ITIS 6210/8210 Access Control and Security ... - Marc Grosz Wiki

ITIS 6210/8210
Access Control and
Security Architecture
Lecture 1
Professor Mohamed Shehab
mshehab@uncc.edu
Woodward Hall 333F
Office Hours: TUE 1:00-3:00 PM
O Or b by appointment.
it t

IT IS 6210/8210
A Access Control C l and d Security S i Architecture
A hi
�� Discusses objectives objectives, formal models models, and
mechanisms for access control, access
control on commercial off-the-shelf systems systems,
and security architecture for authorization.
�� Current topics of advanced research in
access control. Content varies depending on
faculty interests, interests research developments developments, and
student demand.
�� The course provides the students with
hands-on experience in secure system
development through a project project.

Topics include:
�� Access Control Basics
◦ Access Control Matrix
◦ Access Control List
� Access Control Models
◦ Mandatory y Access Control
� Chinese Wall Policy
� Biba Model
� BllLPdl Bell-LaPadula MModel d l
� Lattice-based Access Control
◦ Discretionary y Access Control
◦ Role Based Access Control
◦ Location/Temporal/Context p
Based Access
Control

Topics include: (Cont (Cont.) )
�� Delegation Models
� Policy Specification and Management
◦ Security Assertion Markup Language (SAML)
◦ XACML
◦ XML Security
� Network Firewall Access Control
� Security Architectures
◦ Trust negotiations and management
◦ Identity Management
◦ Web Services Security

Grading Policy
�� Midterm Exam 25%
� Final Exam 25%
� Project 50%
◦ Presentation 20%
◦ Report 30%
� Both a project proposal and final report
are required. q

Recommended Reference Material
�� Books:
◦ Computer Security: Art and Science,
Matt Bishop, Addison-Wesley
� Research Papers: p
◦ Will be provided.
�� PowerPoint Slides and Papers will be posted
on course website:
� http://www.sis.uncc.edu/~mshehab/fall2009/itis6210/

Information If Information ti S Security it
Basic Concepts

Lecture Outline
�� Security Overview
� Security Design Principles
� Privacy Overview
�� Cryptography Overview

Information Protection - Why?
�� Information is an important strategic and
operational asset for any organization.
� Damages and misuses of information affect
not only y a single g user or an application; pp ; they y
may have disastrous consequences on the
entire organization organization.
� Additionally, the advent of the Internet as
well as networking capabilities has made the
access to information much easier.

Information Security: Examples
�� Consider a payroll database in a corporation corporation,
it must be ensured that:
◦ Salaries of individual employees are not disclosed
to arbitrary users of the database.
◦ Salaries are modified by only those individuals
that are properly p p y authorized.
◦ Paychecks are verified by individuals different
than the ones who issued them.
◦ Paychecks are printed on time at the end of each
pay period period.

What is Information Security?
� Confidentiality
◦ Is this all?
◦ Why not?
� Availability
◦ To whom?
�� Authentication
◦ Still not there
� IIntegrity i

Confidentiality
�� Refers to information protection from
unauthorized read operations.
� First formal work in computer security was
motivated by y the military’s y attempt p to
implement controls to enforce a “need to
know” know principle. principle
� Confidentiality also applies to the existence
of data, which is sometimes more revealing
than the data itself.

Integrity
�� Refers to information protection from
modifications; it involves several goals:
◦ Data integrity, ensuring the integrity of
information with respect to the original
information.
◦ Origin g integrity, g y, ensuring g source of the data, ,
often referred to as authentication.
◦ Semantic Integrity, protecting information from
incorrect modifications.

Integrity Example
�� A newspaper may print information
obtained from a leak at the White house,
but attributes it to the wrong source.
◦ This obeys data integrity.
y g y
◦ Violates origin integrity.

Availability
�� It ensures that access to information is
not denied to authorized subjects.
�� Attempts to block availability, availability are called
denial of service attacks.
� Example, p ,
SMURF attack.

