Security  - AS3

Determines how Flash Player or AIR chooses the domain to use for certain content settings, including settings for camera and microphone permissions, storage quotas, and storage of persistent shared objects. To have the SWF file use the same settings that were used in Flash Player 6, set exactSettings to false.

In Flash Player 6, the domain used for these player settings was based on the trailing portion of the domain of the SWF file. If the domain of a SWF file includes more than two segments, such as www.example.com, the first segment of the domain ("www") is removed, and the remaining portion of the domain is used: example.com. So, in Flash Player 6, www.example.com and store.example.com both use example.com as the domain for these settings. Similarly, www.example.co.uk and store.example.co.uk both use example.co.uk as the domain for these settings. In Flash Player 7 and later, player settings are chosen by default according to a SWF file's exact domain; for example, a SWF file from www.example.com would use the player settings for www.example.com, and a SWF file from store.example.com would use the separate player settings for store.example.com.

When Security.exactSettings is set to true, Flash Player or AIR uses exact domains for player settings. The default value for exactSettings is true. If you change exactSettings from its default value, do so before any events occur that require Flash Player or AIR to choose player settings — for example, using a camera or microphone, or retrieving a persistent shared object.

If you previously published a version 6 SWF file and created persistent shared objects from it, and you now need to retrieve those persistent shared objects from that SWF file after porting it to version 7 or later, or from a different SWF file of version 7 or later, set Security.exactSettings to false before calling SharedObject.getLocal().

The domain portion of the HTML page containing the swf.

For security reasons, the method does not return the full URL, only the page domain, such as http://www.example.com. If this SWF is not contained in an HTML page, or cannot access the page domain for security reasons, this property returns the string, undefined.

Indicates the type of security sandbox in which the calling file is operating.

Security.sandboxType has one of the following values:

• remote (Security.REMOTE)—This file is from an Internet URL and operates under domain-based sandbox rules.
• localWithFile (Security.LOCAL_WITH_FILE)—This file is a local file, has not been trusted by the user, and it is not a SWF file that was published with a networking designation. The file may read from local data sources but may not communicate with the Internet.
• localWithNetwork (Security.LOCAL_WITH_NETWORK)—This SWF file is a local file, has not been trusted by the user, and was published with a networking designation. The SWF file can communicate with the Internet but cannot read from local data sources.
• localTrusted (Security.LOCAL_TRUSTED)—This file is a local file and has been trusted by the user, using either the Flash Player Settings Manager or a FlashPlayerTrust configuration file. The file can read from local data sources and communicate with the Internet.
• application (Security.APPLICATION)—This file is running in an AIR application, and it was installed with the package (AIR file) for that application. By default, files in the AIR application sandbox can cross-script any file from any domain (although files outside the AIR application sandbox may not be permitted to cross-script the AIR file). By default, files in the AIR application sandbox can load content and data from any domain.

For more information related to security, see the Flash Player Developer Center Topic: Security.

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Lets SWF files in the identified domains access objects and variables in the SWF file that contains the allowDomain() call.

Note: Calling this method from code in the AIR application sandbox throws a SecurityError exception. Content outside of the application security domain cannot directly cross-script content in the application sandbox. However, content outside of the application sandbox can communicate with content in the application security sandbox using a sandbox bridge.

If two SWF files are served from the same domain — for example, http://mysite.com/swfA.swf and http://mysite.com/swfB.swf — then swfA.swf can examine and modify variables, objects, properties, methods, and so on in swfB.swf, and swfB.swf can do the same for swfA.swf. This is called cross-movie scripting or cross-scripting.

If two SWF files are served from different domains — for example, http://siteA.com/swfA.swf and http://siteB.com/siteB.swf — then, by default, Flash Player does not allow swfA.swf to script swfB.swf, nor swfB.swf to script swfA.swf. A SWF file gives permission to SWF files from other domains by calling Security.allowDomain(). This is called cross-domain scripting. By calling Security.allowDomain("siteA.com"), siteB.swf gives siteA.swf permission to script it.

