Re: Anyone can modify the modification time of a symbolic link owned by root

[Pádraig Brady]

On 14/04/2021 19:08, develop@nobes.com wrote:
> As a regular user I am able to update the modification time of symbolic links 
> that are owned by root.
>
> Is this intentional? Other than making the device read only is there any other 
> way to prevent this?
>
> I realize that using the command "ls -l" shows up as all users having write 
> permissions on the symbolic link. Just wondering what the reasoning is to allow any user 
> to change the modification time. It would seem to be more logical if only the owner 
> (group?) could change the modification time.

You are correct:

  $ strace -e utimensat touch -h /bin
  utimensat(AT_FDCWD, "/bin", NULL, AT_SYMLINK_NOFOLLOW) = 0

However enforcement would need to be done in the kernel,
so this is more a kernel question.

Related to this is how perms on symlinks are handled.
There was some previous discussion of that at:
https://lists.gnu.org/archive/html/bug-coreutils/2009-09/msg00268.html

Also I saw mention that NetBSD may have a symperm mount option
to honor permissions for symlinks.

cheers,
Pádraig