System Administation: Maximizing System Security, Part 1
Package ftp Location COPS ftp.cert.org:/pub/tools/cops Courtney ftp.best.com:/pub/lat Crack ftp.cert.org:/pub/tools/crack Gabriel ftp.best.com:/pub/lat Merlin ciac.llnl.gov:/pub/ciac/sectools/unix/merlin Netscape ftp.netscape.com:/netscape/unix npasswd ee.utah.edu:/admin/passwd/npasswd passwd+ ee.utah.edu:/admin/passwd/passwd+ Perl prep.ai.mit.edu:/pub/gnu Satan ftp.win.tue.nl:/pub/security shadow sunsite.unc.edu:/pub/Linux/system/Admin sudo sunsite.unc.edu:/pub/Linux/system/Admin swatch sierra.stanford.edu:/pub/sources TCP Wrappers ftp.win.tue.nl:/pub/security/tcp_wrapper Tripwire coast.cs.purdue.edu:/pub/COAST/Tripwire
Passwords are the primary way of securing user accounts on Linux systems. However, the protection offered by passwords is only as good as the passwords themselves. If a hacker decides to attack the accounts on your system, bad passwords are almost as bad as no passwords at all.
There are several things you can do to ensure that the password facility is providing the best protection it is capable of:
Make sure all active accounts have passwords and that system accounts not intended for user logins (e.g. bin) are disabled (do this by placing an asterisk in the password field for that account).
Secure the encoded versions of the system's passwords by using a shadow password file.
Educate users about keeping passwords secret, selecting hard-to-crack passwords, changing passwords as necessary, using different passwords at different sites, and similar security practices. Institute password aging and/or new password obscurity checking if appropriate.
The first item is self-explanatory; we look at the others in detail.
Shadow password files are designed to correct the security hole resulting from the normal password file being world-readable. Everyone needs to be able to view the contents of /etc/passwd so that things like file ownership displays properly (UIDs are translated into usernames). However, since the file is readable, anyone can make a copy of it. This means someone with legitimate or illegitimate access to an ordinary user account can copy it and attempt to crack the passwords of more powerful accounts at his leisure.
A shadow password file facility removes the encoded passwords from the normal password file and places them in another file, conventionally /etc/shadow, which can be read only by root. The shadow package provides shadow password file capabilities for a variety of UNIX systems including Linux. It is included in some Linux distributions by default. It includes replacements for the login, passwd, and su commands as well as many utilities for creating and manipulating the shadow password file and account entries within it.
Building the shadow package is quite straightforward. If you've retrieved a version that has been ported to Linux, you'll generally only have to modify the config.h file. I recommend the following settings (culled from various points within that file):
/* Use shadow password file. */ #define SHADOWPWD /* Use up to 16 char. passwords. */ #define DOUBLESIZE /* Enable password aging checks. */ #define AGING /* Log events to syslog facility. */ #define USE_SYSLOG /* Support for remote logins. */ #define RLOGIN #define UT_HOST /* Data file for most recent login time records */ #define LASTFILE "/var/adm/lastlog"
Once the package is built and installed, the pwconv command may be used to create an initial /etc/shadow file. It creates the files /etc/npasswd and /etc/nshadow. The former is an altered version of the original password file in which the password field in each entry has been replaced by an x; the latter is the corresponding shadow password file. In order to activate them, you must rename them by hand:
# cd /etc # mv passwd passwd.prev # cp npasswd passwd # cp nshadow shadow
Practical Task Scheduling Deployment
One of the best things about the UNIX environment (aside from being stable and efficient) is the vast array of software tools available to help you do your job. Traditionally, a UNIX tool does only one thing, but does that one thing very well. For example, grep is very easy to use and can search vast amounts of data quickly. The find tool can find a particular file or files based on all kinds of criteria. It's pretty easy to string these tools together to build even more powerful tools, such as a tool that finds all of the .log files in the /home directory and searches each one for a particular entry. This erector-set mentality allows UNIX system administrators to seem to always have the right tool for the job.
Cron traditionally has been considered another such a tool for job scheduling, but is it enough? This webinar considers that very question. The first part builds on a previous Geek Guide, Beyond Cron, and briefly describes how to know when it might be time to consider upgrading your job scheduling infrastructure. The second part presents an actual planning and implementation framework.
Join Linux Journal's Mike Diehl and Pat Cameron of Help Systems.
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|The Firebird Project's Firebird Relational Database||Jul 29, 2016|
|Stunnel Security for Oracle||Jul 28, 2016|
|SUSE LLC's SUSE Manager||Jul 21, 2016|
|My +1 Sword of Productivity||Jul 20, 2016|
|Non-Linux FOSS: Caffeine!||Jul 19, 2016|
|Murat Yener and Onur Dundar's Expert Android Studio (Wrox)||Jul 18, 2016|
- Stunnel Security for Oracle
- The Firebird Project's Firebird Relational Database
- Murat Yener and Onur Dundar's Expert Android Studio (Wrox)
- SUSE LLC's SUSE Manager
- Managing Linux Using Puppet
- My +1 Sword of Productivity
- Non-Linux FOSS: Caffeine!
- Doing for User Space What We Did for Kernel Space
- SuperTuxKart 0.9.2 Released
- Google's SwiftShader Released
With all the industry talk about the benefits of Linux on Power and all the performance advantages offered by its open architecture, you may be considering a move in that direction. If you are thinking about analytics, big data and cloud computing, you would be right to evaluate Power. The idea of using commodity x86 hardware and replacing it every three years is an outdated cost model. It doesn’t consider the total cost of ownership, and it doesn’t consider the advantage of real processing power, high-availability and multithreading like a demon.
This ebook takes a look at some of the practical applications of the Linux on Power platform and ways you might bring all the performance power of this open architecture to bear for your organization. There are no smoke and mirrors here—just hard, cold, empirical evidence provided by independent sources. I also consider some innovative ways Linux on Power will be used in the future.Get the Guide