1.4 Creating User Accounts

Introduction

Outlined here are the minimal security steps the Bonsa Framework uses in server builds. Given that these account names are on the Internet you may want to change them. However, this may be greatly mitigated with RSA SSH key based authentication.

Naming Convention

You may want to understand the naming convention used here if you want to build your own. Otherwise, the examples are self-explanatory and have not encountered any issues.

Create Catch-All serveradmin user

The purpose of serveradmin is the catch-all place to setup things like scripts. It may also, depending on requirements for your organization be used to manually setup software like application servers.

Our user convention is firstName.lastName, however, we chose to user serveradmin rather than server.admin for fast typing as this and similar accounts are often used via sudo.

Also, the serveradmin account is limited in that it can not use sudo. If an attacker compromises the application, sudo is still out of reach.

Finally, in order to easily use Zero Footprint, create serveradmin consistently (same GID's and name) across all your systems.

Add the user and assign a password to that user,

sudo addgroup --gid 3000 serveradmin
sudo useradd -d /home/serveradmin -m -g serveradmin -u 3000 -c "Admin catch-all" -s /bin/bash serveradmin
sudo passwd serveradmin

Create Staff Users

We will also create staff users associated with the built in staff group so we know who is working on the machine. As a policy, our team requires that unless absolutely necessary, staff log in as their own account and then su to serveradmin or use sudo for maintenance work. That way we can have a trail of who does what.

sudo useradd -d /home/brian.hitch -m -g staff -u 2000 -c "Support Bryan Hitch" -s /bin/bash brian.hitch
sudo useradd -d /home/john.cassaday -m -g staff -u 2001 -c "Support John Cassaday" -s /bin/bash john.cassaday
sudo useradd -d /home/warren.ellis -m -g staff -u 2002 -c "Support Warren Ellis" -s /bin/bash warren.ellis

Notice the -u which set's the user's GUIDs. We found it essential to standardize on the GUID of the accounts across all our systems consistently. Not doing so causes problems when it comes to cloning systems or moving programs across different environments. As a practice, we use the following GUID's ranges,

• Staff 2000-2499
• Guest Staff Users 2500-2999

• Custom services 3000 - 3999

Additionally, we use the GUID range 4000-4999 for clients who would send in staff to work on the servers. Since the number of users with this kind of access should not be too large we can make the group blocks match the user blocks,

Next, we add to the Staff users the following groups,

• adm - so staff can view logs in apps setup without having to use the sudo command

Here is the command,

sudo usermod -a -G adm brian.hitch
sudo usermod -a -G adm john.cassaday
sudo usermod -a -G adm warren.ellis

Do not forget to set a passwords for the new accounts,

sudo passwd brian.hitch
Enter new Unix password:
Reenter new Unix password:
passwd: password updated successfully
sudo passwd john.cassaday
sudo passwd warren.ellis

Allow staff Group to sudo

Rather then editing the /etc/sudoers using visudo, this approach ensures that system upgrades will not overwrite your changes. 

Download File Using tscripts

Download tscripts,

sudo su - root
cd /etc/sudoers.d/
sudo wget www.bonsaiframework.com/tscripts/01_enable_sudo_for_staff
sudo chmod o-r /etc/sudoers.d/01_enable_sudo_for_staff
exit

Manual Method

If you want to create the file manually,

# Locks the file for single user access (important in a multi-user system) and validates for syntax errors.
sudo visudo -f /etc/sudoers.d/01_bonsai_disable_password_auth

visudo launches your default editor to a special file. Add the following to the file,

# Members of the staff group may gain root privileges.
%staff ALL=(ALL) ALL

Going forward, make sure to use visudo to edit the 01_bonsai_disable_password_auth file to ensure proper permissions and locking,

Create Auxiliary Users

If you want to make this into a truly enterprise system we will also need a few more users.

remotebackup - User to create remote backups. The assigned UID will be 3001.

sudo useradd -d /home/remotebackup -m -g backup -u 3001 -c "Remote Backup" -s /bin/bash remotebackup

Create regular Users

If you would like to add regular users without giving them sudo access then follow below instructions

Create regular group

sudo addgroup support

Create users and add them to group "support"

sudo useradd -d /home/tom.hitch -m -g support -u 2500 -c "Support Tom Hitch" -s /bin/bash tom.hitch
sudo useradd -d /home/rohan.cassaday -m -g support -u 2501 -c "Support Rohan Cassaday" -s /bin/bash rohan.cassaday
sudo useradd -d /home/dennis.ellis -m -g support -u 2502 -c "Support Dennis Ellis" -s /bin/bash dennis.ellis

Granting Non-staff User to use sudo with Certain Commands

In some cases you might want a non-staff user (Roderick can we do group too, it would be better) to certain commands. Usual scenarios are to restart services that require root such as Apache (that would be a better example here)

sudo visudo

Scroll to the bottom and enter the username in this case we use the name bob and enter the commands you would like bob to be able to sudo with, in this case we want bob to be able to create directories

bob ALL=(root) /bin/mkdir

Now test the command

sudo mkdir bob

Lets use the find command if you do not know what to add the error message tells you the path that needs to be added to the file as an example lets display the find command error

Sorry, user bob is not allowed to execute '/usr/bin/find something' as root on prodserver

Now that we have the command path just add that to bob in the visudo file and test. For multiple commands separate with a comma

bob ALL=(root) /bin/mkdir, /usr/bin/find

To use sudo without being prompted for a password add NOPASSWD: 

bob ALL=(root) NOPASSWD: /bin/mkdir, /usr/bin/find