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** Changed in: linux (Ubuntu)
Status: New => Confirmed
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https://bugs.launchpad.net/bugs/1909937
Title:
Physical Ethernet interfaces leak MAC addresses on link up
Status in linux package in Ubuntu:
Confirmed
Bug description:
An Ethernet interface without IPv4 or IPv6 link-local addresses still
emits IPv6 ICMPv6 Multicast Listener Report Messages. These messages
include the source MAC address of the Ethernet interface itself,
leaking that address to a network being monitored for (e.g.) security
purposes.
TO REPLICATE
============
1. Confirm that interface is configured without IPv6 or IPv6 link-
local addresses:
root@sniff:~# ip addr show dev enp1s0f2
5: enp1s0f2: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc mq state UP
group default qlen 1000
link/ether a0:36:9f:21:14:0c brd ff:ff:ff:ff:ff:ff
2. Start (e.g.) netsniff-ng to watch that interface, filtering for the
source MAC address:
root@sniff:~# netsniff-ng -i enp1s0f2 ether host a0:36:9f:21:14:0c
Running! Hang up with ^C!
3. In another window, temporarily shut down and bring up that Ethernet
interface:
root@sniff:~# ip link set dev enp1s0f2 down ; sleep 5 ; ip link set
dev enp1s0f2 up
4. In the netsniff-ng window, observe the emitted packets with the
source MAC address of the physical device, and an IPv6 source address
of all zeros (::) (consistent with no link-local address being
configured on the interface):
> enp1s0f2 110 1609708972s.966716675ns #1
[ Eth MAC (a0:36:9f:21:14:0c => 33:33:00:00:00:16), Proto (0x86dd, IPv6) ]
[ Vendor (Intel Corporate => Multicast) ]
[ IPv6 Addr (:: => ff02::16), Version (6), TrafficClass (0), FlowLabel (0),
Len (56), NextHdr (0), HopLimit (1) ]
[ Hop-by-Hop Options NextHdr (58), HdrExtLen (0, 8 Bytes), Option(s)
recognized ]
[ ICMPv6 Multicast Listener Report v2 (143), Unknown Code (0), Chks
(0x6b6d), Res (0x0), Nr. Mcast Addr Records (2), Rec Type
CHANGE_TO_EXCLUDE_MODE (4), Aux Data Len (0, 0 bytes), Nr. of Sources (0),
Address: ff05::2, Aux Data: , Rec Type CHANGE_TO_EXCLUDE_MODE (4), Aux Data Len
(0, 0 by
tes), Nr. of Sources (0), Address: ff02::2, Aux Data: ]
> enp1s0f2 110 1609708973s.262732732ns #2
[ Eth MAC (a0:36:9f:21:14:0c => 33:33:00:00:00:16), Proto (0x86dd, IPv6) ]
[ Vendor (Intel Corporate => Multicast) ]
[ IPv6 Addr (:: => ff02::16), Version (6), TrafficClass (0), FlowLabel (0),
Len (56), NextHdr (0), HopLimit (1) ]
[ Hop-by-Hop Options NextHdr (58), HdrExtLen (0, 8 Bytes), Option(s)
recognized ]
[ ICMPv6 Multicast Listener Report v2 (143), Unknown Code (0), Chks
(0x6b6d), Res (0x0), Nr. Mcast Addr Records (2), Rec Type
CHANGE_TO_EXCLUDE_MODE (4), Aux Data Len (0, 0 bytes), Nr. of Sources (0),
Address: ff05::2, Aux Data: , Rec Type CHANGE_TO_EXCLUDE_MODE (4), Aux Data Len
(0, 0 by
tes), Nr. of Sources (0), Address: ff02::2, Aux Data: ]
TO WORKAROUND
=============
Add an ip6tables rule to suppress any host-generated IPv6 packets from being
emitted from that interface, e.g.:
ip6tables -A OUTPUT -o enp1s0f2 -j DROP
ProblemType: Bug
DistroRelease: Ubuntu 20.04
Package: linux-image-5.4.0-58-generic 5.4.0-58.64
ProcVersionSignature: Ubuntu 5.4.0-58.64-generic 5.4.73
Uname: Linux 5.4.0-58-generic x86_64
ApportVersion: 2.20.11-0ubuntu27.14
Architecture: amd64
AudioDevicesInUse:
USER PID ACCESS COMMAND
/dev/snd/controlC0: bill 877 F.... pulseaudio
CasperMD5CheckResult: skip
CurrentDesktop: ubuntu:GNOME
Date: Sun Jan 3 13:06:20 2021
InstallationDate: Installed on 2020-12-23 (11 days ago)
InstallationMedia: Ubuntu 20.04.1 LTS "Focal Fossa" - Release amd64 (20200731)
Lsusb:
Bus 002 Device 001: ID 1d6b:0003 Linux Foundation 3.0 root hub
Bus 001 Device 003: ID 051d:0002 American Power Conversion Uninterruptible
Power Supply
Bus 001 Device 002: ID 413c:2113 Dell Computer Corp. Dell KB216 Wired
Keyboard
Bus 001 Device 004: ID 413c:301a Dell Computer Corp. Dell MS116 USB Optical
Mouse
Bus 001 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub
MachineType: Dell Inc. OptiPlex 3050
ProcEnviron:
TERM=xterm-256color
PATH=(custom, no user)
XDG_RUNTIME_DIR=<set>
LANG=en_US.UTF-8
SHELL=/bin/bash
ProcFB: 0 i915drmfb
ProcKernelCmdLine: BOOT_IMAGE=/boot/vmlinuz-5.4.0-58-generic
root=UUID=baec5de5-b743-482b-8850-65f96d50ecbf ro quiet splash vt.handoff=7
RelatedPackageVersions:
linux-restricted-modules-5.4.0-58-generic N/A
linux-backports-modules-5.4.0-58-generic N/A
linux-firmware 1.187.6
RfKill:
SourcePackage: linux
UpgradeStatus: No upgrade log present (probably fresh install)
dmi.bios.date: 07/03/2020
dmi.bios.vendor: Dell Inc.
dmi.bios.version: 1.14.0
dmi.board.name: 08NPPY
dmi.board.vendor: Dell Inc.
dmi.board.version: A00
dmi.chassis.type: 3
dmi.chassis.vendor: Dell Inc.
dmi.modalias:
dmi:bvnDellInc.:bvr1.14.0:bd07/03/2020:svnDellInc.:pnOptiPlex3050:pvr:rvnDellInc.:rn08NPPY:rvrA00:cvnDellInc.:ct3:cvr:
dmi.product.family: OptiPlex
dmi.product.name: OptiPlex 3050
dmi.product.sku: 07A3
dmi.sys.vendor: Dell Inc.
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