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Re: LYNX-DEV [Fwd: BoS: A vulnerability in Lynx (all versions)]

From: Kari E. Hurtta
Subject: Re: LYNX-DEV [Fwd: BoS: A vulnerability in Lynx (all versions)]
Date: Wed, 7 May 1997 23:51:48 +0300 (EDT)

Hynek Med:
> On Wed, 7 May 1997, Alan Cox wrote:
> > > a) create the file with 600 pemissions anyway, to guarantee privacy
> > > b) pick a very random name for the file
> > > c) check if the file about to be created isn't already a symlink/hardlink
> > > d) optionally do all this in a subdirectory with 700 permissions as your
> > > script suggests
> > > 
> > > I don't know any C, does some kind of standart mktemp() function do this
> > > all? Is it available on all systems?
> > 
> > mktemp isnt sufficient. mkstemp() is but not on all OS's. The algorithm
> > above has a race condition...
> Yes, but a hard to win race, and provided the filename is really random
> it's almost impossible. (Please correct me if I'm wrong.) 

Well. It is possible to use:

        if (fd=open(name,O_RDWR|O_EXCL|O_CREAT) < 0) {

        f = fdopen(fd,"r+");

O_EXCL does not follow symbol links [exception: HP-UX prior
the version 9.07]

Using of mktemp is not necessary here.
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