Re: Publically writable directories

[wfp5p () tigger itc virginia edu (Bill Pemberton)]

Thomas Koenig writes:
> Is there a safe way of opening a temporary file in a publically writable
> directory as a normal user, given a system with symbolic links?
> I'm even willing to assume a sticky bit on the directory.
>
> Main problem: How do I disallow a malicious
>
> $ ln -s /tmp/some.file $MYHOME/.somedotfile
>
> at the wrong times, without getting into race conditions?

You need to open it like so:

fp_handle = open(fname, O_RDWR|O_CREAT|O_EXCL,0600)


The open() call does not follow symlinks.

--
Bill Pemberton                           wfp5p () virginia edu
ITC/Unix Systems                         flash () virginia edu
University of Virginia                   uunet!virginia!wfp5p