Re: [PATCH] Completely honor prctl(PR_SET_KEEPCAPS, 1)

On Wed, 8 May 2002, Dax Kelson wrote:

> With the current behaviour an app has to link against libcap and do:
>
> prtctl(PR_SET_KEEPCAPS, 1)
> pre_caps = (capgetp(0, cap_init())  // save our caps into a struct
> setuid(uid)
> setgid(gid)
> capsetp(0,pre_caps)  // Restore them
>
> With this patch, the app does:
>
> prtctl(PR_SET_KEEPCAPS, 1)
> setuid(uid)
> setgid(gid)

Are you sure about the current behaviour? Taking vsftpd as an example, it
does

prctl()
setuid()
setgid()
cap_set_proc()

i.e. it only fiddles with capabilities after dropping euid == 0. Of
course, someone is welcome to fiddle with capabilities while euid == 0.
But, euid == 0 is hugely privileged even without any capabilities. So, the
benefit of running with euid == 0 and less than full capabilities is a bit
limited.

Cheers
Chris