In any cross-domain situation, it is important to be clear about the two parties involved. For the purposes of this discussion, the side performing the cross-scripting is called the accessing party (usually the accessing SWF), and the other side is called the party being accessed (usually the SWF file being accessed). When siteA.swf scripts siteB.swf, siteA.swf is the accessing party, and siteB.swf is the party being accessed.

Cross-domain permissions that are established with allowDomain() are asymmetrical. In the previous example, siteA.swf can script siteB.swf, but siteB.swf cannot script siteA.swf, because siteA.swf has not called allowDomain() to give SWF files at siteB.com permission to script it. You can set up symmetrical permissions by having both SWF files call allowDomain().

In addition to protecting SWF files from cross-domain scripting originated by other SWF files, Flash Player protects SWF files from cross-domain scripting originated by HTML files. HTML-to-SWF scripting can occur with older browser functions such as SetVariable or callbacks established through ExternalInterface.addCallback(). When HTML-to-SWF scripting crosses domains, the SWF file being accessed must call allowDomain(), just as when the accessing party is a SWF file, or the operation will fail.

Specifying an IP address as a parameter to allowDomain() does not permit access by all parties that originate at the specified IP address. Instead, it permits access only by a party that contains the specified IP address it its URL, rather than a domain name that maps to that IP address.

Version-specific differences

Flash Player's cross-domain security rules have evolved from version to version. The following table summarizes the differences.

The versions that control the behavior of Flash Player are SWF versions (the published version of a SWF file), not the version of Flash Player itself. For example, when Flash Player 8 is playing a SWF file published for version 7, it applies behavior that is consistent with version 7. This practice ensures that player upgrades do not change the behavior of Security.allowDomain() in deployed SWF files.

The version column in the previous table shows the latest SWF version involved in a cross-scripting operation. Flash Player determines its behavior according to either the accessing SWF file's version or the version of the SWF file that is being accessed, whichever is later.

The following paragraphs provide more detail about Flash Player security changes involving Security.allowDomain().

Version 5. There are no cross-domain scripting restrictions.

Version 6. Cross-domain scripting security is introduced. By default, Flash Player forbids cross-domain scripting; Security.allowDomain() can permit it. To determine whether two files are in the same domain, Flash Player uses each file's superdomain, which is the exact host name from the file's URL, minus the first segment, down to a minimum of two segments. For example, the superdomain of www.mysite.com is mysite.com. SWF files from www.mysite.com and store.mysite.com to script each other without a call to Security.allowDomain().

Version 7. Superdomain matching is changed to exact domain matching. Two files are permitted to script each other only if the host names in their URLs are identical; otherwise, a call to Security.allowDomain() is required. By default, files loaded from non-HTTPS URLs are no longer permitted to script files loaded from HTTPS URLs, even if the files are loaded from exactly the same domain. This restriction helps protect HTTPS files, because a non-HTTPS file is vulnerable to modification during download, and a maliciously modified non-HTTPS file could corrupt an HTTPS file, which is otherwise immune to such tampering. Security.allowInsecureDomain() is introduced to allow HTTPS SWF files that are being accessed to voluntarily disable this restriction, but the use of Security.allowInsecureDomain() is discouraged.

Version 8. There are two major areas of change:

• Calling Security.allowDomain() now permits cross-scripting operations only if the SWF file being accessed is the SWF file that called Security.allowDomain(). In other words, a SWF file that calls Security.allowDomain() now permits access only to itself. In previous versions, calling Security.allowDomain() permitted cross-scripting operations where the SWF file being accessed could be any SWF file in the same domain as the SWF file that called Security.allowDomain(). Calling Security.allowDomain() previously opened up the entire domain of the calling SWF file.
• Support has been added for wildcard values with Security.allowDomain("*") and Security.allowInsecureDomain("*"). The wildcard (*) value permits cross-scripting operations where the accessing file is any file at all, loaded from anywhere. Think of the wildcard as a global permission. Wildcard permissions are required to enable certain kinds of operations under the local file security rules. Specifically, for a local SWF file with network-access permissions to script a SWF file on the Internet, the Internet SWF file being accessed must call Security.allowDomain("*"), reflecting that the origin of a local SWF file is unknown. (If the Internet SWF file is loaded from an HTTPS URL, the Internet SWF file must instead call Security.allowInsecureDomain("*").)

