Friday, July 13, 2007


There have been times during LoadRunner scripting that I needed to see the low-level HTTP request that is being sent from my client (which I am using to record, e.g., a browser, or a custom client) to the server. Earlier, I used Ethereal ( successfully but the problem is that it doesn't support SSL directly. So if the communication is over SSL, all I would see is encrypted data and there was no way to see the headers/data being transferred. This made me look for alternatives. I recently came across WebScarab and I wouldn't say it's free of bugs but I'm sticking with this tool for as far as I can see in future. Here's how I was able to solve some of the problems in LoadRunner scripting using this tool.

Solution 1: (SSL Intercept)
First things first, WebScarab proxy
is able to observe both HTTP and encrypted HTTPS traffic, by negotiating an SSL connection between WebScarab and the browser instead of simply connecting the browser to the server and allowing an encrypted stream to pass through it.
This is a major advantage. So I no longer have to hope that one of the test environments will not have SSL implemented and will let me observe the non-SSL HTTP traffic. Watching browser traffic was just as easy as starting the WebScrarab proxy and pointing the browser to the local proxy. It gives the options to intercept request and/or responses and lets you modify the requests in any way before passing them on the server. For a custom client, I can capture the exact headers being sent and add them to my web_custom_request:
    web_add_header("Cache-Control", "no-cache");
web_add_header("SOAPAction", "\"\"");
web_add_header("Accept-Encoding", "gzip, deflate");

And I can also copy the body if it's an HTTP XML post for example, to get the exact XML data being sent and put that in the body of the request:
"EncType=text/xml; charset=utf-8",

and so on. See screenshot.

Solution 2: (Reverse Proxy/Act as a web server)
As it happened, the client I was using (for more details on this, see my previous post) had pre-configured options of selecting the URL. So I didn't have any way to point the client to the local WebScarab proxy. I looked through the help contents and found this:
WebScarab allows you to specify a "base address" for a Listener. The base address instructs the Listener to operate as a reverse proxy, and should be formatted as a HTTP or HTTPS URL. In this mode, it will act as a web server, rather than as a proxy server, and will construct the URL by concatenating the base URL and the path that appears in the request line. If the base URL is an HTTPS URL, it will immediately negotiate an SSL tunnel prior to trying to read the request from the browser. This is useful for the situation where you are using a custom HTTP-based client that does not support configuring an upstream proxy. Simply change the hosts file on the computer on which the custom client is running to point the site in question to the computer on which WebScarab is running on, and WebScarab will receive requests for the targeted website.
This meant that I could use the hosts file to point to the proxy and specify the base address in the proxy listener to intercept the requests. In a few tries, I was able to intercept the SSL requests over a non-local base address. Again, I could get the headers and body and use it in the web_custom_request. See screenshot.

Solution 3: (SSL Server Certificate)
Another client that I was recording my script against had a similar issue. The client didn't support pointing to an upstream proxy so I configured the hosts file to point to the listener proxy. However when running the client, it threw this exception:

{} PKIX path building failed: unable to find valid certification path to requested target.

I tried adding the WebScarab certificate to the keystore through Java Control Panel but no luck. After googling a little more, I came across this forum thread:
Apparently, Java uses its default keystore and to use another keystore, it has to be created and provided in one of the arguments. So after importing the WebScarab certificates into IE trusted certificates and then exporting it into .cer, creating a keystore with the certificates and modifying the batch run file to add

I had my fingers crossed when running the client again. But fortunately, this time it worked as expected and intercepted the HTTPS requests without any errors. Once again, I used the custom headers and the XML body to create LR web_custom_header request.


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