[krbdev.mit.edu #6002] krb5_rc_io_creat should use mkstemp

[Ken Raeburn via RT]

On Jul 17, 2008, at 23:09, Tom Yu via RT wrote:
> Ok, so this is a case where using mkstemp() is clearly less safe.
> What should we do?  tmpnam() and open(O_CREAT|O_EXCL)?  Some
> development environments are evolving toward warning about uses of
> mktemp(), which is similar to tmpnam(), so they may also flag uses of
> tmpnam().

Coming up with names not already taken isn't all that hard, it just  
requires setting up a loop and having a reasonably large space of  
names to work through.  With a large enough namespace and a halfway  
decent PRNG, we ought to be able to find an unused name in one or two  
tries, actually: dir + "/krb5_RC" + base64(random).

Do we have this sort of thing happening elsewhere, such that a utility  
function mkstemp_mode_0600 would help?

Ken