gecko-dev/dom/media/AutoplayPolicy.cpp

/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
/* vim: set ts=8 sts=2 et sw=2 tw=80: */
/* This Source Code Form is subject to the terms of the Mozilla Public
 * License, v. 2.0. If a copy of the MPL was not distributed with this file,
 * You can obtain one at http://mozilla.org/MPL/2.0/. */

#include "AutoplayPolicy.h"

#include "mozilla/EventStateManager.h"
#include "mozilla/Logging.h"
#include "mozilla/Preferences.h"
#include "mozilla/dom/AudioContext.h"
#include "mozilla/dom/FeaturePolicyUtils.h"
#include "mozilla/dom/HTMLMediaElement.h"
#include "mozilla/dom/HTMLMediaElementBinding.h"
#include "nsGlobalWindowInner.h"
#include "nsIAutoplay.h"
#include "nsContentUtils.h"
#include "mozilla/dom/Document.h"
#include "MediaManager.h"
#include "nsIDocShell.h"
#include "nsIDocShellTreeItem.h"
#include "nsPIDOMWindow.h"
#include "mozilla/Services.h"
#include "nsIPermissionManager.h"

mozilla::LazyLogModule gAutoplayPermissionLog("Autoplay");

#define AUTOPLAY_LOG(msg, ...) \
  MOZ_LOG(gAutoplayPermissionLog, LogLevel::Debug, (msg, ##__VA_ARGS__))

namespace mozilla {
namespace dom {

static Document* ApproverDocOf(const Document& aDocument) {
  nsCOMPtr<nsIDocShell> ds = aDocument.GetDocShell();
  if (!ds) {
    return nullptr;
  }

  nsCOMPtr<nsIDocShellTreeItem> rootTreeItem;
  ds->GetSameTypeRootTreeItem(getter_AddRefs(rootTreeItem));
  if (!rootTreeItem) {
    return nullptr;
  }

  return rootTreeItem->GetDocument();
}

static bool IsActivelyCapturingOrHasAPermission(nsPIDOMWindowInner* aWindow) {
  // Pages which have been granted permission to capture WebRTC camera or
  // microphone or screen are assumed to be trusted, and are allowed to
  // autoplay.
  if (MediaManager::GetIfExists()) {
    return MediaManager::GetIfExists()->IsActivelyCapturingOrHasAPermission(
        aWindow->WindowID());
  }

  auto principal = nsGlobalWindowInner::Cast(aWindow)->GetPrincipal();
  return (nsContentUtils::IsExactSitePermAllow(principal,
                                               NS_LITERAL_CSTRING("camera")) ||
          nsContentUtils::IsExactSitePermAllow(
              principal, NS_LITERAL_CSTRING("microphone")) ||
          nsContentUtils::IsExactSitePermAllow(principal,
                                               NS_LITERAL_CSTRING("screen")));
}

static uint32_t SiteAutoplayPerm(const Document* aDocument) {
  if (!aDocument) {
    return nsIPermissionManager::DENY_ACTION;
  }
  nsIPrincipal* principal = aDocument->NodePrincipal();
  nsCOMPtr<nsIPermissionManager> permMgr = services::GetPermissionManager();
  NS_ENSURE_TRUE(permMgr, nsIPermissionManager::DENY_ACTION);

  uint32_t perm;
  nsresult rv = permMgr->TestExactPermissionFromPrincipal(principal, NS_LITERAL_CSTRING("autoplay-media"), &perm);
  NS_ENSURE_SUCCESS(rv, nsIPermissionManager::DENY_ACTION);
  return perm;
}

static bool IsWindowAllowedToPlay(nsPIDOMWindowInner* aWindow) {
  if (!aWindow) {
    return false;
  }

  if (IsActivelyCapturingOrHasAPermission(aWindow)) {
    AUTOPLAY_LOG(
        "Allow autoplay as document has camera or microphone or screen"
        " permission.");
    return true;
  }

  if (!aWindow->GetExtantDoc()) {
    return false;
  }

  Document* approver = ApproverDocOf(*aWindow->GetExtantDoc());
  if (!approver) {
    return false;
  }

  if (approver->HasBeenUserGestureActivated()) {
    AUTOPLAY_LOG("Allow autoplay as document activated by user gesture.");
    return true;
  }

  if (approver->IsExtensionPage()) {
    AUTOPLAY_LOG("Allow autoplay as in extension document.");
    return true;
  }

  if (approver->MediaDocumentKind() == Document::MediaDocumentKind::Video) {
    AUTOPLAY_LOG("Allow video document to autoplay.");
    return true;
  }

  return false;
}

static uint32_t DefaultAutoplayBehaviour() {
  int prefValue =
      Preferences::GetInt("media.autoplay.default", nsIAutoplay::ALLOWED);
  if (prefValue == nsIAutoplay::ALLOWED) {
    return nsIAutoplay::ALLOWED;
  }
  if (prefValue == nsIAutoplay::BLOCKED_ALL) {
    return nsIAutoplay::BLOCKED_ALL;
  }
  return nsIAutoplay::BLOCKED;
}

static bool IsMediaElementInaudible(const HTMLMediaElement& aElement) {
  if (aElement.Volume() == 0.0 || aElement.Muted()) {
    AUTOPLAY_LOG("Media %p is muted.", &aElement);
    return true;
  }

  if (!aElement.HasAudio() &&
      aElement.ReadyState() >= HTMLMediaElement_Binding::HAVE_METADATA) {
    AUTOPLAY_LOG("Media %p has no audio track", &aElement);
    return true;
  }

  return false;
}

static bool IsAudioContextAllowedToPlay(const AudioContext& aContext) {
  // Offline context won't directly output sound to audio devices.
  return aContext.IsOffline() ||
         IsWindowAllowedToPlay(aContext.GetParentObject());
}

static bool IsEnableBlockingWebAudioByUserGesturePolicy() {
  return DefaultAutoplayBehaviour() != nsIAutoplay::ALLOWED &&
         Preferences::GetBool("media.autoplay.block-webaudio", false) &&
         StaticPrefs::media_autoplay_enabled_user_gestures_needed();
}

