Suse Hardening

1. Modify /etc/sudoers to allow members of wheel group to su to root. 
2. ___ Delete redundant accounts:
   • uucp -- obsolite account
   • ftp -- unless you need anonymous ftp access; this account is often abused)
   • games  -- useless for a server
   • possibly wwwrun (unless you need a webserver on the box)
   • Note: Do not delete news account or logrotate will stop working
      
3. ___ Delete redundant groups
    
4. ___  Modify /etc/issue & motd according to company standards
    
5. ____ Configure syslog-ng to report to remote host if such infrastructure (central log server) exists in your company (it should !)
    
6. Enroll primary and secondary administrators into the wheel group and  activate this group in sudo: \

   • Edit /etc/group by appending primary and secondary administrators to wheel group (do not overcrowd the group)

   • Edit  /etc/sudoers and uncomment the line in the line

   %wheel ALL=(ALL) NOPASSWD: ALL

   Note: this is preferred method of controlling root access as linux does not have RBAC.
    

7. Install writable files checking script into cron 
    
8. Verify correctness of home directories permissions
    
9. Populate all home directories and /root directory with .profile  and .kshrc files  (for bash users this is .bash_profile and .bashrc) and verify they are properly owned and have permissions  701
    
10. ___  Important Check and if necessary disable test, guest and any other unused accounts if any were created during the installation.
     
11.  ___  Modify default local security policies
    • min passwd length=8,
    • 5 Sec delay
    • 5 retries in case of wrong password
    • Alt-Ctrl-Del ignore
    • Allow Remote Graphical,
    • userID limits 100-999999, guid limits 100-999999,
12. Verify that all users are configured using user private groups
     
13. Install writable file check script into cron
     
14. Configure VNC to allow remote administration
     
15. Disable SSH1
     
16. Verify correctness of users home directories permissions (no writable directories allowed)
     
17. Enroll primary and secondary administrators into the wheel group and  activate this group in sudo: \

    • Edit /etc/group by appending primary and secondary administrators to wheel group (do not overcrowd the group)

    • Edit  /etc/sudoers and uncomment the line in the line

    %wheel ALL=(ALL) NOPASSWD: ALL

    Note: this is preferred method of controlling root access as linux does not have RBAC.
     

18. Configure Sudo to allow members of the wheel group to became root
     

19. Populate all home directories and /root directory with standard BASF .profile  and .kshrc files  (for bash users this is .bash_profile and .bashrc)

20. Create baseline
    1. ___ Create the baseline of key config files for the server

       Tar /etc directory and put the tar ball

       mkdir /root/Baseline

       tar cvzf /root/Baseline/etc`date +"%Y%M%D"` /etc

       You can also use provided by Nikolai Bezroukov script.
        

    2. Create list of SUID, SGID and world writable files and put is into /root/Baseline
       • SUID and SGID files on your system are a potential security risk, and should be monitored closely. Because these programs grant special privileges to the user who is executing them, it is necessary to ensure that insecure programs are not installed. A favorite trick of crackers is to exploit SUID-root programs, then leave a SUID program as a back door to get in the next time, even if the original hole is plugged.

         Find all SUID/SGID programs on your system, and keep track of what they are, so you are aware of any changes which could indicate a potential intruder. Use the following command to find all SUID/SGID programs on your system:

           find / -type f \( -perm -04000 -o -perm -02000 \)

         The Debian distribution runs a job each night to determine what SUID files exist. It then compares this to the previous night's run. You can look in /var/log/setuid* for this log.

         You can remove the SUID or SGID permissions on a suspicious program with chmod, then restore them back if you absolutely feel it is necessary.

         World-writable files, particularly system files, can be a security hole if a cracker gains access to your system and modifies them. Additionally, world-writable directories are dangerous, since they allow a cracker to add or delete files as he wishes. To locate all world-writable files on your system, use the following command:

          find / -perm -2 ! -type l -ls

         and be sure you know why those files are writable. In the normal course of operation, several files will be world-writable, including some from /dev, and symbolic links, thus the ! -type l which excludes these from the previous find command.

         Unowned files may also be an indication an intruder has accessed your system. You can locate files on your system that have no owner, or belong to no group with the command:

          find / \( -nouser -o -nogroup \) -print

    3. Put ISO file from which you installed in /var/ISO directory to make possible checking and reinstallation of packages.
    4. Save content of  /boot/grub/menu.lst to /root/Baseline
21. ___  Check and if necessary disable or delete test, guest, uucp and any other unused accounts
22. ___ Enable firewall.
23. Modify /etc/fstab according to Protective partitioning
    • Noexec on everything possible
    • Nodev everywhere except / and chroot partitions
    • Nosuid everywhere except /
    • Consider making /var/tmp link to /tmp, or maybe mount –bind option

    A example of "privilege minimized"  /etc/fstab from RHEL:

    LABEL=/              /              ext3 defaults                           1 1

    LABEL=/tmp           /tmp           ext3 defaults,nosuid,noexec,nodev       1 2

    LABEL=/var/log/audit /var/log/audit ext3 defaults,nosuid,noexec,nodev       1 2

    LABEL=/home          /home          ext3 defaults,nosuid,nodev              1 2

    LABEL=/var           /var           ext3 defaults,nosuid                    1 2

    LABEL=/boot          /boot          ext3 defaults,nosuid,noexec,nodev       1 2

    /tmp                 /var/tmp       ext3 defaults,bind,nosuid,noexec,nodev  1 2

    tmpfs                /dev/shm       tmpfs defaults                          0 0

    devpts               /dev/pts       devpts gid=5,mode=620                   0 0

    sysfs                /sys           sysfs defaults                          0 0

    proc                 /proc          proc defaults                           0 0

    LABEL=SWAP-sda6      swap           swap defaults                           0 0

24. Notes
    •  __________________________________________________________________________________
    •  __________________________________________________________________________________
    •  __________________________________________________________________________________
    •  __________________________________________________________________________________
    •  __________________________________________________________________________________

Etc

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Last modified: March 12, 2019