Additional Information Security
Requirements
�� Information Quality – it is not considered
traditionally as part of information
security but it is very relevant.
� Completeness – it refers to ensure that
subjects bj t receive i all ll iinformation f ti th they are
entitled to access, according to the stated
security policies.

Classes of Threats
�� Disclosure
◦ Snooping,Trojan Horses
� Deception
◦ Modification, spoofing, repudiation of origin,
denial of receipt
�� Disruption
◦ Modification
� Usurpation (Unauthorized Control)
◦ Modification, spoofing, delay, denial of service

Goals of Security
�� Prevention
◦ Prevent attackers from violating security
policy
� Detection
◦ Detect attackers’ violation of security policy
�� Recovery
◦ Stop attack, assess and repair damage
◦ Continue to function correctly even if attack
succeeds

Policy and Mechanism
�� A Security Policy:
◦ Is a statement of what is and what is not
allowed allowed.
� A Security Mechanism:
◦ I Is a method, h d tool, l or procedure d for f enforcing f
a security policy.
E l
� Example:
◦ Policy - “Students should not copy from each
other”.
◦ Mechanism – Use an online paper correlator.

Policy and Mechanism (Cont (Cont.) )
�� Policies define security security, and mechanisms
enforce security
◦ Confidentiality
◦ Integrity g y
◦ Availability
�� Composition of policies
◦ If policies conflict, discrepancies may create
security vulnerabilities

Policy and Mechanism (Cont (Cont.) )
� PPolicies li i
◦ Unambiguously g y partition p system y states
◦ Correctly capture security requirements
� Mechanisms
◦ Assumed to enforce policy
◦ Support mechanisms work correctly

Types of Mechanism
Secure Precise Broad
Set of reachable
Set of secure
states states

Information Security – Mechanisms
�� Confidentiality is enforced by the access
control mechanism.
� Integrity is enforced by the access control
mechanism and by y the semantic integrity g y
constraints
� Availability is enforced by the recovery
mechanism and by detection techniques for
DDoS S attacks k – an example l of f which hi h is i query
flood

Information Security Security- Additional
Mechanisms:
�� User authentication - to verify the identity of
subjects wishing to access the information.
� IInformation f i authentication h i i - to ensure
information authenticity - it is supported by
signature i t mechanisms. h i
� Encryption - to protect information when being
transmitted across systems and when being
stored on secondary storage.
� Intrusion detection – to protect against
impersonation of legitimate users and also
against insider threats.

Information Security – How?
�� Information must be protected at various
levels:
◦ The operating system
◦ The network
◦ The data management system
◦ Physical protection is also important

Data vs Information
�� Computer security is about controlling access
to information and resources
� Controlling access to information can
sometimes be quite elusive and it is often
replaced by the more straightforward goal of
controlling ll access to data d
� The distinction between data and information
i is subtle btl but b t it i is also l the th root t of f some of f the th
more difficult problems in computer security
� Data represents information Information is the
� Data represents information. Information is the
(subjective) interpretation of data

Data vs Information Information (Cont.) (Cont (Cont.) )
Data Physical phenomena chosen by convention
to represent certain aspects of our conceptual
and real world. The meaning we assign to data
are called information. Data is used to transmit
and store information and to derive new
information by manipulating the data according
to formal rules.
from:
P.Brinch Hansen. Operating Systems Principles.
Prentice Prentice-Hall, Hall 1973 1973.

