Re: [PATCH] root-uid: new module

[Eric Blake]

On 06/26/2012 05:49 PM, Paul Eggert wrote:

>    /* The super-user can read and write any file, and execute any file
>       that anyone can execute.  */
> -  if (euid == 0 && ((mode & X_OK) == 0
> -                    || (stats.st_mode & (S_IXUSR | S_IXGRP | S_IXOTH))))
> +  if (euid == ROOT_UID
> +      && ((mode & X_OK) == 0
> +          || (stats.st_mode & (S_IXUSR | S_IXGRP | S_IXOTH))))

Rather than forcing comparison to a single value, would it be better to
have a function is_privileged_uid(euid)?  That's because on Cygwin, the
Administrator group is typically equated with root privileges, but while
there is just one well-known gid for the Administrator group, it is
feasible to have a system with multiple uids all belonging to that group
and thus all having equal root privileges.

On traditional Unix systems, you would have:

bool is_privileged_uid (uid_t id) { return !id; }

On Tandem, you would have:

bool is_privileged_uid (uid_t id) { return id == ROOT_UID; }

and on Cygwin, you would have:

bool is_privileged_uid (uid_t id) {
  /* some function call that determines if id has admin privileges,
although I don't know off-hand what it would look like */
}

-- 
Eric Blake   address@hidden    +1-919-301-3266
Libvirt virtualization library http://libvirt.org

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