WebApp Sec mailing list archives
RE: advice needed - secure transfer of client details
From: "Michael Silk" <michaels () phg com au>
Date: Mon, 1 Nov 2004 09:25:45 +1100
Hi Tim, > How can a client communicate details that are only known to the client, up to a server, > in a way that cannot be tampered with ? Why should a server trust the supplied values > ? The data for the workstation next to me is known by everyone - why can't I create an > applet to reproduce those details, and hence impersonate that workstation ? Well what you need here is basically SSL (to secure the transfer between two previously unrelated clients) + a certificate to identify the client. Obviously, if you can get the information required to identify yourself as another workstation there is a problem ... So the solution is to make that information very hard to get ... I.e. consider securing it's access (the certificate) via some key ... Common systems are smartcards, etc. -- Michael -----Original Message----- From: Tim James [mailto:jimtames () yahoo com] Sent: Friday, 29 October 2004 8:18 PM To: webappsec () securityfocus com Subject: advice needed - secure transfer of client details Hi all, This is a brain teaser. I have an application to review which supplies details from the client's workstation (derived from files on disk, hostname, IP address). It currently implements a Java applet whose job is to obtain these details and send them up to the server in an ordinary HTTP POST. This sends alarm bells ringing for me. I have developed a simple attack whereby I can replace the applet at will with my own code, which can send different details for workstation ID, hostname, IP address. This falsifies the audit trail from this point on and the server is none the wiser. So, the general problem is this :- How can a client communicate details that are only known to the client, up to a server, in a way that cannot be tampered with ? Why should a server trust the supplied values ? The data for the workstation next to me is known by everyone - why can't I create an applet to reproduce those details, and hence impersonate that workstation ? I have some ideas but none are totally satisfactory. 1) Encrypt the data This shifts the problem to one of key management. 2) Checksum the applet 3) Keep the details on the server in the first place and supply some token from the client which cannot be impersonated I would *really* appreciate a different perspective on this problem because I'm kind of stalled..... Thanks a lot Tim Send instant messages to your online friends http://uk.messenger.yahoo.com ********************************************************************** This email message and accompanying data may contain information that is confidential and/or subject to legal privilege. If you are not the intended recipient, you are notified that any use, dissemination, distribution or copying of this message or data is prohibited. If you have received this email message in error, please notify us immediately and erase all copies of this message and attachments. This email is for your convenience only, you should not rely on any information contained herein for contractual or legal purposes. You should only rely on information and/or instructions in writing and on company letterhead signed by authorised persons. **********************************************************************
Current thread:
- advice needed - secure transfer of client details Tim James (Oct 29)
- New Whitepaper - "Second-order Code Injection Attacks" WebAppSecurity [Technicalinfo.net] (Nov 01)
- Re: advice needed - secure transfer of client details Peter Conrad (Nov 01)
- Re: advice needed - secure transfer of client details Ido Rosen (Nov 01)
- Re: advice needed - secure transfer of client details focus (Nov 01)
- Re: advice needed - secure transfer of client details GuidoZ (Nov 01)
- Re: advice needed - secure transfer of client details Alex Russell (Nov 01)
- Re: advice needed - secure transfer of client details Richard Moore (Nov 05)
- <Possible follow-ups>
- RE: advice needed - secure transfer of client details Michael Silk (Nov 01)
- RE: advice needed - secure transfer of client details Scovetta, Michael V (Nov 01)
- RE: advice needed - secure transfer of client details Glenn_Everhart (Nov 05)
- re: advice needed - secure transfer of client details Tim James (Nov 05)