[Cryptography] Can crypto implement OS/FS protections ?
Dave Horsfall
dave at horsfall.org
Mon Nov 21 16:06:27 EST 2022
On Mon, 21 Nov 2022, Jerrold Leichter wrote:
> You can certainly control *read* access by encryption (though there are
> limits to the protection - e.g., suppose I want to say that if you don’t
> have read access to a file, you can’t even tell if it’s been changed
> since you last looked).
Unless I've misunderstood you, under *Nix you don't need read access to a
file to access its metadata (the inode); you merely need to be able to
access it from its parent directly. In the case above, you "stat" the
file and examine "st_mtime".
For example, on my FreeBSD box (this one):
aneurin% ls -l /etc/master.passwd
-rw------- 1 root wheel 2785 Nov 3 15:07 /etc/master.passwd
I can't read it, but I can see that it was last changed on 3rd November.
-- Dave
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