xref: /art/runtime/hidden_api.cc

/*
 * Copyright (C) 2018 The Android Open Source Project
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

#include "hidden_api.h"

#include <atomic>

#include "art_field-inl.h"
#include "art_method-inl.h"
#include "base/dumpable.h"
#include "base/file_utils.h"
#include "class_root-inl.h"
#include "compat_framework.h"
#include "dex/class_accessor-inl.h"
#include "dex/dex_file_loader.h"
#include "mirror/class_ext.h"
#include "mirror/proxy.h"
#include "nativehelper/scoped_local_ref.h"
#include "oat/oat_file.h"
#include "scoped_thread_state_change.h"
#include "stack.h"
#include "thread-inl.h"
#include "well_known_classes.h"

namespace art HIDDEN {
namespace hiddenapi {

// Should be the same as dalvik.system.VMRuntime.HIDE_MAXTARGETSDK_P_HIDDEN_APIS,
// dalvik.system.VMRuntime.HIDE_MAXTARGETSDK_Q_HIDDEN_APIS, and
// dalvik.system.VMRuntime.ALLOW_TEST_API_ACCESS.
// Corresponds to bug ids.
static constexpr uint64_t kHideMaxtargetsdkPHiddenApis = 149997251;
static constexpr uint64_t kHideMaxtargetsdkQHiddenApis = 149994052;
static constexpr uint64_t kAllowTestApiAccess = 166236554;

static constexpr uint64_t kMaxLogAccessesToLogcat = 100;

// Should be the same as dalvik.system.VMRuntime.PREVENT_META_REFLECTION_BLOCKLIST_ACCESS.
// Corresponds to a bug id.
static constexpr uint64_t kPreventMetaReflectionBlocklistAccess = 142365358;

// Set to true if we should always print a warning in logcat for all hidden API accesses, not just
// conditionally and unconditionally blocked. This can be set to true for developer preview / beta
// builds, but should be false for public release builds.
// Note that when flipping this flag, you must also update the expectations of test 674-hiddenapi
// as it affects whether or not we warn for unsupported APIs that have been added to the exemptions
// list.
static constexpr bool kLogAllAccesses = false;

// Exemptions for logcat warning. Following signatures do not produce a warning as app developers
// should not be alerted on the usage of these unsupported APIs. See b/154851649.
static const std::vector<std::string> kWarningExemptions = {
    "Ljava/nio/Buffer;",
    "Llibcore/io/Memory;",
    "Lsun/misc/Unsafe;",
};

// TODO(b/377676642): Fix API annotations and delete this.
static const std::vector<std::string> kCorePlatformApiExemptions = {
    // Intra-core APIs that aren't also core platform APIs. These may be used by
    // the non-updatable ICU module and hence are effectively de-facto core
    // platform APIs.
    "Ldalvik/annotation/compat/VersionCodes;",
    "Ldalvik/annotation/optimization/ReachabilitySensitive;",
    "Ldalvik/system/BlockGuard/Policy;->onNetwork",
    "Ljava/nio/charset/CharsetEncoder;-><init>(Ljava/nio/charset/Charset;FF[BZ)V",
    "Ljava/security/spec/ECParameterSpec;->getCurveName",
    "Ljava/security/spec/ECParameterSpec;->setCurveName",
    "Llibcore/api/CorePlatformApi;",
    "Llibcore/io/AsynchronousCloseMonitor;",
    "Llibcore/util/NonNull;",
    "Llibcore/util/Nullable;",
    "Lsun/security/util/DerEncoder;",
    "Lsun/security/x509/AlgorithmId;->derEncode",
    "Lsun/security/x509/AlgorithmId;->get",
    // These are new system module APIs that are accessed unflagged (cf.
    // b/400041178 and b/400041556).
    "Ldalvik/system/VMDebug;->setCurrentProcessName",
    "Ldalvik/system/VMDebug;->addApplication",
    "Ldalvik/system/VMDebug;->removeApplication",
    "Ldalvik/system/VMDebug;->setUserId",
    "Ldalvik/system/VMDebug;->setWaitingForDebugger",
};

static inline std::ostream& operator<<(std::ostream& os, AccessMethod value) {
  switch (value) {
    case AccessMethod::kCheck:
    case AccessMethod::kCheckWithPolicy:
      LOG(FATAL) << "Internal access to hidden API should not be logged";
      UNREACHABLE();
    case AccessMethod::kReflection:
      os << "reflection";
      break;
    case AccessMethod::kJNI:
      os << "JNI";
      break;
    case AccessMethod::kLinking:
      os << "linking";
      break;
  }
  return os;
}

static inline std::ostream& operator<<(std::ostream& os, Domain domain) {
  switch (domain) {
    case Domain::kCorePlatform:
      os << "core-platform";
      break;
    case Domain::kPlatform:
      os << "platform";
      break;
    case Domain::kApplication:
      os << "app";
      break;
  }
  return os;
}

