gecko-dev/dom/base/PostMessageEvent.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 "PostMessageEvent.h"

#include "MessageEvent.h"
#include "mozilla/dom/BlobBinding.h"
#include "mozilla/dom/File.h"
#include "mozilla/dom/FileList.h"
#include "mozilla/dom/FileListBinding.h"
#include "mozilla/dom/MessageEventBinding.h"
#include "mozilla/dom/MessagePort.h"
#include "mozilla/dom/MessagePortBinding.h"
#include "mozilla/dom/PMessagePort.h"
#include "mozilla/dom/StructuredCloneTags.h"
#include "mozilla/dom/UnionConversions.h"
#include "mozilla/EventDispatcher.h"
#include "nsContentUtils.h"
#include "nsGlobalWindow.h"
#include "nsIPresShell.h"
#include "nsIPrincipal.h"
#include "nsIScriptError.h"
#include "nsPresContext.h"
#include "nsQueryObject.h"

namespace mozilla {
namespace dom {

PostMessageEvent::PostMessageEvent(nsGlobalWindow* aSource,
                                   const nsAString& aCallerOrigin,
                                   nsGlobalWindow* aTargetWindow,
                                   nsIPrincipal* aProvidedPrincipal,
                                   nsIDocument* aSourceDocument,
                                   bool aTrustedCaller)
: StructuredCloneHolder(CloningSupported, TransferringSupported,
                        StructuredCloneScope::SameProcessSameThread),
  mSource(aSource),
  mCallerOrigin(aCallerOrigin),
  mTargetWindow(aTargetWindow),
  mProvidedPrincipal(aProvidedPrincipal),
  mSourceDocument(aSourceDocument),
  mTrustedCaller(aTrustedCaller)
{
}

PostMessageEvent::~PostMessageEvent()
{
}

NS_IMETHODIMP
PostMessageEvent::Run()
{
  MOZ_ASSERT(mTargetWindow->IsOuterWindow(),
             "should have been passed an outer window!");
  MOZ_ASSERT(!mSource || mSource->IsOuterWindow(),
             "should have been passed an outer window!");

  // Note: We don't init this AutoJSAPI with targetWindow, because we do not
  // want exceptions during message deserialization to trigger error events on
  // targetWindow.
  AutoJSAPI jsapi;
  jsapi.Init();
  JSContext* cx = jsapi.cx();

  // The document is just used for the principal mismatch error message below.
  // Use a stack variable so mSourceDocument is not held onto after this method
  // finishes, regardless of the method outcome.
  nsCOMPtr<nsIDocument> sourceDocument;
  sourceDocument.swap(mSourceDocument);

  // If we bailed before this point we're going to leak mMessage, but
  // that's probably better than crashing.

  RefPtr<nsGlobalWindow> targetWindow;
  if (mTargetWindow->IsClosedOrClosing() ||
      !(targetWindow = mTargetWindow->GetCurrentInnerWindowInternal()) ||
      targetWindow->IsClosedOrClosing())
    return NS_OK;

  MOZ_ASSERT(targetWindow->IsInnerWindow(),
             "we ordered an inner window!");
  JSAutoCompartment ac(cx, targetWindow->GetWrapper());

  // Ensure that any origin which might have been provided is the origin of this
  // window's document.  Note that we do this *now* instead of when postMessage
  // is called because the target window might have been navigated to a
  // different location between then and now.  If this check happened when
  // postMessage was called, it would be fairly easy for a malicious webpage to
  // intercept messages intended for another site by carefully timing navigation
  // of the target window so it changed location after postMessage but before
  // now.
  if (mProvidedPrincipal) {
    // Get the target's origin either from its principal or, in the case the
    // principal doesn't carry a URI (e.g. the system principal), the target's
    // document.
    nsIPrincipal* targetPrin = targetWindow->GetPrincipal();
    if (NS_WARN_IF(!targetPrin))
      return NS_OK;

    // Note: This is contrary to the spec with respect to file: URLs, which
    //       the spec groups into a single origin, but given we intentionally
    //       don't do that in other places it seems better to hold the line for
    //       now.  Long-term, we want HTML5 to address this so that we can
    //       be compliant while being safer.
    if (!BasePrincipal::Cast(targetPrin)->EqualsIgnoringAddonId(mProvidedPrincipal)) {
      nsAutoString providedOrigin, targetOrigin;
      nsresult rv = nsContentUtils::GetUTFOrigin(targetPrin, targetOrigin);
      NS_ENSURE_SUCCESS(rv, rv);
      rv = nsContentUtils::GetUTFOrigin(mProvidedPrincipal, providedOrigin);
      NS_ENSURE_SUCCESS(rv, rv);

      MOZ_DIAGNOSTIC_ASSERT(providedOrigin != targetOrigin ||
                            (BasePrincipal::Cast(mProvidedPrincipal)->OriginAttributesRef() ==
                              BasePrincipal::Cast(targetPrin)->OriginAttributesRef()),
                            "Unexpected postMessage call to a window with mismatched "
                            "origin attributes");

      const char16_t* params[] = { providedOrigin.get(), targetOrigin.get() };

      nsContentUtils::ReportToConsole(nsIScriptError::errorFlag,
        NS_LITERAL_CSTRING("DOM Window"), sourceDocument,
        nsContentUtils::eDOM_PROPERTIES,
        "TargetPrincipalDoesNotMatch",
        params, ArrayLength(params));

      return NS_OK;
    }
  }

  ErrorResult rv;
  JS::Rooted<JS::Value> messageData(cx);
  nsCOMPtr<nsPIDOMWindowInner> window = targetWindow->AsInner();

  Read(window, cx, &messageData, rv);
  if (NS_WARN_IF(rv.Failed())) {
    return rv.StealNSResult();
  }

  // Create the event
  nsCOMPtr<mozilla::dom::EventTarget> eventTarget = do_QueryObject(targetWindow);
  RefPtr<MessageEvent> event =
    new MessageEvent(eventTarget, nullptr, nullptr);


  Nullable<WindowProxyOrMessagePort> source;
  source.SetValue().SetAsWindowProxy() = mSource ? mSource->AsOuter() : nullptr;

  Sequence<OwningNonNull<MessagePort>> ports;
  if (!TakeTransferredPortsAsSequence(ports)) {
    return NS_ERROR_OUT_OF_MEMORY;
  }

  event->InitMessageEvent(nullptr, NS_LITERAL_STRING("message"),
                          false /*non-bubbling */, false /*cancelable */,
                          messageData, mCallerOrigin,
                          EmptyString(), source, ports);

  // We can't simply call dispatchEvent on the window because doing so ends
  // up flipping the trusted bit on the event, and we don't want that to
  // happen because then untrusted content can call postMessage on a chrome
  // window if it can get a reference to it.

  nsIPresShell *shell = targetWindow->GetExtantDoc()->GetShell();
  RefPtr<nsPresContext> presContext;
  if (shell)
    presContext = shell->GetPresContext();

  event->SetTrusted(mTrustedCaller);
  WidgetEvent* internalEvent = event->WidgetEventPtr();

  nsEventStatus status = nsEventStatus_eIgnore;
  EventDispatcher::Dispatch(window,
                            presContext,
                            internalEvent,
                            static_cast<dom::Event*>(event.get()),
                            &status);
  return NS_OK;
}

} // namespace dom
} // namespace mozilla