Skip to main content

Enforce stronger password in Linux

The pam_cracklib module checks the password against dictionary words and other constraints.
E.g. if you define password length minlen=10, then you will get 1 credit for e.g. using a single digit number in your password if you defined dredit=1. This means that pam_cracklib will accept a password of the length of minlen-credit. If you don't use a digit number, then the minimum length of the password would be minlen. There was no way to tell the module that a password _must_include a digit number.

The following example shows how to enforce the following password rules:
pam_cracklib.so minlen=8 Minimum length of password is 8
pam_cracklib.so lcredit=-1 Minimum number of lower case letters is 1
pam_cracklib.so ucredit=-1 Minimum number of upper case letters is 1
pam_cracklib.so dcredit=-1 Minimum number of digits is 1
pam_cracklib.so ocredit=-1 Minimum number of other characters is 1

To setup these password restrictions, edit the /etc/pam.d/system-auth file and add/change the following pam_cracklib arguments

auth required /lib/security/$ISA/pam_env.so
auth sufficient /lib/security/$ISA/pam_unix.so likeauth nullok
auth required /lib/security/$ISA/pam_deny.so
account required /lib/security/$ISA/pam_unix.so
account sufficient /lib/security/$ISA/pam_succeed_if.so uid < 100 quiet
account required /lib/security/$ISA/pam_permit.so
password requisite /lib/security/$ISA/pam_cracklib.so retry=3 minlen=8 lcredit=-1 ucredit=-1 dcredit=-1 ocredit=-1
password sufficient /lib/security/$ISA/pam_unix.so nullok use_authtok md5 shadow
password required /lib/security/$ISA/pam_deny.so
session required /lib/security/$ISA/pam_limits.so
session required /lib/security/$ISA/pam_unix.so

Comments

Popular posts from this blog

Check remote UDP connectivity from Linux

Hi there, You all know how to check TCP port connectivity from a Linux or UNIX machine to a remote machine using telnet as per th example below $ telnet 127.0.0.1 25 but we can't adopt TELNET to check UDP connectivity. Linux and most of the UNIXes come with a network layer utility called nc (abbreviation for netcat) which is very useful to check UDP connectivity and to explore a lot with both TCP and UDP. An example is shown below # nc -v -u -z -w 3 172.24.16.131 123 Connection to 172.24.16.131 123 port [udp/ntp] succeeded!

The best putty package available

Bored of Black screened Task bar filling putty? Issues with porting Saved sessions from machine to machine? Do you like tabbed SSH sessions? Start using portaputty instead of normal putty and link it with puttycm . Puttycm supports sessions to be saved in its own Database files. You can use the Putty sessions you have saved already right inside putty. You can have any number of databases which allow you to arrange Remote servers in folders and convenient namings. I personally recommend creating Database with puttycm rather than using the sessions saved in putty which doesn't offer any option to create folders and saving sessions under that directory tree. You can even save username/password to get it logged automatically and there is an option to pass commands to be run soon after login. I can't recommend this since some bug was found with these options. Portaputty is a variant of putty which stores all the Configuration data in text files instead of MS Window

PING.sh

#!/usr/bin/env bash ## Ping all machines in a Network PING="$(which ping) -c 1 -W 1" echo "Enter Subnet(eg:192.168.0)" read Subnet echo "Do you want to PING the entire network or a RANGE of IPs ? Enter your choice" echo 1. Ping Entire Network echo 2. Ping a RANGE read choice if [ $choice = 1 ]; then { echo Pinging..... for((i=1;i<255;i++)); do ${PING} ${Subnet}.${i} > /dev/null 2> /dev/null if [ $? -eq 0 ]; then echo -e "${Subnet}.${i} is up" fi done } fi if [ $choice = 2 ]; then { echo Enter the Starting IP of Range read a echo Enter the Last IP of Range read b echo Pinging..... for((i=$a;i<$b;i++)); do ${PING} ${Subnet}.${i} > /dev/null 2> /dev/null if [ $? -eq 0 ]; then echo -e "${Subnet}.${i} is up" fi done } fi exit 0