[jcifs] Even-byte-alignment padding in Write AndX Request

[David D. Kilzer]

On Thu, Jul 15, 2004 at 03:55:01PM -0400, Michael B Allen wrote:

> On Thu, 15 Jul 2004 11:57:00 -0500, David D. Kilzer wrote:
> 
> > [...]
> > I have hacked up jTDS so that it emits a TDS 4.2 logon packet (which is
> > the data after the Write AndX Request) that is identical to what the SQL
> > Enterprise Manager tool sends.  Unfortunately, there are still a few
> > minor differences between the two packets:
> > 
> >   - The SQL Enterprise Manager packet has the TDS 4.2 logon packet
> >     even-byte-aligned by including a padding byte of 0xEE between the
> >     Write AndX Request and the data (TDS 4.2 logon packet).
> > 
> > [...]
> > 
> >   - Fields that differ in the Write AndX Request:
> > 
> >     Fields        SQL-E-M   JCIFS
> >     ------------- --------  --------
> >     Reserved:     FFFFFFFF  00000000
> >     Write Mode:   0x0008    0x0000
> 
> Mmm, Ethereal claims 0x0008 is "write start". We don't do anything with
> that flag. Try setting writeMode = 0x0008 in the SmbComWriteAndX.java
> constructor (temporarily just to see if it works).

I set writeMode to 0x0008, but it made no effect on the behavior of SQL
Server 6.5.

> >     Remaining:    512       0
> 
> Probably doesn't matter.
> 
> >     Data Offset:  64        63
> >     Byte Count:   513       512
> >     Padding:      EE        (n/a)
> 
> Alignment could be an issue. Try uncommenting
> jcifs/smb/SmbComWriteAndX.java:110 where the comment reads "Netware
> doesn't like this". Make it 0xEE if you like. I don't think it should
> make any difference.

I added a 1-byte alignment byte of 0xEE.  This caused JCIFS to throw a
different exception:

  jcifs.smb.SmbException: The pipe is being closed.

At this point, I took a look at previous SMB packets, and noted the
following:

  - The Tree Connect AndX Request/Response occur with NO session using
    SQL Enterprise Manager (SQLEM), but within a session using JCIFS.
    (I'm using an "anonymous" NtlmPasswordAuthentication with domain,
    user and pass set to empty strings.)  The only difference in the
    Tree Connect AndX Request is:

    Fields        SQLEM     JCIFS
    ------------- --------  --------
    Flags:        0x0008    0x0000

  - The NT Create AndX Request have more differing fields:

    Fields        SQLEM      JCIFS
    ------------- ---------- ----------
    AndXOffset:   57054      0
    Create Flags: 0x00000016 0x00000000
    Access Mask:  0x0002019f 0x0000008b
    Share Access: 0x00000001 0x00000007
    Disposition:  3          1

Thanks for any more insight you have, or suggestions of what to try.

I'm going to sniffing a working driver next (running the same test code)
to see what it does differently.  Comparing the SQLEM output to the
output running the AsTest.java class from jTDS is a bit like comparing
apples to oranges.

Dave