Bug #1858: Lots of TCP 'duplicated option/DNS malformed request data' after upgrading from 3.0.1 to 3.1.1 - Suricata - Open Information Security Foundation

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Bug #1858

closed

Lots of TCP 'duplicated option/DNS malformed request data' after upgrading from 3.0.1 to 3.1.1

Added by . . over 8 years ago. Updated over 8 years ago.

Status:

Closed

Priority:

High

Assignee:

Victor Julien

Target version:

3.1.2

Affected Versions:

Effort:

Difficulty:

Label:

Description

Running:
CentOS 7.2.1511 (Core)
Suricata 3.1.1 RELEASE w/ libpcap

After upgrading from 3.0.1 to 3.1.1 i am seeing tons of "TCP duplicated option" and "DNS malformed request data" events which is creating a log of noise on my dashboard.

I noticed suricata.yaml received an overhaul, i already migrated my old config to the (rpm)new one (in case some defaults had been changed) but to no avail.

What am i missing here, except disabling the rules/adding a threshold, to get rid of this?

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Updated by Andreas Herz over 8 years ago

Assignee set to Anonymous
Target version set to TBD

How do you run suricata?
And can you try to reproduce it with a pcap?

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Updated by Victor Julien over 8 years ago

Status changed from New to Assigned
Assignee changed from Anonymous to Victor Julien
Priority changed from Normal to High
Target version changed from TBD to 3.1.2

I can confirm the TCP issue. Will work on a fix. Haven't investigated the DNS one yet.

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Updated by . . over 8 years ago

Sorry for being late!

Andreas Herz wrote:

How do you run Suricata?

Nothing fancy really, the installation is acting as a router (iptables w/ nat & ip_forward) for a "small" private network.

Suricata installed from epel, running on the local facing interface:

pcap:
  - interface: eth1

with SG/GRO/LRO/TSO/GSO disabled:

ethtool -K eth1 sg off gro off lro off tso off gso off

since Suricata logged a warning suggesting this after upgrading from 3.0.1 - it was just

ethtool -K eth1 rx off tx off gro off

pre 3.1.1

I am also running unbound as a reverse DNS proxy for the local network on this box, binding to eth1.

The alerts logged are:

{"timestamp":"2016-08-16T18:58:55.285853+0200","flow_id":4250627771,"in_iface":"eth1","event_type":"alert","src_ip":"x.x.x.x","src_port":53,"dest_ip":"x.x.x.x","dest_port":42924,"proto":"UDP","tx_id":0,"alert":{"action":"allowed","gid":1,"signature_id":2240002,"rev":1,"signature":"SURICATA DNS malformed request data","category":"","severity":3}}

over and over again.

dest_ip is pretty much every active client on the network including Desktops, Smartphones and Tablets ranging from Windows over Linux/Android to OSX/iOS

The src_ip is listed under DNS_SERVERS in

vars:
  address-groups:

For the time being i disabled the two noisy messages

suppress gen_id 1, sig_id 2240002
suppress gen_id 1, sig_id 2200037

to stop it from spamming my dashboard.

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Updated by . . over 8 years ago

Victor Julien wrote:

I can confirm the TCP issue. Will work on a fix. Haven't investigated the DNS one yet.

Update on the DNS issue since i had some spare time.

It does look like rDNS requests (e.g. nslookup 10.0.0.1) are triggering the alerts.
I am able to reproduce this reliable from any random client on the network.

Dunno why Suricata thinks this is "malformed request data" especially since nsd (running behind unbound) has a reverse lookup zone (in-addr.arpa) configured and is responding to all rDNS requests with the expected answer.

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