有没有一种方法可以检查SWF以查看其使用的RSL？

Question

I'm investigating an issue with a Flex app that is attempting to download (at least) one of the Flex framework RSLs from an unexpected URL. I'm unable to reproduce the issue, but I'm also a bit uncertain about some aspects of the RSL specification in my mxmlc build configuration.

Given all that, it would be helpful to be able to inspect the SWF file that lists the RSL dependencies to see exactly what dependencies are present, and the URLs associated therewith.

Is there a method for doing so? I've tried Adobe's SWF Investigator, but I didn't see any obvious place where such dependencies are called out. (I guess they're handled by code generated by mxmlc rather than natively by Flash Player, so they aren't listed as attributes of the SWF?)

The app is built with/against Flex 4.6, FWIW.

Answer 1

I haven't located a tool to do this in an automated fashion, but I've found that it's easy enough to find the information by studying the disassembled version of a SWF, available using Adobe's SWF Investigator tool .

To do so, load a SWF that specifies RSL dependencies into SWF Investigator, then view the disassembled code on the 'SWF Disassembler' tab (easiest to pop open an external editor using the 'Open with text view...' button).

The RSL dependencies are specified in the definition of the SWF's info() function, a block beginning with something like this:

 function info():Object /* disp_id=0 method_id=57 nameIndex = 75 */

Cross-domain RSL dependencies are listed in a cdRsls property, and others in an rsls property. These lists are populated with a number of RSLData objects, and it's easy to see the parameters to the RSLData constructor being pushed onto the stack. For example, the following section adds two possible URLs to retrieve the Flex 4.6 'framework' library:

   13   findpropstrict  mx.core::RSLData //nameIndex = 6
   15   pushstring      "http://fpdownload.adobe.com/pub/swz/flex/4.6.0.23201/framework_4.6.0.23201.swz"
   18   pushstring      "http://fpdownload.adobe.com/pub/swz/crossdomain.xml"
   21   pushstring      "abd49354324081cebb8f60184cf5fee81f0f9298e64dbec968c96d68fe16c437"
   24   pushstring      "SHA-256"
   27   pushtrue        
   28   pushtrue        
   29   pushstring      "default"
   31   constructprop   mx.core::RSLData (7) //nameIndex = 6
   34   findpropstrict  mx.core::RSLData //nameIndex = 6
   36   pushstring      "framework_4.6.0.23201.swz"
   39   pushstring      ""
   41   pushstring      "abd49354324081cebb8f60184cf5fee81f0f9298e64dbec968c96d68fe16c437"
   44   pushstring      "SHA-256"
   47   pushtrue        
   48   pushtrue        
   49   pushstring      "default"
   51   constructprop   mx.core::RSLData (7) //nameIndex = 6
   54   newarray        [2]

The newarray [2] line at the bottom appears to indicate that these represent two possible locations for the same file (ie, a fallback URL). If a single URL was provided, there would be a single RSLData object created, and a newarray [1] line.

This code corresponds to the following definitions from the standard flex-config.xml file bundled with the Flex SDK:

  <!-- Framework SWC -->
<runtime-shared-library-path>
    <path-element>libs/framework.swc</path-element>
    <rsl-url>http://fpdownload.adobe.com/pub/swz/flex/4.6.0.23201/framework_4.6.0.23201.swz</rsl-url>
    <policy-file-url>http://fpdownload.adobe.com/pub/swz/crossdomain.xml</policy-file-url>
    <rsl-url>framework_4.6.0.23201.swz</rsl-url>
    <policy-file-url></policy-file-url>
</runtime-shared-library-path>

Finally, for reference, here is the signature of the constructor for the RSLData class, to see what parameters the values correspond to:

public function RSLData(rslURL:String = null, 
                        policyFileURL:String = null, 
                        digest:String = null, 
                        hashType:String = null, 
                        isSigned:Boolean = false, 
                        verifyDigest:Boolean = false,
                        applicationDomainTarget:String = "default")