Shadow-4.0.18.1

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 LASTLOG_ENAB MAIL_CHECK_ENAB \
                PORTTIME_CHECKS_ENAB CONSOLE \
                MOTD_FILE NOLOGINS_FILE PASS_MIN_LEN \
                SU_WHEEL_ONLY MD5_CRYPT_ENAB \
                CONSOLE_GROUPS ENVIRON_FILE \
                ULIMIT ENV_TZ ENV_HZ ENV_SUPATH \
                ENV_PATH QMAIL_DIR MAIL_DIR MAIL_FILE \
                CHFN_AUTH FAILLOG_ENAB QUOTAS_ENAB FTMP_FILE \
                OBSCURE_CHECKS_ENAB CRACKLIB_DICTPATH \
                PASS_CHANGE_TRIES PASS_ALWAYS_WARN ISSUE_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 /etc/pam.d directory with the following command:

install -v -d -m755 /etc/pam.d

While still the root user, add the following Linux-PAM configuration files to the /etc/pam.d/ directory (or add the contents to the /etc/pam.conf file) with the following commands:

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

auth        requisite      pam_nologin.so
auth        required       pam_securetty.so
auth        required       pam_unix.so
account     required       pam_access.so
account     required       pam_unix.so
session     required       pam_env.so
session     required       pam_motd.so
session     required       pam_limits.so
session     optional       pam_mail.so      dir=/var/mail standard
session     optional       pam_lastlog.so
session     required       pam_unix.so
password    required       pam_cracklib.so  retry=3
password    required       pam_unix.so      md5 shadow use_authtok

# End /etc/pam.d/login
EOF

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

auth        requisite      pam_nologin.so
auth        required       pam_securetty.so
auth        required       pam_env.so
auth        required       pam_unix.so
account     required       pam_access.so
account     required       pam_unix.so
session     required       pam_motd.so
session     required       pam_limits.so
session     optional       pam_mail.so      dir=/var/mail standard
session     optional       pam_lastlog.so
session     required       pam_unix.so
password    required       pam_unix.so      md5 shadow

# End /etc/pam.d/login
EOF

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

password    required       pam_cracklib.so  type=Linux retry=1 \
                                            difok=5 diffignore=23 minlen=9 \
                                            dcredit=1 ucredit=1 lcredit=1 \
                                            ocredit=1 \
                                            dictpath=/lib/cracklib/pw_dict
password    required       pam_unix.so      md5 shadow use_authtok

# End /etc/pam.d/passwd
EOF

Note

In its default configuration, owing to credits, pam_cracklib will allow multiple case passwords as short as 6 characters, even with the minlen value set to 11. You should review the pam_cracklib(8) man page and determine if these default values are acceptable for the security of your system.

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

password    required       pam_unix.so      md5 shadow

# End /etc/pam.d/passwd
EOF

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

auth        sufficient      pam_rootok.so
auth        required        pam_unix.so
account     required        pam_unix.so
session     optional        pam_mail.so     dir=/var/mail standard
session     optional        pam_xauth.so
session     required        pam_env.so
session     required        pam_unix.so

# End /etc/pam.d/su
EOF

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

auth        sufficient      pam_rootok.so
auth        required        pam_unix.so
account     required        pam_unix.so
session     required        pam_unix.so
password    required        pam_permit.so

# End /etc/pam.d/chage
EOF

for PROGRAM in chpasswd chgpasswd 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. 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.

Currently, /etc/pam.d/other is configured to allow anyone with an account on the machine to use PAM-aware programs without a configuration file for that program. After testing Linux-PAM for proper configuration, install a more restrictive other file so that program-specific configuration files are required:

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

auth        required        pam_deny.so
auth        required        pam_warn.so
account     required        pam_deny.so
session     required        pam_deny.so
password    required        pam_deny.so
password    required        pam_warn.so

# End /etc/pam.d/other
EOF

If you preserved the source tree from the Linux-PAM package (or you feel like unpacking that tarball, then running configure and make), now would be a good time to run the test suite from this package. This test suite will use the configuration you just finished during the tests. All the tests should pass.

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:

if [ -f /etc/login.access ]; then
    mv -v /etc/login.access /etc/login.access.NOUSE
fi

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:

if [ -f /etc/limits ]; then
    mv -v /etc/limits /etc/limits.NOUSE
fi

During previous configuration, several items were removed from /etc/login.defs. Some of these items are now controlled by the pam_env.so module and the /etc/security/pam_env.conf configuration file. In particular, the default path has been changed. To recover your default path, execute the following commands:

ENV_PATH=`grep '^ENV_PATH' /etc/login.defs.orig | \
    awk '{ print $2 }' | sed 's/PATH=//'` &&
echo 'PATH        DEFAULT='`echo "${ENV_PATH}"`\
'        OVERRIDE=${PATH}' \
    >> /etc/security/pam_env.conf &&
unset ENV_PATH

Note

ENV_SUPATH is no longer supported. You must create a valid /root/.bashrc file to provide a modified path for the super-user.