//===-- IteratorRangeChecker.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

//

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

//

// Defines a checker for dereference of the past-the-end iterator and

// out-of-range increments and decrements.

//

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

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

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

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

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

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

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

#include "Iterator.h"

using namespace clang;

using namespace ento;

using namespace iterator;

namespace {

class IteratorRangeChecker

  : public Checker<check::PreCall, check::PreStmt<UnaryOperator>,

                   check::PreStmt<BinaryOperator>,

                   check::PreStmt<ArraySubscriptExpr>,

                   check::PreStmt<MemberExpr>> {

  std::unique_ptr<BugType> OutOfRangeBugType;

  void verifyDereference(CheckerContext &C, SVal Val) const;

  void verifyIncrement(CheckerContext &C, SVal Iter) const;

  void verifyDecrement(CheckerContext &C, SVal Iter) const;

  void verifyRandomIncrOrDecr(CheckerContext &C, OverloadedOperatorKind Op,

                              SVal LHS, SVal RHS) const;

  void verifyAdvance(CheckerContext &C, SVal LHS, SVal RHS) const;

  void verifyPrev(CheckerContext &C, SVal LHS, SVal RHS) const;

  void verifyNext(CheckerContext &C, SVal LHS, SVal RHS) const;

  void reportBug(const StringRef &Message, SVal Val, CheckerContext &C,

                 ExplodedNode *ErrNode) const;

public:

  IteratorRangeChecker();

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

  void checkPreStmt(const UnaryOperator *UO, CheckerContext &C) const;

  void checkPreStmt(const BinaryOperator *BO, CheckerContext &C) const;

  void checkPreStmt(const ArraySubscriptExpr *ASE, CheckerContext &C) const;

  void checkPreStmt(const MemberExpr *ME, CheckerContext &C) const;

  using AdvanceFn = void (IteratorRangeChecker::*)(CheckerContext &, SVal,

                                                   SVal) const;

  CallDescriptionMap<AdvanceFn> AdvanceFunctions = {

      {{{"std", "advance"}, 2}, &IteratorRangeChecker::verifyAdvance},

      {{{"std", "prev"}, 2}, &IteratorRangeChecker::verifyPrev},

      {{{"std", "next"}, 2}, &IteratorRangeChecker::verifyNext},

  };

};

bool isPastTheEnd(ProgramStateRef State, const IteratorPosition &Pos);

bool isAheadOfRange(ProgramStateRef State, const IteratorPosition &Pos);

bool isBehindPastTheEnd(ProgramStateRef State, const IteratorPosition &Pos);

bool isZero(ProgramStateRef State, const NonLoc &Val);

} //namespace

IteratorRangeChecker::IteratorRangeChecker() {

  OutOfRangeBugType.reset(

      new BugType(this, "Iterator out of range", "Misuse of STL APIs"));

}

void IteratorRangeChecker::checkPreCall(const CallEvent &Call,

                                        CheckerContext &C) const {

  // Check for out of range access

  const auto *Func = dyn_cast_or_null<FunctionDecl>(Call.getDecl());

  if (!Func)

    return;

  if (Func->isOverloadedOperator()) {

    if (isIncrementOperator(Func->getOverloadedOperator())) {

      // Check for out-of-range incrementions

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

        verifyIncrement(C, InstCall->getCXXThisVal());

      } else {

        if (Call.getNumArgs() >= 1) {

          verifyIncrement(C, Call.getArgSVal(0));

        }

      }

    } else if (isDecrementOperator(Func->getOverloadedOperator())) {

      // Check for out-of-range decrementions

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

        verifyDecrement(C, InstCall->getCXXThisVal());

      } else {

        if (Call.getNumArgs() >= 1) {

          verifyDecrement(C, Call.getArgSVal(0));

        }

      }

    } else if (isRandomIncrOrDecrOperator(Func->getOverloadedOperator())) {

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

        // Check for out-of-range incrementions and decrementions

        if (Call.getNumArgs() >= 1 &&

            Call.getArgExpr(0)->getType()->isIntegralOrEnumerationType()) {

          verifyRandomIncrOrDecr(C, Func->getOverloadedOperator(),

                                 InstCall->getCXXThisVal(),

                                 Call.getArgSVal(0));

        }

      } else {

        if (Call.getNumArgs() >= 2 &&

            Call.getArgExpr(1)->getType()->isIntegralOrEnumerationType()) {

          verifyRandomIncrOrDecr(C, Func->getOverloadedOperator(),

                                 Call.getArgSVal(0), Call.getArgSVal(1));

