Arthur Fuller
fuller.artful at gmail.com
Sun Jul 22 20:59:05 CDT 2012
I lifted the following snippet from nixCraft: Granted, it's intended for Linux, but I think most of us have a Linux VM handy, if for nothing else but occasional experimentation You can always flip to Linux to test out your various passwords: HowTo: Linux Check Password Strength With Cracklib-check Command<http://www.cyberciti.biz/security/linux-password-strength-checker/> Using the same password on different servers allows attackers to access your accounts if cracker manage to steal your password from a less secure server. This is true for online website accounts too. So solution is to create unique passwords for server accounts like your email, sftp and ssh accounts. General guideline to create a strong and unique password is as follows: 1. Create a password with mix of numbers, special symbols, and alphabets. 2. Make sure your password is hard to guess. You can use tool such as makepasswd <http://www.cyberciti.biz/faq/generating-random-password/> to create hard to guess password. 3. Do not use simple words like "password", "123456", "123abc" or "qwerty". 4. Use a unique password for all your server accounts. 5. A minimum password length of 12 to 14 characters should be used. See how to configure CentOS / RHEL / Fedora Linux based server<http://www.cyberciti.biz/faq/rhel-fedora-centos-linux-password-quality-control/> password quality requirements. 6. Generating passwords randomly where feasible. You can do this with a simple shell script<http://www.cyberciti.biz/faq/linux-random-password-generator/> function. 7. If possible use two-factor authentication. 8. Use pam_crack to ensure strong passwords<http://www.cyberciti.biz/tips/linux-check-passwords-against-a-dictionary-attack.html> and to check passwords against a dictionary attack. But, how do you test the effectiveness of a password in resisting guessing and brute-force attacks under Linux? The answer is simple use cracklib-check command. Say hello to cracklib-check This command takes a list of passwords from keyboard (stdin<http://bash.cyberciti.biz/guide/Input_and_Output>) and checks them using libcrack2. The idea is simple: try to prevent users from choosing passwords that could be guessed by "crack" by filtering them out, at source. Examples Test a simple password like "password", enter: $ echo "password" | cracklib-check Sample outputs: password: it is based on a dictionary word Try sequential patterns such as "abc123456": $ echo "abc123456" | cracklib-check Sample outputs: abc123456: it is too simplistic/systematic Try a password with a mix of letters, numbers, and symbols: $ echo 'i1oVe|DiZza' | cracklib-check Sample outputs: i1oVe|DiZza: OK The above password increases the difficulty of guessing or cracking your password. I used a random phrase (easy to remember) "I Love Pizza" and inserted random characters to create hard a strong password - "i1oVe|DiZza". Putting it all together #!/bin/bash# A sample shell script to add user to the system# Check password for strength # Written by Vivek Gite under GPL v2.x+# ----------------------------------------------read -p "Enter username : " userread -sp "Enter password : " passwordechoecho "Tesing password strength..."echoresult="$(cracklib-check <<<"$password")"# okay awk is bad choice but this is a demo okay="$(awk -F': ' '{ print $2}' <<<"$result")"if [[ "$okay" == "OK" ]]then echo "Adding a user account please wait..." /sbin/useradd -m -s /bin/bash $user echo "$user:$password" | /sbin/chpasswdelse echo "Your password was rejected - $result" echo "Try again."fi Hope this helps someone. -- Arthur Cell: 647.710.1314 Prediction is difficult, especially of the future. -- Niels Bohr