Penetration Testing mailing list archives
Re: [PEN-TEST] Exploiting sequence number predictability
From: Haroon Meer <meer2 () NU AC ZA>
Date: Tue, 22 Aug 2000 10:05:18 +0200
Hi.. Try... http://packetstorm.securify.com/docs/infosec/sequence_attacks.txt and http://www.s0d.org/books/www.bitpunk.com/ipext.pdf Both give comprehensive detail on TCP Sequence attacks, and how / y they wrk. Haroon Meer +27 83 786 6637 Meer2 () nu ac za It took the computing power of three C-64s to fly us to the Moon. It takes a Pentium to run Windows 95. Something's not right here...
simon () SNOSOFT COM 08/21/00 04:20AM >>>
I am interested in learning more about this subject. I know nothing about it and feel that I need to. Does anyone have any documents that will explain this to me from ground 0? At 02:37 PM 8/18/2000 +0200, you wrote:
Hi folks, I was wondering if anyone knew of any tools for exploiting predictable initial sequence numbers? I understand the concept, and always see tools like nmap reporting on the quality of the ISN. But I am wondering how serious the vulnerability really is. How easy is it to actually exploit the weak ISN's? I've also used tools like hunt, for session hijacking, but that presupposes knowlege of the sequence numbers on the network, and doesn't really exploit the predictability aspect. Are there any tools around that exploit this, or are they mostly limited to custom tools written for a specific situation? What level of skill is required to exploit a TCPWrappered telnet daemon, for example, assuming I know the username and password, and the exact banner and prompts? I imagine it is a case of: 1. determine the predictability algorithm (64k rule, or whatever) 2. Craft the packets required to execute the commands desired with the IP address of a permitted workstation. (packet 1 : SYN packet 2 : ACK xxxxx/username^M packet 3 : ACK xxxxy/password^M packet 4 : ACK xxxxz/echo > /etc/hosts.deny; echo attacker >> /etc/hosts.allow; exit^M, or whatever) where xxxxx-xxxxz are determined by the ISN, the number of bytes in the banner and login prompt, password prompt, and welcome banner/motd) (I can see why the R services are an easier target, cos you avoid all the variables in the login sequence, and can include your credentials and issue your command in the (same) second packet sent, I think) 3. Check where the target machine is in its sequence numbers by making a legit connection to, say echo, or whatever. 4. spam out a flood of packets that cover the range of ISN's based on the time between the target machine answering the legit connection, and your crafted packet arriving at the target. Is this how it works? Thanks. Sincerely, Rogan -- In God we Trust -- all others must submit an X.509 certificate. -- Charles Forsythe <forsythe () alum mit edu> -- Rogan Dawes Deloitte & Touche Enterprise Risk Services Network & System Quality Tel: +27 11 806 6216 Fax: +27 11 806 5202 Cell: +27 82 784 9498 Email: rdawes () deloitte co za -- NOTE: This e-mail message and its attachments is subject to the disclaimers as published at: http://www.deloitte.co.za/disc.htm#emaildisc
Current thread:
- Re: [PEN-TEST] Exploiting sequence number predictability, (continued)
- Re: [PEN-TEST] Exploiting sequence number predictability l0rtamus prime (Aug 21)
- [PEN-TEST] Online Security Vulnerability Services Teicher, Mark (Aug 22)
- Re: [PEN-TEST] Exploiting sequence number predictability Ben Lull (Aug 22)
- Re: [PEN-TEST] Exploiting sequence number predictability Hiromi Yanaoka (Aug 22)
- Re: [PEN-TEST] Exploiting sequence number predictability Riley Hassell (Aug 22)
- Re: [PEN-TEST] Exploiting sequence number predictability Jose Nazario (Aug 22)
- Re: [PEN-TEST] Exploiting sequence number predictability Todd, George (Aug 22)
- Re: [PEN-TEST] Exploiting sequence number predictability Iván Arce (Aug 23)
- Re: [PEN-TEST] Exploiting sequence number predictability Jean-Simon Durand (Aug 22)
- Re: [PEN-TEST] Exploiting sequence number predictability Pedro Quintanilha (Aug 23)
- Re: [PEN-TEST] Exploiting sequence number predictability Haroon Meer (Aug 22)
- Re: [PEN-TEST] Exploiting sequence number predictability l0rtamus prime (Aug 21)