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/* -*- 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
/* Utilities for managing the script settings object stack defined in webapps */
#ifndef mozilla_dom_ScriptSettings_h
#define mozilla_dom_ScriptSettings_h
#include "xpcpublic.h"
#include "mozilla/dom/JSExecutionManager.h"
#include "mozilla/Maybe.h"
#include "jsapi.h"
#include "js/Exception.h"
#include "js/Warnings.h" // JS::WarningReporter
class JSObject;
class nsIGlobalObject;
class nsIPrincipal;
class nsPIDOMWindowInner;
class nsGlobalWindowInner;
class nsIScriptContext;
struct JSContext;
namespace JS {
class ExceptionStack;
class Value;
} // namespace JS
namespace mozilla {
namespace dom {
class Document;
/*
* Per thread setup/teardown routines. Init and Destroy should be invoked
* once each, at startup and shutdown of the script runtime (respectively).
*/
void InitScriptSettings();
void DestroyScriptSettings();
// To implement a web-compatible browser, it is often necessary to obtain the
// global object that is "associated" with the currently-running code. This
// process is made more complicated by the fact that, historically, different
// algorithms have operated with different definitions of the "associated"
// global.
//
// HTML5 formalizes this into two concepts: the "incumbent global" and the
// "entry global". The incumbent global corresponds to the global of the
// current script being executed, whereas the entry global corresponds to the
// global of the script where the current JS execution began.
//
// There is also a potentially-distinct third global that is determined by the
// current compartment. This roughly corresponds with the notion of Realms in
// ECMAScript.
//
// Suppose some event triggers an event listener in window |A|, which invokes a
// scripted function in window |B|, which invokes the |window.location.href|
// setter in window |C|. The entry global would be |A|, the incumbent global
// would be |B|, and the current compartment would be that of |C|.
//
// In general, it's best to use to use the most-closely-associated global
// unless the spec says to do otherwise. In 95% of the cases, the global of
// the current compartment (GetCurrentGlobal()) is the right thing. For
// example, WebIDL constructors (new C.XMLHttpRequest()) are initialized with
// the global of the current compartment (i.e. |C|).
//
// The incumbent global is very similar, but differs in a few edge cases. For
// example, if window |B| does |C.location.href = "..."|, the incumbent global
// used for the navigation algorithm is B, because no script from |C| was ever
// run.
//
// The entry global is used for various things like computing base URIs, mostly
// for historical reasons.
//
// Note that all of these functions return bonafide global objects. This means
// that, for Windows, they always return the inner.
// Returns the global associated with the top-most Candidate Entry Point on
// the Script Settings Stack. See the HTML spec. This may be null.
nsIGlobalObject* GetEntryGlobal();
// If the entry global is a window, returns its extant document. Otherwise,
// returns null.
Document* GetEntryDocument();
// Returns the global associated with the top-most entry of the the Script
// Settings Stack. See the HTML spec. This may be null.
nsIGlobalObject* GetIncumbentGlobal();
// Returns the global associated with the current compartment. This may be null.
nsIGlobalObject* GetCurrentGlobal();
// 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();
// Returns whether JSAPI is active right now. If it is not, working with a
// JSContext you grab from somewhere random is not OK and you should be doing
// AutoJSAPI or AutoEntryScript to get yourself a properly set up JSContext.
bool IsJSAPIActive();
namespace danger {
// Get the JSContext for this thread. This is in the "danger" namespace because
// we generally want people using AutoJSAPI instead, unless they really know
// what they're doing.
JSContext* GetJSContext();
} // namespace danger
JS::RootingContext* RootingCx();
class ScriptSettingsStack;
class ScriptSettingsStackEntry {
friend class ScriptSettingsStack;
public:
~ScriptSettingsStackEntry();
bool NoJSAPI() const { return mType == eNoJSAPI; }
bool IsEntryCandidate() const {
return mType == eEntryScript || mType == eNoJSAPI;
}
bool IsIncumbentCandidate() { return mType != eJSAPI; }
bool IsIncumbentScript() { return mType == eIncumbentScript; }
protected:
enum Type { eEntryScript, eIncumbentScript, eJSAPI, eNoJSAPI };
ScriptSettingsStackEntry(nsIGlobalObject* aGlobal, Type aEntryType);
nsCOMPtr<nsIGlobalObject> mGlobalObject;
Type mType;
private:
ScriptSettingsStackEntry* mOlder;
};
/*
* For any interaction with JSAPI, an AutoJSAPI (or one of its subclasses)
* must be on the stack.
*
* This base class should be instantiated as-is when the caller wants to use
* JSAPI but doesn't expect to run script. The caller must then call one of its
* Init functions before being able to access the JSContext through cx().
