reget reput again...

Damien Miller djm at
Mon Dec 6 16:48:43 EST 2004

I think a better option is to have an extension to take a checksum over
a file, or an arbitrary subset of one. re(get|put) could then validate
the file before continuing with it.

This would be quite easy to do using the draft-secsh-filexfer
protocol's vendor extension mechanism, if someone want to try to
beat in implementing it :)

If anyone is interested, please discuss your proposed design on-list.


Darryl L. Miles wrote:
> Ben Lindstrom wrote (a very long time ago) :
>  >The problem is in some cases the data being sent to you may be out of
>  >order (thankful no sftp server does this yet). So reget/reput without RFC
>  >clearifications can lead to bad file transfers.
>  >
>  >I'm trying to drag up in my mind which one was the problem... I believe
>  >reput is fine since the client has control over the ordering. reget is
>  >the troublesome some one without RFC clarifications stating out of order
>  >transfers are denied.
>  >
>  >if the RFC get clarified to disallow out of order transfers then a cleaned
>  >up version of this patch may not have a problem getting in.
> It seems everyone body has a patch for this but it still can't quite 
> make it into any official distribution.  Not wanting to stifle technical 
> progress down surely the standards body have mechanism to allow new 
> concepts to be experimentally deployed without affecting non-cooperating 
> parties ?
> Is it really necessary to get RFC clarification on this, maybe its 
> useful to leave as-is and have the option to execute out-of-order for in 
> uses.
> Would it be possible to extend the channel initialisation options to 
> negotiate a feature requesting "mandatory in-sequence execution of 
> commands within this channel".  I'm not sure how these options are 
> created or assigned but maybe use some OpenSSH naming space until a 
> standard group either accepts or rejects the concept and assigns it a 
> standard option name.
> Non-conforming servers would not understand the option and the client 
> could then disable the reget/reput commands from use in that session.
> I do not know enough about the OpenSSH implementation to know if its 
> possible for it to ever execute commands out of sequence with respect to 
> the channel they are in nor the contraints this may pose to future 
> maintainace of OpenSSH.
> To confirm the scope of the option suggested, it says nothing about any 
> other channel nor the order in which channels are attended to within the 
> server, this stays as-is.
> RFC ?  Please Cc your reply Thanks.

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