespace clang;
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using namespace ento;
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namespace {
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class CastToStructVisitor : public RecursiveASTVisitor<CastToStructVisitor> {
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BugReporter &BR;
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const CheckerBase *Checker;
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AnalysisDeclContext *AC;
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public:
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explicit CastToStructVisitor(BugReporter &B, const CheckerBase *Checker,
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AnalysisDeclContext *A)
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: BR(B), Checker(Checker), AC(A) {}
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bool VisitCastExpr(const CastExpr *CE);
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};
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}
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bool CastToStructVisitor::VisitCastExpr(const CastExpr *CE) {
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const Expr *E = CE->getSubExpr();
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ASTContext &Ctx = AC->getASTContext();
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QualType OrigTy = Ctx.getCanonicalType(E->getType());
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QualType ToTy = Ctx.getCanonicalType(CE->getType());
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const PointerType *OrigPTy = dyn_cast<PointerType>(OrigTy.getTypePtr());
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const PointerType *ToPTy = dyn_cast<PointerType>(ToTy.getTypePtr());
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if (!ToPTy || !OrigPTy)
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return true;
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QualType OrigPointeeTy = OrigPTy->getPointeeType();
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QualType ToPointeeTy = ToPTy->getPointeeType();
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if (!ToPointeeTy->isStructureOrClassType())
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return true;
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// We allow cast from void*.
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if (OrigPointeeTy->isVoidType())
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return true;
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// Now the cast-to-type is struct pointer, the original type is not void*.
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if (!OrigPointeeTy->isRecordType()) {
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SourceRange Sr[1] = {CE->getSourceRange()};
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PathDiagnosticLocation Loc(CE, BR.getSourceManager(), AC);
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BR.EmitBasicReport(
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AC->getDecl(), Checker, "Cast from non-struct type to struct type",
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categories::LogicError, "Casting a non-structure type to a structure "
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"type and accessing a field can lead to memory "
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"access errors or data corruption.",
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Loc, Sr);
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} else {
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// Don't warn when size of data is unknown.
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const auto *U = dyn_cast<UnaryOperator>(E);
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if (!U || U->getOpcode() != UO_AddrOf)
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return true;
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// Don't warn for references
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const ValueDecl *VD = nullptr;
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if (const auto *SE = dyn_cast<DeclRefExpr>(U->getSubExpr()))
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VD = SE->getDecl();
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else if (const auto *SE = dyn_cast<MemberExpr>(U->getSubExpr()))
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VD = SE->getMemberDecl();
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if (!VD || VD->getType()->isReferenceType())
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return true;
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if (ToPointeeTy->isIncompleteType() ||
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OrigPointeeTy->isIncompleteType())
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return true;
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// Warn when there is widening cast.
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unsigned ToWidth = Ctx.getTypeInfo(ToPointeeTy).Width;
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unsigned OrigWidth = Ctx.getTypeInfo(OrigPointeeTy).Width;
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if (ToWidth <= OrigWidth)
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return true;
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PathDiagnosticLocation Loc(CE, BR.getSourceManager(), AC);
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BR.EmitBasicReport(AC->getDecl(), Checker, "Widening cast to struct type",
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categories::LogicError,
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"Casting data to a larger structure type and accessing "
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"a field can lead to memory access errors or data "
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"corruption.",
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Loc, CE->getSourceRange());
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}
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return true;
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}
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namespace {
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class CastToStructChecker : public Checker<check::ASTCodeBody> {
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public:
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void checkASTCodeBody(const Decl *D, AnalysisManager &Mgr,
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BugReporter &BR) const {
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CastToStructVisitor Visitor(BR, this, Mgr.getAnalysisDeclContext(D));
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Visitor.TraverseDecl(const_cast<Decl *>(D));
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}
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};
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} // end anonymous namespace
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void ento::registerCastToStructChecker(CheckerManager &mgr) {
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mgr.registerChecker<CastToStructChecker>();
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}
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bool ento::shouldRegisterCastToStructChecker(const CheckerManager &mgr) {
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return true;
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}
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