LLVM Image Activator

[Konstantin Belousov]

On Sun, Jan 13, 2013 at 08:21:37AM -0800, Nathan Whitehorn wrote:
> On 01/13/13 05:20, Konstantin Belousov wrote:
> > On Sun, Jan 13, 2013 at 12:41:09PM +0100, Ed Schouten wrote:
> >> Hi Kostik,
> >>
> >> 2013/1/7 Konstantin Belousov <kostikbel at gmail.com>:
> >>> I still do remember the buzz about the binary format 0xCAFEBABE, which
> >>> AFAIR gained image activator support on several OSes, to be garbage
> >>> collected.
> >>
> >> Maybe it would then be a good idea then to add some kind of general
> >> purpose remapping imgact? Example:
> >>
> >> /etc/imgacttab:
> >>
> >> cafebabe /usr/local/bin/java
> >> cffaedfe /usr/local/bin/osx_emulator
> >> 4243c0de /usr/bin/lli
> >>
> >> That way we still give people the freedom to play around with mapping
> >> their own executable formats, but don't need to maintain a bunch of
> >> imgacts.
> > 
> > A generic module that could be somewhat customized at runtime to map
> > offset+signature into the shebang path could be a possibility indeed.
> > I strongly prefer to have it as module and not enabled by default.
> > 
> > Asking Nathan for writing the thing is too much, IMHO, esp. in
> > the response to the 50-lines hack.
> > 
> 
> I think this is a good idea, since it both prevents a profusion of
> similar activators and works nicely in jails and similar environments. I
> probably won't write it quickly, but it should not take more than about
> 50 lines, so I can't imagine it will be that bad. There are some
> complications with this kind of design from the things in the XXX
> comment in imgact_llvm.c about handling argv[0] that I need to think
> some more about.
Great. I do not believe in the 50 lines, but I am happy that you want
to work this out.

> 
> Why are you opposed to having it there by default? I think it's actually
> quite important that it be there by default. Having it not "standard"
> would be fine, but it should at least be in GENERIC. There are minimal
> security risks since it just munges begin_argv and doesn't even load the
> executable and it's little enough code that there should not be any
> kernel bloat to speak of. If things like this aren't enabled by default,
> no one can depend on them being there, no one will use it, and the point
> is entirely lost.
All image activators demonstrated a constant stream of security holes.
Even our ELF activator, and I was guilty there too.

I definitely do not fight over the inclusion of the proposed activator
into GENERIC, but do insist on the config option + module.
-------------- next part --------------
A non-text attachment was scrubbed...
Name: not available
Type: application/pgp-signature
Size: 834 bytes
Desc: not available
URL: <http://lists.freebsd.org/pipermail/freebsd-arch/attachments/20130113/0eaa316c/attachment.sig>