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Linux Server Security, Second Edition
book

Linux Server Security, Second Edition

by Michael D. Bauer
January 2005
Intermediate to advanced content levelIntermediate to advanced
544 pages
23h 44m
English
O'Reilly Media, Inc.
Content preview from Linux Server Security, Second Edition
This is the Title of the Book, eMatter Edition
Copyright © 2007 O’Reilly & Associates, Inc. All rights reserved.
OS Hardening Principles
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71
Many important network daemons now support command-line flags and other built-
in means of being run chrooted. Subsequent chapters on these daemons describe in
detail how to use this functionality.
(Actually, almost any process can be run chrooted if invoked via the chroot com-
mand, but this usually requires a much more involved chroot jail than do com-
mands with built-in chroot functionality. Most applications are compiled to use
shared libraries and won’t work unless they can find those libraries in the expected
locations. Therefore, copies of those libraries must be placed in particular subdirec-
tories of the chroot jail.)
chroot is not an absolute control: a chroot jail can be subverted via
techniques such as using a hard link that points outside of the chroot
jail or by using mknod to access the hard disk directly. However, since
none of these techniques is very easy to execute without root privi-
leges, chroot is a useful tool for hindering an attacker who has not yet
achieved root privileges.
Minimizing Use of SUID root
Normally, when you execute a command or application, it runs with your user and
group privileges. This is how file and directory permissions are enforced: when I,
as user mick, issue the command
ls /root, the system doesn’t really know ...
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Publisher Resources

ISBN: 0596006705Supplemental ContentCatalog PageErrata