Re: Relax the prohibition of usage fchdir(2) to quit a chroot
Matt Thomas <[email protected]>
| Newsgroups | gmane.os.netbsd.devel.security |
|---|---|
| Message-ID | <[email protected]> |
On Sep 20, 2014, at 5:02 PM, Kamil Rytarowski <[email protected]> wrote: > Hello, > > There is a security feature in sys_fchdir [1] with the following comment: > /* > * Disallow changing to a directory not under the process's > * current root directory (if there is one). > */ Yes, that's intentional. Even if you get sent a fd to directory outside of the chroot, it won't you do any good. The rule is inviolate. > This feature actually kills functionality of i.e. misc/rpm with the '--root' feature. So it's broken by design. :) > Linux by default doesn't make this restriction, it's enabled i.e. with grecurity [2]. > I need to use this feature, without tools like fakechroot.. so am I free to propose a patch swapping this feature on and off in runtime with sysctl? In my humble personal opinions, hell no. > My proposition is: > security.chroot.allow_fchdir_out_of_chroot (sorry I'm bad at brief names). How security.chroot.just_kidding? > Maybe try to implement other chroot restrictions and make them swappable in runtime as well? Again, my opinion, absolutely not. It's not broken, and doesn't need to broken.