openssh unix dev - Jun 2004 - [patch] sftp-server writes uploads to a temporary file then renames them when finished

Well, my boss asked me to write this patch and I figured I'd share it in 
case someone else wanted to use it. It's clearly not for incorporating 
into the main tree. It would need to be configurable, and since there is 
no configuration system for sftp, it can't easily be.

I could make it look for an environment variable for the tmp-name-suffix 
and use it's existence to indicate weather or not to use tmp files.

- Gabriel
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gabriel russell wrote:
> Well, my boss asked me to write this patch and I figured I'd share it
in
> case someone else wanted to use it. It's clearly not for incorporating 
> into the main tree.
This isn't going to be reliable because the filexfer protocol (sftp)
doesn't really have a notion of an "upload" - it sees a open, a
bunch
of writes and a close. While this will usually represent an upload, it
could also be modifications to a different file. You could make this
a bit more robust by only activating it for creations or truncations.
> It would need to be configurable, and since there is 
> no configuration system for sftp, it can't easily be.
When I have made modifications to sftp-server that have required passing
in configuration options, I just pass them on the commandline and use
a wrapper script in sshd_config's SubSystem directive (because
sshd_config doesn't allow the passing of commandline options to
subsystems.)
> I could make it look for an environment variable for the tmp-name-suffix 
> and use it's existence to indicate weather or not to use tmp files.
You should just use mkstemp to give you a fd to a temporary file, rather
than making something that could be clobbered by multiple simultaneous
uploads.

-d