static inline std::ostream& operator<<(std::ostream& os, const AccessContext& value)
    REQUIRES_SHARED(Locks::mutator_lock_) {
  if (!value.GetClass().IsNull()) {
    std::string tmp;
    os << value.GetClass()->GetDescriptor(&tmp);
  } else if (value.GetDexFile() != nullptr) {
    os << value.GetDexFile()->GetLocation();
  } else {
    os << "<unknown_caller>";
  }
  return os;
}

static const char* FormatHiddenApiRuntimeFlags(uint32_t runtime_flags) {
  switch (runtime_flags & kAccHiddenapiBits) {
    case 0:
      return "0";
    case kAccPublicApi:
      return "PublicApi";
    case kAccCorePlatformApi:
      return "CorePlatformApi";
    default:
      return "?";
  }
}

static Domain DetermineDomainFromLocation(const std::string& dex_location,
                                          ObjPtr<mirror::ClassLoader> class_loader) {
  // If running with APEX, check `path` against known APEX locations.
  // These checks will be skipped on target buildbots where ANDROID_ART_ROOT
  // is set to "/system".
  if (ArtModuleRootDistinctFromAndroidRoot()) {
    if (LocationIsOnArtModule(dex_location) || LocationIsOnConscryptModule(dex_location)) {
      return Domain::kCorePlatform;
    }

    if (LocationIsOnApex(dex_location)) {
      return Domain::kPlatform;
    }
  }

  if (LocationIsOnSystemFramework(dex_location)) {
    return Domain::kPlatform;
  }

  if (LocationIsOnSystemExtFramework(dex_location)) {
    return Domain::kPlatform;
  }

  if (class_loader.IsNull()) {
    if (kIsTargetBuild && !kIsTargetLinux) {
      // This is unexpected only when running on Android.
      LOG(WARNING) << "hiddenapi: DexFile " << dex_location
                   << " is in boot class path but is not in a known location";
    }
    return Domain::kPlatform;
  }

  return Domain::kApplication;
}

void InitializeDexFileDomain(const DexFile& dex_file, ObjPtr<mirror::ClassLoader> class_loader) {
  Domain dex_domain = DetermineDomainFromLocation(dex_file.GetLocation(), class_loader);

  // Assign the domain unless a more permissive domain has already been assigned.
  // This may happen when DexFile is initialized as trusted.
  if (IsDomainAtLeastAsTrustedAs(dex_domain, dex_file.GetHiddenapiDomain())) {
    dex_file.SetHiddenapiDomain(dex_domain);
  }
}

void InitializeCorePlatformApiPrivateFields() {
  // The following fields in WellKnownClasses correspond to private fields in the Core Platform
  // API that cannot be otherwise expressed and propagated through tooling (b/144502743).
  ArtField* private_core_platform_api_fields[] = {
      WellKnownClasses::java_io_FileDescriptor_descriptor,
      WellKnownClasses::java_nio_Buffer_address,
      WellKnownClasses::java_nio_Buffer_elementSizeShift,
      WellKnownClasses::java_nio_Buffer_limit,
      WellKnownClasses::java_nio_Buffer_position,
  };

  ScopedObjectAccess soa(Thread::Current());
  for (ArtField* field : private_core_platform_api_fields) {
    const uint32_t access_flags = field->GetAccessFlags();
    uint32_t new_access_flags = access_flags | kAccCorePlatformApi;
    DCHECK(new_access_flags != access_flags);
    field->SetAccessFlags(new_access_flags);
  }
}

hiddenapi::AccessContext GetReflectionCallerAccessContext(Thread* self)
    REQUIRES_SHARED(Locks::mutator_lock_) {
  // Walk the stack and find the first frame not from java.lang.Class,
  // java.lang.invoke or java.lang.reflect. This is very expensive.
  // Save this till the last.
  struct FirstExternalCallerVisitor : public StackVisitor {
    explicit FirstExternalCallerVisitor(Thread* thread)
        : StackVisitor(thread, nullptr, StackVisitor::StackWalkKind::kIncludeInlinedFrames),
          caller(nullptr) {}

    bool VisitFrame() override REQUIRES_SHARED(Locks::mutator_lock_) {
      ArtMethod* m = GetMethod();
      if (m == nullptr) {
        // Attached native thread. Assume this is *not* boot class path.
        caller = nullptr;
        return false;
      } else if (m->IsRuntimeMethod()) {
        // Internal runtime method, continue walking the stack.
        return true;
      }

      ObjPtr<mirror::Class> declaring_class = m->GetDeclaringClass();
      if (declaring_class->IsBootStrapClassLoaded()) {
        if (declaring_class->IsClassClass()) {
          return true;
        }

        // MethodHandles.makeIdentity is doing findStatic to find hidden methods,
        // where reflection is used.
        if (m == WellKnownClasses::java_lang_invoke_MethodHandles_makeIdentity) {
          return false;
        }

