On Fri, 19 Sep 2008, Barney Wolff wrote: | Date: Fri, 19 Sep 2008 01:54:42 -0400 | From: Barney Wolff <[EMAIL PROTECTED]> | To: EMC IMAP <[EMAIL PROTECTED]> | Cc: Cryptography <cryptography@metzdowd.com> | Subject: Re: Cookie Monster | | On Wed, Sep 17, 2008 at 06:39:54PM -0400, EMC IMAP wrote: | > Yet another web attack: | > | > As I understand the attack, it's this: Cookies can be marked Secure. | > A Secure cookie can only be returned over an HTTPS session. An cookie | > not marked Secure can be returned over any session. So: If a site | > puts security-sensitive data into a non-Secure cookie, an attacker who | > can spoof DNS or otherwise grab sessions can send a HTTP page | > allegedly from the site that set the cookie asking that it be returned | > - and it will be. | | Why on earth would anyone put security-sensitive data in a cookie, | unencrypted? It's the server talking to itself or its siblings, after | all, and it's vulnerable to attack on the client's machine. a) It depends on who you think it has to be secure against. Typical reasoning: If it's effectively the *client's* information, why/from whom do I need to protect it while it's on the *client's* machine? After all, it can only be seen by the client and me.
b) The way this attack is actually likely to be used is to steal a "logged-in session". If I have the cookie, and can MITM the stream to the server, I can act "within the logged-in session." I don't need to be able to decrypt the cookied - the real client has no need to (but in fact there isn't much point in encrypting, while at rest, the nonce that identifies the "logged-in session.") I put "logged-in session" in quotes in agreement with James Donald's message on this subject. -- Jerry --------------------------------------------------------------------- The Cryptography Mailing List Unsubscribe by sending "unsubscribe cryptography" to [EMAIL PROTECTED]