//= UnixAPIChecker.h - Checks preconditions for various Unix APIs --*- 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 defines UnixAPIChecker, which is an assortment of checks on calls

// to various, widely used UNIX/Posix functions.

//

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

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

#include "clang/Basic/TargetInfo.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"

#include "llvm/ADT/STLExtras.h"

#include "llvm/ADT/SmallString.h"

#include "llvm/ADT/StringExtras.h"

#include "llvm/Support/raw_ostream.h"

#include <optional>

using namespace clang;

using namespace ento;

enum class OpenVariant {

  /// The standard open() call:

  ///    int open(const char *path, int oflag, ...);

  Open,

  /// The variant taking a directory file descriptor and a relative path:

  ///    int openat(int fd, const char *path, int oflag, ...);

  OpenAt

};

namespace {

class UnixAPIMisuseChecker : public Checker< check::PreStmt<CallExpr> > {

  mutable std::unique_ptr<BugType> BT_open, BT_pthreadOnce;

  mutable std::optional<uint64_t> Val_O_CREAT;

public:

  void checkPreStmt(const CallExpr *CE, CheckerContext &C) const;

  void CheckOpen(CheckerContext &C, const CallExpr *CE) const;

  void CheckOpenAt(CheckerContext &C, const CallExpr *CE) const;

  void CheckPthreadOnce(CheckerContext &C, const CallExpr *CE) const;

  void CheckOpenVariant(CheckerContext &C,

                        const CallExpr *CE, OpenVariant Variant) const;

  void ReportOpenBug(CheckerContext &C,

                     ProgramStateRef State,

                     const char *Msg,

                     SourceRange SR) const;

};

class UnixAPIPortabilityChecker : public Checker< check::PreStmt<CallExpr> > {

public:

  void checkPreStmt(const CallExpr *CE, CheckerContext &C) const;

private:

  mutable std::unique_ptr<BugType> BT_mallocZero;

  void CheckCallocZero(CheckerContext &C, const CallExpr *CE) const;

  void CheckMallocZero(CheckerContext &C, const CallExpr *CE) const;

  void CheckReallocZero(CheckerContext &C, const CallExpr *CE) const;

  void CheckReallocfZero(CheckerContext &C, const CallExpr *CE) const;

  void CheckAllocaZero(CheckerContext &C, const CallExpr *CE) const;

  void CheckAllocaWithAlignZero(CheckerContext &C, const CallExpr *CE) const;

  void CheckVallocZero(CheckerContext &C, const CallExpr *CE) const;

  bool ReportZeroByteAllocation(CheckerContext &C,

                                ProgramStateRef falseState,

                                const Expr *arg,

                                const char *fn_name) const;

  void BasicAllocationCheck(CheckerContext &C,

                            const CallExpr *CE,

                            const unsigned numArgs,

                            const unsigned sizeArg,

                            const char *fn) const;

};

} //end anonymous namespace

static void LazyInitialize(const CheckerBase *Checker,

                           std::unique_ptr<BugType> &BT,

                           const char *name) {

  if (BT)

    return;

  BT.reset(new BugType(Checker, name, categories::UnixAPI));

}

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

// "open" (man 2 open)

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

void UnixAPIMisuseChecker::checkPreStmt(const CallExpr *CE,

                                        CheckerContext &C) const {

  const FunctionDecl *FD = C.getCalleeDecl(CE);

  if (!FD || 
FD->getKind() != Decl::Function1.59k
)

    return;

  // Don't treat functions in namespaces with the same name a Unix function

  // as a call to the Unix function.

  const DeclContext *NamespaceCtx = FD->getEnclosingNamespaceContext();

  if (isa_and_nonnull<NamespaceDecl>(NamespaceCtx))

    return;

  StringRef FName = C.getCalleeName(FD);

  if (FName.empty())

    return;

  if (FName == "open")

    CheckOpen(C, CE);

  else if (FName == "openat")

    CheckOpenAt(C, CE);

  else if (FName == "pthread_once")

    CheckPthreadOnce(C, CE);

}

void UnixAPIMisuseChecker::ReportOpenBug(CheckerContext &C,

                                         ProgramStateRef State,

                                         const char *Msg,

                                         SourceRange SR) const {

  ExplodedNode *N = C.generateErrorNode(State);

  if (!N)

    return;

  LazyInitialize(this, BT_open, "Improper use of 'open'");

  auto Report = std::make_unique<PathSensitiveBugReport>(*BT_open, Msg, N);

  Report->addRange(SR);

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

}

void UnixAPIMisuseChecker::CheckOpen(CheckerContext &C,

                                     const CallExpr *CE) const {

  CheckOpenVariant(C, CE, OpenVariant::Open);