Occasionally, you may encounter the following situation: You load a child SWF file from a different domain and want to allow the child SWF file to script the parent SWF file, but you don't know the final domain of the child SWF file. This can happen, for example, when you use load-balancing redirects or third-party servers.

In this situation, you can use the url property of the URLRequest object that you pass to Loader.load(). For example, if you load a child SWF file into a parent SWF, you can access the contentLoaderInfo property of the Loader object for the parent SWF:

Security.allowDomain(loader.contentLoaderInfo.url)

Make sure that you wait until the child SWF file begins loading to get the correct value of the url property. To determine when the child SWF has begun loading, use the progress event.

The opposite situation can also occur; that is, you might create a child SWF file that wants to allow its parent to script it, but doesn't know what the domain of its parent will be. In this situation, you can access the loaderInfo property of the display object that is the SWF's root object. In the child SWF, call Security.allowDomain( this.root.loaderInfo.loaderURL). You don't have to wait for the parent SWF file to load; the parent will already be loaded by the time the child loads.

If you are publishing for Flash Player 8 or later, you can also handle these situations by calling Security.allowDomain("*"). However, this can sometimes be a dangerous shortcut, because it allows the calling SWF file to be accessed by any other SWF file from any domain. It is usually safer to use the _url property.

For more information related to security, see the Flash Player Developer Center Topic: Security.

Parameters

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Lets SWF files and HTML files in the identified domains access objects and variables in the calling SWF file, which is hosted by means of the HTTPS protocol.

Flash Player provides allowInsecureDomain() to maximize flexibility, but calling this method is not recommended. Serving a file over HTTPS provides several protections for you and your users, and calling allowInsecureDomain weakens one of those protections.

Note: Calling this method from code in the AIR application sandbox throws a SecurityError exception. Content outside of the application security domain cannot directly cross-script content in the application sandbox. However, content outside of the application sandbox can communicate with content in the application security sandbox using a sandbox bridge.

This method works in the same way as Security.allowDomain(), but it also permits operations in which the accessing party is loaded with a non-HTTPS protocol, and the party being accessed is loaded with HTTPS. In Flash Player 7 and later, non-HTTPS files are not allowed to script HTTPS files. The allowInsecureDomain() method lifts this restriction when the HTTPS SWF file being accessed uses it.

Use allowInsecureDomain() only to enable scripting from non-HTTPS files to HTTPS files. Use it to enable scripting when the accessing non-HTTPS file and the HTTPS file being accessed are served from the same domain, for example, if a SWF file at http://mysite.com wants to script a SWF file at https://mysite.com. Do not use this method to enable scripting between non-HTTPS files, between HTTPS files, or from HTTPS files to non-HTTPS files. For those situations, use allowDomain() instead.

Note that the following information is only one possible scenario, designed to help you understand allowInsecureDomain() through a real-world example of cross-scripting. It does not cover all issues with security architecture and should be used for background information only. The Flash Player Developer Center contains extensive information on Flash Player and security. For more information, see the Flash Player Developer Center Topic Security.

Suppose you are building an e-commerce site that consists of two components: a catalog, which does not need to be secure, because it contains only public information; and a shopping cart/checkout component, which must be secure to protect users' financial and personal information. Suppose you are considering serving the catalog from http://mysite.com/catalog.swf and the cart from https://mysite.com/cart.swf. One requirement for your site is that a third party should not be able to steal your users' credit card numbers by taking advantage of a weakness in your security architecture.

