CIS 527

Users & Permissions

User Accounts

• Allows multiple people to share resources
• Each user can have different permissions
• Aids in auditing (who did what)
• Protects system from unauthorized use

Authentication vs. Authorization

• Authentication - Confirming a user is who he or she claims to be (logging in)
• Authorization - Allow an authenticated user access to specific resources
• Authentication DOES NOT IMPLY Authorization

Authentication Methods

One or more of the following factors

• Ownership factors - something user has
• Knowledge factors - something user knows
• Inherence factors - something user is or does

Authorization Methods

• Security Policies
• Access Control Lists (ACL)
• File System Security Settings

User Identification

• Operating systems refer to users by a unique identifier
  • Linux: user identifier (UID)
  • Windows: security identifier (SID)
• This allows user to change usernames without affecting the account

User Account Information

• UID / SID
• Username
• Password
• Home directory
• Group(s)

Groups

• List of user accounts
• Aid in assigning access to users
• Each user may be a part of one or many groups
• Unique identifier
  • Linux: group identifier (GID)
  • Windows: security identifier (SID)

Windows 10 Default Accounts

• Administrator
  • Access to everything
  • Cannot be deleted
  • Disabled by default
  • Has no password by default
• Guest
  • Limited access
  • Disabled by default

Windows 10 Pseudo Accounts

• LocalSystem - system-level tasks & services
• LocalService - fewer rights than LocalSystem
• NetworkService - fewer rights than LocalService, but allows network access

Windows 10 Default Groups

• Administrators - complete access
• Event Log Readers - read event logs
• Guests - access system only
• Power Users - not used
• Remote Desktop Users - log on remotely
• Users - normal users

Many others, refer to documentation

User Account Control

• Protects the system from unwanted changes
• Allows administrators to run commands from a non-administrator account

Local Group Policy Editor

WIN+R - gpedit.msc

Ubuntu Account Types

• Super User (root)
  • Complete control of the system
  • Disabled by default on Ubuntu
  • UID = 0; GID = 0
• Regular User
  • User who can log on to the system
• System User
  • Used by programs and services to interact with the system

Ubuntu Accounts

Regular Users:

• UID: starting at 1000 and up
• Each account has a private group created with matching GID and is made a member of that group
• Each account receives a skeleton directory in /home

Commands

• groupadd - add a group
• groupdel - remove a group
• groupmod - modify group
• gpasswd - change group administrator or password
• useradd - add a system user
• userdel - remove a user
• usermod - modify a user
• adduser - add a regular user
• passwd - change password

sudo

• Short for "super user do"
• Allows regular users to run commands as root user
• User and rights listed in /etc/sudoers
• Add users to the "sudo" or "admin" group to give them access
• Use 'visudo' command to edit file

Best Practices

• Each person must have a unique account
• Enforce strong passwords & regular changes
• Assign minimal rights by default
• Log any logins/logouts/sudo usage
• Remove unneeded users ASAP
• Don't use admin account for daily use

File Permissions

• Determines which users can read/write files or folders
• Based on user and group memberships and file settings
• Helps prevent unwanted access to files

Windows Permissions

• Full Control - Can take ownership & change permissions
• Modify - Read/Write/Change/Delete
• Read & Execute
• List Folder Contents - Folders Only
• Read - Access files
• Write - Modify files

Ubuntu Permissions

• 3 classes: User, Group, Others
• 3 rights:
  • Read - Can read contents
  • Write - Can create/modify/delete
  • Execute - Can run programs/scripts

Modifying Ubuntu Permissions

• chmod - Change permissions
  • chmod [class][op][mode] file/folder
  • chmod [octal_mode] filename/folder
• chown - Change User/Group (sudo)
  • chown [user]:[group] filename/folder
• chgrp - Change Group (must own file)
  • chgrp [group] filename/folder

Ubuntu Permission Example

• Users: acct, hr, user, guest, root
• /files: All users except guest should have rwx, guest r only
• /files/acctg: acct should have rwx, hr should have r, all else no access
• /files/hr: hr and acct should have rwx, user should have rx, all else no access

Ubuntu Permission Example

• group1: acct, hr, user
• group2: acct, hr
• group3: hr


• /files: root:group1 rwxrwxr__
• /files/acctg: acct:group3 rwxr_____
• /files/hr: user:group2 r_xrwx___

Assignments

• Lab 1 - Building Secure Workstations: Due Monday Jan 30th by 10:30 AM