        }

      }

    } else 
if (46
isDereferenceOperator(Func->getOverloadedOperator())46
) {

      // Check for dereference of out-of-range iterators

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

        verifyDereference(C, InstCall->getCXXThisVal());

      } else {

        verifyDereference(C, Call.getArgSVal(0));

      }

    }

  } else {

    const AdvanceFn *Verifier = AdvanceFunctions.lookup(Call);

    if (Verifier) {

      if (Call.getNumArgs() > 1) {

        (this->**Verifier)(C, Call.getArgSVal(0), Call.getArgSVal(1));

      } else {

        auto &BVF = C.getSValBuilder().getBasicValueFactory();

        (this->**Verifier)(

            C, Call.getArgSVal(0),

            nonloc::ConcreteInt(BVF.getValue(llvm::APSInt::get(1))));

      }

    }

  }

}

void IteratorRangeChecker::checkPreStmt(const UnaryOperator *UO,

                                        CheckerContext &C) const {

  if (isa<CXXThisExpr>(UO->getSubExpr()))

    return;

  ProgramStateRef State = C.getState();

  UnaryOperatorKind OK = UO->getOpcode();

  SVal SubVal = State->getSVal(UO->getSubExpr(), C.getLocationContext());

  if (isDereferenceOperator(OK)) {

    verifyDereference(C, SubVal);

  } else if (isIncrementOperator(OK)) {

    verifyIncrement(C, SubVal);

  } else if (isDecrementOperator(OK)) {

    verifyDecrement(C, SubVal);

  }

}

void IteratorRangeChecker::checkPreStmt(const BinaryOperator *BO,

                                        CheckerContext &C) const {

  ProgramStateRef State = C.getState();

  BinaryOperatorKind OK = BO->getOpcode();

  SVal LVal = State->getSVal(BO->getLHS(), C.getLocationContext());

  if (isDereferenceOperator(OK)) {

    verifyDereference(C, LVal);

  } else if (isRandomIncrOrDecrOperator(OK)) {

    SVal RVal = State->getSVal(BO->getRHS(), C.getLocationContext());

    if (!BO->getRHS()->getType()->isIntegralOrEnumerationType())

      return;

    verifyRandomIncrOrDecr(C, BinaryOperator::getOverloadedOperator(OK), LVal,

                           RVal);

  }

}

void IteratorRangeChecker::checkPreStmt(const ArraySubscriptExpr *ASE,

                                        CheckerContext &C) const {

  ProgramStateRef State = C.getState();

  SVal LVal = State->getSVal(ASE->getLHS(), C.getLocationContext());

  verifyDereference(C, LVal);

}

void IteratorRangeChecker::checkPreStmt(const MemberExpr *ME,

                                        CheckerContext &C) const {

  if (!ME->isArrow() || 
ME->isImplicitAccess()317
)

    return;

  ProgramStateRef State = C.getState();

  SVal BaseVal = State->getSVal(ME->getBase(), C.getLocationContext());

  verifyDereference(C, BaseVal);

}

void IteratorRangeChecker::verifyDereference(CheckerContext &C,

                                             SVal Val) const {

  auto State = C.getState();

  const auto *Pos = getIteratorPosition(State, Val);

  if (Pos && 
isPastTheEnd(State, *Pos)54
) {

    auto *N = C.generateErrorNode(State);

    if (!N)

      return;

    reportBug("Past-the-end iterator dereferenced.", Val, C, N);

    return;

  }

}

void IteratorRangeChecker::verifyIncrement(CheckerContext &C, SVal Iter) const {

  auto &BVF = C.getSValBuilder().getBasicValueFactory();

  verifyRandomIncrOrDecr(C, OO_Plus, Iter,

                     nonloc::ConcreteInt(BVF.getValue(llvm::APSInt::get(1))));

}

void IteratorRangeChecker::verifyDecrement(CheckerContext &C, SVal Iter) const {

  auto &BVF = C.getSValBuilder().getBasicValueFactory();

  verifyRandomIncrOrDecr(C, OO_Minus, Iter,

                     nonloc::ConcreteInt(BVF.getValue(llvm::APSInt::get(1))));

}

void IteratorRangeChecker::verifyRandomIncrOrDecr(CheckerContext &C,

                                                  OverloadedOperatorKind Op,

                                                  SVal LHS, SVal RHS) const {

  auto State = C.getState();

  auto Value = RHS;

  if (auto ValAsLoc = RHS.getAs<Loc>()) {

    Value = State->getRawSVal(*ValAsLoc);

  }

  if (Value.isUnknownOrUndef() || 
!isa<NonLoc>(Value)738
)

    return;

