Re: LYNX-DEV fotemods.zip update (97/05/25)

[Bela Lubkin]

Foteos Macrides wrote:

> 1997-05-25
> * Mods in LYMain.c to convert $USER if present in the TEMP_SPACE
>   definition or LYNX_TEMP_SPACE enviroment variable to the string
>   returned by getenv("USER"). - FM
> * Fixed two typos for me->inFONT settings in HTML.c - TD
> * Added chmod(file, 0600) calls for most files created by Lynx. - FM

I haven't looked at these mods -- I am now living in Moscow and my ISP
is usually too slow to attempt large downloads.  I have a security
concern with the described change: the sequence open-then-chmod tends to
open race conditions which can lead to security holes.  It is also
unnecessary, since the mode is specified in the open-or-creat call
itself:

  fd = open(filename, O_CREAT | whatever, 0600);
  fd = creat(filename, 0600);

If an open-then-chmod sequence is really necessary, it should use
fchmod(), if available.  Not all systems support it; so:

  fd = open(filename, O_CREAT | whatever, 0666);
  #if defined(HAS_FCHMOD)
  fchmod(fd, 0600);
  #else   /* !HAS_FCHMOD; note possible race condition here */
  chmod(filename, 0600);
  #endif   /* HAS_FCHMOD */

(then -DHAS_FCHMOD in your Makefile entry, and the autoconfig guys make
a Configure test for it...)

>Bela<
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