Data vs Information Information (Cont.) (Cont (Cont.) )
�� Protecting information means to protect
not only the data directly representing
the information
� Information must be protected also
i i i h h
against transmissions through:
◦ Covert channels
◦ Inference
� It is typical of database systems
� It refers to the derivation of sensitive information
from non-sensitive data

Inference - Example
Name Sex Programme Units Grade Ave
Alma F MBA 8 63
Bill M CS 15 58
Carol F CS 16 70
DDon M MIS 22 75
Errol M CS 8 66
Flora F MIS 16 81
Gala F MBA 23 68
Homer M CS 7 50
Igor M MIS 21 70

Inference – Example Example (Cont.) (Cont (Cont.) )
� Assume that there is a policy stating that the average grade
of a single student cannot be disclosed; however statistical
summaries can be disclosed
� Suppose that an attacker knows that Carol is a female CS
student
� B By combining bi i the h results l of f the h ffollowing ll i llegitimate i i
queries:
◦ Q1: SELECT Count (*) FROM Students WHERE Sex =‘F’ = F AND
Programme = ‘CS’
◦ Q2: SELECT Avg (Grade Ave) FROM Students WHERE Sex =‘F’
AND Programme = ‘CS’
� The attacker learns from Q1 that there is only one female
student t d t so th the value l 70 returned t d b by Q2 is i precisely i l h her
average grade

Information Security:
A Complete Solution.
�It consists of:
◦ First defining a security policy policy.
◦ Then choosing g some mechanism to
enforce the policy.
◦ Fi Finally ll providing idi assurance that h bboth h
the mechanism and the policy p y are
sound.

Security Design Principles

Overview
� Saltzer and Schroeder [1975] defined the 8 principles that
are based on the ideas of f simplicity and restriction
� Simplicity
◦ Less to go wrong
◦ Fewer possible inconsistencies
◦ Easy to understand
� Restriction
◦ Minimize access – an entity can access only information
it needs (also known as “need to know” principle)
◦ Inhibit communication – an entity can communicate
with other entities only when necessary, and in few (and
narrow) ways as possible

Principle of Least Privilege
�� The principle of least privilege states that an
entity should be given only those privileges
that it needs in order to complete its task
◦ The function of an entity, y and not its identity, y
should control the assignment of rights
◦ Rights should be added as needed, discarded
after use

Principle of Fail Fail-Safe Safe Defaults
�� The principle of fail fail-safe safe defaults state
that, unless an entity is given explicit
access to an object, it should be denied
access to that object j
◦ This principle requires that the default access
permission to an object be none

Principle of Economy of Mechanism
�� The principle of economy of mechanism
states that security mechanisms should be as
simple as possible
� Simpler means less can go wrong
◦ And when errors occur, occur they are easier to
understand and fix
�� Interfaces and interactions
◦ Interfaces to other modules are crucial, because
modules often make implicit assumptions about
input or output parameters or the current
system state

Principle of Complete Mediation
�� The principle of complete mediation
requires that all accesses to objects be
checked to ensure that they are allowed
� Usually done once, on first action
◦ UNIX: access checked on open, not checked
thereafter
◦ If permissions change after, may get
unauthorized access
◦ This approach violates the principle of
complete mediation

Principle of Open Design
�� The principle of open design states that the
security of a mechanism should not depend
on secrecy of f it its ddesign i or iimplementation l t ti
◦ If the strength of a program’s security depends on
the ignorance of f user, a knowledgeable user can
defeat the security mechanism
� “S “Security through h h obscurity” b ” is not a good d principle l
◦ This principles does not apply to information
such h as passwords d or cryptographic hi keys k (these ( h
are data and not algorithms)

Principle of Open Design (Cont (Cont.) )
�� Issues of proprietary software and trade
secrets complicate the application of this
principle
� In some cases companies do not want
their hi ddesigns i made d public bli to protect them h
from competitors
� The principle then requires that the
design g and implementation p
be available to
people barred from disclosing it outside
the company p y

Principle of Separation of Privilege
�� The principle of separation of privileges
states that a system should not grant
permission based on a single condition condition.
� In other words: more than one condition
must b be verified ifi d i in order d to gain i access
◦ Separation of duty
� Example: company check for more than $75,000 must
be signed by two officers of the company
� EExample: l O On BBerkeley-based k l b d versions i of f Unix, U i a user
is not allowed to change from his accounts to the
root account unless two conditions are verified: (i) ( ) the
user knows the root password; (ii) the user is in the
wheel group (with GID 0)

Principle of Least Common Mechanism
�� The principle of least common
mechanism states that mechanisms used
to access resources should not be shared
◦ Information can flow along g shared channels
◦ Covert channels
�� Isolation
◦ Virtual machines
◦ Sandboxes

Principle of Least Common Mechanism
(Example)
�� For example example, serving an application on the
Internet allows both attackers and users to
gain access to the application application. Sensitive
information can potentially be shared
between the subjects via the mechanism.
� A different mechanism for each subject or
class of subjects can provide flexibility of
access control among various users and
prevent potential security violations that
would otherwise occur if only one
mechanism was implemented.

