Writeable yet undeletable Samba share? [Partially solved]

[Elembis]

For a fileserver I'm building, I'd like to have a public share so people can easily contribute their data without an administrator (me) needing to be on the scene. However, I'd also like to eliminate the possibility of a malicious guest rapidly deleting the product of hours (perhaps days) of uploading. As far as I know, doing this would mean monitoring traffic to the share and changing each file's permissions as they were added.

It'd be easy to get a script to change the permissions of everything in the guest share every X minutes, but someone could simply refresh the share repeatedly and delete any files before the script got around to protecting them. With this in mind, is it even possible for a script to be fast enough? If it is feasable, how might I go about scripting it? (I.e., how would I monitor the incoming traffic, and how would I pick out specific files?) It'd be nice if there were a way of setting "write" permissions to something like "add nomodify nodelete", but I don't think this is possible.

Thanks.

Update: That was easy. I found and experimented with Samba's "directory mask" and "create mask" options, and they do exactly what I want. I first thought setting each to 444 would work, but a directory with those permissions can't be filled, so I set them to 744 and 444, respectively. Note that if the share itself is writeable, these masks won't ever prevent a user from writing to it, because they only take effect once a file or directory is written.

Perfect.

Update 2: Oops. Written data can be renamed. It can't be deleted, and that's a good thing, but it can still be messed up. Even if I create a file in the public share as root and "chmod 000" it, any guest can rename it. Help?

[donjuan]

Something like the drop boxes my university uses would probably work. All you do is give everybody write permission but don't give them read and execute permission. That way they can't find out what's in there.
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