Date: Sun, 15 Nov 1998 09:56:32 -0800 From: Mike Smith <mike@smith.net.au> To: zhihuizhang <bf20761@binghamton.edu> Cc: hackers <freebsd-hackers@FreeBSD.ORG> Subject: Re: Question on chroot() Message-ID: <199811151756.JAA13251@dingo.cdrom.com> In-Reply-To: Your message of "Sun, 15 Nov 1998 10:31:47 EST." <Pine.SOL.L3.93.981115102202.5823A-100000@bingsun2>
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> > I am quite confused with the usage of chroot(). It is said that chroot() > can only be performed by superuser and the chroot()'ed environment is > valid only for superuser that calls chroot() and its descendent (I assume > that a descendent inherits its parent's UID). > > However, a root can escape the environment withoud much difficulty. I > even find on the Web a page telling you how to break the chroot jail by > root. > > With these in mind, I can not figure out why the chroot() is really useful > to set up a ristricted access to a system and how a NORMAL user can be > setup to access only the chroot()'ed environment. Breaking out of a chroot'ed environment is less easy if you're not root, so when it's used for security purposes, the chroot() call is made as root as part of the login process, and then root priviledges are surrendered. See how login() arranges for the login shell to run as the user, while itself running as root to access the password database. However, chroot() is more usful as a functional tool, allowing you to perform tasks that expect to operate on a system-wide scope without having them actually change your system. Eg. we use chroot to provide an environment for building the FreeBSD package collection, where packages must be installed and removed on a frequent basis, without actually affecting the package set installed on the host system. -- \\ Sometimes you're ahead, \\ Mike Smith \\ sometimes you're behind. \\ mike@smith.net.au \\ The race is long, and in the \\ msmith@freebsd.org \\ end it's only with yourself. \\ msmith@cdrom.com To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-hackers" in the body of the message
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