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 <nativehelper/scoped_local_ref.h>

#include "art_field-inl.h"
#include "art_method-inl.h"
#include "base/dumpable.h"
#include "dex/class_accessor-inl.h"
#include "scoped_thread_state_change.h"
#include "thread-inl.h"
#include "well_known_classes.h"

#ifdef ART_TARGET_ANDROID
#include <metricslogger/metrics_logger.h>
using android::metricslogger::ComplexEventLogger;
using android::metricslogger::ACTION_HIDDEN_API_ACCESSED;
using android::metricslogger::FIELD_HIDDEN_API_ACCESS_METHOD;
using android::metricslogger::FIELD_HIDDEN_API_ACCESS_DENIED;
using android::metricslogger::FIELD_HIDDEN_API_SIGNATURE;
#endif

namespace art {
namespace hiddenapi {

// Set to true if we should always print a warning in logcat for all hidden API accesses, not just
// dark grey and black. 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 light grey APIs that have been added to the exemptions
// list.
static constexpr bool kLogAllAccesses = false;

static inline std::ostream& operator<<(std::ostream& os, AccessMethod value) {
  switch (value) {
    case AccessMethod::kNone:
      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;
}

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) {
  class_name_ = field->GetDeclaringClass()->GetDescriptor(&tmp_);
  member_name_ = field->GetName();
  type_signature_ = field->GetTypeDescriptor();
  type_ = kField;
}

MemberSignature::MemberSignature(ArtMethod* method) {
  // If this is a proxy method, print the signature of the interface method.
  method = method->GetInterfaceMethodIfProxy(
      Runtime::Current()->GetClassLinker()->GetImagePointerSize());

  class_name_ = method->GetDeclaringClass()->GetDescriptor(&tmp_);
  member_name_ = method->GetName();
  type_signature_ = method->GetSignature().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::IsExempted(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::WarnAboutAccess(AccessMethod access_method, hiddenapi::ApiList list) {
  LOG(WARNING) << "Accessing hidden " << (type_ == kField ? "field " : "method ")
               << Dumpable<MemberSignature>(*this) << " (" << list << ", " << access_method << ")";
}

#ifdef ART_TARGET_ANDROID
// Convert an AccessMethod enum to a value for logging from the proto enum.
// This method may look odd (the enum values are current the same), but it
// prevents coupling the internal enum to the proto enum (which should never
// be changed) so that we are free to change the internal one if necessary in
// future.
inline static int32_t GetEnumValueForLog(AccessMethod access_method) {
  switch (access_method) {
    case AccessMethod::kNone:
      return android::metricslogger::ACCESS_METHOD_NONE;
    case AccessMethod::kReflection:
      return android::metricslogger::ACCESS_METHOD_REFLECTION;
    case AccessMethod::kJNI:
      return android::metricslogger::ACCESS_METHOD_JNI;
    case AccessMethod::kLinking:
      return android::metricslogger::ACCESS_METHOD_LINKING;
    default:
      DCHECK(false);
  }
}
#endif

void MemberSignature::LogAccessToEventLog(AccessMethod access_method, bool access_denied) {
#ifdef ART_TARGET_ANDROID
  if (access_method == AccessMethod::kLinking || access_method == AccessMethod::kNone) {
    // Linking warnings come from static analysis/compilation of the bytecode
    // and can contain false positives (i.e. code that is never run). We choose
    // not to log these in the event log.
    // None does not correspond to actual access, so should also be ignored.
    return;
  }
  ComplexEventLogger log_maker(ACTION_HIDDEN_API_ACCESSED);
  log_maker.AddTaggedData(FIELD_HIDDEN_API_ACCESS_METHOD, GetEnumValueForLog(access_method));
  if (access_denied) {
    log_maker.AddTaggedData(FIELD_HIDDEN_API_ACCESS_DENIED, 1);
  }
  const std::string& package_name = Runtime::Current()->GetProcessPackageName();
  if (!package_name.empty()) {
    log_maker.SetPackageName(package_name);
  }
  std::ostringstream signature_str;
  Dump(signature_str);
  log_maker.AddTaggedData(FIELD_HIDDEN_API_SIGNATURE, signature_str.str());
  log_maker.Record();
#else
  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()) {
    ScopedObjectAccessUnchecked soa(Thread::Current());

    ScopedLocalRef<jobject> consumer_object(soa.Env(),
        soa.Env()->GetStaticObjectField(
            WellKnownClasses::dalvik_system_VMRuntime,
            WellKnownClasses::dalvik_system_VMRuntime_nonSdkApiUsageConsumer));
    // 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);

      ScopedLocalRef<jobject> signature_str(
          soa.Env(),
          soa.Env()->NewStringUTF(member_signature_str.str().c_str()));

