Tutorial: Sniffing iSCSI traffic for a spoofing attack

June 21, 2007

Also known as “Why you need some kind of iSCSI security”

Okay, after reading Himanshu Dwivedi’s presentation[PDF] on iSCSI security (insecure-SCSI hur hur hur) I decided to try and replicate one of the attacks that he mentioned in the presentation. Following is how I managed to get the data shown of a different machine.

Firstly, I needed to get the initiatorname for the iscsi daemon on the target host. In this case the /etc/initiatorname.iscsi file is -rw-------, so I needed a way to find out the initiator name without root privileges. In this case I used wireshark (used to be ethereal) to sniff the traffic for a plain-text initiator name. Okay, so here’s what I did:

Fire up Wireshark (Ethereal) and set it to promiscuous mode, with a filter for port 3260 (the iscsid port), feel free to filter by host, etc. Run the live capture for a while, what you’re going to be looking for is a sequence of packets that look more like this:

iSCSI Login Command
TCP [PSH,ACK] <other information>
TCP [ACK] <other information>
iSCSI Login Response (Success)

I can’t say how long it’s going to take this, but it’s much easier to get when the iscsi service is being started on the machine you’re trying to sniff, therefore, if you can sniff while a machine is coming online from a reboot you will most likely have a much better chance of detecting this.

There’s another easier way of getting what you want just doing a string search. Search for the string “Initiator” below you can see a picture what you should be looking for in Wireshark:

Note the highlighted text at the bottom, this is what you’re looking for. Copied straight out you get something like this:

All we really care about in that text is the part that is bolded, using this, we can manually set the /etc/initiatorname.iscsi file on a different Linux server to have the line “InitiatorName=iqn.1987-05.com.cisco:01.87956e84f925“. Don’t forget to change the /etc/iscsi.conf file to have the following line in it:
DiscoveryAddress=<ip of iscsi target host>
Fill in the host with the IP address that your sniffing showed (in this case, it was as you can see in the picture)

After this step, if this were a real attack it would probably be a good idea to preform a DOS attack on the original target to knock it out of connection with the server (you don’t really want 2 hosts attempting to get the same information from an iSCSI target). Then start the iscsi daemon with “/etc/init.d/iscsi start” and you should be seeing the data originally meant for the other host.

This is really a simple attack and barely requires any technical knowledge of iSCSI to exploit it. It’s nothing special, but it does show that you really need to implement some kind of security in your network (CHAP or whatever else suits you).

What kind of security do you use for iSCSI? CHAP? None? Leave a comment and let me know!

EDIT: Blog O’Matty has an article on the Solaris iSCSI stack in the August issue of SysAdmin magazine if you’re interested. I find his articles to be very insightful and I highly recommend checking out some of the other ones at prefetch.net. Check it out!

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