1. Chapter 27: System Security
Dr. Wayne Summers
Department of Computer Science
Columbus State University

2. Comparison of Web Server (in DMZ) and Development Systems (internal)
Policy
Networks
Users
Authentication
Processes
Files

3. Policy for Web Server System in DMZ
All incoming Web connections and replies go through the outer firewall
All users log in from an internal trusted server running SSH. Web pages not updated locally, but downloaded through SSH tunnel
Log messages transmitted to DMZ log server only
Web server may query DMZ DNS for IP addresses
No other network services provided
Web server runs CGI scripts
Web server must implement services correctly & restrict access to services
Public key of principal who will decipher and process transaction data resides on DMZ Web server

4. Policy for Development System
Only authorized users are allowed to use the devnet systems. All actions / system accesses tied to individual user
Workstation sysadmins must be able to access workstations at all times
Users on devnet are trusted not to attack devnet systems, other users not trusted
All network communications (except ) are confidential and are checked for alteration
Base standard configuration cannot be changed
Sysadmin must be able to restore system from backup with at most one day’s loss
Security officers must perform periodic and ongoing audits of devnet systems

5. Networks Web Server System in the DMZ
External users can reach system only by using Web services connecting through outer firewall
Internal users can reach system only by using SSH from trusted admin system
All attempts to connect must be monitored
Server will not accept requests from other DMZ systems
Server requires both host and user to be authenticated (via SSH server)
Only web & SSH servers running; all attempts to connect to other ports are logged

6. Networks Development System
Only accept authenticated and encrypted user connections (SSH server)
Runs print spooler, logging server, access to file server and user database system
No ftp/web servers
Simple SMTP server for convenience with mail kept remotely
Uses access control wrappers
Systems scanned by sysadmin for vulnerabilities

7. Users Web Server System in the DMZ Two users & one sysadmin
One user – read/serve Web pages & write to Web server transaction area
Second user – move files from Web transaction area to commerce transaction area
Minimize # of accounts vs. minimize privileges of accounts
Sysadmin cannot login directly, except from console as root

8. Users Development System One user account per developer
Administrative account
Groups based on projects
Use consistent naming between development systems (use central repository - NIS)
Each developer workstation must have local root account and local account for sysadmin
Special accounts, e.g. mail, daemon
Development system noot accessible by Internet users

9. Authentication Web Server System in the DMZ
SSH server only allows connections from trusted hosts and requires cryptographic authentication
Web Server uses MD-5-based password hashing
Development System
Physically secure site
Passwords (with aging)
Use SSH for remote access

10. Processes Web Server System in the DMZ Run a minimum set of processes
Commerce server
SSH server
Login server
OS services
Interprocess communications only through well-defined communicaiton channels
Development System
Servers run with fewest privileges necessary to perform tasks
Processes must be logged

11. Files Web Server System in the DMZ
System programs & configuration files – static (keep on CD)
CGI programs – keep on CD
Web server files kept in separate partition shielded from commerce server
Development System
Use CD to boot and install system and configuration
Forward log messages to separate log server
Keep developers files on separate file server