      // Call through to Consumer.accept(String memberSignature);
      soa.Env()->CallVoidMethod(consumer_object.get(),
                                WellKnownClasses::java_util_function_Consumer_accept,
                                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 MaybeWhitelistMember(Runtime* runtime, T* member)
    REQUIRES_SHARED(Locks::mutator_lock_) {
  if (CanUpdateRuntimeFlags(member) && runtime->ShouldDedupeHiddenApiWarnings()) {
    member->SetAccessFlags(member->GetAccessFlags() | kAccPublicApi);
  }
}

static constexpr uint32_t kNoDexFlags = 0u;
static constexpr uint32_t kInvalidDexFlags = static_cast<uint32_t>(-1);

uint32_t GetDexFlags(ArtField* field) REQUIRES_SHARED(Locks::mutator_lock_) {
  ObjPtr<mirror::Class> declaring_class = field->GetDeclaringClass();
  DCHECK(declaring_class != nullptr) << "Fields always have a declaring class";

  const DexFile::ClassDef* class_def = declaring_class->GetClassDef();
  if (class_def == nullptr) {
    return kNoDexFlags;
  }

  uint32_t flags = kInvalidDexFlags;
  DCHECK(!AreValidDexFlags(flags));

  ClassAccessor accessor(declaring_class->GetDexFile(),
                         *class_def,
                         /* parse_hiddenapi_class_data= */ true);
  auto fn_visit = [&](const ClassAccessor::Field& dex_field) {
    if (dex_field.GetIndex() == field->GetDexFieldIndex()) {
      flags = dex_field.GetHiddenapiFlags();
    }
  };
  accessor.VisitFields(fn_visit, fn_visit);

  CHECK_NE(flags, kInvalidDexFlags) << "Could not find flags for field " << field->PrettyField();
  DCHECK(AreValidDexFlags(flags));
  return flags;
}

uint32_t GetDexFlags(ArtMethod* method) REQUIRES_SHARED(Locks::mutator_lock_) {
  ObjPtr<mirror::Class> declaring_class = method->GetDeclaringClass();
  if (declaring_class.IsNull()) {
    DCHECK(method->IsRuntimeMethod());
    return kNoDexFlags;
  }

  const DexFile::ClassDef* class_def = declaring_class->GetClassDef();
  if (class_def == nullptr) {
    return kNoDexFlags;
  }

  uint32_t flags = kInvalidDexFlags;
  DCHECK(!AreValidDexFlags(flags));

  ClassAccessor accessor(declaring_class->GetDexFile(),
                         *class_def,
                         /* parse_hiddenapi_class_data= */ true);
  auto fn_visit = [&](const ClassAccessor::Method& dex_method) {
    if (dex_method.GetIndex() == method->GetDexMethodIndex()) {
      flags = dex_method.GetHiddenapiFlags();
    }
  };
  accessor.VisitMethods(fn_visit, fn_visit);

  CHECK_NE(flags, kInvalidDexFlags) << "Could not find flags for method " << method->PrettyMethod();
  DCHECK(AreValidDexFlags(flags));
  return flags;
}

template<typename T>
bool ShouldDenyAccessToMemberImpl(T* member,
                                  hiddenapi::ApiList api_list,
                                  AccessMethod access_method) {
  DCHECK(member != nullptr);

  Runtime* runtime = Runtime::Current();
  EnforcementPolicy policy = runtime->GetHiddenApiEnforcementPolicy();

  const bool deny_access =
      (policy == EnforcementPolicy::kEnabled) &&
      IsSdkVersionSetAndMoreThan(runtime->GetTargetSdkVersion(),
                                 api_list.GetMaxAllowedSdkVersion());

  MemberSignature member_signature(member);

  // Check for an exemption first. Exempted APIs are treated as white list.
  if (member_signature.IsExempted(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 whitelist.
    MaybeWhitelistMember(runtime, member);
    return false;
  }

  if (access_method != AccessMethod::kNone) {
    // 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.WarnAboutAccess(access_method, api_list);
    }

    // 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 &&
          (static_cast<uint32_t>(std::rand()) & 0xffff) < eventLogSampleRate) {
        member_signature.LogAccessToEventLog(access_method, deny_access);
      }
    }

    // If this access was not denied, move the member into whitelist and skip
    // the warning the next time the member is accessed.
    if (!deny_access) {
      MaybeWhitelistMember(runtime, member);
    }
  }

  return deny_access;
}

// Need to instantiate this.
template bool ShouldDenyAccessToMemberImpl<ArtField>(ArtField* member,
                                                     hiddenapi::ApiList api_list,
                                                     AccessMethod access_method);
template bool ShouldDenyAccessToMemberImpl<ArtMethod>(ArtMethod* member,
                                                      hiddenapi::ApiList api_list,
                                                      AccessMethod access_method);
}  // namespace detail

}  // namespace hiddenapi
}  // namespace art