Date: Sun, 24 Feb 2002 10:47:02 +0200 From: Ruslan Ermilov <ru@FreeBSD.ORG> To: cjclark@alum.mit.edu Cc: net@FreeBSD.ORG Subject: Re: TCP Connections to a Broadcast Address Message-ID: <20020224084702.GB31243@sunbay.com> In-Reply-To: <20020223072520.J16048@blossom.cjclark.org> References: <20020222022626.A83807@blossom.cjclark.org> <20020223115033.GB47437@sunbay.com> <20020223042828.E16048@blossom.cjclark.org> <20020223124535.GB52291@sunbay.com> <20020223072520.J16048@blossom.cjclark.org>
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On Sat, Feb 23, 2002 at 07:25:20AM -0800, Crist J. Clark wrote:
> On Sat, Feb 23, 2002 at 02:45:35PM +0200, Ruslan Ermilov wrote:
> [snip]
>
> > Router B: if0 (192.168.1.1/24) and if1 (192.168.4.1/24)
> > Router A: if0 (192.168.1.2/24)
> >
> > On router A: route add -net 192.168.4 192.168.1.1, telnet 192.168.4.255.
> >
> > Or even simpler:
> >
> > Router: if0 (192.168.1.1/24 and 192.168.100.1/24)
> > Host: if0 (192.168.1.2, default gateway 192.168.1.1)
>
> Did 192.168.4.1/24 just become 192.168.100.1/24?
>
Yes, these were two different examples.
> > On host:
> >
> > $ ping 192.168.100.255
> > PING 192.168.100.255 (192.168.100.255): 56 data bytes
> > 64 bytes from 192.168.100.1: icmp_seq=0 ttl=64 time=0.245 ms
> > 64 bytes from 192.168.100.1: icmp_seq=1 ttl=64 time=0.207 ms
> > 64 bytes from 192.168.100.1: icmp_seq=2 ttl=64 time=0.207 ms
> > ^C
> > --- 192.168.100.255 ping statistics ---
> > 3 packets transmitted, 3 packets received, 0% packet loss
> > round-trip min/avg/max/stddev = 0.207/0.220/0.245/0.018 ms
> > $ telnet 192.168.100.255 25
> > Trying 192.168.100.255...
> > Connected to 192.168.100.255.
> > Escape character is '^]'.
> > 220 my.router.local.net ESMTP Sendmail 8.11.6/8.11.2; Sat, 23 Feb 2002 14:39:21 +0200 (EET)
>
> I can't reproduce this. I was only ever able to connect to the
> broadcast on the local interface.
>
> On victim "router (192.168.64.50):"
>
> $ netstat -rn -f inet
> Routing tables
>
> Internet:
> Destination Gateway Flags Refs Use Netif Expire
> default 192.168.64.254 UGSc 14 1768 dc0
> 127.0.0.1 127.0.0.1 UH 1 137708 lo0
> 172.16 link#3 UC 3 0 ep0
> 172.16.0.1 0:20:af:17:f:11 UHLW 0 2 lo0
> 192.168.64 link#1 UC 6 0 dc0
> 192.168.64.50 0:4:5a:40:d9:e5 UHLW 11 5310274 lo0
> 192.168.64.60 0:c0:f0:5a:6c:a UHLW 4 11416791 dc0 514
>
> On attacker "host (192.168.64.60):"
>
> $ netstat -rn -f
> Routing tables
>
> Internet:
> Destination Gateway Flags Refs Use Netif Expire
> default 192.168.64.254 UGSc 1 0 dc0
> 127 127.0.0.1 UGSc 0 0 lo0
> 127.0.0.1 127.0.0.1 UH 1 1776 lo0
> 172.16 192.168.64.50 UGSc 1 4 dc0
> 192.168.64 link#1 UC 3 0 dc0
> 192.168.64.50 0:4:5a:40:d9:e5 UHLW 6 1318188 dc0 1003
>
> Now on "host,"
>
> $ ping 172.16.0.1
> PING 172.16.0.1 (172.16.0.1): 56 data bytes
> 64 bytes from 172.16.0.1: icmp_seq=0 ttl=64 time=0.518 ms
> 64 bytes from 172.16.0.1: icmp_seq=1 ttl=64 time=0.541 ms
> ^C
> --- 172.16.0.1 ping statistics ---
> 2 packets transmitted, 2 packets received, 0% packet loss
> round-trip min/avg/max/stddev = 0.518/0.530/0.541/0.011 ms
>
> This works fine as expected with the weak-ES model. But for me,
>
> $ ping 172.16.255.255
> PING 172.16.255.255 (172.16.255.255): 56 data bytes
> ^C
> --- 172.16.255.255 ping statistics ---
> 4 packets transmitted, 0 packets received, 100% packet loss
> $ telnet 172.16.255.255
> Trying 172.16.255.255...
> telnet: connect to address 172.16.255.255: Operation timed out
> telnet: Unable to connect to remote host
>
> I can't reach the broadcast on the other interface. The "router" is
> FreeBSD 4.5-RELEASE without any patches.
>
> I'm not sure what I might be doing wrong.
>
> If you are correct, and you can cross interfaces, this is a much
> bigger problem. I didn't mention it in your first mail, but the
> in_broadcast() function as used in the patch you sent is different
> than the current implementation. in_broadacast() currently takes an
> address and an interface. If you are correct, we'd have to loop
> through the interface list... which makes this uglier.
>
No, I can't cross interfaces, /* Check for broadcast addresses. */
in ip_input() doesn't allow this. I'm talking about a different
scenario here, multiple IP networks per interface:
host# netstat -rn -finet | grep -w default
default 192.168.4.65 UGSc 4 387 rl0
gateway# ifconfig fxp0 inet
fxp0: flags=8843<UP,BROADCAST,RUNNING,SIMPLEX,MULTICAST> mtu 1500
inet 192.168.4.65 netmask 0xffffff00 broadcast 192.168.4.255
inet 192.168.100.1 netmask 0xffffff00 broadcast 192.168.100.255
host# telnet 192.168.100.255 25
Trying 192.168.100.255...
Connected to 192.168.100.255.
Escape character is '^]'.
Cheers,
--
Ruslan Ermilov Sysadmin and DBA,
ru@sunbay.com Sunbay Software AG,
ru@FreeBSD.org FreeBSD committer,
+380.652.512.251 Simferopol, Ukraine
http://www.FreeBSD.org The Power To Serve
http://www.oracle.com Enabling The Information Age
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