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List:       busybox
Subject:    Re: NOFORK and NOEXEC without PREFER_APPLETS
From:       Denys Vlasenko <vda.linux () googlemail ! com>
Date:       2016-08-26 15:52:03
Message-ID: CAK1hOcOCxaPdWR7AuOGQNPHr_q0xmT93WKX3CED27QdUTN=qcg () mail ! gmail ! com
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On Wed, Aug 24, 2016 at 1:25 PM, Bruno Chevalier
<bmgg.chevalier@gmail.com> wrote:
> On 19 August 2016 at 10:53, Denys Vlasenko <vda.linux@googlemail.com> wrote:
>>
>>
>> I don't understand what you are trying to achieve by this code.
>> If executable can be found in PATH, what are the benefits from
>> not running it but running an applet?
>>
>> This can be confusing to the user.
>
>
> If the executable can be found in PATH, we are going to execute it.
> That's the whole point.
>
> If busybox contains f.e. the nandwrite applet, and the symlink from
> nandwrite to busybox is replaced by the actual nandwrite program, we want to
> execute the nandwrite program and not the busybox applet.

Ok so far.

> If in another case (without reconfiguring busybox) that link is not
> overwritten, we want to execute the applet, while still making use of the
> NOEXEC trick.

I don't like it. A program is found in PATH. Whether it will be executed
or not magically depends on where it points to (if it is a symlink).

Such behavior is not expected by users. Users do know that shells
have builtins and that "echo" may not necessarily run /bin/echo.
But this decision is made *statically*. Does not depend on what /bin/echo is.

With your patch, it will start depending on that too.

> In the current implementation, when you want to make use of the NOEXEC trick
> for busybox applets, you automatically have to accept that your PATH won't
> be searched for programs with that applet's name.

Yes. I understand that you don't like it and want to use external tools.

Will it work for you to simply unset FEATURE_SH_STANDALONE?

FEATURE_SH_STANDALONE is meant for situations where user doesn't want
to be bothered by the need to create /bin/foo -> /bin/busybox links,
IOW: a very minimalistic system.

Your situation is clearly different.
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