Messages in this thread | | | Date | Sun, 29 Jun 2003 16:24:59 +0200 | From | Willy TARREAU <> | Subject | Re: [RFC][PATCH-2.4] Prevent mounting on ".." |
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On Sun, Jun 29, 2003 at 04:09:40PM +0200, Arjan van de Ven wrote: > On Sun, 2003-06-29 at 15:09, Willy TARREAU wrote: > > Hi Al and Marcelo, > > > > while I was trying to get maximum restrictions on a chroot on 2.4.21-pre, > > I found that it's always possible to mount a ramfs or a tmpfs on "..", > > and then upload whatever I wanted in it. It's a shame because I was > > trying to isolate network daemons inside empty, read-only file-systems, > > and I discovered that this effort was worthless. To resume, imagine a > > network daemon which does : > > well... > you need to be root to mount. If you're root you can break out of a > chroot anyway....
not in all cases. for the classical "mkdir a; chroot a; chdir ..", you need a writable directory to create "a" or an existing directory somewhere to serve as a mount point. If neither of them is true, I don't see other means of escaping the chroot. And here, ".." is the only one I could exploit, that's why I proposed this patch which closes what is, to me, the only weakness in this very particular case.
Cheers, Willy
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