        // Check classes in the java.lang.invoke package. At the time of writing, the
        // classes of interest are MethodHandles and MethodHandles.Lookup, but this
        // is subject to change so conservatively cover the entire package.
        // NB Static initializers within java.lang.invoke are permitted and do not
        // need further stack inspection.
        ObjPtr<mirror::Class> lookup_class = GetClassRoot<mirror::MethodHandlesLookup>();
        if ((declaring_class == lookup_class || declaring_class->IsInSamePackage(lookup_class)) &&
            !m->IsClassInitializer()) {
          return true;
        }
        // Check for classes in the java.lang.reflect package, except for java.lang.reflect.Proxy.
        // java.lang.reflect.Proxy does its own hidden api checks (https://r.android.com/915496),
        // and walking over this frame would cause a null pointer dereference
        // (e.g. in 691-hiddenapi-proxy).
        ObjPtr<mirror::Class> proxy_class = GetClassRoot<mirror::Proxy>();
        CompatFramework& compat_framework = Runtime::Current()->GetCompatFramework();
        if (declaring_class->IsInSamePackage(proxy_class) && declaring_class != proxy_class) {
          if (compat_framework.IsChangeEnabled(kPreventMetaReflectionBlocklistAccess)) {
            return true;
          }
        }
      }

      caller = m;
      return false;
    }

    ArtMethod* caller;
  };

  FirstExternalCallerVisitor visitor(self);
  visitor.WalkStack();

  // Construct AccessContext from the calling class found on the stack.
  // If the calling class cannot be determined, e.g. unattached threads,
  // we conservatively assume the caller is trusted.
  ObjPtr<mirror::Class> caller =
      (visitor.caller == nullptr) ? nullptr : visitor.caller->GetDeclaringClass();
  return caller.IsNull() ? AccessContext(/* is_trusted= */ true) : AccessContext(caller);
}

namespace detail {

// Do not change the values of items in this enum, as they are written to the
// event log for offline analysis. Any changes will interfere with that analysis.
enum AccessContextFlags {
  // Accessed member is a field if this bit is set, else a method
  kMemberIsField = 1 << 0,
  // Indicates if access was denied to the member, instead of just printing a warning.
  kAccessDenied = 1 << 1,
};

MemberSignature::MemberSignature(ArtField* field) {
  // Note: `ArtField::GetDeclaringClassDescriptor()` does not support proxy classes.
  class_name_ = field->GetDeclaringClass()->GetDescriptor(&tmp_);
  member_name_ = field->GetNameView();
  type_signature_ = field->GetTypeDescriptorView();
  type_ = kField;
}

MemberSignature::MemberSignature(ArtMethod* method) {
  DCHECK(method == method->GetInterfaceMethodIfProxy(kRuntimePointerSize))
      << "Caller should have replaced proxy method with interface method";
  class_name_ = method->GetDeclaringClassDescriptorView();
  member_name_ = method->GetNameView();
  type_signature_ = method->GetSignature().ToString();
  type_ = kMethod;
}

MemberSignature::MemberSignature(const ClassAccessor::Field& field) {
  const DexFile& dex_file = field.GetDexFile();
  const dex::FieldId& field_id = dex_file.GetFieldId(field.GetIndex());
  class_name_ = dex_file.GetFieldDeclaringClassDescriptor(field_id);
  member_name_ = dex_file.GetFieldName(field_id);
  type_signature_ = dex_file.GetFieldTypeDescriptor(field_id);
  type_ = kField;
}

MemberSignature::MemberSignature(const ClassAccessor::Method& method) {
  const DexFile& dex_file = method.GetDexFile();
  const dex::MethodId& method_id = dex_file.GetMethodId(method.GetIndex());
  class_name_ = dex_file.GetMethodDeclaringClassDescriptor(method_id);
  member_name_ = dex_file.GetMethodName(method_id);
  type_signature_ = dex_file.GetMethodSignature(method_id).ToString();
  type_ = kMethod;
}

inline std::vector<const char*> MemberSignature::GetSignatureParts() const {
  if (type_ == kField) {
    return {class_name_.c_str(), "->", member_name_.c_str(), ":", type_signature_.c_str()};
  } else {
    DCHECK_EQ(type_, kMethod);
    return {class_name_.c_str(), "->", member_name_.c_str(), type_signature_.c_str()};
  }
}

bool MemberSignature::DoesPrefixMatch(const std::string& prefix) const {
  size_t pos = 0;
  for (const char* part : GetSignatureParts()) {
    size_t count = std::min(prefix.length() - pos, strlen(part));
    if (prefix.compare(pos, count, part, 0, count) == 0) {
      pos += count;
    } else {
      return false;
    }
  }
  // We have a complete match if all parts match (we exit the loop without
  // returning) AND we've matched the whole prefix.
  return pos == prefix.length();
}

