Android之隐藏api介绍

static jobject Class_getDeclaredMethodInternal(JNIEnv* env, jobject javaThis,
                                               jstring name, jobjectArray args) {
  ScopedFastNativeObjectAccess soa(env);
  StackHandleScope<1> hs(soa.Self());
  DCHECK_EQ(Runtime::Current()->GetClassLinker()->GetImagePointerSize(), kRuntimePointerSize);
  DCHECK(!Runtime::Current()->IsActiveTransaction());
  Handle<mirror::Method> result = hs.NewHandle(
      mirror::Class::GetDeclaredMethodInternal<kRuntimePointerSize, false>(
          soa.Self(),
          DecodeClass(soa, javaThis),
          soa.Decode<mirror::String>(name),
          soa.Decode<mirror::ObjectArray<mirror::Class>>(args)));
  if (result == nullptr || ShouldBlockAccessToMember(result->GetArtMethod(), soa.Self())) {
    return nullptr;
  }
  return soa.AddLocalReference<jobject>(result.Get());
}

// Returns true if the first non-ClassClass caller up the stack should not be
// allowed access to `member`.
template<typename T>
ALWAYS_INLINE static bool ShouldBlockAccessToMember(T* member, Thread* self)
    REQUIRES_SHARED(Locks::mutator_lock_) {
  hiddenapi::Action action = hiddenapi::GetMemberAction(
      member, self, IsCallerTrusted, hiddenapi::kReflection);
  if (action != hiddenapi::kAllow) {
    hiddenapi::NotifyHiddenApiListener(member);
  }

  return action == hiddenapi::kDeny;
}

template<typename T>
inline Action GetMemberAction(T* member,
                              Thread* self,
                              std::function<bool(Thread*)> fn_caller_is_trusted,
                              AccessMethod access_method)
    REQUIRES_SHARED(Locks::mutator_lock_) {
  DCHECK(member != nullptr);

  // Decode hidden API access flags.
  // NB Multiple threads might try to access (and overwrite) these simultaneously,
  // causing a race. We only do that if access has not been denied, so the race
  // cannot change Java semantics. We should, however, decode the access flags
  // once and use it throughout this function, otherwise we may get inconsistent
  // results, e.g. print whitelist warnings (b/78327881).
  HiddenApiAccessFlags::ApiList api_list = member->GetHiddenApiAccessFlags();

  Action action = GetActionFromAccessFlags(member->GetHiddenApiAccessFlags());
  if (action == kAllow) {
    // Nothing to do.
    return action;
  }

  // Member is hidden. Invoke `fn_caller_in_platform` and find the origin of the access.
  // This can be *very* expensive. Save it for last.
  if (fn_caller_is_trusted(self)) {
    // Caller is trusted. Exit.
    return kAllow;
  }

  // Member is hidden and caller is not in the platform.
  return detail::GetMemberActionImpl(member, api_list, action, access_method);
}

emplate<typename T>
Action GetMemberActionImpl(T* member,
                           HiddenApiAccessFlags::ApiList api_list,
                           Action action,
                           AccessMethod access_method) {
  DCHECK_NE(action, kAllow);

  // Get the signature, we need it later.
  MemberSignature member_signature(member);

  Runtime* runtime = Runtime::Current();

  // Check for an exemption first. Exempted APIs are treated as white list.
  // We only do this if we're about to deny, or if the app is debuggable. This is because:
  // - we only print a warning for light greylist violations for debuggable apps
  // - for non-debuggable apps, there is no distinction between light grey & whitelisted APIs.
  // - we want to avoid the overhead of checking for exemptions for light greylisted APIs whenever
  //   possible.
  const bool shouldWarn = kLogAllAccesses || runtime->IsJavaDebuggable();
  if (shouldWarn || action == kDeny) {
    if (member_signature.IsExempted(runtime->GetHiddenApiExemptions())) {
      action = kAllow;
      // 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 kAllow;
    }

    if (access_method != kNone) {
      // Print a log message with information about this class member access.
      // We do this if we're about to block access, or the app is debuggable.
      member_signature.WarnAboutAccess(access_method, api_list);
    }
  }

  if (kIsTargetBuild) {
    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, action);
    }
  }

  if (action == kDeny) {
    // Block access
    return action;
  }

  // Allow access to this member but print a warning.
  DCHECK(action == kAllowButWarn || action == kAllowButWarnAndToast);

  if (access_method != kNone) {
    // Depending on a runtime flag, we might move the member into whitelist and
    // skip the warning the next time the member is accessed.
    MaybeWhitelistMember(runtime, member);

    // If this action requires a UI warning, set the appropriate flag.
    if (shouldWarn &&
        (action == kAllowButWarnAndToast || runtime->ShouldAlwaysSetHiddenApiWarningFlag())) {
      runtime->SetPendingHiddenApiWarning(true);
    }
  }

  return action;
}

    if (member_signature.IsExempted(runtime->GetHiddenApiExemptions())) {
      action = kAllow;
      // 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 kAllow;
    }

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