ldd runs linux programs

[Mateusz Guzik]

On Mon, Jul 29, 2013 at 10:33:53AM +0800, Julian Elischer wrote:
> On 7/29/13 4:49 AM, Mateusz Guzik wrote:
> >On Sun, Jul 28, 2013 at 11:31:10PM +0400, Gennady Proskurin wrote:
> >>Hello.
> >>When linux binary is passed to FreeBSD's ldd as argument, this binary is executed.
> >>I'm sure this is bug :)
> >>(with security involved)
> >>
> >I have a patch for this, but never got around to commit it.
> >
> >http://people.freebsd.org/~mjg/patches/ldd-non-freebsd-ignore.diff
> >
> >If someone wants, go ahead and steal it.
> >
> For those of us that are not ldd experts, why does this happen,
> what's the history and
> what happends on Linux?
> I vagualy remember that linux may somehow execute something in this
> case but my memory is very vague on the topic.

right, sorry.

Short version is that both FreeBSD and Linux ldd set
LD_TRACE_LOADED_OBJECTS environment variable and run the binary
expecting runtime linker to act accordingly.

However, FreeBSD sets LD*32*_TRACE_LOADED_OBJECTS for 32-bit binaries,
thus Linux linker just proceeds with execution.

Looks like we have several PRs related to this, notably
http://www.freebsd.org/cgi/query-pr.cgi?pr=bin/127276 .

and looks like markj (cc-ed) took another PR, someone should clean this
up.

127276 suggests running the binary as is (which I don't like) and
achieves this with a hacky way. So if we really want to do this, the
patch should be reworked to detect Linux binaries properly.

In general we should gain linux_ldd (like linux_kdump) and our ldd
should work only on FreeBSD binaries. The last part is achieved with my
patch.

markj, are you working on this?

-- 
Mateusz Guzik <mjguzik gmail.com>