bool MemberSignature::DoesPrefixMatchAny(const std::vector<std::string>& exemptions) {
  for (const std::string& exemption : exemptions) {
    if (DoesPrefixMatch(exemption)) {
      return true;
    }
  }
  return false;
}

void MemberSignature::Dump(std::ostream& os) const {
  for (const char* part : GetSignatureParts()) {
    os << part;
  }
}

void MemberSignature::LogAccessToLogcat(AccessMethod access_method,
                                        ApiList api_list,
                                        bool access_denied,
                                        uint32_t runtime_flags,
                                        const AccessContext& caller_context,
                                        const AccessContext& callee_context,
                                        EnforcementPolicy policy) {
  static std::atomic<uint64_t> logged_access_count_ = 0;
  if (logged_access_count_ > kMaxLogAccessesToLogcat) {
    return;
  }
  LOG(access_denied ? (policy == EnforcementPolicy::kEnabled ? ERROR : WARNING) : INFO)
      << "hiddenapi: Accessing hidden " << (type_ == kField ? "field " : "method ")
      << Dumpable<MemberSignature>(*this)
      << " (runtime_flags=" << FormatHiddenApiRuntimeFlags(runtime_flags)
      << ", domain=" << callee_context.GetDomain() << ", api=" << api_list << ") from "
      << caller_context << " (domain=" << caller_context.GetDomain() << ") using " << access_method
      << (access_denied ? ": denied" : ": allowed");
  if (access_denied && api_list.IsTestApi()) {
    // see b/177047045 for more details about test api access getting denied
    LOG(WARNING) << "hiddenapi: If this is a platform test consider enabling "
                 << "VMRuntime.ALLOW_TEST_API_ACCESS change id for this package.";
  }
  if (logged_access_count_ >= kMaxLogAccessesToLogcat) {
    LOG(WARNING) << "hiddenapi: Reached maximum number of hidden api access messages.";
  }
  ++logged_access_count_;
}

bool MemberSignature::Equals(const MemberSignature& other) {
  return type_ == other.type_ && class_name_ == other.class_name_ &&
         member_name_ == other.member_name_ && type_signature_ == other.type_signature_;
}

bool MemberSignature::MemberNameAndTypeMatch(const MemberSignature& other) {
  return member_name_ == other.member_name_ && type_signature_ == other.type_signature_;
}

void MemberSignature::LogAccessToEventLog(uint32_t sampled_value,
                                          AccessMethod access_method,
                                          bool access_denied) {
#ifdef ART_TARGET_ANDROID
  if (access_method == AccessMethod::kCheck || access_method == AccessMethod::kCheckWithPolicy ||
      access_method == AccessMethod::kLinking) {
    // Checks do not correspond to actual accesses, so should be ignored.
    // Linking warnings come from static analysis/compilation of the bytecode
    // and can contain false positives (i.e. code that is never run). Hence we
    // choose to not log those either in the event log.
    return;
  }
  Runtime* runtime = Runtime::Current();
  if (runtime->IsAotCompiler()) {
    return;
  }

  const std::string& package_name = runtime->GetProcessPackageName();
  std::ostringstream signature_str;
  Dump(signature_str);

  ScopedObjectAccess soa(Thread::Current());
  StackHandleScope<2u> hs(soa.Self());
  Handle<mirror::String> package_str =
      hs.NewHandle(mirror::String::AllocFromModifiedUtf8(soa.Self(), package_name.c_str()));
  if (soa.Self()->IsExceptionPending()) {
    soa.Self()->ClearException();
    LOG(ERROR) << "hiddenapi: Unable to allocate string for package name which called hidden api";
  }
  Handle<mirror::String> signature_jstr =
      hs.NewHandle(mirror::String::AllocFromModifiedUtf8(soa.Self(), signature_str.str().c_str()));
  if (soa.Self()->IsExceptionPending()) {
    soa.Self()->ClearException();
    LOG(ERROR) << "hiddenapi: Unable to allocate string for hidden api method signature";
  }
  WellKnownClasses::dalvik_system_VMRuntime_hiddenApiUsed
      ->InvokeStatic<'V', 'I', 'L', 'L', 'I', 'Z'>(soa.Self(),
                                                   static_cast<jint>(sampled_value),
                                                   package_str.Get(),
                                                   signature_jstr.Get(),
                                                   static_cast<jint>(access_method),
                                                   access_denied);
  if (soa.Self()->IsExceptionPending()) {
    soa.Self()->ClearException();
    LOG(ERROR) << "hiddenapi: Unable to report hidden api usage";
  }
#else
  UNUSED(sampled_value);
  UNUSED(access_method);
  UNUSED(access_denied);
#endif
}

void MemberSignature::NotifyHiddenApiListener(AccessMethod access_method) {
  if (access_method != AccessMethod::kReflection && access_method != AccessMethod::kJNI) {
    // We can only up-call into Java during reflection and JNI down-calls.
    return;
  }

