Firewall Wizards mailing list archives
Re: chroot useful?
From: "Douglas R. Steinbaum" <steinbau () itd nrl navy mil>
Date: Thu, 13 Nov 97 17:05:25 -0500
Regarding the comment made by Steve Bellovin (pasted at the end of this message): I was under the impression that running the chroot() command on a UNIX box would make it impossible for all subsequently launched programs to access files located above the newly defined root point, even if such programs are launched with a UID of 0. Thus, the command could be used as a simple "wrapper" to prevent a user application program which is not completely trusted (for example, a commercial SW package for which source code is unavailable) from being misused to access critical system files. That is, chroot could be run to define the root point such that critical files are inaccessible, and then the untrusted application would subsequently be launched. Is this not correct? (I am new to this list, so I apologize if this question has already been answered.) - Doug Steinbaum
It is important to understand what chroot() is and what it isn't. It is not a virtualization of the machine. Attempts to use it as such are quite likely doomed. It is a mechanism to virtualize file name access; at that, it does quite a good job, and has since shortly after the first public release in 1979. (That version permitted chroot("..") out of the subtree.) Standard UNIX systems do not have a complete virtual environment. There have been various attempts to add these on, with more or less success. But it's an area where one should tread cautiously. --Steve Bellovin
Current thread:
- chroot useful? Claudio Telmon (Nov 08)
- Re: chroot useful? Darren Reed (Nov 09)
- Re: chroot useful? Claudio Telmon (Nov 09)
- Re: chroot useful? Joseph S. D. Yao (Nov 10)
- Re: chroot useful? Andreas Siegert (Nov 12)
- Re: chroot useful? chuck+fwwiz (Nov 10)
- <Possible follow-ups>
- Re: chroot useful? Paul McNabb (Nov 12)
- Re: chroot useful? Steven M. Bellovin (Nov 13)
- Re: chroot useful? C Matthew Curtin (Nov 21)
- Re: chroot useful? Steven M. Bellovin (Nov 13)
- Re: chroot useful? Paul McNabb (Nov 12)
- Re: chroot useful? Douglas R. Steinbaum (Nov 13)
- Re: chroot useful? Darren Reed (Nov 14)
- Re: chroot useful? Steven M. Bellovin (Nov 14)
- Re: chroot useful? Aleph One (Nov 14)
- Re: chroot useful? Steven M. Bellovin (Nov 15)
- Re: chroot useful? Bernhard Schneck (Nov 14)
- Re: chroot useful? Darren Reed (Nov 09)
- Re: chroot useful? Paul McNabb (Nov 14)
- Re: chroot useful? Paul McNabb (Nov 14)
- Re: chroot useful? Paul McNabb (Nov 14)
- Re: chroot useful? Anton J Aylward (Nov 15)
- Re: chroot useful? Steven M. Bellovin (Nov 16)