Suppose that a middle-party attacker intervenes between your server and your users, attempting to steal the credit card numbers that your users enter into your shopping cart application. A middle party might, for example, be an unscrupulous ISP used by some of your users, or a malicious administrator at a user's workplace — anyone who has the ability to view or alter network packets transmitted over the public Internet between your users and your servers. This situation is not uncommon.

If cart.swf uses HTTPS to transmit credit card information to your servers, then the middle-party attacker can't directly steal this information from network packets, because the HTTPS transmission is encrypted. However, the attacker can use a different technique: altering the contents of one of your SWF files as it is delivered to the user, replacing your SWF file with an altered version that transmits the user's information to a different server, owned by the attacker.

The HTTPS protocol, among other things, prevents this "modification" attack from working, because, in addition to being encrypted, HTTPS transmissions are tamper-resistant. If a middle-party attacker alters a packet, the receiving side detects the alteration and discards the packet. So the attacker in this situation can't alter cart.swf, because it is delivered over HTTPS.

However, suppose that you want to allow buttons in catalog.swf, served over HTTP, to add items to the shopping cart in cart.swf, served over HTTPS. To accomplish this, cart.swf calls allowInsecureDomain(), which allows catalog.swf to script cart.swf. This action has an unintended consequence: Now the attacker can alter catalog.swf as it is initially being downloaded by the user, because catalog.swf is delivered with HTTP and is not tamper-resistant. The attacker's altered catalog.swf can now script cart.swf, because cart.swf contains a call to allowInsecureDomain(). The altered catalog.swf file can use ActionScript to access the variables in cart.swf, thus reading the user's credit card information and other sensitive data. The altered catalog.swf can then send this data to an attacker's server.

Obviously, this implementation is not desired, but you still want to allow cross-scripting between the two SWF files on your site. Here are two possible ways to redesign this hypothetical e-commerce site to avoid allowInsecureDomain():

• Serve all SWF files in the application over HTTPS. This is by far the simplest and most reliable solution. In the scenario described, you would serve both catalog.swf and cart.swf over HTTPS. You might experience slightly higher bandwidth consumption and server CPU load when switching a file such as catalog.swf from HTTP to HTTPS, and your users might experience slightly longer application load times. You need to experiment with real servers to determine the severity of these effects; usually they are no worse than 10-20% each, and sometimes they are not present at all. You can usually improve results by using HTTPS-accelerating hardware or software on your servers. A major benefit of serving all cooperating SWF files over HTTPS is that you can use an HTTPS URL as the main URL in the user's browser without generating any mixed-content warnings from the browser. Also, the browser's padlock icon becomes visible, providing your users with a common and trusted indicator of security.
• Use HTTPS-to-HTTP scripting, rather than HTTP-to-HTTPS scripting. In the scenario described, you could store the contents of the user's shopping cart in catalog.swf, and have cart.swf manage only the checkout process. At checkout time, cart.swf could retrieve the cart contents from ActionScript variables in catalog.swf. The restriction on HTTP-to-HTTPS scripting is asymmetrical; although an HTTP-delivered catalog.swf file cannot safely be allowed to script an HTTPS-delivered cart.swf file, an HTTPS cart.swf file can script the HTTP catalog.swf file. This approach is more delicate than the all-HTTPS approach; you must be careful not to trust any SWF file delivered over HTTP, because of its vulnerability to tampering. For example, when cart.swf retrieves the ActionScript variable that describes the cart contents, the ActionScript code in cart.swf cannot trust that the value of this variable is in the format that you expect. You must verify that the cart contents do not contain invalid data that might lead cart.swf to take an undesired action. You must also accept the risk that a middle party, by altering catalog.swf, could supply valid but inaccurate data to cart.swf; for example, by placing items in the user's cart. The usual checkout process mitigates this risk somewhat by displaying the cart contents and total cost for final approval by the user, but the risk remains present.

Web browsers have enforced separation between HTTPS and non-HTTPS files for years, and the scenario described illustrates one good reason for this restriction. Flash Player gives you the ability to work around this security restriction when you absolutely must, but be sure to consider the consequences carefully before doing so.