  Runtime* runtime = Runtime::Current();
  if (!runtime->IsAotCompiler()) {
    ScopedObjectAccess soa(Thread::Current());
    StackHandleScope<2u> hs(soa.Self());

    ArtField* consumer_field = WellKnownClasses::dalvik_system_VMRuntime_nonSdkApiUsageConsumer;
    DCHECK(consumer_field->GetDeclaringClass()->IsInitialized());
    Handle<mirror::Object> consumer_object =
        hs.NewHandle(consumer_field->GetObject(consumer_field->GetDeclaringClass()));

    // If the consumer is non-null, we call back to it to let it know that we
    // have encountered an API that's in one of our lists.
    if (consumer_object != nullptr) {
      std::ostringstream member_signature_str;
      Dump(member_signature_str);

      Handle<mirror::String> signature_str = hs.NewHandle(
          mirror::String::AllocFromModifiedUtf8(soa.Self(), member_signature_str.str().c_str()));
      // FIXME: Handle OOME. For now, crash immediatelly (do not continue with a pending exception).
      CHECK(signature_str != nullptr);

      // Call through to Consumer.accept(String memberSignature);
      WellKnownClasses::java_util_function_Consumer_accept->InvokeInterface<'V', 'L'>(
          soa.Self(), consumer_object.Get(), signature_str.Get());
    }
  }
}

static ALWAYS_INLINE bool CanUpdateRuntimeFlags(ArtField*) { return true; }

static ALWAYS_INLINE bool CanUpdateRuntimeFlags(ArtMethod* method) {
  return !method->IsIntrinsic();
}

template <typename T>
static ALWAYS_INLINE void MaybeUpdateAccessFlags(Runtime* runtime, T* member, uint32_t flag)
    REQUIRES_SHARED(Locks::mutator_lock_) {
  // Update the access flags unless:
  // (a) `member` is an intrinsic
  // (b) this is AOT compiler, as we do not want the updated access flags in the boot/app image
  // (c) deduping warnings has been explicitly switched off.
  if (CanUpdateRuntimeFlags(member) && !runtime->IsAotCompiler() &&
      runtime->ShouldDedupeHiddenApiWarnings()) {
    member->SetAccessFlags(member->GetAccessFlags() | flag);
  }
}

static ALWAYS_INLINE uint32_t GetMemberDexIndex(ArtField* field) {
  return field->GetDexFieldIndex();
}

static ALWAYS_INLINE uint32_t GetMemberDexIndex(ArtMethod* method)
    REQUIRES_SHARED(Locks::mutator_lock_) {
  // Use the non-obsolete method to avoid DexFile mismatch between
  // the method index and the declaring class.
  return method->GetNonObsoleteMethod()->GetDexMethodIndex();
}

static void VisitMembers(const DexFile& dex_file,
                         const dex::ClassDef& class_def,
                         const std::function<void(const ClassAccessor::Field&)>& fn_visit) {
  ClassAccessor accessor(dex_file, class_def, /* parse_hiddenapi_class_data= */ true);
  accessor.VisitFields(fn_visit, fn_visit);
}

static void VisitMembers(const DexFile& dex_file,
                         const dex::ClassDef& class_def,
                         const std::function<void(const ClassAccessor::Method&)>& fn_visit) {
  ClassAccessor accessor(dex_file, class_def, /* parse_hiddenapi_class_data= */ true);
  accessor.VisitMethods(fn_visit, fn_visit);
}

template <typename T>
uint32_t GetDexFlags(T* member) REQUIRES_SHARED(Locks::mutator_lock_) {
  static_assert(std::is_same<T, ArtField>::value || std::is_same<T, ArtMethod>::value);
  constexpr bool kMemberIsField = std::is_same<T, ArtField>::value;
  using AccessorType = typename std::conditional<std::is_same<T, ArtField>::value,
                                                 ClassAccessor::Field,
                                                 ClassAccessor::Method>::type;

  ObjPtr<mirror::Class> declaring_class = member->GetDeclaringClass();
  DCHECK(!declaring_class.IsNull()) << "Attempting to access a runtime method";

  ApiList flags = ApiList::Invalid();

