Shadow-4.9

The login program currently performs many functions which Linux-PAM modules should now handle. The following sed command will comment out the appropriate lines in /etc/login.defs, and stop login from performing these functions (a backup file named /etc/login.defs.orig is also created to preserve the original file's contents). Issue the following commands as the root user:

install -v -m644 /etc/login.defs /etc/login.defs.orig &&
for FUNCTION in FAIL_DELAY               \
                FAILLOG_ENAB             \
                LASTLOG_ENAB             \
                MAIL_CHECK_ENAB          \
                OBSCURE_CHECKS_ENAB      \
                PORTTIME_CHECKS_ENAB     \
                QUOTAS_ENAB              \
                CONSOLE MOTD_FILE        \
                FTMP_FILE NOLOGINS_FILE  \
                ENV_HZ PASS_MIN_LEN      \
                SU_WHEEL_ONLY            \
                CRACKLIB_DICTPATH        \
                PASS_CHANGE_TRIES        \
                PASS_ALWAYS_WARN         \
                CHFN_AUTH ENCRYPT_METHOD \
                ENVIRON_FILE
do
    sed -i "s/^${FUNCTION}/# &/" /etc/login.defs
done

As mentioned previously in the Linux-PAM instructions, Linux-PAM has two supported methods for configuration. The commands below assume that you've chosen to use a directory based configuration, where each program has its own configuration file. You can optionally use a single /etc/pam.conf configuration file by using the text from the files below, and supplying the program name as an additional first field for each line.

As the root user, create the following Linux-PAM configuration files in the /etc/pam.d/ directory (or add the contents to the /etc/pam.conf file) using the following commands:

cat > /etc/pam.d/login << "EOF"
# Begin /etc/pam.d/login

# Set failure delay before next prompt to 3 seconds
auth      optional    pam_faildelay.so  delay=3000000

# Check to make sure that the user is allowed to login
auth      requisite   pam_nologin.so

# Check to make sure that root is allowed to login
# Disabled by default. You will need to create /etc/securetty
# file for this module to function. See man 5 securetty.
#auth      required    pam_securetty.so

# Additional group memberships - disabled by default
#auth      optional    pam_group.so

# include system auth settings
auth      include     system-auth

# check access for the user
account   required    pam_access.so

# include system account settings
account   include     system-account

# Set default environment variables for the user
session   required    pam_env.so

# Set resource limits for the user
session   required    pam_limits.so

# Display date of last login - Disabled by default
#session   optional    pam_lastlog.so

# Display the message of the day - Disabled by default
#session   optional    pam_motd.so

# Check user's mail - Disabled by default
#session   optional    pam_mail.so      standard quiet

# include system session and password settings
session   include     system-session
password  include     system-password

# End /etc/pam.d/login
EOF

cat > /etc/pam.d/passwd << "EOF"
# Begin /etc/pam.d/passwd

password  include     system-password

# End /etc/pam.d/passwd
EOF

cat > /etc/pam.d/su << "EOF"
# Begin /etc/pam.d/su

# always allow root
auth      sufficient  pam_rootok.so

# Allow users in the wheel group to execute su without a password
# disabled by default
#auth      sufficient  pam_wheel.so trust use_uid

# include system auth settings
auth      include     system-auth

# limit su to users in the wheel group
auth      required    pam_wheel.so use_uid

# include system account settings
account   include     system-account

# Set default environment variables for the service user
session   required    pam_env.so

# include system session settings
session   include     system-session

# End /etc/pam.d/su
EOF

cat > /etc/pam.d/chage << "EOF"
# Begin /etc/pam.d/chage

# always allow root
auth      sufficient  pam_rootok.so

# include system auth, account, and session settings
auth      include     system-auth
account   include     system-account
session   include     system-session

# Always permit for authentication updates
password  required    pam_permit.so

# End /etc/pam.d/chage
EOF

for PROGRAM in chfn chgpasswd chpasswd chsh groupadd groupdel \
               groupmems groupmod newusers useradd userdel usermod
do
    install -v -m644 /etc/pam.d/chage /etc/pam.d/${PROGRAM}
    sed -i "s/chage/$PROGRAM/" /etc/pam.d/${PROGRAM}
done

Warning

At this point, you should do a simple test to see if Shadow is working as expected. Open another terminal and log in as a user, then su to root. If you do not see any errors, then all is well and you should proceed with the rest of the configuration. If you did receive errors, stop now and double check the above configuration files manually. One obvious reason for an error is if the user is not in group wheel. You may want to run (as root): usermod -a -G wheel <user>. Any other error is the sign of an error in the above procedure. You can also run the test suite from the Linux-PAM package to assist you in determining the problem. If you cannot find and fix the error, you should recompile Shadow adding the --without-libpam switch to the configure command in the above instructions (also move the /etc/login.defs.orig backup file to /etc/login.defs). If you fail to do this and the errors remain, you will be unable to log into your system.

Instead of using the /etc/login.access file for controlling access to the system, Linux-PAM uses the pam_access.so module along with the /etc/security/access.conf file. Rename the /etc/login.access file using the following command:

[ -f /etc/login.access ] && mv -v /etc/login.access{,.NOUSE}

Instead of using the /etc/limits file for limiting usage of system resources, Linux-PAM uses the pam_limits.so module along with the /etc/security/limits.conf file. Rename the /etc/limits file using the following command:

[ -f /etc/limits ] && mv -v /etc/limits{,.NOUSE}

Caution

Be sure to test the login capabilities of the system before logging out. Errors in the configuration can cause a permanent lockout requiring a boot from an external source to correct the problem.