INLS 187

1
INLS 187

• September 22, 2004
• Authority and Privilege

2
Housekeeping

• Any questions about material so far?
• Need copies of Linux live CDs?
• Next assignment details on class website
• Loose ends
• Dont log passwords or usernames
• Let Google do your password guessing ?
• Any interesting security news? (5 min)

3
Pop Quiz

• UNC requires that any device attached to the
  campus Ethernet network must have its MAC address
  registered and associated with an ONYEN. Is
  this
• An identification policy?
• An authentication policy?
• An authorization, or access control policy?
• Some other kind of policy?

4
Authorization

• Windows user rights
• group membership (not like UNIX groups)
• Restricted user
• User
• Power user
• Administrator
• UNIX normal user or root (UID 0)
• root has all possible privilege
• Others basically use file access rules
• Special mechanisms increase/decrease authority

5
UNIX Privilege (basic)

• setUID / setGID attribute on program file,
  program runs with specified user/group ID
• If setUID root, runs with all privileges
• If setUID / setGID non-root, can use the files
  accessible by that user/group ID
• E.g., mail program typically setGID mail
• Your mailbox typically allows r/w by group mail
• The mail program can write to your mailbox
• chroot sandbox (hard to administer)
• Mount w/ restrictions (r/o, no setUID)

6
Why Talk About This?

• A security policy specifies what should and
  should not happen
• The security mechanisms of each system make it
  happen (or not)
• Knowing how the tools work may influence the
  design of your policy (or vice versa, but
  expensive)

7
Back to Access Control

• Discretionary access control (DAC) owner sets
  access
• Mandatory access control (MAC) owner cannot
  change (except by use of privilege)

8
Discretionary Access Control

• Windows Properties -gt Security
• UNIX chmod command (note UNIX can also chgrp
  chown)
• AFS has Access Control Lists
• Other examples? (discussion)

9
Mandatory Access Control

• Modeled on secret, top secret, etc.
• User not allowed to change classification
• Whole different set of read/write rules
• Lower level information may be read by higher
  level user, but not vice versa
• Lower level information may be written to higher
  level object, but not vice versa
• Finance? Health care? Personnel data? Other
  examples? (discussion)