  // Check if the declaring class has ClassExt allocated. If it does, check if
  // the pre-JVMTI redefine dex file has been set to determine if the declaring
  // class has been JVMTI-redefined.
  ObjPtr<mirror::ClassExt> ext(declaring_class->GetExtData());
  const DexFile* original_dex = ext.IsNull() ? nullptr : ext->GetPreRedefineDexFile();
  if (LIKELY(original_dex == nullptr)) {
    // Class is not redefined. Find the class def, iterate over its members and
    // find the entry corresponding to this `member`.
    const dex::ClassDef* class_def = declaring_class->GetClassDef();
    if (class_def == nullptr) {
      // ClassDef is not set for proxy classes. Only their fields can ever be inspected.
      DCHECK(declaring_class->IsProxyClass())
          << "Only proxy classes are expected not to have a class def";
      DCHECK(kMemberIsField)
          << "Interface methods should be inspected instead of proxy class methods";
      flags = ApiList::Unsupported();
    } else {
      uint32_t member_index = GetMemberDexIndex(member);
      auto fn_visit = [&](const AccessorType& dex_member) {
        if (dex_member.GetIndex() == member_index) {
          flags = ApiList::FromDexFlags(dex_member.GetHiddenapiFlags());
        }
      };
      VisitMembers(declaring_class->GetDexFile(), *class_def, fn_visit);
    }
  } else {
    // Class was redefined using JVMTI. We have a pointer to the original dex file
    // and the class def index of this class in that dex file, but the field/method
    // indices are lost. Iterate over all members of the class def and find the one
    // corresponding to this `member` by name and type string comparison.
    // This is obviously very slow, but it is only used when non-exempt code tries
    // to access a hidden member of a JVMTI-redefined class.
    uint16_t class_def_idx = ext->GetPreRedefineClassDefIndex();
    DCHECK_NE(class_def_idx, DexFile::kDexNoIndex16);
    const dex::ClassDef& original_class_def = original_dex->GetClassDef(class_def_idx);
    MemberSignature member_signature(member);
    auto fn_visit = [&](const AccessorType& dex_member) {
      MemberSignature cur_signature(dex_member);
      if (member_signature.MemberNameAndTypeMatch(cur_signature)) {
        DCHECK(member_signature.Equals(cur_signature));
        flags = ApiList::FromDexFlags(dex_member.GetHiddenapiFlags());
      }
    };
    VisitMembers(*original_dex, original_class_def, fn_visit);
  }

  CHECK(flags.IsValid()) << "Could not find hiddenapi flags for "
                         << Dumpable<MemberSignature>(MemberSignature(member));
  return flags.GetDexFlags();
}

template <typename T>
bool HandleCorePlatformApiViolation(T* member,
                                    ApiList api_list,
                                    uint32_t runtime_flags,
                                    const AccessContext& caller_context,
                                    const AccessContext& callee_context,
                                    AccessMethod access_method,
                                    EnforcementPolicy policy) {
  DCHECK(policy != EnforcementPolicy::kDisabled)
      << "Should never enter this function when access checks are completely disabled";

  if (access_method == AccessMethod::kCheck) {
    // Always return true for internal checks, so the current enforcement policy
    // won't affect the caller.
    return true;
  }

  if (access_method != AccessMethod::kCheckWithPolicy) {
    LOG(policy == EnforcementPolicy::kEnabled ? ERROR : WARNING)
        << "hiddenapi: Core platform API violation: "
        << Dumpable<MemberSignature>(MemberSignature(member))
        << " (runtime_flags=" << FormatHiddenApiRuntimeFlags(runtime_flags)
        << ", domain=" << callee_context.GetDomain() << ", api=" << api_list << ") from "
        << caller_context << " (domain=" << caller_context.GetDomain() << ")"
        << " using " << access_method;

    // If policy is set to just warn, add kAccCorePlatformApi to access flags of
    // `member` to avoid reporting the violation again next time.
    if (policy == EnforcementPolicy::kJustWarn) {
      MaybeUpdateAccessFlags(Runtime::Current(), member, kAccCorePlatformApi);
    }
  }

  // Deny access if enforcement is enabled.
  return policy == EnforcementPolicy::kEnabled;
}

template <typename T>
bool ShouldDenyAccessToMemberImpl(T* member,
                                  ApiList api_list,
                                  uint32_t runtime_flags,
                                  const AccessContext& caller_context,
                                  const AccessContext& callee_context,
                                  AccessMethod access_method)
    REQUIRES_SHARED(Locks::mutator_lock_) {
  DCHECK(member != nullptr);
  Runtime* runtime = Runtime::Current();
  CompatFramework& compatFramework = runtime->GetCompatFramework();

  EnforcementPolicy hiddenApiPolicy = runtime->GetHiddenApiEnforcementPolicy();
  DCHECK(hiddenApiPolicy != EnforcementPolicy::kDisabled)
      << "Should never enter this function when access checks are completely disabled";

  MemberSignature member_signature(member);

  // Check for an exemption first. Exempted APIs are treated as SDK.
  if (member_signature.DoesPrefixMatchAny(runtime->GetHiddenApiExemptions())) {
    // Avoid re-examining the exemption list next time.
    // Note this results in no warning for the member, which seems like what one would expect.
    // Exemptions effectively adds new members to the public API list.
    MaybeUpdateAccessFlags(runtime, member, kAccPublicApi);
    return false;
  }

