avahi: CVE-2017-6519: DNS amplification and reflection to spoofed addresses

Debian Bug report logs - #917047
avahi: CVE-2017-6519: DNS amplification and reflection to spoofed addresses

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Message #5 received at submit@bugs.debian.org (full text, mbox, reply):

From: Salvatore Bonaccorso <carnil@debian.org>

To: Debian Bug Tracking System <submit@bugs.debian.org>

Subject: avahi: CVE-2018-1000845: DNS amplification and reflection to spoofed addresses

Date: Sat, 22 Dec 2018 00:06:45 +0100

Source: avahi
Version: 0.6.32-2
Severity: important
Tags: security upstream
Forwarded: https://github.com/lathiat/avahi/issues/203
Control: found -1 0.7-4

Hi,

The following vulnerability was published for avahi, filling to start
tracking the issue.

CVE-2018-1000845[0]:
| Avahi version 0.7 contains a Incorrect Access Control vulnerability in
| avahi-daemon that can result in Traffic reflection and amplification
| for DDoS attacks.. This attack appear to be exploitable via unicast IP
| network packet with spoofed source address.

If you fix the vulnerability please also make sure to include the
CVE (Common Vulnerabilities & Exposures) id in your changelog entry.

For further information see:

[0] https://security-tracker.debian.org/tracker/CVE-2018-1000845
    https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2018-1000845
[1] https://github.com/lathiat/avahi/issues/203
[2] https://bugzilla.redhat.com/show_bug.cgi?id=1661252

Regards,
Salvatore

Message #12 received at 917047@bugs.debian.org (full text, mbox, reply):

From: Trent Lloyd <trent@lloyd.id.au>

To: 917047@bugs.debian.org

Subject: Re: Bug#917047: avahi: CVE-2018-1000845: DNS amplification and reflection to spoofed addresses

Date: Sat, 22 Dec 2018 09:30:03 +0800

I have pushed a fix upstream for the issue here:
https://github.com/lathiat/avahi/commit/e111def44a7df4624a4aa3f85fe98054bffb6b4f

I have only performed basic validation so far, however the following 
scapy query now fails:
send(IP(src="1.1.1.1",dst="DEST_IP")/UDP(sport=53, 
dport=5353)/DNS(rd=1,qd=DNSQR(qtype="PTR", qname="_ssh._tcp.local.")))

And the following legitimate legacy unicast query still works:
dig HOSTNAME.local @DEST_IP -p 5353


Note that for the test scapy to work, you have to publish an _ssh._tcp 
service, e.g. put the example ssh.service into /etc/avahi/services. To 
avoid that, you can query for the machine's mdns hostname as an A record 
instead.
send(IP(src="1.1.1.1",dst="DEST_IP")/UDP(sport=53, 
dport=5353)/DNS(rd=1,qd=DNSQR(qtype="A", qname="HOSTNAME.local.")))

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