}

void UnixAPIMisuseChecker::CheckOpenAt(CheckerContext &C,

                                       const CallExpr *CE) const {

  CheckOpenVariant(C, CE, OpenVariant::OpenAt);

}

void UnixAPIMisuseChecker::CheckOpenVariant(CheckerContext &C,

                                            const CallExpr *CE,

                                            OpenVariant Variant) const {

  // The index of the argument taking the flags open flags (O_RDONLY,

  // O_WRONLY, O_CREAT, etc.),

  unsigned int FlagsArgIndex;

  const char *VariantName;

  switch (Variant) {

  case OpenVariant::Open:

    FlagsArgIndex = 1;

    VariantName = "open";

    break;

  case OpenVariant::OpenAt:

    FlagsArgIndex = 2;

    VariantName = "openat";

    break;

  };

  // All calls should at least provide arguments up to the 'flags' parameter.

  unsigned int MinArgCount = FlagsArgIndex + 1;

  // If the flags has O_CREAT set then open/openat() require an additional

  // argument specifying the file mode (permission bits) for the created file.

  unsigned int CreateModeArgIndex = FlagsArgIndex + 1;

  // The create mode argument should be the last argument.

  unsigned int MaxArgCount = CreateModeArgIndex + 1;

  ProgramStateRef state = C.getState();

  if (CE->getNumArgs() < MinArgCount) {

    // The frontend should issue a warning for this case. Just return.

    return;

  } else if (CE->getNumArgs() == MaxArgCount) {

    const Expr *Arg = CE->getArg(CreateModeArgIndex);

    QualType QT = Arg->getType();

    if (!QT->isIntegerType()) {

      SmallString<256> SBuf;

      llvm::raw_svector_ostream OS(SBuf);

      OS << "The " << CreateModeArgIndex + 1

         << llvm::getOrdinalSuffix(CreateModeArgIndex + 1)

         << " argument to '" << VariantName << "' is not an integer";

      ReportOpenBug(C, state,

                    SBuf.c_str(),

                    Arg->getSourceRange());

      return;

    }

  } else if (CE->getNumArgs() > MaxArgCount) {

    SmallString<256> SBuf;

    llvm::raw_svector_ostream OS(SBuf);

    OS << "Call to '" << VariantName << "' with more than " << MaxArgCount

       << " arguments";

    ReportOpenBug(C, state,

                  SBuf.c_str(),

                  CE->getArg(MaxArgCount)->getSourceRange());

    return;

  }

  // The definition of O_CREAT is platform specific.  We need a better way

  // of querying this information from the checking environment.

  if (!Val_O_CREAT) {

    if (C.getASTContext().getTargetInfo().getTriple().getVendor()

                                                      == llvm::Triple::Apple)

      Val_O_CREAT = 0x0200;

    else {

      // FIXME: We need a more general way of getting the O_CREAT value.

      // We could possibly grovel through the preprocessor state, but

      // that would require passing the Preprocessor object to the ExprEngine.

      // See also: MallocChecker.cpp / M_ZERO.

      return;

    }

  }

  // Now check if oflags has O_CREAT set.

  const Expr *oflagsEx = CE->getArg(FlagsArgIndex);

  const SVal V = C.getSVal(oflagsEx);

  if (!isa<NonLoc>(V)) {

    // The case where 'V' can be a location can only be due to a bad header,

    // so in this case bail out.

    return;

  }

  NonLoc oflags = V.castAs<NonLoc>();

  NonLoc ocreateFlag = C.getSValBuilder()

                           .makeIntVal(*Val_O_CREAT, oflagsEx->getType())

                           .castAs<NonLoc>();

  SVal maskedFlagsUC = C.getSValBuilder().evalBinOpNN(state, BO_And,

                                                      oflags, ocreateFlag,

                                                      oflagsEx->getType());

  if (maskedFlagsUC.isUnknownOrUndef())

    return;

  DefinedSVal maskedFlags = maskedFlagsUC.castAs<DefinedSVal>();

  // Check if maskedFlags is non-zero.

  ProgramStateRef trueState, falseState;

  std::tie(trueState, falseState) = state->assume(maskedFlags);

  // Only emit an error if the value of 'maskedFlags' is properly

  // constrained;

  if (!(trueState && 
!falseState8
))

    return;

  if (CE->getNumArgs() < MaxArgCount) {

    SmallString<256> SBuf;

    llvm::raw_svector_ostream OS(SBuf);

    OS << "Call to '" << VariantName << "' requires a "

       << CreateModeArgIndex + 1

       << llvm::getOrdinalSuffix(CreateModeArgIndex + 1)

       << " argument when the 'O_CREAT' flag is set";

    ReportOpenBug(C, trueState,

                  SBuf.c_str(),

                  oflagsEx->getSourceRange());

  }

}

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

// pthread_once

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

void UnixAPIMisuseChecker::CheckPthreadOnce(CheckerContext &C,

                                      const CallExpr *CE) const {

  // This is similar to 'CheckDispatchOnce' in the MacOSXAPIChecker.

