Re: RFC/PATCH: Random pid generation

[Sean Hunter]

On Wed, Jan 12, 2000 at 03:05:03PM +0100, Marcus Sundberg wrote:
> "Sean Hunter" <[e-mail]> writes:
> 
> > On Tue, Jan 11, 2000 at 08:20:54PM +0100, Marcus Sundberg wrote:
> > > Stephen Frost <[e-mail]> writes:
> > > 
> > > > 	People use the PID to create temp files and whatnot,
> > > > from what I've seen.
> > > 
> > > And they do that in order to get a unique number, not a random number.
> > 
> > This is also a really bad idea, because with easily guessable pids you
> > are opening yourself to /tmp races.
> 
> There can be only one process with a given pid at a time, so there can't
> be anything I'd call a race.

You run your program, but I have created a simlink in /tmp with the
same name (because the name is guessable).  That is a race because it
relies on contention between two processes (my "ln -s" and your broken
program) over a shared resource (the easily-guessable name in the
shared namespace of the filesystem).  This is the definition of a
race.  You may not call it that, but everyone else would.

> Ofcourse there are security implications of handling files in /tmp, but
> that is independent of how the filenames are generated and a completely
> different story. A program that relies on non-guessable filenames in
> /tmp to be secure is severly broken.

Agreed.

Sean