Subject: Ftp-WG: FTP over SSL

From: Jeffrey Altman <[email-masked]>
Date: Tue, 7 Aug 2001 09:56:57 -0500

> > occuring.  At which point the peer receiving the error should shutdown
> > the SSL stack and close the connection.
> 
> Which connection ?  If the error occurs on the data connections are you
> suggesting that the control connection should be terminated ?  If so,
> I'm not sure I agree, if not then I don't think there is any value in
> specifying anything in the draft.

The Data connection should be terminated.  The fact that the Data
channel has been interrupted does not imply in any way that the
security of the Control channel has been violated.

> I do agree that it might be nice to point out that TLS requires this
> behaviour and implementations could be considered broken if they don't
> send close_notifys.

Although, unnecessary.

 Jeffrey Altman * Sr.Software Designer      C-Kermit 8.0 Beta available
 The Kermit Project @ Columbia University   includes Secure Telnet and FTP
 http://www.kermit-project.org/             using Kerberos, SRP, and 
 [email-masked]          OpenSSL.  SSH soon to follow.

---

From: Alun Jones <[email-masked]>
Date: Tue, 7 Aug 2001 11:23:27 -0500

>security of the Control channel has been violated.

Could you clarify - does this mean that you think if a sender gracefully 
closes the socket without first closing the TLS connection, the receiver 
should treat this as a successful completion of the transfer?  Or not?

> > behaviour and implementations could be considered broken if they don't

There's at least one implementation out there - specifically, CuteFTP, that 
closes the socket without shutting down the TLS session on that 
socket.  When I have time, I'll be getting onto them about this 
behaviour.  However, it may be worth putting in a note as to whether it 
really matters for the purposes of FTP as to whether the client shuts down 
TLS properly, or just closes the socket gracefully underneath it.

There are two RFCs at question here that may not be adequately read in 
depth - the first is venereal old RFC 959, with its concept of closing the 
socket to indicate end of transfer in stream mode.  The second is whatever 
TLS RFC says that a TLS shutdown must be performed prior to closure.  Now, 
seriously, while you and I may have bothered to read through that RFC, how 
many FTP app authors are going to do more than read the SDK documentation 
for whatever SSL library they're using?

Alun.
~~~~
P.S. Sorry I haven't raised anything about the FTP / TLS draft until now - 
I haven't managed to get my own implementation working until recently, and 
I didn't want to post while my own understanding was apparently in such a 
seriously poor situation.

--
Texas Imperial Software   | Try WFTPD, the Windows FTP Server. Find us at
1602 Harvest Moon Place   | http://www.wftpd.com or email [email-masked]
Cedar Park TX 78613-1419  | VISA/MC accepted.  NT-based sites, be sure to
Fax/Voice +1(512)378-3246 | read details of WFTPD Pro for NT.