Re: iSCSI padding should be 0

["Eddy Quicksall" <ESQuicksall@hotmail.com>]

Software padding can be expensive if their is a requirement that the pad
must be 0. I have given the reason below.

BTW, where is the security problem? In an earlier EMAIL, I suggested a
security issue but I gave a paranoid case. Do you have a simple security
case?

Eddy
----- Original Message -----
From: "Julian Satran" <Julian_Satran@il.ibm.com>
To: <ips@ece.cmu.edu>
Sent: Saturday, July 28, 2001 12:36 AM
Subject: Re: iSCSI padding should be 0


> Is the software padding more expensive than checking if there is a CRC (or
> any other digest)?
> On the other hand CRCs don't require the bytes to be 0 they can be
> arbitrary values.
> The 0 was brought in to avoid "leakage" (security) by somebody on the
list.
> We can choose to revert to arbitrary and leave the burden of cleaning to
> the applications for which security is a concern.
>
> Julo
>
> "Eddy Quicksall" <ESQuicksall@hotmail.com> on 27-07-2001 22:05:59
>
> Please respond to "Eddy Quicksall" <ESQuicksall@hotmail.com>
>
> To:   Julian Satran/Haifa/IBM@IBMIL
> cc:   "ips" <ips@ece.cmu.edu>
> Subject:  Re: iSCSI padding should be 0
>
>
>
>
> I saw one objection to this by Michael Fischer
> [Michael_Fischer@adaptec.com]. He pointed out that if there is no CRC then
> why require the padding to be 0. I agree with his point.
>
> The problem is with software only implementations ... if they use the
> sockets send function and if they are sending from a ULP buffer and if the
> data being sent needs padding, they will have to either copy to another
> buffer or do an extra tiny send for the pad.
>
> So, my thinking is that we say:
>
>     iSCSI PDUs are padded to an integer number of 4 byte words. If CRC is
> being used, the padding MUST be 0. If CRC is not being used, the content
of
> the padding is unpredictable and irrelevent.
>
> What do you think?
>
> Eddy
> ----- Original Message -----
> From: "Julian_Satran/Haifa/IBM%IBMIL" <julian_satran@il.ibm.com>
> To: <eddy_quicksall@ivivity.com>
> Cc: "ips" <ips@ece.cmu.edu>
> Sent: Friday, July 27, 2001 11:45 AM
> Subject: Re: iSCSI padding should be 0
>
>
> >
> > Perhaps we should say MUST be sent as 0 and keep quiet about what the
> > receiver should  do (check for 0 - we don't want that).
> >
> > Thanks,Julo
> >
> > "Eddy Quicksall" <eddy_quicksall@ivivity.com> on 27-07-2001 18:18:33
> >
> > Please respond to eddy_quicksall@ivivity.com
> >
> > To:   Julian Satran/Haifa/IBM@IBMIL, ips@ece.cmu.edu
> > cc:
> > Subject:  iSCSI padding should be 0
> >
> >
> >
> >
> > Julian,
> >
> > Section 2.1 says the padding should be 0. I guess that is correct
because
> > one may not use CRC and therefore may not want to set them to 0.
Wouldn't
> > it
> > be better if section 2.1 was more specific and mentioned when they must
> be
> > 0
> > if there is a CRC. Also, I noticed at the UNH plug fest that at least
one
> > person thought "should" meant "must". Therefore, I don't think it should
> > say
> > "should" ... I think it should not mention the 0'ness unless there is a
> CRC
> > present.
> >
> > Also,
> >
> >         transmission.  Padding bytes, when presents in a segment covered
> by
> > a
> >         CRC, have to be set to 0 and are included in the CRC.
> >
> > should say "when present in".
> >
> > Eddy_Quicksall@iVivity.com
> >
> >
> >
> >
> >
>
>
>
>