getcwd() and friends.

[MFHorn]

>From article <811 at mtxinu.UUCP>, by ed at mtxinu.COM (Ed Gould):
>  >It is possible to be handed a file descriptor
>  >which you would not be able to have opened because some component of
>  >the search path denies access now, but at some point in the past did
>  >allow access.
> 
> Worse than that, the permission required to open a directory is "r"
> (since one may not open a directory for writing), whereas the
> permission required to change to one is "x".  Hence, Unix protection
> would be completely violated by the existance of fchdir().

Why can't the kernel check access permissions *at the time* of the
fchdir() call just like it does for chdir() and open()?

There is a function in the BSD kernel called iaccess() that is called
every time one of these (and maybe other) system calls are made.  It
is passed a pointer to an inode struct and the type of access being
requested (read, write, execute).

I see no compromise in security.

--
Andy Rosen           | arosen at hawk.ulowell.edu | "I got this guitar and I
ULowell, Box #3031   | ulowell!arosen          |  learned how to make it
Lowell, Ma 01854     |                         |  talk" -Thunder Road
		RD in '88 - The way it should've been