Re: post to bugtraq about "session fixation"

Based on the paper's description it appears that there are two critical points for this attack to succeed:

1. attack the victim's browser and set the Session-ID: which I think is an erroneous assumption especially for banking applications. If a browser tries to use a session ID with a web application other than the one that it has issued the session ID, it will fail. Well developed web applications will not accept session id's set by the user! It defeats the purpose of user session management.
2. Compromise the web application in order to issue a specific session ID that it was generated by the attacker. In this case, if an attacker has already compromised the web application/server they can manipulate or gather sensitive information without going through the exercise of setting their own session ID generator. Does "man in the middle" attack sound familiar?

The paper states that this vulnerability exists in "almost all web based systems
(including many high profile web banking systems) that we've ever come across".
I'm curious to see if there are any credible statistical information to support this
conclusion. Not to be picky, but when you say in 15 pages that "there is a major
vulnerability in Web based banking applications", it can cause arrhythmia (a change in the rhythm of your heartbeat ) to some people that maintain and develop web financial applications.

So providing verifiable and usable information is helpful versus some scenario
that is supported with assumptions and generalizations.

                                                                                                              
                    securityarchitec                                                                          
                    t@hush.com              To:     webappsec@securityfocus.com, alex@netWindows.org          
                                            cc:     (bcc: Panayiotis A. Thermos/Telcordia)                    
                    12/18/2002 02:28        Subject:     Re: post to bugtraq about "session fixation"         
                    PM                                                                                        
                                                                                                              
                                                                                                              

With respect I think its a great marketing paper but nothing more. You should never allow the same token to be used over HTTP that is then valid over SSL. At least one variant of this attack relies on that assumption.

Correct way if for the user to enter username and password over SSL and session cookie is set to that browser session over SSL. A pre-fixed cookie would get you to the public site (which maybe customized for a user experience but not show logged in details) but shouldn't get you to anywhere other than a login screen.

This paper also assumes that application session management is closely tied to web server session management. IMHO its not and this is a good reason why not. People think it is cause IIS and others still sends ASPSession IDs by default but just because the cookie protcol says they get returned if the domain path matches, doesn't mean to say they get processed by an app.

This is nothing new (although a good write-up).

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On Wed, 18 Dec 2002 12:13:26 -0800 Alex Russell <alex@netWindows.org> wrote:
>I don't know if anyone else has seen this yet:

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