//=== InnerPointerChecker.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 file defines a check that marks a raw pointer to a C++ container's

// inner buffer released when the object is destroyed. This information can

// be used by MallocChecker to detect use-after-free problems.

//

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

#include "AllocationState.h"

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

#include "InterCheckerAPI.h"

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

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

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

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

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

using namespace clang;

using namespace ento;

// Associate container objects with a set of raw pointer symbols.

REGISTER_SET_FACTORY_WITH_PROGRAMSTATE(PtrSet, SymbolRef)

REGISTER_MAP_WITH_PROGRAMSTATE(RawPtrMap, const MemRegion *, PtrSet)

namespace {

class InnerPointerChecker

    : public Checker<check::DeadSymbols, check::PostCall> {

  CallDescription AppendFn, AssignFn, ClearFn, CStrFn, DataFn, EraseFn,

      InsertFn, PopBackFn, PushBackFn, ReplaceFn, ReserveFn, ResizeFn,

      ShrinkToFitFn, SwapFn;

public:

  class InnerPointerBRVisitor : public BugReporterVisitor {

    SymbolRef PtrToBuf;

  public:

    InnerPointerBRVisitor(SymbolRef Sym) : PtrToBuf(Sym) {}

    static void *getTag() {

      static int Tag = 0;

      return &Tag;

    }

    void Profile(llvm::FoldingSetNodeID &ID) const override {

      ID.AddPointer(getTag());

    }

    virtual PathDiagnosticPieceRef

    VisitNode(const ExplodedNode *N, BugReporterContext &BRC,

              PathSensitiveBugReport &BR) override;

    // FIXME: Scan the map once in the visitor's constructor and do a direct

    // lookup by region.

    bool isSymbolTracked(ProgramStateRef State, SymbolRef Sym) {

      RawPtrMapTy Map = State->get<RawPtrMap>();

      for (const auto &Entry : Map) {

        if (Entry.second.contains(Sym))

          return true;

      }

      return false;

    }

  };

  InnerPointerChecker()

      : AppendFn({"std", "basic_string", "append"}),

        AssignFn({"std", "basic_string", "assign"}),

        ClearFn({"std", "basic_string", "clear"}),

        CStrFn({"std", "basic_string", "c_str"}),

        DataFn({"std", "basic_string", "data"}),

        EraseFn({"std", "basic_string", "erase"}),

        InsertFn({"std", "basic_string", "insert"}),

        PopBackFn({"std", "basic_string", "pop_back"}),

        PushBackFn({"std", "basic_string", "push_back"}),

        ReplaceFn({"std", "basic_string", "replace"}),

        ReserveFn({"std", "basic_string", "reserve"}),

        ResizeFn({"std", "basic_string", "resize"}),

        ShrinkToFitFn({"std", "basic_string", "shrink_to_fit"}),

        SwapFn({"std", "basic_string", "swap"}) {}

  /// Check whether the called member function potentially invalidates

  /// pointers referring to the container object's inner buffer.

  bool isInvalidatingMemberFunction(const CallEvent &Call) const;

  /// Mark pointer symbols associated with the given memory region released

  /// in the program state.

  void markPtrSymbolsReleased(const CallEvent &Call, ProgramStateRef State,

                              const MemRegion *ObjRegion,

                              CheckerContext &C) const;

  /// Standard library functions that take a non-const `basic_string` argument by

  /// reference may invalidate its inner pointers. Check for these cases and

  /// mark the pointers released.

  void checkFunctionArguments(const CallEvent &Call, ProgramStateRef State,

                              CheckerContext &C) const;

  /// Record the connection between raw pointers referring to a container

  /// object's inner buffer and the object's memory region in the program state.

  /// Mark potentially invalidated pointers released.

  void checkPostCall(const CallEvent &Call, CheckerContext &C) const;

  /// Clean up the program state map.

  void checkDeadSymbols(SymbolReaper &SymReaper, CheckerContext &C) const;

};

} // end anonymous namespace

bool InnerPointerChecker::isInvalidatingMemberFunction(

        const CallEvent &Call) const {

  if (const auto *MemOpCall = dyn_cast<CXXMemberOperatorCall>(&Call)) {

    OverloadedOperatorKind Opc = MemOpCall->getOriginExpr()->getOperator();

    if (Opc == OO_Equal || 
Opc == OO_PlusEqual1.27k
)

      return true;

    return false;

  }

  return (isa<CXXDestructorCall>(Call) || 
Call.isCalled(AppendFn)559
 ||

          Call.isCalled(AssignFn) || 
Call.isCalled(ClearFn)557
 ||

          Call.isCalled(EraseFn) || 
Call.isCalled(InsertFn)554
 ||

          Call.isCalled(PopBackFn) || 
Call.isCalled(PushBackFn)552
 ||

          Call.isCalled(ReplaceFn) || 
Call.isCalled(ReserveFn)550
 ||

          Call.isCalled(ResizeFn) || 
Call.isCalled(ShrinkToFitFn)548
 ||

          Call.isCalled(SwapFn));

}

void InnerPointerChecker::markPtrSymbolsReleased(const CallEvent &Call,

                                                 ProgramStateRef State,

                                                 const MemRegion *MR,

                                                 CheckerContext &C) const {

  if (const PtrSet *PS = State->get<RawPtrMap>(MR)) {

    const Expr *Origin = Call.getOriginExpr();

    for (const auto Symbol : *PS) {

      // NOTE: `Origin` may be null, and will be stored so in the symbol's

      // `RefState` in MallocChecker's `RegionState` program state map.

      State = allocation_state::markReleased(State, Symbol, Origin);

    }

    State = State->remove<RawPtrMap>(MR);

    C.addTransition(State);

    return;

  }

}

void InnerPointerChecker::checkFunctionArguments(const CallEvent &Call,

                                                 ProgramStateRef State,

                                                 CheckerContext &C) const {

  if (const auto *FC = dyn_cast<AnyFunctionCall>(&Call)) {

    const FunctionDecl *FD = FC->getDecl();

    if (!FD || 
!FD->isInStdNamespace()28.9k
)

      return;

    
for (unsigned I = 0, E = FD->getNumParams(); 429
I != E; 
++I1.09k
) {

      QualType ParamTy = FD->getParamDecl(I)->getType();

      if (!ParamTy->isReferenceType() ||

          ParamTy->getPointeeType().isConstQualified())

        continue;

      // In case of member operator calls, `this` is counted as an

      // argument but not as a parameter.

      bool isaMemberOpCall = isa<CXXMemberOperatorCall>(FC);

      unsigned ArgI = isaMemberOpCall ? 
I+10
 : I;

      SVal Arg = FC->getArgSVal(ArgI);

      const auto *ArgRegion =

          dyn_cast_or_null<TypedValueRegion>(Arg.getAsRegion());

      if (!ArgRegion)

        continue;

      markPtrSymbolsReleased(Call, State, ArgRegion, C);

    }

  }

}

// [string.require]

//

// "References, pointers, and iterators referring to the elements of a

// basic_string sequence may be invalidated by the following uses of that

// basic_string object:

//

// -- As an argument to any standard library function taking a reference

// to non-const basic_string as an argument. For example, as an argument to

// non-member functions swap(), operator>>(), and getline(), or as an argument

// to basic_string::swap().

//

// -- Calling non-const member functions, except operator[], at, front, back,

// begin, rbegin, end, and rend."

void InnerPointerChecker::checkPostCall(const CallEvent &Call,

                                        CheckerContext &C) const {

  ProgramStateRef State = C.getState();

  if (const auto *ICall = dyn_cast<CXXInstanceCall>(&Call)) {

    // TODO: Do we need these to be typed?

    const auto *ObjRegion = dyn_cast_or_null<TypedValueRegion>(

        ICall->getCXXThisVal().getAsRegion());

    if (!ObjRegion)

      return;

    if (Call.isCalled(CStrFn) || 
Call.isCalled(DataFn)2.27k
) {

      SVal RawPtr = Call.getReturnValue();

      if (SymbolRef Sym = RawPtr.getAsSymbol(/*IncludeBaseRegions=*/true)) {

        // Start tracking this raw pointer by adding it to the set of symbols

        // associated with this container object in the program state map.

