/*

 * Copyright (C) 2009 Google Inc. All rights reserved.

 * 

 * Redistribution and use in source and binary forms, with or without

 * modification, are permitted provided that the following conditions are

 * met:

 * 

 *     * Redistributions of source code must retain the above copyright

 * notice, this list of conditions and the following disclaimer.

 *     * Redistributions in binary form must reproduce the above

 * copyright notice, this list of conditions and the following disclaimer

 * in the documentation and/or other materials provided with the

 * distribution.

 *     * Neither the name of Google Inc. nor the names of its

 * contributors may be used to endorse or promote products derived from

 * this software without specific prior written permission.

 * 

 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS

 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT

 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR

 * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT

 * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,

 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT

 * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,

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 */

#include "config.h"

#include "BindingSecurityBase.h"

#include "DOMWindow.h"

#include "Frame.h"

#include "SecurityOrigin.h"

namespace WebCore {

DOMWindow* BindingSecurityBase::getDOMWindow(Frame* frame)

{

    return frame->domWindow();

}

Frame* BindingSecurityBase::getFrame(Node* node)

{

    return node->document()->frame();

}

// Same origin policy implementation:

//

// Same origin policy prevents JS code from domain A from accessing JS & DOM

// objects in a different domain B. There are exceptions and several objects

// are accessible by cross-domain code. For example, the window.frames object

// is accessible by code from a different domain, but window.document is not.

//

// The JS binding code sets security check callbacks on a function template,

// and accessing instances of the template calls the callback function.

// The callback function enforces the same origin policy.

//

// Callback functions are expensive. Binding code should use a security token

// string to do fast access checks for the common case where source and target

// are in the same domain. A security token is a string object that represents

// the protocol/url/port of a domain.

//

// There are special cases where security token matching is not enough.

// For example, JS can set its domain to a super domain by calling

// document.setDomain(...). In these cases, the binding code can reset

// a context's security token to its global object so that the fast access

// check will always fail.

// Helper to check if the current execution context can access a target frame.

// First it checks same domain policy using the lexical context.

//

// This is equivalent to KJS::Window::allowsAccessFrom(ExecState*).

bool BindingSecurityBase::canAccess(DOMWindow* activeWindow,

                                    DOMWindow* targetWindow)

{

    ASSERT(targetWindow);

    String message;

    if (activeWindow == targetWindow)

        return true;

    if (!activeWindow)

        return false;

    const SecurityOrigin* activeSecurityOrigin = activeWindow->securityOrigin();

    const SecurityOrigin* targetSecurityOrigin = targetWindow->securityOrigin();

    // We have seen crashes were the security origin of the target has not been

    // initialized. Defend against that.

    if (!targetSecurityOrigin)

        return false;

    if (activeSecurityOrigin->canAccess(targetSecurityOrigin))

        return true;

    // Allow access to a "about:blank" page if the dynamic context is a

    // detached context of the same frame as the blank page.

    if (targetSecurityOrigin->isEmpty() && activeWindow->frame() == targetWindow->frame())

        return true;

    return false;

}

} // namespace WebCore