/* static */
bool AutoplayPolicy::WouldBeAllowedToPlayIfAutoplayDisabled(
    const HTMLMediaElement& aElement) {
  return IsMediaElementInaudible(aElement) ||
         IsWindowAllowedToPlay(aElement.OwnerDoc()->GetInnerWindow());
}

/* static */
bool AutoplayPolicy::WouldBeAllowedToPlayIfAutoplayDisabled(
    const AudioContext& aContext) {
  return IsAudioContextAllowedToPlay(aContext);
}

static bool IsAllowedToPlayByBlockingModel(const HTMLMediaElement& aElement) {
  if (!StaticPrefs::media_autoplay_enabled_user_gestures_needed()) {
    // If element is blessed, it would always be allowed to play().
    return aElement.IsBlessed() || EventStateManager::IsHandlingUserInput();
  }
  return IsWindowAllowedToPlay(aElement.OwnerDoc()->GetInnerWindow());
}

static bool IsAllowedToPlayInternal(const HTMLMediaElement& aElement) {
  Document* approver = ApproverDocOf(*aElement.OwnerDoc());

  bool isInaudible = IsMediaElementInaudible(aElement);
  bool isUsingAutoplayModel = IsAllowedToPlayByBlockingModel(aElement);

  uint32_t defaultBehaviour = DefaultAutoplayBehaviour();
  uint32_t sitePermission = SiteAutoplayPerm(approver);

  AUTOPLAY_LOG("IsAllowedToPlayInternal, isInaudible=%d,"
    "isUsingAutoplayModel=%d, sitePermission=%d, defaultBehaviour=%d",
    isInaudible, isUsingAutoplayModel, sitePermission, defaultBehaviour);

  // For site permissions we store permissionManager values except
  // for BLOCKED_ALL, for the default pref values we store
  // nsIAutoplay values.
  if (sitePermission == nsIPermissionManager::ALLOW_ACTION) {
    return true;
  }

  if (sitePermission == nsIPermissionManager::DENY_ACTION) {
    return isInaudible || isUsingAutoplayModel;
  }

  if (sitePermission == nsIAutoplay::BLOCKED_ALL) {
    return isUsingAutoplayModel;
  }

  if (defaultBehaviour == nsIAutoplay::ALLOWED) {
    return true;
  }

  if (defaultBehaviour == nsIAutoplay::BLOCKED) {
    return isInaudible || isUsingAutoplayModel;
  }

  MOZ_ASSERT(defaultBehaviour == nsIAutoplay::BLOCKED_ALL);
  return isUsingAutoplayModel;
}

/* static */
bool AutoplayPolicy::IsAllowedToPlay(const HTMLMediaElement& aElement) {
  const bool result = IsAllowedToPlayInternal(aElement);
  AUTOPLAY_LOG("IsAllowedToPlay, mediaElement=%p, isAllowToPlay=%s", &aElement,
               result ? "allowed" : "blocked");
  return result;
}

/* static */
bool AutoplayPolicy::IsAllowedToPlay(const AudioContext& aContext) {
  /**
   * The autoplay checking has 4 different phases,
   * 1. check whether audio context itself meets the autoplay condition
   * 2. check whethr the site is in the autoplay whitelist
   * 3. check global autoplay setting and check wether the site is in the
   *    autoplay blacklist.
   * 4. check whether media is allowed under current blocking model
   *    (only support user-gesture-activation)
   */
  if (aContext.IsOffline()) {
    return true;
  }

  nsPIDOMWindowInner* window = aContext.GetParentObject();
  Document* approver = aContext.GetParentObject()
                           ? ApproverDocOf(*(window->GetExtantDoc()))
                           : nullptr;
  uint32_t sitePermission = SiteAutoplayPerm(approver);

  if (sitePermission == nsIPermissionManager::ALLOW_ACTION) {
    AUTOPLAY_LOG(
        "Allow autoplay as document has permanent autoplay permission.");
    return true;
  }

  if (DefaultAutoplayBehaviour() == nsIAutoplay::ALLOWED &&
      sitePermission != nsIPermissionManager::DENY_ACTION &&
      sitePermission != nsIAutoplay::BLOCKED_ALL) {
    AUTOPLAY_LOG(
        "Allow autoplay as global autoplay setting is allowing autoplay by "
        "default.");
    return true;
  }

  if (!IsEnableBlockingWebAudioByUserGesturePolicy()) {
    return true;
  }
  return IsWindowAllowedToPlay(window);
}

/* static */
DocumentAutoplayPolicy AutoplayPolicy::IsAllowedToPlay(
    const Document& aDocument) {
  if (DefaultAutoplayBehaviour() == nsIAutoplay::ALLOWED ||
      IsWindowAllowedToPlay(aDocument.GetInnerWindow())) {
    return DocumentAutoplayPolicy::Allowed;
  }

  if (DefaultAutoplayBehaviour() == nsIAutoplay::BLOCKED) {
    return DocumentAutoplayPolicy::Allowed_muted;
  }

  return DocumentAutoplayPolicy::Disallowed;
}

}  // namespace dom
}  // namespace mozilla