rsync - Jan 2007 - How to Vary Module Path Based on User

I want to vary the path rsync uses based on the user that authenitcated to the
module.

I can see doing this in one of two ways:

1)  Append the username that was used for the connection to the path string of
the module on the fly.  What was /path/to/dir is now /path/to/dir/username

2)  Append the username into the dest_path that was sent from the other side. 
The effect of this would do the same thing for me - instead of changing the
module path, it would in effect, simply look like the far end had specified an
extra directory.

What was  test@server.com::Module/directory is now
test@server.com::Module/username/directory

I want to do this to facilitate having multiple logins use one module to store
data.  I am using a gui on the far end that autolists the available modules.  I
want it to be as simple as to select the one available module, enter the correct
username and password, and have your files go to the right place.  I don't
want to recompile the gui, I'd rather make the magic happen on the rsyncd
end.

Is there a function in rsync that does this?  Is there an ability to use the pre
transfer execute to modify a variable to make that happen?

I've been playing in main.c attempting to hard code something to work just
for me, but I'd prefer to use something that was actually meant for the
task.

Thanks,
Bill Gade
83 North Inc.
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On 1/3/07, Bill @ 83 North <bill@83north.com>
wrote:
> I want to vary the path rsync uses based on the user that authenitcated to
> the module.
> [...]
> Is there a function in rsync that does this?
No, the standard rsync does not support appending the username to the
module path.  However, this would be easy to implement in a custom
version of rsync.  In fact, I implemented it; the patch to rsync is
attached.
> Is there an ability to use the
> pre transfer execute to modify a variable to make that happen?
You could have the module path point to a symlink and have the
pre-xfer command modify that symlink to point to the appropriate
directory based on $RSYNC_USER_NAME.  However, concurrent connections
might fight over the symlink so that some clients would end up
accessing the wrong user's directory, so you should set max
connections = 1 for that module.

I feel that having a module that behaves differently for different
users is kludgy.  It would be better to have a different module for
each user but only show each user his/her own module.  To this end,
the daemon could ask a client requesting a module listing to provide a
username and password and then show the client the modules it could
access with those credentials.  The standard rsync daemon never asks
the client to provide credentials for a module listing, but it looks
like the standard rsync client would prompt the user  and provide the
credentials correctly; I can't speak for your GUI wrapper for the
client.

However, this technique is awkward to implement because checking a
single username and password against many modules (which might even
have different secrets files) would require significant rearrangements
to authenticate.c .  It would become even more awkward if support for
keyboard-interactive PAM authentication were added to the rsync
daemon, because authentication for different modules might even
require different PAM conversations.

Matt
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