        PtrSet::Factory &F = State->getStateManager().get_context<PtrSet>();

        const PtrSet *SetPtr = State->get<RawPtrMap>(ObjRegion);

        PtrSet Set = SetPtr ? 
*SetPtr5
 : F.getEmptySet();

        assert(C.wasInlined || !Set.contains(Sym));

        Set = F.add(Set, Sym);

        State = State->set<RawPtrMap>(ObjRegion, Set);

        C.addTransition(State);

      }

      return;

    }

    // Check [string.require] / second point.

    if (isInvalidatingMemberFunction(Call)) {

      markPtrSymbolsReleased(Call, State, ObjRegion, C);

      return;

    }

  }

  // Check [string.require] / first point.

  checkFunctionArguments(Call, State, C);

}

void InnerPointerChecker::checkDeadSymbols(SymbolReaper &SymReaper,

                                           CheckerContext &C) const {

  ProgramStateRef State = C.getState();

  PtrSet::Factory &F = State->getStateManager().get_context<PtrSet>();

  RawPtrMapTy RPM = State->get<RawPtrMap>();

  for (const auto &Entry : RPM) {

    if (!SymReaper.isLiveRegion(Entry.first)) {

      // Due to incomplete destructor support, some dead regions might

      // remain in the program state map. Clean them up.

      State = State->remove<RawPtrMap>(Entry.first);

    }

    if (const PtrSet *OldSet = State->get<RawPtrMap>(Entry.first)) {

      PtrSet CleanedUpSet = *OldSet;

      for (const auto Symbol : Entry.second) {

        if (!SymReaper.isLive(Symbol))

          CleanedUpSet = F.remove(CleanedUpSet, Symbol);

      }

      State = CleanedUpSet.isEmpty()

                  ? State->remove<RawPtrMap>(Entry.first)

                  : State->set<RawPtrMap>(Entry.first, CleanedUpSet);

    }

  }

  C.addTransition(State);

}

namespace clang {

namespace ento {

namespace allocation_state {

std::unique_ptr<BugReporterVisitor> getInnerPointerBRVisitor(SymbolRef Sym) {

  return std::make_unique<InnerPointerChecker::InnerPointerBRVisitor>(Sym);

}

const MemRegion *getContainerObjRegion(ProgramStateRef State, SymbolRef Sym) {

  RawPtrMapTy Map = State->get<RawPtrMap>();

  for (const auto &Entry : Map) {

    if (Entry.second.contains(Sym)) {

      return Entry.first;

    }

  }

  return nullptr;

}

} // end namespace allocation_state

} // end namespace ento

} // end namespace clang

PathDiagnosticPieceRef InnerPointerChecker::InnerPointerBRVisitor::VisitNode(

    const ExplodedNode *N, BugReporterContext &BRC, PathSensitiveBugReport &) {

  if (!isSymbolTracked(N->getState(), PtrToBuf) ||

      isSymbolTracked(N->getFirstPred()->getState(), PtrToBuf))

    return nullptr;

  const Stmt *S = N->getStmtForDiagnostics();

  if (!S)

    return nullptr;

  const MemRegion *ObjRegion =

      allocation_state::getContainerObjRegion(N->getState(), PtrToBuf);

  const auto *TypedRegion = cast<TypedValueRegion>(ObjRegion);

  QualType ObjTy = TypedRegion->getValueType();

  SmallString<256> Buf;

  llvm::raw_svector_ostream OS(Buf);

  OS << "Pointer to inner buffer of '" << ObjTy.getAsString()

     << "' obtained here";

  PathDiagnosticLocation Pos(S, BRC.getSourceManager(),

                             N->getLocationContext());

  return std::make_shared<PathDiagnosticEventPiece>(Pos, OS.str(), true);

}

void ento::registerInnerPointerChecker(CheckerManager &Mgr) {

  registerInnerPointerCheckerAux(Mgr);

  Mgr.registerChecker<InnerPointerChecker>();

}

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

  return true;

}