  EnforcementPolicy testApiPolicy = runtime->GetTestApiEnforcementPolicy();

  bool deny_access = false;
  if (hiddenApiPolicy == EnforcementPolicy::kEnabled) {
    if (api_list.IsTestApi() && (testApiPolicy == EnforcementPolicy::kDisabled ||
                                 compatFramework.IsChangeEnabled(kAllowTestApiAccess))) {
      deny_access = false;
    } else {
      switch (api_list.GetMaxAllowedSdkVersion()) {
        case SdkVersion::kP:
          deny_access = compatFramework.IsChangeEnabled(kHideMaxtargetsdkPHiddenApis);
          break;
        case SdkVersion::kQ:
          deny_access = compatFramework.IsChangeEnabled(kHideMaxtargetsdkQHiddenApis);
          break;
        default:
          deny_access = IsSdkVersionSetAndMoreThan(runtime->GetTargetSdkVersion(),
                                                   api_list.GetMaxAllowedSdkVersion());
      }
    }
  }

  if (access_method != AccessMethod::kCheck && access_method != AccessMethod::kCheckWithPolicy) {
    // Warn if blocked signature is being accessed or it is not exempted.
    if (deny_access || !member_signature.DoesPrefixMatchAny(kWarningExemptions)) {
      // Print a log message with information about this class member access.
      // We do this if we're about to deny access, or the app is debuggable.
      if (kLogAllAccesses || deny_access || runtime->IsJavaDebuggable()) {
        member_signature.LogAccessToLogcat(access_method,
                                           api_list,
                                           deny_access,
                                           runtime_flags,
                                           caller_context,
                                           callee_context,
                                           hiddenApiPolicy);
      }

      // If there is a StrictMode listener, notify it about this violation.
      member_signature.NotifyHiddenApiListener(access_method);
    }

    // If event log sampling is enabled, report this violation.
    if (kIsTargetBuild && !kIsTargetLinux) {
      uint32_t eventLogSampleRate = runtime->GetHiddenApiEventLogSampleRate();
      // Assert that RAND_MAX is big enough, to ensure sampling below works as expected.
      static_assert(RAND_MAX >= 0xffff, "RAND_MAX too small");
      if (eventLogSampleRate != 0) {
        const uint32_t sampled_value = static_cast<uint32_t>(std::rand()) & 0xffff;
        if (sampled_value <= eventLogSampleRate) {
          member_signature.LogAccessToEventLog(sampled_value, access_method, deny_access);
        }
      }
    }

    // If this access was not denied, flag member as SDK and skip
    // the warning the next time the member is accessed. Don't update for
    // non-debuggable apps as this has a memory cost.
    if (!deny_access && runtime->IsJavaDebuggable()) {
      MaybeUpdateAccessFlags(runtime, member, kAccPublicApi);
    }
  }

  return deny_access;
}

// Need to instantiate these.
template uint32_t GetDexFlags<ArtField>(ArtField* member);
template uint32_t GetDexFlags<ArtMethod>(ArtMethod* member);
template bool HandleCorePlatformApiViolation(ArtField* member,
                                             ApiList api_list,
                                             uint32_t runtime_flags,
                                             const AccessContext& caller_context,
                                             const AccessContext& callee_context,
                                             AccessMethod access_method,
                                             EnforcementPolicy policy);
template bool HandleCorePlatformApiViolation(ArtMethod* member,
                                             ApiList api_list,
                                             uint32_t runtime_flags,
                                             const AccessContext& caller_context,
                                             const AccessContext& callee_context,
                                             AccessMethod access_method,
                                             EnforcementPolicy policy);
template bool ShouldDenyAccessToMemberImpl<ArtField>(ArtField* member,
                                                     ApiList api_list,
                                                     uint32_t runtime_flags,
                                                     const AccessContext& caller_context,
                                                     const AccessContext& callee_context,
                                                     AccessMethod access_method);
template bool ShouldDenyAccessToMemberImpl<ArtMethod>(ArtMethod* member,
                                                      ApiList api_list,
                                                      uint32_t runtime_flags,
                                                      const AccessContext& caller_context,
                                                      const AccessContext& callee_context,
                                                      AccessMethod access_method);

}  // namespace detail

template <typename T>
bool ShouldDenyAccessToMember(T* member,
                              const std::function<AccessContext()>& fn_get_access_context,
                              AccessMethod access_method) {
  DCHECK(member != nullptr);

  // First check if we have an explicit sdk checker installed that should be used to
  // verify access. If so, make the decision based on it.
  //
  // This is used during off-device AOT compilation which may want to generate verification
  // metadata only for a specific list of public SDKs. Note that the check here is made
  // based on descriptor equality and it's aim to further restrict a symbol that would
  // otherwise be resolved.
  //
  // The check only applies to boot classpaths dex files.
  Runtime* runtime = Runtime::Current();
  if (UNLIKELY(runtime->IsAotCompiler())) {
    if (member->GetDeclaringClass()->IsBootStrapClassLoaded() &&
        runtime->GetClassLinker()->DenyAccessBasedOnPublicSdk(member)) {
      return true;
    }
  }

