RE: iSCSI CONNECT message

[Joshua Tseng <jtseng@NishanSystems.com>]

Hi Jim,

<snip..snip>
>Use of DNS: there may be security concerns here (about DNS itself).  But
>this also assumes that every iSCSI target has a "public" ipname (or perhaps
>ipname:port combo).This may or may not be the case (correct?) if the
>controller lives deep in the bowels of some private network.

If the controller is in the bowels of some private network, it should still
be addressable by DNS, as long as the root authority is talking to the 
root ICANN servers.  Hence, the following DNS name:

     disk4.hpnetworkA3D.hpnetworkA3.hpnetworkA.hp.com 

is resolvable on the public Internet as long as the DNS server for
"hp.com" is talking to the ICANN ".com" server, and the DNS server
for hpnetworkA.hp.com is talking to the server for hp.com, and....

Security concerns about DNS can be handled separately through independent
authentication and/or encryption mechanisms between iSCSI entities and/or
proxies.

<snip..snip>
>the pipe is open for them to talk to each other).  iSCSI security may be
>completely independent of the link security (e.g., that the gateway might
>want to impose).  The iSCSI login security involves a context that is only
>relevant to the two end points as iSCSI entities, not as TCP/IP entities
>(i.e., at a different layer).  The link security is potentially independent
>from the iSCSI security context and is a function of the two ends of an
>intermediary link (as TCP or IP entities). 

Jim, I am in complete agreement here.  I would like to add that IPSec
provides
security between IP endpoints.  IPSec provides network level security, while
TLS or iSCSI security can provide security for iSCSI entities, since
SSL, TLS, and iSCSI security only protects the TCP payload (or a subset of
the payload) and not the IP or TCP header, so it can be proxied without 
changing the payload.  IPSec protects the IP header, so it can't be proxied.
Rather, the proxy must authenticate and/or decrypt the IPSec before it can
forward the data to the next IP endpoint.

    network domain 1  |   network domain 2   |    network domain 3
                      |                      |
iSCSI initiator-----proxy1-----------------proxy2-----------iSCSI target
      |               |                      |                  |
      |<---IPSec----->|<-------IPSec-------->|<-----IPSec------>|
      |<---TCP 1----->|<-------TCP 2-------->|<-----TCP 3------>|
      |                                                         |
      |<-------------------iSCSI security or SSL/TLS----------->|
      |<-------------------iSCSI session----------------------->|
      |                                                         |
      |<--------------------SCSI session----------------------->|

I believe this security model is quite practical as well, since there
is no dependency between IPSec and iSCSI.  If the administrator wants
to protect the proxys, then IPSec can be added and the iSCSI layer and
your CONNECT mechanism will be completely ignorant of the presence or
nonpresence of IPSec (IPSec has its own key distribution mechanism).
IPSec can be managed separately and independently.

<snip..snip>
>In short, I think I can summarize the issues:
>A) if an initiator can ALWAYS open a connection to a target through normal
>TCP/IP mechanisms, then there is no need for my proposal. (I didn't think
>this was necessarily possible).  Additionally, this assumption implies that
>target naming is pure and simply an ipname:port and nothing more (that is,
>I don't need URLs or any other complicated naming scheme).
>B) if NOT, then my proposal defines a means whereby that initiatial
>connection can get established, in order that the rest of the iSCSI process
>can begin. I think you need a two-part naming mechanism in this case.  If
>one was enough, then option A holds.

My experience with the Public Internet and corporate WANs says that A is
not true.  Sure, there will always be cases in a private network where the
administrator uses IP addresses only with no NAT, and is completely cut off
from the Public Internet (military/national defense concerns come to mind).
But if iSCSI is to be used through the Public Internet, then I believe
your B) might be the case.

