Capturing HTTPS traffic in the clear?

Question

I've got a local application (which I didn't write, and can't change) that talks to a remote web service. It uses HTTPS, and I'd like to see what's in the traffic.

Is there any way I can do this? I'd prefer a Windows system, but I'm happy to set up a proxy on Linux if this makes things easier.

What I'm considering:

1. Redirecting the web site by hacking my hosts file (or setting up alternate DNS).
2. Installing an HTTPS server on that site, with a self-signed (but trusted) certificate.
3. Apparently, WireShark can see what's in HTTPS if you feed it the private key. I've never tried this.
4. Somehow, proxy this traffic to the real server (i.e. it's a full-blown man-in-the-middle "attack").

Does this sound sensible? Can WireShark really see what's in HTTPS traffic? Can anyone point me at a suitable proxy (and configuration for same)?

Answer 1

You should also consider Charles. From the product description at the time of this answer:

Charles is an HTTP proxy / HTTP monitor / Reverse Proxy that enables a developer to view all of the HTTP and SSL / HTTPS traffic between their machine and the Internet. This includes requests, responses and the HTTP headers (which contain the cookies and caching information).

Answer 2

You need to setup a proxy for your local application and if it doesnt honour proxy settings, put a transparent proxy and route all https traffic into it before going outside. Something like this can be the "man" in the middle: http://crypto.stanford.edu/ssl-mitm

Also, here's brief instructions on how to archive this with wireshark: http://predev.wikidot.com/decrypt-ssl-traffic

Answer 3

1. For using https proxy to monitor, it depends on the type of handshake. If you local application does not check the server's certificate by CA's signature which you can not fake, and the server does not check your local application's certificate ( or if you have one to setup on https proxy) then you can set up a https proxy to monitor the https traffic. Otherwise, I think it is impossible to monitor traffic with https proxy.

2. Another way you can try is to add instrumentation probe at the routines of your client program where it send and receive messages from its https library. It needs some reverse engineering work, but should work for you for all situations.

Answer 4

Wireshark can definitely display TLS/SSL encrypted streams as plaintext. However, you will definitely need the private key of the server to do so. The private key must be added to Wireshark as an SSL option under preferences. Note that this only works if you can follow the SSL stream from the start. It will not work if an SSL connection is reused.

For Internet Explorer this (SSL session reuse) can be avoided by clearing the SSL state using the Internet Options dialog. Other environments may require restarting a browser or even rebooting a system (to avoid SSL session reuse).

The other key constraint is that an RSA cipher must be used. Wireshark can not decode TLS/SSL stream that use DFH (Diffie-Hellman).

Assuming you can satisfy the constraints above, the "Follow SSL Stream" right-click command works rather well.

Answer 5

Does Fiddler do what you want?

What is Fiddler?

Fiddler is a Web Debugging Proxy which logs all HTTP(S) traffic between your computer and the Internet. Fiddler allows you to inspect all HTTP(S) traffic, set breakpoints, and "fiddle" with incoming or outgoing data. Fiddler includes a powerful event-based scripting subsystem, and can be extended using any .NET language.

Fiddler is freeware and can debug traffic from virtually any application, including Internet Explorer, Mozilla Firefox, Opera, and thousands more.

Answer 6

I would recommend WireShark, it is the best tool to follow on different pieces of traffic. Although, I am not sure what can you see with SSL turned on. Maybe, if you supply it with a certificate?