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Shadow Passwords

Password shadowing is an enhancement in password security. It creates a file called /etc/shadow from the passwd file in /etc/. In the passwd file all the encrypted passwords are replaced by asterisks. Actual encrypted strings are moved into the shadow password file. The trick is that /etc/passwd is world readable, but  /etc/shadow is not. It makes more difficult obtaining the  /etc/shadow file, or doing anything with it.

Packages

  1.  Unix Authentication Tools (also in John F. Haugh II's shadow package) -- includes the shadow program by John F. Haugh, II. A replacement for login and passwd that can enable any system to use shadow password files. Includes support for shadow password files, shadow group files, DBM password files, double length passwords, and password aging. This is perhaps one of the best shadowing programs. It includes aging passwords, restrictions on which port root logs in, logs failed attempts, proactive password check. Allows 16 character passwords. This is definitely a must have!

Other packages:

  1. Shadow in a Box by Micheal Quan. It's a compilation of utilies for managing all your shadow passwords. It includes tools for FTP, POP, sudo, xlock, as well as a crack library.
  2. passwd+: Matt Bishop's passwd+ offers extensive logging of successful and failure logins, as well as significant characters in the password.
  3. anlpasswd: By Argonne National Laboratory. It features these rules out of the box : number and spaces, uppercase, lowercase, all numbers, and leading capital letters.

    shadow

    William Colburn -- old precompiled binaries

Password documentation


The Shadow-HOWTO

How do I enable long passwords

shadow support in linux conf
Foiling the Cracker: A Survey of, and Improvements to, Password Security
OPUS: Preventing Weak Password Choices
UNIX Password Securty - Ten Years Later
Unix Password Security
Password Security: A Case of History

Knowledge Base - What are shadow passwords

Shadow Passwords -- slides from nasa.gov

The Linux NIS(YP)NYSNIS+ HOWTO Shadow Passwords with NIS and PAM -- Shadow passwords over NIS are always a bad idea. You lost the security, which shadow gives you. A good way to avoid shadow passwords over NIS is, to put only the local system users in /etc/shadow. Remove the NIS user entries from the shadow database, and put the password back in passwd. So you could use shadow for the root login, and normal passwd for NIS user. This has the advantage, that it will work with every NIS client.

the Shadow Password HOWTO

Shadow Utilities RedHat

- 11.5 Shadow Utilities Support for shadow
passwords has been enhanced significantly for Red Hat Linux 5.2.
Shadow passwords are a method of improving system security by
moving the encrypted passwords (normally found in /etc/passwd) to
another file..

Unix Shadow Passwords
When shadow files were first implemented some systems created or modified the system calls so they would return the encrytped password. This kept users from downloading the password file, but if you could make the system calls you could recreate the files yourself


deshadow.c
shcrack.c cracks too
unshad.c tiny deshadow program

Etc

Society

Groupthink : Two Party System as Polyarchy : Corruption of Regulators : Bureaucracies : Understanding Micromanagers and Control Freaks : Toxic Managers :   Harvard Mafia : Diplomatic Communication : Surviving a Bad Performance Review : Insufficient Retirement Funds as Immanent Problem of Neoliberal Regime : PseudoScience : Who Rules America : Neoliberalism  : The Iron Law of Oligarchy : Libertarian Philosophy

Quotes

War and Peace : Skeptical Finance : John Kenneth Galbraith :Talleyrand : Oscar Wilde : Otto Von Bismarck : Keynes : George Carlin : Skeptics : Propaganda  : SE quotes : Language Design and Programming Quotes : Random IT-related quotes :  Somerset Maugham : Marcus Aurelius : Kurt Vonnegut : Eric Hoffer : Winston Churchill : Napoleon Bonaparte : Ambrose Bierce :  Bernard Shaw : Mark Twain Quotes

Bulletin:

Vol 25, No.12 (December, 2013) Rational Fools vs. Efficient Crooks The efficient markets hypothesis : Political Skeptic Bulletin, 2013 : Unemployment Bulletin, 2010 :  Vol 23, No.10 (October, 2011) An observation about corporate security departments : Slightly Skeptical Euromaydan Chronicles, June 2014 : Greenspan legacy bulletin, 2008 : Vol 25, No.10 (October, 2013) Cryptolocker Trojan (Win32/Crilock.A) : Vol 25, No.08 (August, 2013) Cloud providers as intelligence collection hubs : Financial Humor Bulletin, 2010 : Inequality Bulletin, 2009 : Financial Humor Bulletin, 2008 : Copyleft Problems Bulletin, 2004 : Financial Humor Bulletin, 2011 : Energy Bulletin, 2010 : Malware Protection Bulletin, 2010 : Vol 26, No.1 (January, 2013) Object-Oriented Cult : Political Skeptic Bulletin, 2011 : Vol 23, No.11 (November, 2011) Softpanorama classification of sysadmin horror stories : Vol 25, No.05 (May, 2013) Corporate bullshit as a communication method  : Vol 25, No.06 (June, 2013) A Note on the Relationship of Brooks Law and Conway Law

History:

Fifty glorious years (1950-2000): the triumph of the US computer engineering : Donald Knuth : TAoCP and its Influence of Computer Science : Richard Stallman : Linus Torvalds  : Larry Wall  : John K. Ousterhout : CTSS : Multix OS Unix History : Unix shell history : VI editor : History of pipes concept : Solaris : MS DOS :  Programming Languages History : PL/1 : Simula 67 : C : History of GCC development :  Scripting Languages : Perl history   : OS History : Mail : DNS : SSH : CPU Instruction Sets : SPARC systems 1987-2006 : Norton Commander : Norton Utilities : Norton Ghost : Frontpage history : Malware Defense History : GNU Screen : OSS early history

Classic books:

The Peter Principle : Parkinson Law : 1984 : The Mythical Man-Month :  How to Solve It by George Polya : The Art of Computer Programming : The Elements of Programming Style : The Unix Hater’s Handbook : The Jargon file : The True Believer : Programming Pearls : The Good Soldier Svejk : The Power Elite

Most popular humor pages:

Manifest of the Softpanorama IT Slacker Society : Ten Commandments of the IT Slackers Society : Computer Humor Collection : BSD Logo Story : The Cuckoo's Egg : IT Slang : C++ Humor : ARE YOU A BBS ADDICT? : The Perl Purity Test : Object oriented programmers of all nations : Financial Humor : Financial Humor Bulletin, 2008 : Financial Humor Bulletin, 2010 : The Most Comprehensive Collection of Editor-related Humor : Programming Language Humor : Goldman Sachs related humor : Greenspan humor : C Humor : Scripting Humor : Real Programmers Humor : Web Humor : GPL-related Humor : OFM Humor : Politically Incorrect Humor : IDS Humor : "Linux Sucks" Humor : Russian Musical Humor : Best Russian Programmer Humor : Microsoft plans to buy Catholic Church : Richard Stallman Related Humor : Admin Humor : Perl-related Humor : Linus Torvalds Related humor : PseudoScience Related Humor : Networking Humor : Shell Humor : Financial Humor Bulletin, 2011 : Financial Humor Bulletin, 2012 : Financial Humor Bulletin, 2013 : Java Humor : Software Engineering Humor : Sun Solaris Related Humor : Education Humor : IBM Humor : Assembler-related Humor : VIM Humor : Computer Viruses Humor : Bright tomorrow is rescheduled to a day after tomorrow : Classic Computer Humor

The Last but not Least Technology is dominated by two types of people: those who understand what they do not manage and those who manage what they do not understand ~Archibald Putt. Ph.D

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Last modified: March 12, 2019