Josh

-----Original Message-----
From: Jim Hafner/Almaden/IBM [mailto:hafner@almaden.ibm.com]
Sent: Thursday, October 05, 2000 9:33 AM
To: ips@ece.cmu.edu
Subject: Re: iSCSI CONNECT message


Folks,

Let's see if I can handle a bunch of these questions at once.  I'll admit
upfront that I'm not the most knowledgeable about how the IP network works,
how DNS works, how tunnelling works, etc.  As a consequence, I may be using
terms well-known in the network community in the wrong way.  Please correct
me if I am.

Definition: I'm using the term gateway here to mean any device (proxy,
etc.) with the following properites:
1) it sits between an initiator and a target (an implementation of a proxy
or any other sort of firewall)
2) it obscures the ipname/address of the target on its back-side from the
initiator on the front-side.
3) it is NOT an iSCSI target device; it is a device that enables connecting
two iSCSI devices
(in effect, a gateway is a device that must provide some sort of
tunnelling).  Or is "intermediary" a better term here?

Tunneling:  As Costa said, the only standardized tunnelling mechanism
defined (AFAIK) is in specific protocols like the HTTP GET URL protocol.
As I mentioned in my note, I'm suggesting that perhaps an analogous
function is required here.

Use of DNS: there may be security concerns here (about DNS itself).  But
this also assumes that every iSCSI target has a "public" ipname (or perhaps
ipname:port combo).This may or may not be the case (correct?) if the
controller lives deep in the bowels of some private network.

If the controller has a public IPname, then the normal mechanisms for
connecting to it should work (even through gateways as described by
Joshua).  In my proposal, the CONNECT message effectively gets delivered
directly to the target in the first step.

Is this the same as the login?  To me, the login is an initiator to target
operation, to validate the iSCSI to iSCSI layer connection end-to-end (once
the pipe is open for them to talk to each other).  iSCSI security may be
completely independent of the link security (e.g., that the gateway might
want to impose).  The iSCSI login security involves a context that is only
relevant to the two end points as iSCSI entities, not as TCP/IP entities
(i.e., at a different layer).  The link security is potentially independent
from the iSCSI security context and is a function of the two ends of an
intermediary link (as TCP or IP entities).  The CONNECT message then is the
instruction to the intermediary to request it's tunnelling services.
This gets to one of David's concerns about tunnel autoconfig.  My third
option (my favorite) for security in the CONNECT was effectivly leveraging
whatever tunneling autoconfig policies are in place between the two
endpoints of a hop (in the picture below, G1 and G2 may have their own
policies, which I assume they impose on each other, independent, perhaps,
of the type of traffic).

Julo's Topology(a):  I---G1---G2---G3---T

This is exactly the topology that Daniel and I discussed and the CONNECT
message was supposed to enable.  If this is "of little interest", then I
don't see the point of the CONNECT, either.  It may be that a gateway is
just a passthru or a proxy or any other mechanism that the gateway utilizes
in order to provide the services (QoS, security, etc.) that motivated the
placement of that gateway in that spot in the first place!

David also mentioned an issue about QoS and such.  If I'm a gateway doing
all this obsuring, then perhaps I'd like to have policies for QoS as well.
Whether they are blind to the type of traffic (iSCSI or http or ...), is a
different issue.

In short, I think I can summarize the issues:
A) if an initiator can ALWAYS open a connection to a target through normal
TCP/IP mechanisms, then there is no need for my proposal. (I didn't think
this was necessarily possible).  Additionally, this assumption implies that
target naming is pure and simply an ipname:port and nothing more (that is,
I don't need URLs or any other complicated naming scheme).
B) if NOT, then my proposal defines a means whereby that initiatial
connection can get established, in order that the rest of the iSCSI process
can begin. I think you need a two-part naming mechanism in this case.  If
one was enough, then option A holds.

Did I miss anybody's questions?  Am I completely off base here?  Can
somebody say whether (A) holds?  Does (A) hold with the requisite security
requirements (or is that a separate issue)?

Jim Hafner