Using tshark to Decrypt SSL/TLS Packets

I’m going to walk you through the process of decoding SSL/TLS traffic from a pcap file with the server’s private key using tshark (command-line version of Wireshark). You can, of course, always use ssldump for the same purpose.

I assume you know how SSL/TLS works, and basic understanding of how Wireshark works, and why we use it.

I will start with getting a sample encrypted traffic that includes the handshake part (important for decryption later). For that purpose, we are going to use openssl command to generate a pair of server certificate and key. And then run the HTTPS server with openssl’s s_server command on port 4443 (or any other port you may like) using the generated certificate and key. Then we will issue a GET request to HTTPS server via curl. In the mean time, we will collect the traffic with tshark and will save the data into ssltest.pcap file.

At this point, we should have the file called ssltest.pcap from tshark, and server.crt/server.pem from openssl commands.

Next, we are going to read the pcap file and decode the traffic.

In Wireshark GUI, we can follow “SSL stream” that will dump the ASCII output from the stream. How are we going to do it with tshark?

You will see the output similar to below:

Running WordPress with Nginx on ArchLinux

I just moved this blog over to Nginx server from Apache httpd server. I’m pretty satisfied with the overall result. I had to take some time to convert my current httpd configuration over to Nginx, since the new server does not support .htaccess or mod_redirects. This is my current requirements for move over:

  • The site is available on both HTTP and HTTPS.
  • “wp-admin” session is forced to use SSL.
  • I have “quicklook” (to check my server status) and “webalizer” directories under the blog, and they are protected by HTTP BasicAuth.
  • HTTP BasicAuth is to be carried out via SSL.
  • To enforce gzip compression on HTTP connection while disabling it on HTTPS.

Basically I followed the ArchLinux wiki for the implementation, and I will briefly describe what I did.

Nginx (pronounced “Engine X”) is a light-weight open-source http server. Its low resource consumption is the primary purpose for the moveover, and it’s suitable for my server on the cloud.

Firstly, I needed to install the package. And installed “php-cgi” package which is used to provide fastcgi interface to PHP.

Then, I configured fastcgi daemon, and add it to rc.d. So the following script was needed to be added to /etc/rc.d as “fastcgi”

And I gave it an executable permission:

What that script does is to have php-cgi process to listen on port 9000. Now, we would be able to start/stop/restart the daemon with “sudo /etc/rc.d/fastcgi start”. But the script will not be automatically started when the unit is rebooted. It needs to be added to /etc/rc.conf. So I added fastcgi to the rc.conf. Here’s the snippet.

Then I edited the /etc/nginx/conf/nginx.conf file to point to my blog physical directory. We need to add two servers, one for HTTP and one for HTTPS. This is my sample configuration for server myfineblog.local

Line 3 defines the server name (so we can configure virtual hosts based on names).
Line 4-5 defines the access logs for this web site.
Line 6 is the physical location of the web site on local system.
Line 7 is used to turn on gzip.
Line 9-11 is redirect to SSL by sending HTTP redirect if the uri contains any of wp-admin or quicklook or webalizer)
Line 13-21 is the definition of website directory and an equivalent scripts for Apache’s mod_rewrite.
Line 23-29 is the connection to the fastcgi daemon we configured above. It is *important* to change the SCRIPT_FILENAME variable to suit the real physical path of the wordpress script.

To enable SSL server, I assume we already have the certificate and key for the website. The configuration looks the same but it will have SSL options enabled and Basic HTTPAuth section for a certain directories.

This configuration turned on “SSL”, disabling SSLv2 and weak ciphers. It enabled HTTP Basic Authentication for two directories. I disabled gzip on SSL stream. And it tells the fastcgi server to turn HTTPS on.

And started the daemons with “/etc/rc.d/fastcgi start” and “/etc/rc.d/nginx start”.

SSL and HTTP Basic Authentication

In general, when I want to force the browser to access certain part of my website via https if the request is made with http, I would put a .htaccess inside that web directory.

But when I want to protect the directory with HTTP Basic Auth, it creates double authentication. I’ll expand this section after I captures the headers.

As a quick workaround, I use this hack in .htaccess