November 12, 2016

What is Encrypted in HTTPS and SSL Stripping

"Everything in the HTTPS message is encrypted, including the headers, and the request/response load." []


"A sophisticated type of man-in-the-middle attack called SSL stripping was presented at the Blackhat Conference 2009. This type of attack defeats the security provided by HTTPS by changing the https: link into an http: link, taking advantage of the fact that few Internet users actually type "https" into their browser interface: they get to a secure site by clicking on a link, and thus are fooled into thinking that they are using HTTPS when in fact they are using HTTP." []

SSL Stripping Mitigation

Strict-Transport-Security: max-age=31536000; includeSubDomains; preload

1 comment:

Magnus K Karlsson said...

HTTPS Establishes an underlying SSL conenction before any HTTP data is transferred. This ensures that all URL data (with the exception of hostname, which is used to establish the connection) is carried solely within this encrypted connection and is protected from man-in-the-middle attacks in the same way that any HTTPS data is.

All HTTP-level transactions within an HTTPS connection are conducted within the established SSL session, and no query data is transferred before the secure connection is established.

From the outside the only data that is visible to the world it the hostname and port you are connecting to. Everything else is simply a stream of binary data which is encrypted using a private key shared only between you and the server.

In the example you provide your browser would do this:

1. Derive hostname (and port if present) from from URL.
2. Connect with to host.
3. Check certificate (it must be 'signed' by known authority, apply specifically to correct IP address and port, and be current).
4. The browser and server exchange cryptographic data and the browser receives a private key.
5. The HTTP request is made, encrypted with established cryptography.
6. HTTP response is received. Also encrypted.

HTTP is an 'Application Layer' protocol, it is carried on top of the secure layer. According the SSL specification, drawn up by Netscape, dictates that no application layer data may be transmitted until a secure connection is established - as outlined in the following paragraph:

"At this point, a change cipher spec message is sent by the client, and the client copies the pending Cipher Spec into the current Cipher Spec. The client then immediately sends the finished message under the new algorithms, keys, and secrets. In response, the server will send its own change cipher spec message, transfer the pending to the current Cipher Spec, and send its finished message under the new Cipher Spec. At this point, the handshake is complete and the client and server may begin to exchange application layer data."

So yes. The data contained in the URL query on an HTTPS connection is encrypted. However it is very poor practice to include such sensitive data as a password in the a 'GET' request. While it cannot be intercepted, the data would be logged in plaintext serverlogs on the receiving HTTPS server, and quite possibly also in browser history. It is probably also available to browser plugins and possibly even other applications on the client computer. At most an HTTPS URL could be reasonably allowed to include a session ID or similar non-reusable variable. It should NEVER contain static authentication tokens.

The HTTP connection concept is most clearly explained here: