NetBSD Security Advisory 2017-002: Several vulnerabilities in ARP
18 February, 2017 by security-officer@netbsd.org | netbsd
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NetBSD Security Advisory 2017-002
=================================
Topic: Several vulnerabilities in ARP
Version: NetBSD-current: source prior to Tue, Jan 24th 2017
NetBSD 7.0 - 7.0.2: affected
NetBSD 6.1 - 6.1.4: affected
NetBSD 6.0 - 6.0.5: affected
Severity: Remote DoS, remote information disclosure
Fixed: NetBSD-current: Tue, Jan 24th 2017
NetBSD-7-0 branch: Sun, Feb 5th 2017
NetBSD-7 branch: Sun, Feb 5th 2017
NetBSD-6-0 branch: Sun, Feb 5th 2017
NetBSD-6-1 branch: Sun, Feb 5th 2017
NetBSD-6 branch: Sun, Feb 5th 2017
Teeny versions released later than the fix date will contain the fix.
Please note that NetBSD releases prior to 6.0 are no longer supported.
It is recommended that all users upgrade to a supported release.
Abstract
========
Two vulnerabilities were found in NetBSD's ARP implementation:
- A memory leak could allow an attacker to remotely cause the system to
run out of memory and eventually panic.
- Missing validation checks on a received ARP packet header could cause
the system to reply with uninitialized kernel data which may lead to
information disclosure.
Technical Details
=================
- When replying to an ARP request, a particular branch taken in the
output code did not free the mbuf that was being sent. An attacker
could send specially-crafted ARP requests that trigger this memory
leak.
- When processing a received ARP request, the system did not properly
check the hardware and protocol lengths in the ARP header. These fields
being used to reply to the request in memcpys, an attacker could send
an ARP packet with the highest encodable lengths and cause the kernel
to copy in the reply packet more data than is available. It has been
demonstrated that a remote machine can thereby retrieve 249 bytes of
kernel memory over an Ethernet link.
Solutions and Workarounds
=========================
For all NetBSD versions, you need to obtain fixed kernel sources,
rebuild and install the new kernel, and reboot the system.
The fixed source may be obtained from the NetBSD CVS repository.
The following instructions briefly summarise how to upgrade your
kernel. In these instructions, replace:
ARCH with your architecture (from uname -m),
KERNCONF with the name of your kernel configuration file and
VERSION with the file version below
File versions containing the fixes:
FILE HEAD netbsd-7 netbsd-7-0 netbsd-6 netbsd-6-1 netbsd-6-0
---- ---- -------- ---------- -------- ---------- ----------
sys/netinet/if_arp.c
1.239 1.158.2.2 1.158.4.1 1.154.2.3 1.154.16.2 1.154.8.2
sys/net/if_arcsubr.c
1.76 1.66.2.1 1.66.6.1 1.63.14.2 1.63.14.1.2.1 1.63.20.1
sys/net/if_ecosubr.c
1.50 1.40.2.2 1.40.2.1.2.1 1.36.4.2 1.36.18.1 1.36.10.1
sys/net/if_ethersubr.c
1.236 1.204.2.1 1.204.4.1 1.188.8.5 1.188.8.3.2.2 1.188.8.2.4.2
sys/net/if_fddisubr.c
1.104 1.88.2.1 1.88.6.1 1.81.14.2 1.81.14.1.2.1 1.81.20.1
sys/net/if_tokensubr.c
1.81 1.65.2.1 1.65.4.1 1.61.8.1 1.61.18.1 1.61.14.1
To update from CVS, re-build, and re-install the kernel:
# cd src
# cvs update -d -P -r VERSION sys/netinet/if_arp.c
# cvs update -d -P -r VERSION sys/net/if_arcsubr.c
# cvs update -d -P -r VERSION sys/net/if_ecosubr.c
# cvs update -d -P -r VERSION sys/net/if_ethersubr.c
# cvs update -d -P -r VERSION sys/net/if_fddisubr.c
# cvs update -d -P -r VERSION sys/net/if_tokensubr.c
# ./build.sh kernel=KERNCONF
# mv /netbsd /netbsd.old
# cp sys/arch/ARCH/compile/obj/KERNCONF/netbsd /netbsd
# shutdown -r now
For more information on how to do this, see:
http://www.NetBSD.org/guide/en/chap-kernel.html
Thanks To
=========
Maxime Villard for finding the issues and writing fixes.
Revision History
================
2017-02-17 Initial release
More Information
================
Advisories may be updated as new information becomes available.
The most recent version of this advisory (PGP signed) can be found at
http://ftp.NetBSD.org/pub/NetBSD/security/advisories/NetBSD-SA2017-002.txt.asc
Information about NetBSD and NetBSD security can be found at
http://www.NetBSD.org/ and http://www.NetBSD.org/Security/ .
Copyright 2017, The NetBSD Foundation, Inc. All Rights Reserved.
Redistribution permitted only in full, unmodified form.
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