  // Get the runtime flags encoded in member's access flags.
  // Note: this works for proxy methods because they inherit access flags from their
  // respective interface methods.
  const uint32_t runtime_flags = GetRuntimeFlags(member);

  // Exit early if member is public API. This flag is also set for non-boot class
  // path fields/methods.
  if ((runtime_flags & kAccPublicApi) != 0) {
    return false;
  }

  // Determine which domain the caller and callee belong to.
  // This can be *very* expensive. This is why ShouldDenyAccessToMember
  // should not be called on every individual access.
  const AccessContext caller_context = fn_get_access_context();
  const AccessContext callee_context(member->GetDeclaringClass());

  // Non-boot classpath callers should have exited early.
  DCHECK(!callee_context.IsApplicationDomain());

  // Check if the caller is always allowed to access members in the callee context.
  if (caller_context.CanAlwaysAccess(callee_context)) {
    return false;
  }

  // Check if this is platform accessing core platform. We may warn if `member` is
  // not part of core platform API.
  switch (caller_context.GetDomain()) {
    case Domain::kApplication: {
      DCHECK(!callee_context.IsApplicationDomain());

      // Exit early if access checks are completely disabled.
      EnforcementPolicy policy = runtime->GetHiddenApiEnforcementPolicy();
      if (policy == EnforcementPolicy::kDisabled) {
        return false;
      }

      // If this is a proxy method, look at the interface method instead.
      member = detail::GetInterfaceMemberIfProxy(member);

      // Decode hidden API access flags from the dex file.
      // This is an O(N) operation scaling with the number of fields/methods
      // in the class. Only do this on slow path and only do it once.
      ApiList api_list = ApiList::FromDexFlags(detail::GetDexFlags(member));
      DCHECK(api_list.IsValid());

      // Member is hidden and caller is not exempted. Enter slow path.
      return detail::ShouldDenyAccessToMemberImpl(
          member, api_list, runtime_flags, caller_context, callee_context, access_method);
    }

    case Domain::kPlatform: {
      DCHECK(callee_context.GetDomain() == Domain::kCorePlatform);

      // Member is part of core platform API. Accessing it is allowed.
      if ((runtime_flags & kAccCorePlatformApi) != 0) {
        return false;
      }

      // Allow access if access checks are disabled.
      EnforcementPolicy policy = Runtime::Current()->GetCorePlatformApiEnforcementPolicy();
      if (policy == EnforcementPolicy::kDisabled) {
        return false;
      }

      // If this is a proxy method, look at the interface method instead.
      member = detail::GetInterfaceMemberIfProxy(member);

      // Decode hidden API access flags from the dex file. This is a slow path,
      // like in the kApplication case above.
      ApiList api_list = ApiList::FromDexFlags(detail::GetDexFlags(member));
      DCHECK(api_list.IsValid());

      // Max target SDK versions don't matter for platform callers, but they may
      // still depend on unsupported APIs. Let's compare against the "max" SDK
      // version to only allow that (and also proper SDK APIs, but they are
      // typically combined with kCorePlatformApi already).
      if (api_list.GetMaxAllowedSdkVersion() == SdkVersion::kMax) {
        // Allow access and attempt to update the access flags to avoid
        // re-examining the dex flags next time.
        detail::MaybeUpdateAccessFlags(Runtime::Current(), member, kAccCorePlatformApi);
        return false;
      }

      // Check for exemptions.
      // TODO(b/377676642): Fix API annotations and delete this.
      detail::MemberSignature member_signature(member);
      if (member_signature.DoesPrefixMatchAny(kCorePlatformApiExemptions)) {
        // Avoid re-examining the exemption list next time.
        detail::MaybeUpdateAccessFlags(Runtime::Current(), member, kAccCorePlatformApi);
        return false;
      }

      // Access checks are not disabled, report the violation.
      // This may also add kAccCorePlatformApi to the access flags of `member`
      // so as to not warn again on next access.
      return detail::HandleCorePlatformApiViolation(
          member, api_list, runtime_flags, caller_context, callee_context, access_method, policy);
    }

    case Domain::kCorePlatform: {
      LOG(FATAL) << "CorePlatform domain should be allowed to access all domains";
      UNREACHABLE();
    }
  }
}

// Need to instantiate these.
template bool ShouldDenyAccessToMember<ArtField>(
    ArtField* member,
    const std::function<AccessContext()>& fn_get_access_context,
    AccessMethod access_method);
template bool ShouldDenyAccessToMember<ArtMethod>(
    ArtMethod* member,
    const std::function<AccessContext()>& fn_get_access_context,
    AccessMethod access_method);

}  // namespace hiddenapi
}  // namespace art