WebApp Sec mailing list archives
Re: post to bugtraq about "session fixation"
From: "Panayiotis A. Thermos" <pthermos () telcordia com>
Date: Wed, 18 Dec 2002 15:49:31 -0500
Based on the paper's description it appears that there are two critical points for this attack to succeed: a) 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. b) 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). 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: http://online.securityfocus.com/archive/1/303838/2002-12-15/2002- 12-21/0 but I thought it would be on topic here. I realize that it's something of a rehash of the session authentication discussions we've had before, but I'd like to point out that it does expose a weak property of the "one sessionID for everything" model that's been proposed thust far, which is that it does not allow a interaction with the client to re-instate whatever security may have been previously broken. I think that in earlier discussions, I wasn't able to adequately articulate why I felt that issuing a new nonce for ever privledged operation made more sense (and why, correspondingly, you should never send the "real" session ID along with said nonce), but this article confirms what my gut was telling me: if you guard each action individually and require that there is a continuious line of known good iteractions, you'll be safer in the long run. The paper also points out the folly of assuming that client input is somehow "right" without validating it. Why in the world would an app server ever allow the end user to present to it the session ID that it will use for that client's continued interactions? -- Alex Russell alex () netWindows org alex () SecurePipe com
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Current thread:
- post to bugtraq about "session fixation" Alex Russell (Dec 18)
- <Possible follow-ups>
- Re: post to bugtraq about "session fixation" securityarchitect (Dec 18)
- Re: post to bugtraq about "session fixation" Kevin Spett (Dec 18)
- Re: post to bugtraq about "session fixation" Alex Russell (Dec 18)
- Re: post to bugtraq about "session fixation" Kevin Spett (Dec 18)
- Re: post to bugtraq about "session fixation" Panayiotis A. Thermos (Dec 18)
- Re: post to bugtraq about "session fixation" Steven M. Christey (Dec 19)
- Re: post to bugtraq about "session fixation" Cesar (Dec 20)
- Re: post to bugtraq about "session fixation" H D Moore (Dec 20)
- Re: post to bugtraq about "session fixation" Cesar (Dec 20)