Re: Secure temporary fifo creation

[Philippe Troin <phil@fifi.org>]

Greg Deitrick <gdeitrick@mylinuxisp.com> writes:

> Hello,
> 
> What is the recommended method for securely creating a temporary named pipe in 
> C code?
> 
> Looking at the man pages for various library calls it appears that tmpfile(3) 
> is probably an acceptable means of creating a temporary file, but this 
> returns a FILE *.  The upstram source I'm packaging needs to make a temporary 
> fifo.  It uses tempnam(3) to get a temporary file name as a char *, and then 
> mkfifo(3) to make the fifo named pipe from the file name.  Is this 
> sufficiently secure?

Not needed... This should be race-free:

  char *s;
  while (s = (tempnam("/tmp", "foo")) {
    if (mknod(s, S_IFIFO|0600, 0) == 0)
      break;
    if (errno != EEXIST)
      /* error */
  }
  if (!s)
    /* error */

You might want to use tmpnam if maximum portability is needed.

Phil.