gecko-dev/dom/base/ScriptSettings.h

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5.2 KiB
C++

/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
// vim: ft=cpp tw=78 sw=2 et ts=2
/* 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/. */
/* Utilities for managing the script settings object stack defined in webapps */
#ifndef mozilla_dom_ScriptSettings_h
#define mozilla_dom_ScriptSettings_h
#include "nsCxPusher.h"
#include "MainThreadUtils.h"
#include "nsIGlobalObject.h"
#include "nsIPrincipal.h"
#include "mozilla/Maybe.h"
class nsIGlobalObject;
namespace mozilla {
namespace dom {
/*
* System-wide setup/teardown routines. Init and Destroy should be invoked
* once each, at startup and shutdown (respectively).
*/
void InitScriptSettings();
void DestroyScriptSettings();
// This mostly gets the entry global, but doesn't entirely match the spec in
// certain edge cases. It's good enough for some purposes, but not others. If
// you want to call this function, ping bholley and describe your use-case.
nsIGlobalObject* BrokenGetEntryGlobal();
// Note: We don't yet expose GetEntryGlobal, because in order for it to be
// correct, we first need to replace a bunch of explicit cx pushing in the
// browser with AutoEntryScript. But GetIncumbentGlobal is simpler, because it
// can mostly be inferred from the JS stack.
nsIGlobalObject* GetIncumbentGlobal();
// JS-implemented WebIDL presents an interesting situation with respect to the
// subject principal. A regular C++-implemented API can simply examine the
// compartment of the most-recently-executed script, and use that to infer the
// responsible party. However, JS-implemented APIs are run with system
// principal, and thus clobber the subject principal of the script that
// invoked the API. So we have to do some extra work to keep track of this
// information.
//
// We therefore implement the following behavior:
// * Each Script Settings Object has an optional WebIDL Caller Principal field.
// This defaults to null.
// * When we push an Entry Point in preparation to run a JS-implemented WebIDL
// callback, we grab the subject principal at the time of invocation, and
// store that as the WebIDL Caller Principal.
// * When non-null, callers can query this principal from script via an API on
// Components.utils.
nsIPrincipal* GetWebIDLCallerPrincipal();
// This may be used by callers that know that their incumbent global is non-
// null (i.e. they know there have been no System Caller pushes since the
// inner-most script execution).
inline JSObject& IncumbentJSGlobal()
{
return *GetIncumbentGlobal()->GetGlobalJSObject();
}
class ScriptSettingsStack;
struct ScriptSettingsStackEntry {
nsCOMPtr<nsIGlobalObject> mGlobalObject;
bool mIsCandidateEntryPoint;
ScriptSettingsStackEntry(nsIGlobalObject *aGlobal, bool aCandidate)
: mGlobalObject(aGlobal)
, mIsCandidateEntryPoint(aCandidate)
{
MOZ_ASSERT(mGlobalObject);
MOZ_ASSERT(mGlobalObject->GetGlobalJSObject(),
"Must have an actual JS global for the duration on the stack");
MOZ_ASSERT(JS_IsGlobalObject(mGlobalObject->GetGlobalJSObject()),
"No outer windows allowed");
}
~ScriptSettingsStackEntry() {
// We must have an actual JS global for the entire time this is on the stack.
MOZ_ASSERT_IF(mGlobalObject, mGlobalObject->GetGlobalJSObject());
}
bool IsSystemSingleton() { return this == &SystemSingleton; }
static ScriptSettingsStackEntry SystemSingleton;
private:
ScriptSettingsStackEntry() : mGlobalObject(nullptr)
, mIsCandidateEntryPoint(true)
{}
};
/*
* A class that represents a new script entry point.
*/
class AutoEntryScript : protected ScriptSettingsStackEntry {
public:
AutoEntryScript(nsIGlobalObject* aGlobalObject,
bool aIsMainThread = NS_IsMainThread(),
// Note: aCx is mandatory off-main-thread.
JSContext* aCx = nullptr);
~AutoEntryScript();
void SetWebIDLCallerPrincipal(nsIPrincipal *aPrincipal) {
mWebIDLCallerPrincipal = aPrincipal;
}
private:
dom::ScriptSettingsStack& mStack;
nsCOMPtr<nsIPrincipal> mWebIDLCallerPrincipal;
mozilla::Maybe<AutoCxPusher> mCxPusher;
mozilla::Maybe<JSAutoCompartment> mAc; // This can de-Maybe-fy when mCxPusher
// goes away.
friend nsIPrincipal* GetWebIDLCallerPrincipal();
};
/*
* A class that can be used to force a particular incumbent script on the stack.
*/
class AutoIncumbentScript : protected ScriptSettingsStackEntry {
public:
AutoIncumbentScript(nsIGlobalObject* aGlobalObject);
~AutoIncumbentScript();
private:
dom::ScriptSettingsStack& mStack;
JS::AutoHideScriptedCaller mCallerOverride;
};
/*
* A class used for C++ to indicate that existing entry and incumbent scripts
* should not apply to anything in scope, and that callees should act as if
* they were invoked "from C++".
*/
class AutoSystemCaller {
public:
AutoSystemCaller(bool aIsMainThread = NS_IsMainThread());
~AutoSystemCaller();
private:
dom::ScriptSettingsStack& mStack;
mozilla::Maybe<AutoCxPusher> mCxPusher;
};
} // namespace dom
} // namespace mozilla
#endif // mozilla_dom_ScriptSettings_h