Re: SSL and TCP RST/SYN attack

[Radmilo Racic <rracic () gmail com>]

David,
what you describe is a MITM attack on TCP not SSL. Sending fake TCP
RST packets is not trivial as one would have to guess the sequence
number (a number between 1 and 2^32-1) correctly. Granted, given a
fixed TCP window size you only need to guess a number that falls
within the window range (total of 2^32 / window_size guesses). Sending
TCP SYN is similar but it closes the local end of the connection.
There are various ways to defend against the DoS attacks on TCP. I
would encourage you to look into the OpenBSD solution and/or some
academic/theory-based approaches.

Either way, it would be incorrect to state that is an intrinsic
vulnerability in SSL.

Cheers,
-- Radmilo

On Sun, Sep 20, 2009 at 9:29 AM, David Zhang <david.zhang1965 () gmail com> wrote:
> Hi all:
> I would like to ask a question about SSL. Consider the situation that
> a man in the middle. Because he can always fake TCP RST/SYN packet, so
> he can always block the client to get service from the https server.
>
> So can I say that this is an intrinsic vulnerable in SSL, as
> considering the situation that the attacker is in the same LAN with
> the client, the attacker can always block the client to reach his
> server (say on-line banking)?
>
> Thanks
> David
>
> ------------------------------------------------------------------------
> Securing Apache Web Server with thawte Digital Certificate
> In this guide we examine the importance of Apache-SSL and who needs an SSL certificate.  We look at how SSL works, 
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------------------------------------------------------------------------
Securing Apache Web Server with thawte Digital Certificate
In this guide we examine the importance of Apache-SSL and who needs an SSL certificate.  We look at how SSL works, how 
it benefits your company and how your customers can tell if a site is secure. You will find out how to test, purchase, 
install and use a thawte Digital Certificate on your Apache web server. Throughout, best practices for set-up are 
highlighted to help you ensure efficient ongoing management of your encryption keys and digital certificates.

http://www.dinclinx.com/Redirect.aspx?36;4175;25;1371;0;5;946;e13b6be442f727d1
------------------------------------------------------------------------