  // They can possibly be refactored.

  if (CE->getNumArgs() < 1)

    return;

  // Check if the first argument is stack allocated.  If so, issue a warning

  // because that's likely to be bad news.

  ProgramStateRef state = C.getState();

  const MemRegion *R = C.getSVal(CE->getArg(0)).getAsRegion();

  if (!R || !isa<StackSpaceRegion>(R->getMemorySpace()))

    return;

  ExplodedNode *N = C.generateErrorNode(state);

  if (!N)

    return;

  SmallString<256> S;

  llvm::raw_svector_ostream os(S);

  os << "Call to 'pthread_once' uses";

  if (const VarRegion *VR = dyn_cast<VarRegion>(R))

    os << " the local variable '" << VR->getDecl()->getName() << '\'';

  else

    os << " stack allocated memory";

  os << " for the \"control\" value.  Using such transient memory for "

  "the control value is potentially dangerous.";

  if (isa<VarRegion>(R) && isa<StackLocalsSpaceRegion>(R->getMemorySpace()))

    os << "  Perhaps you intended to declare the variable as 'static'?";

  LazyInitialize(this, BT_pthreadOnce, "Improper use of 'pthread_once'");

  auto report =

      std::make_unique<PathSensitiveBugReport>(*BT_pthreadOnce, os.str(), N);

  report->addRange(CE->getArg(0)->getSourceRange());

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

}

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

// "calloc", "malloc", "realloc", "reallocf", "alloca" and "valloc"

// with allocation size 0

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

// FIXME: Eventually these should be rolled into the MallocChecker, but right now

// they're more basic and valuable for widespread use.

// Returns true if we try to do a zero byte allocation, false otherwise.

// Fills in trueState and falseState.

static bool IsZeroByteAllocation(ProgramStateRef state,

                                 const SVal argVal,

                                 ProgramStateRef *trueState,

                                 ProgramStateRef *falseState) {

  std::tie(*trueState, *falseState) =

    state->assume(argVal.castAs<DefinedSVal>());

  return (*falseState && 
!*trueState34
);

}

// Generates an error report, indicating that the function whose name is given

// will perform a zero byte allocation.

// Returns false if an error occurred, true otherwise.

bool UnixAPIPortabilityChecker::ReportZeroByteAllocation(

                                                    CheckerContext &C,

                                                    ProgramStateRef falseState,

                                                    const Expr *arg,

                                                    const char *fn_name) const {

  ExplodedNode *N = C.generateErrorNode(falseState);

  if (!N)

    return false;

  LazyInitialize(this, BT_mallocZero,

                 "Undefined allocation of 0 bytes (CERT MEM04-C; CWE-131)");

  SmallString<256> S;

  llvm::raw_svector_ostream os(S);

  os << "Call to '" << fn_name << "' has an allocation size of 0 bytes";

  auto report =

      std::make_unique<PathSensitiveBugReport>(*BT_mallocZero, os.str(), N);

  report->addRange(arg->getSourceRange());

  bugreporter::trackExpressionValue(N, arg, *report);

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

  return true;

}

// Does a basic check for 0-sized allocations suitable for most of the below

// functions (modulo "calloc")

void UnixAPIPortabilityChecker::BasicAllocationCheck(CheckerContext &C,

                                                     const CallExpr *CE,

                                                     const unsigned numArgs,

                                                     const unsigned sizeArg,

                                                     const char *fn) const {

  // Check for the correct number of arguments.

  if (CE->getNumArgs() != numArgs)

    return;

  // Check if the allocation size is 0.

  ProgramStateRef state = C.getState();

  ProgramStateRef trueState = nullptr, falseState = nullptr;

  const Expr *arg = CE->getArg(sizeArg);

  SVal argVal = C.getSVal(arg);

  if (argVal.isUnknownOrUndef())

    return;

  // Is the value perfectly constrained to zero?

  if (IsZeroByteAllocation(state, argVal, &trueState, &falseState)) {

    (void) ReportZeroByteAllocation(C, falseState, arg, fn);

    return;

  }

  // Assume the value is non-zero going forward.

  assert(trueState);

  if (trueState != state)

    C.addTransition(trueState);

}

void UnixAPIPortabilityChecker::CheckCallocZero(CheckerContext &C,

                                                const CallExpr *CE) const {

  unsigned int nArgs = CE->getNumArgs();

  if (nArgs != 2)

    return;

  ProgramStateRef state = C.getState();

  ProgramStateRef trueState = nullptr, falseState = nullptr;

  unsigned int i;

  for (i = 0; i < nArgs; 
i++6
) {

    const Expr *arg = CE->getArg(i);