For more information related to security, see the Flash Player Developer Center Topic: Security.

Parameters

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Looks for a policy file at the location specified by the url parameter. Adobe AIR and Flash Player use policy files to determine whether to permit applications to load data from servers other than their own. Note that even though the method name is loadPolicyFile(), the file isn't actually loaded until a network request that requires a policy file is made.

With Security.loadPolicyFile(), Flash Player or AIR can load policy files from arbitrary locations, as shown in the following example:

     Security.loadPolicyFile("http://www.example.com/sub/dir/pf.xml");
     

This causes Flash Player or AIR to attempt to retrieve a policy file from the specified URL. Any permissions granted by the policy file at that location will apply to all content at the same level or lower in the virtual directory hierarchy of the server.

For example, following the previous code, these lines do not throw an exception:

 import flash.net.*;
     var request:URLRequest = new URLRequest("http://www.example.com/sub/dir/vars.txt");
     var loader:URLLoader = new URLLoader();
     loader.load(request);
     
     var loader2:URLLoader = new URLLoader();
     var request2:URLRequest = new URLRequest("http://www.example.com/sub/dir/deep/vars2.txt");
     loader2.load(request2);
     

However, the following code does throw a security exception:

 import flash.net.*;
     var request3:URLRequest = new URLRequest("http://www.example.com/elsewhere/vars3.txt");
     var loader3:URLLoader = new URLLoader();
     loader3.load(request3);
     

You can use loadPolicyFile() to load any number of policy files. When considering a request that requires a policy file, Flash Player or AIR always waits for the completion of any policy file downloads before denying a request. As a final fallback, if no policy file specified with loadPolicyFile() authorizes a request, Flash Player or AIR consults the original default locations.

When checking for a master policy file, Flash Player waits three seconds for a server response. If a response isn't received, Flash Player assumes that no master policy file exists. However, there is no default timeout value for calls to loadPolicyFile(); Flash Player assumes that the file being called exists, and waits as long as necessary to load it. Therefore, if you want to make sure that a master policy file is loaded, use loadPolicyFile() to call it explicitly.

You cannot connect to commonly reserved ports. For a complete list of blocked ports, see "Restricting Networking APIs" in the ActionScript 3.0 Developer's Guide.

Using the xmlsocket protocol along with a specific port number lets you retrieve policy files directly from an XMLSocket server, as shown in the following example. Socket connections are not subject to the reserved port restriction described above.

     Security.loadPolicyFile("xmlsocket://foo.com:414");
     

This causes Flash Player or AIR to attempt to retrieve a policy file from the specified host and port. Upon establishing a connection with the specified port, Flash Player or AIR transmits <policy-file-request />, terminated by a null byte. The server must send a null byte to terminate a policy file, and may thereafter close the connection; if the server does not close the connection, Flash Player or AIR does so upon receiving the terminating null byte.

You can prevent a SWF file from using this method by setting the allowNetworking parameter of the object and embed tags in the HTML page that contains the SWF content.

For more information related to security, see the Flash Player Developer Center Topic: Security.

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Displays the Security Settings panel in Flash Player. This method does not apply to content in Adobe AIR; calling it in an AIR application has no effect.

Parameters

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The file is running in an AIR application, and it was installed with the package (the AIR file) for that application. This content is included in the AIR application resource directory (where the application content is installed).

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The file is a local file and has been trusted by the user, using either the Flash Player Settings Manager or a FlashPlayerTrust configuration file. The file can read from local data sources and communicate with the Internet.

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The file is a local file, has not been trusted by the user, and it is not a SWF file that was published with a networking designation. In Adobe AIR, the local file is not in the application resource directory; such files are put in the application security sandbox. The file may read from local data sources but may not communicate with the Internet.

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The file is a local file, has not been trusted by the user, and it is a SWF file that was published with a networking designation. The file can communicate with the Internet but cannot read from local data sources.

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The file is from an Internet URL and operates under domain-based sandbox rules.

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