[oe] tinylogin vs. busybox

[pHilipp Zabel]

On Feb 13, 2008 4:06 PM, Koen Kooi <k.kooi at student.utwente.nl> wrote:
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> Michael 'Mickey' Lauer schreef:
> | On Wednesday 13 February 2008 13:53:18 Koen Kooi wrote:
> |> Michael 'Mickey' Lauer schreef:
> |> | I just realized that we are still using tinylogin which has bugs and
> |>
> |> is dead.
> |>
> |> | Newer busybox releases contain all the functionality. Anyone know a
> |> | compelling reason to keep using tinylogin as the default in
> task-base? If
> |> | not, I'd like to switch to busybox (after changing its defconfig) soon.
> |>
> |> Using busybox as login requires it being setuid root, with all the nasty
> |> security implications stemming from that.
> |
> | http://www.busybox.net/lists/busybox/2004-May/011551.html give me the
> opinion
> | that this is not a problem.
>
> If that email is true, we could dump tinylogin, but frankly, I trust
> busybox as far as I can throw a piano (and toybox as far as I can throw
> a 21" crt) and SUID root binaries make my skin crawl, so we must be very
> carefull and do thorough tests before making this change.
> The last thing we want is $bigcompany to blame OE for the exploitabilty
> of their devices.
>
> |> I don't think OE should force
> |> people to only have one user ('root') on their systems, since that is
> |> exactly what your proposed change would mean.
> |
> | I agree, but I don't see why using busybox login would limit us to
> root-only.
> | Care to give more details?
>
> The way busybox worked before is that *any* busybox applet is SUID root,
> which means 'vi' and 'passwd' are as well, which in practice means there
> is only one user: root.

busybox does drop root priviledges for applets that don't need them,
after reading its configuration file.
The only input from non-root users that I can see until then are the
command line parameters (applets/applets.c)

main() --> run_applet_and_exit() --> run_current_applet_and_exit() -->
check_suid()

regards
Philipp

> | Besides, I think using something old and dead as tinylogin with known
> bugs is
> | more of a security problem than setuid root busybox...
>
> That depends on what those bugs are, I can't do more than handwaving
> about one being less secure as the other without that knowledge.
>
> regards,
>
> Koen
>
> - --
> koen at dominion.kabel.utwente.nl will go go away in december 2007, please
> use k.kooi at student.utwente.nl instead.
>
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