On Sun, Jan 13, 2013 at 12:24:35PM -0800, John-Mark Gurney wrote: > Nathan Whitehorn wrote this message on Sun, Jan 13, 2013 at 10:14 -0800: > > On 01/13/13 09:13, Konstantin Belousov wrote: > > > 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 <[email protected]>: > > >>>>> 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. > > > > > > > OK, that sounds like a plan then. I'll try to code up something > > configurable in the next couple weeks, unless someone else beats me to it. > > I'll point out that file already has the magic (pun intended) that we > are looking for, though I do realize that the code might be a bit much > to import..
As someone who recently stuffed libmagic into a very constrained sandbox environment, I can safely assert that you don't want to go there. The code isn't written in a way that would make this easy and I definitely wouldn't want it in the kernel. -- Brooks
pgp07tnkSUC1K.pgp
Description: PGP signature