    SVal argVal = C.getSVal(arg);

    if (argVal.isUnknownOrUndef()) {

      if (i == 0)

        continue;

      else

        return;

    }

    if (IsZeroByteAllocation(state, argVal, &trueState, &falseState)) {

      if (ReportZeroByteAllocation(C, falseState, arg, "calloc"))

        return;

      else if (i == 0)

        continue;

      else

        return;

    }

  }

  // Assume the value is non-zero going forward.

  assert(trueState);

  if (trueState != state)

    C.addTransition(trueState);

}

void UnixAPIPortabilityChecker::CheckMallocZero(CheckerContext &C,

                                                const CallExpr *CE) const {

  BasicAllocationCheck(C, CE, 1, 0, "malloc");

}

void UnixAPIPortabilityChecker::CheckReallocZero(CheckerContext &C,

                                                 const CallExpr *CE) const {

  BasicAllocationCheck(C, CE, 2, 1, "realloc");

}

void UnixAPIPortabilityChecker::CheckReallocfZero(CheckerContext &C,

                                                  const CallExpr *CE) const {

  BasicAllocationCheck(C, CE, 2, 1, "reallocf");

}

void UnixAPIPortabilityChecker::CheckAllocaZero(CheckerContext &C,

                                                const CallExpr *CE) const {

  BasicAllocationCheck(C, CE, 1, 0, "alloca");

}

void UnixAPIPortabilityChecker::CheckAllocaWithAlignZero(

                                                     CheckerContext &C,

                                                     const CallExpr *CE) const {

  BasicAllocationCheck(C, CE, 2, 0, "__builtin_alloca_with_align");

}

void UnixAPIPortabilityChecker::CheckVallocZero(CheckerContext &C,

                                                const CallExpr *CE) const {

  BasicAllocationCheck(C, CE, 1, 0, "valloc");

}

void UnixAPIPortabilityChecker::checkPreStmt(const CallExpr *CE,

                                             CheckerContext &C) const {

  const FunctionDecl *FD = C.getCalleeDecl(CE);

  if (!FD || 
FD->getKind() != Decl::Function87
)

    return;

  // Don't treat functions in namespaces with the same name a Unix function

  // as a call to the Unix function.

  const DeclContext *NamespaceCtx = FD->getEnclosingNamespaceContext();

  if (isa_and_nonnull<NamespaceDecl>(NamespaceCtx))

    return;

  StringRef FName = C.getCalleeName(FD);

  if (FName.empty())

    return;

  if (FName == "calloc")

    CheckCallocZero(C, CE);

  else if (FName == "malloc")

    CheckMallocZero(C, CE);

  else if (FName == "realloc")

    CheckReallocZero(C, CE);

  else if (FName == "reallocf")

    CheckReallocfZero(C, CE);

  else if (FName == "alloca" || 
FName ==  "__builtin_alloca"61
)

    CheckAllocaZero(C, CE);

  else if (FName == "__builtin_alloca_with_align")

    CheckAllocaWithAlignZero(C, CE);

  else if (FName == "valloc")

    CheckVallocZero(C, CE);

}

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

// Registration.

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

#define REGISTER_CHECKER(CHECKERNAME)                                          \

  void ento::register##CHECKERNAME(CheckerManager &mgr) {                      \

    mgr.registerChecker<CHECKERNAME>();                                        \

  }                                                                            \

clang::ento::registerUnixAPIMisuseChecker(clang::ento::CheckerManager&)

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  void ento::register##CHECKERNAME(CheckerManager &mgr) {                      \

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    mgr.registerChecker<CHECKERNAME>();                                        \

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  }                                                                            \

clang::ento::registerUnixAPIPortabilityChecker(clang::ento::CheckerManager&)

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  void ento::register##CHECKERNAME(CheckerManager &mgr) {                      \

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    mgr.registerChecker<CHECKERNAME>();                                        \

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  }                                                                            \

                                                                               \

  bool ento::shouldRegister##CHECKERNAME(const CheckerManager &mgr) {          \

    return true;                                                               \

  }

clang::ento::shouldRegisterUnixAPIMisuseChecker(clang::ento::CheckerManager const&)

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  bool ento::shouldRegister##CHECKERNAME(const CheckerManager &mgr) {          \

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    return true;                                                               \

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  }

clang::ento::shouldRegisterUnixAPIPortabilityChecker(clang::ento::CheckerManager const&)

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  bool ento::shouldRegister##CHECKERNAME(const CheckerManager &mgr) {          \

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    return true;                                                               \

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  }

REGISTER_CHECKER(UnixAPIMisuseChecker)

REGISTER_CHECKER(UnixAPIPortabilityChecker)