* Its current duties are as-follows (see individual Init comments for details):
*
* * Grabbing an appropriate JSContext, and, on the main thread, pushing it onto
* the JSContext stack.
* * Entering an initial (possibly null) compartment, to ensure that the
* previously entered compartment for that JSContext is not used by mistake.
* * Reporting any exceptions left on the JSRuntime, unless the caller steals
* or silences them.
*
* Additionally, the following duties are planned, but not yet implemented:
*
* * De-poisoning the JSRuntime to allow manipulation of JSAPI. This requires
* implementing the poisoning first. For now, this de-poisoning
* effectively corresponds to having a non-null cx on the stack.
*
* In situations where the consumer expects to run script, AutoEntryScript
* should be used, which does additional manipulation of the script settings
* any attempt to run script without an AutoEntryScript on the stack will
* fail. This prevents system code from accidentally triggering script
* execution at inopportune moments via surreptitious getters and proxies.
*/
class MOZ_STACK_CLASS AutoJSAPI : protected ScriptSettingsStackEntry {
public:
// Trivial constructor. One of the Init functions must be called before
// accessing the JSContext through cx().
AutoJSAPI();
~AutoJSAPI();
// This uses the SafeJSContext (or worker equivalent), and enters a null
// compartment, so that the consumer is forced to select a compartment to
// enter before manipulating objects.
//
// This variant will ensure that any errors reported by this AutoJSAPI as it
// comes off the stack will not fire error events or be associated with any
// particular web-visible global.
void Init();
// This uses the SafeJSContext (or worker equivalent), and enters the
// compartment of aGlobalObject.
// If aGlobalObject or its associated JS global are null then it returns
// false and use of cx() will cause an assertion.
//
// If aGlobalObject represents a web-visible global, errors reported by this
// AutoJSAPI as it comes off the stack will fire the relevant error events and
// show up in the corresponding web console.
//
// Successfully initializing the AutoJSAPI will ensure that it enters the
// Realm of aGlobalObject's JSObject and exposes that JSObject to active JS.
[[nodiscard]] bool Init(nsIGlobalObject* aGlobalObject);
// This is a helper that grabs the native global associated with aObject and
// invokes the above Init() with that. aObject must not be a cross-compartment
// wrapper: CCWs are not associated with a single global.
[[nodiscard]] bool Init(JSObject* aObject);
// Unsurprisingly, this uses aCx and enters the compartment of aGlobalObject.
// If aGlobalObject or its associated JS global are null then it returns
// false and use of cx() will cause an assertion.
// If aCx is null it will cause an assertion.
//
// If aGlobalObject represents a web-visible global, errors reported by this
// AutoJSAPI as it comes off the stack will fire the relevant error events and
// show up in the corresponding web console.
[[nodiscard]] bool Init(nsIGlobalObject* aGlobalObject, JSContext* aCx);
// Convenience functions to take an nsPIDOMWindowInner or nsGlobalWindowInner,
// when it is more easily available than an nsIGlobalObject.
[[nodiscard]] bool Init(nsPIDOMWindowInner* aWindow);
[[nodiscard]] bool Init(nsPIDOMWindowInner* aWindow, JSContext* aCx);
[[nodiscard]] bool Init(nsGlobalWindowInner* aWindow);
[[nodiscard]] bool Init(nsGlobalWindowInner* aWindow, JSContext* aCx);
JSContext* cx() const {
MOZ_ASSERT(mCx, "Must call Init before using an AutoJSAPI");
MOZ_ASSERT(IsStackTop());
return mCx;
}
#ifdef DEBUG
bool IsStackTop() const;
#endif
// If HasException, report it. Otherwise, a no-op.
void ReportException();
bool HasException() const {
MOZ_ASSERT(IsStackTop());
return JS_IsExceptionPending(cx());
};
// Transfers ownership of the current exception from the JS engine to the
// caller. Callers must ensure that HasException() is true, and that cx()
// is in a non-null compartment.
//
// Note that this fails if and only if we OOM while wrapping the exception
// into the current compartment.
[[nodiscard]] bool StealException(JS::MutableHandle<JS::Value> aVal);
// As for StealException(), but uses the JS::ExceptionStack class to also
// include the exception's stack, represented by SavedFrames.
[[nodiscard]] bool StealExceptionAndStack(JS::ExceptionStack* aExnStack);
// Peek the current exception from the JS engine, without stealing it.
// Callers must ensure that HasException() is true, and that cx() is in a
// non-null compartment.
//
// Note that this fails if and only if we OOM while wrapping the exception
// into the current compartment.
[[nodiscard]] bool PeekException(JS::MutableHandle<JS::Value> aVal);
void ClearException() {
MOZ_ASSERT(IsStackTop());
JS_ClearPendingException(cx());
}
protected:
// Protected constructor for subclasses. This constructor initialises the
// AutoJSAPI, so Init must NOT be called on subclasses that use this.