  // Incremention or decremention by 0 is never a bug.

  if (isZero(State, Value.castAs<NonLoc>()))

    return;

  // The result may be the past-end iterator of the container, but any other

  // out of range position is undefined behaviour

  auto StateAfter = advancePosition(State, LHS, Op, Value);

  if (!StateAfter)

    return;

  const auto *PosAfter = getIteratorPosition(StateAfter, LHS);

  assert(PosAfter &&

         "Iterator should have position after successful advancement");

  if (isAheadOfRange(State, *PosAfter)) {

    auto *N = C.generateErrorNode(State);

    if (!N)

      return;

    reportBug("Iterator decremented ahead of its valid range.", LHS,

                        C, N);

  }

  if (isBehindPastTheEnd(State, *PosAfter)) {

    auto *N = C.generateErrorNode(State);

    if (!N)

      return;

    reportBug("Iterator incremented behind the past-the-end "

                        "iterator.", LHS, C, N);

  }

}

void IteratorRangeChecker::verifyAdvance(CheckerContext &C, SVal LHS,

                                         SVal RHS) const {

  verifyRandomIncrOrDecr(C, OO_PlusEqual, LHS, RHS);

}

void IteratorRangeChecker::verifyPrev(CheckerContext &C, SVal LHS,

                                      SVal RHS) const {

  verifyRandomIncrOrDecr(C, OO_Minus, LHS, RHS);

}

void IteratorRangeChecker::verifyNext(CheckerContext &C, SVal LHS,

                                      SVal RHS) const {

  verifyRandomIncrOrDecr(C, OO_Plus, LHS, RHS);

}

void IteratorRangeChecker::reportBug(const StringRef &Message, SVal Val,

                                     CheckerContext &C,

                                     ExplodedNode *ErrNode) const {

  auto R = std::make_unique<PathSensitiveBugReport>(*OutOfRangeBugType, Message,

                                                    ErrNode);

  const auto *Pos = getIteratorPosition(C.getState(), Val);

  assert(Pos && "Iterator without known position cannot be out-of-range.");

  R->markInteresting(Val);

  R->markInteresting(Pos->getContainer());

  C.emitReport(std::move(R));

}

namespace {

bool isLess(ProgramStateRef State, SymbolRef Sym1, SymbolRef Sym2);

bool isGreater(ProgramStateRef State, SymbolRef Sym1, SymbolRef Sym2);

bool isEqual(ProgramStateRef State, SymbolRef Sym1, SymbolRef Sym2);

bool isZero(ProgramStateRef State, const NonLoc &Val) {

  auto &BVF = State->getBasicVals();

  return compare(State, Val,

                 nonloc::ConcreteInt(BVF.getValue(llvm::APSInt::get(0))),

                 BO_EQ);

}

bool isPastTheEnd(ProgramStateRef State, const IteratorPosition &Pos) {

  const auto *Cont = Pos.getContainer();

  const auto *CData = getContainerData(State, Cont);

  if (!CData)

    return false;

  const auto End = CData->getEnd();

  if (End) {

    if (isEqual(State, Pos.getOffset(), End)) {

      return true;

    }

  }

  return false;

}

bool isAheadOfRange(ProgramStateRef State, const IteratorPosition &Pos) {

  const auto *Cont = Pos.getContainer();

  const auto *CData = getContainerData(State, Cont);

  if (!CData)

    return false;

  const auto Beg = CData->getBegin();

  if (Beg) {

    if (isLess(State, Pos.getOffset(), Beg)) {

      return true;

    }

  }

  return false;

}

bool isBehindPastTheEnd(ProgramStateRef State, const IteratorPosition &Pos) {

  const auto *Cont = Pos.getContainer();

  const auto *CData = getContainerData(State, Cont);

  if (!CData)

    return false;

  const auto End = CData->getEnd();

  if (End) {

    if (isGreater(State, Pos.getOffset(), End)) {

      return true;

    }

  }

  return false;

}

bool isLess(ProgramStateRef State, SymbolRef Sym1, SymbolRef Sym2) {

  return compare(State, Sym1, Sym2, BO_LT);

}

bool isGreater(ProgramStateRef State, SymbolRef Sym1, SymbolRef Sym2) {

  return compare(State, Sym1, Sym2, BO_GT);

}

bool isEqual(ProgramStateRef State, SymbolRef Sym1, SymbolRef Sym2) {

  return compare(State, Sym1, Sym2, BO_EQ);

}

} // namespace

void ento::registerIteratorRangeChecker(CheckerManager &mgr) {

  mgr.registerChecker<IteratorRangeChecker>();

}

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

  return true;

}