According to the Microsoft Windows 2000 Server: TCP/IP Core Networking Guide: "When a Windows 2000-based computer received an ICMP Redirect message, IP verifies that it came from the first-hop gateway in the current router and that the gateway is on a directly connected network. If so, a host route with a 10-minute lifetime is added to the router table for that destination IP address." Then goes on to say that, otherwise, the redirect is ignored. Of course, you could spoof the source address (and maybe the source MAC address if necessary?) of the ICMP packet. But, the problem I had, was the ICMP message has to contain data from a previously sent IP packet. If you can sniff traffic, and Pepsi sends something out via its default route, you could send the ICMP redirect, containing the sniffed packet, and forged IP headers. Now Pepsi will add a temporary route for the original host through whatever (local) machine you specify. The book gives no details on what validation is performed on the ICMP payload, but i seem to remember I how no luck with this capture/redirect scenario. Maybe i missed something. If you get anywhere, please pass the results on! Cheers, - foob On Tue, 30 Oct 2001, Blake Frantz wrote: > > > It's my understanding that the ICMP redirect is used in the following > scenario: > > - host1 sends data to gateway1 > - gateway1 looks for the next hop and find gateway2 > - gateway2 is on the same net as host1 > - gateway1 sends redirect to host1 informing it to use gateway2 > - host1 traffic now leaves via gateway2 > > With this in mind, I *think* the redirect has to come from "pepsi"'s > gateway. > > On Win2k, verify the value of: > HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\Services\Tcpip\Parameters\EnableICMPRedirect > > It's set to 1 (enable) by default. > > -blake > > > On Tue, 30 Oct 2001, Naveed Anwar wrote: > > > > > Hi All > > > > I have just been conducting a test in one of our labs by sending ICMP > > redirects to a Windows 2000 Advanced Server using ICMPUSH. Using a > > sniffer I see the packet successfully leave my machine, then again > > from the target box I see the re-direct arrive. Say for example my > > target machine is called Pepsi, and I tell it to redirect any packets > > for a machine called Fanta to a dead gateway, hence communication to > > Fanta will fail for the lifetime of the redirect. > > > > Now my understanding is that the target server (Pepsi) should now > > have updated its local routing table with respect to the Fanta > > machine. Then from Pepsi I try to ping/telnet/http/ftp etc..(i.e > > establish communication) to Fanta I am able to. The point is since I > > told Pepsi via a redirect to send all traffic for Fanta to a > > blackhole, how is the communication working. > > > > One interesting point is that when I issue a netstat -rn to view the > > routing table, I see no route update from the ICMP redirect. > > > > After reading Ofir's excellent paper I understand most ICMP > > implementations are OS specific, therefore I guess redirects do not > > work in Win2000 or Linux 6.2 which I also tested..or am I doing > > something horribly wrong? > > > > Thanks > > Naveed > > > > ---------------------------------------------------------------------------- > > This list is provided by the SecurityFocus Security Intelligence Alert (SIA) > > Service. For more information on SecurityFocus' SIA service which > > automatically alerts you to the latest security vulnerabilities please see: > > https://alerts.securityfocus.com/ > > > > > > > ---------------------------------------------------------------------------- > This list is provided by the SecurityFocus Security Intelligence Alert (SIA) > Service. For more information on SecurityFocus' SIA service which > automatically alerts you to the latest security vulnerabilities please see: > https://alerts.securityfocus.com/ > ---------------------------------------------------------------------------- This list is provided by the SecurityFocus Security Intelligence Alert (SIA) Service. For more information on SecurityFocus' SIA service which automatically alerts you to the latest security vulnerabilities please see: https://alerts.securityfocus.com/
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