AutoJSAPI(nsIGlobalObject* aGlobalObject, bool aIsMainThread, Type aType);
mozilla::Maybe<JSAutoNullableRealm> mAutoNullableRealm;
JSContext* mCx;
// Whether we're mainthread or not; set when we're initialized.
bool mIsMainThread;
Maybe<JS::WarningReporter> mOldWarningReporter;
private:
void InitInternal(nsIGlobalObject* aGlobalObject, JSObject* aGlobal,
JSContext* aCx, bool aIsMainThread);
AutoJSAPI(const AutoJSAPI&) = delete;
AutoJSAPI& operator=(const AutoJSAPI&) = delete;
};
/*
* A class that can be used to force a particular incumbent script on the stack.
*/
class AutoIncumbentScript : protected ScriptSettingsStackEntry {
public:
explicit AutoIncumbentScript(nsIGlobalObject* aGlobalObject);
~AutoIncumbentScript();
private:
JS::AutoHideScriptedCaller mCallerOverride;
};
/*
* A class to put the JS engine in an unusable state. The subject principal
* will become System, the information on the script settings stack is
* rendered inaccessible, and JSAPI may not be manipulated until the class is
* either popped or an AutoJSAPI instance is subsequently pushed.
*
* This class may not be instantiated if an exception is pending.
*/
class AutoNoJSAPI : protected ScriptSettingsStackEntry,
protected JSAutoNullableRealm {
public:
AutoNoJSAPI() : AutoNoJSAPI(danger::GetJSContext()) {}
~AutoNoJSAPI();
private:
// Helper constructor to avoid doing GetJSContext() multiple times
// during construction.
explicit AutoNoJSAPI(JSContext* aCx);
// Stashed JSContext* so we don't need to GetJSContext in our destructor.
// It's probably safe to hold on to this, in the sense that the world should
// not get torn down while we're on the stack, and if it's not, we'd need to
// fix JSAutoNullableRealm to not hold on to a JSContext either, or
// something.
JSContext* mCx;
AutoYieldJSThreadExecution mExecutionYield;
};
} // namespace dom
/**
* Use AutoJSContext when you need a JS context on the stack but don't have one
* passed as a parameter. AutoJSContext will take care of finding the most
* appropriate JS context and release it when leaving the stack.
*/
class MOZ_RAII AutoJSContext {
public:
explicit AutoJSContext();
operator JSContext*() const;
protected:
JSContext* mCx;
dom::AutoJSAPI mJSAPI;
};
/**
* AutoSafeJSContext is similar to AutoJSContext but will only return the safe
* JS context. That means it will never call
* nsContentUtils::GetCurrentJSContext().
*
* Note - This is deprecated. Please use AutoJSAPI instead.
*/
class MOZ_RAII AutoSafeJSContext : public dom::AutoJSAPI {
public:
explicit AutoSafeJSContext();
operator JSContext*() const { return cx(); }
private:
};
/**
* Use AutoSlowOperation when native side calls many JS callbacks in a row
* and slow script dialog should be activated if too much time is spent going
* through those callbacks.
* AutoSlowOperation puts an AutoScriptActivity on the stack so that we don't
* continue to reset the watchdog. CheckForInterrupt can then be used to check
* whether JS execution should be interrupted.
* This class (including CheckForInterrupt) is a no-op when used off the main
* thread.
*/
class MOZ_RAII AutoSlowOperation {
public:
explicit AutoSlowOperation();
void CheckForInterrupt();
private:
bool mIsMainThread;
Maybe<xpc::AutoScriptActivity> mScriptActivity;
};
/**
* A class to disable interrupt callback temporary.
*/
class MOZ_RAII AutoDisableJSInterruptCallback {
public:
explicit AutoDisableJSInterruptCallback(JSContext* aCx)
: mCx(aCx), mOld(JS_DisableInterruptCallback(aCx)) {}
~AutoDisableJSInterruptCallback() { JS_ResetInterruptCallback(mCx, mOld); }
private:
JSContext* mCx;
bool mOld;
};
/**
* A helper class which allows to allow-list legacy callers executing script
* in the AutoEntryScript constructor. The goal is to remove these exceptions
* one by one. Do not add a new one without review from a DOM peer.
*/
class MOZ_RAII AutoAllowLegacyScriptExecution {
public:
AutoAllowLegacyScriptExecution();
~AutoAllowLegacyScriptExecution();
static bool IsAllowed();
private:
static int sAutoAllowLegacyScriptExecution;
};
} // namespace mozilla
#endif // mozilla_dom_ScriptSettings_h