Principle of Psychological Acceptability
� The principle p p of psychological p y g acceptability p y states
that security mechanisms should not make the
resource more difficult to access than if the security
mechanisms were not present
◦ Hide complexity introduced by security mechanisms
◦ Ease of f installation, configuration, f use
◦ Human factors critical here
◦ O On the th other th hand, h d security it requires i that th t th the messages
impart no unnecessary information
� For example, p , if a user supplies pp the wrong g p password, , the system y
should reject the attempt with a message saying that the login
failed. If it were to say that the password was incorrect, the user
would know that the account name was legitimate g

Privacy

Privacy ??
�� Information Privacy is the ability of an
individual to control the use and dissemination
of information that relates to himself or
herself.
�� The word “Privacy” Privacy means different things in
different contexts:
◦ Freedom from intrusion intrusion.
◦ Control of personal information.
◦ Control of one’s one s image or name name.
� The historic driver of the privacy problem is
the “bad bad people” people problem problem.

Approaches to Privacy
Enforcement
� GGovernmental l SStandards d d
◦ Enforcement by regulatory agencies, states, etc.
� Industry Standards
◦ “Codes Codes of conduct” conduct
◦ Limited enforcement through licensing
◦ Limited enforcement from government
� Unregulated g Market
◦ Reputation
�� Technology can help in all of these cases cases.

Fair Fair Credit Credit Reporting Reporting Act, Act 1970
1970
�� Right to:
◦ See your credit report.
◦ Challenge incorrect information.
◦ Information automatically y expire p after 7 years. y
◦ Know who accesses your report.
◦ Free credit report if you are denied credit credit.

The Code of Fair Information
Practice (1973)
�� Included:
◦ No Secret record-keeping systems.
◦ Right to see your record.
◦ Information obtained for one purpose p p may y
not be used for another purpose.
◦ Right to correct or amend incorrect records records.
◦ Organizations must assure the reliability of
data and take precautions to prevent misuse misuse.

Other Privacy Acts
�� HIPAA: Health Insurance Portability
and Accountability Act
� COPPA COPPA: Child Children’s ’ Online O li Privacy P i
Protection Act
◦ Applies to online collection of info on
children under 13.
� Gramm-Leach-Bliley Act
� Sarbanes-Oxley: Public Company
y p y
Accounting Reform and Investor
Protection Act

Other Privacy Acts
�� Gramm Gramm-Leach-Bliley Leach Bliley Act
◦ Consumers must be informed of privacy
policies
� Initial notice
� Annual notice
� Notices were mostly ignored!
◦ Consumers must have a chance to “opt-out”
� Many y different ways y to “opt-out” p
� Have you ever opted out?

Other Privacy Acts
�� Sarbanes Sarbanes-Oxley: Oxley: Public Company
Accounting Reform and Investor
Protection Act
◦ Insider Trading
◦ Conflict of Interest
◦ Public disclosures
◦ Public disclosures
◦ Assessment of internal controls
◦ Mandatory disclosures

Example: Patient Records
Name a e SSN SS DOB O Sex Se Zip p
Code
Disease sease
DOB
1/21/76
4/13/86
2/28/76
1/21/76
4/13/86
2/28/76
Sex Andre
BBarbra b
Male James
Female Bob
Male Carol
Male Alice
Female
Female
Zip 400-44-1234 Disease 1/21/76
Code 420 420-33-1434 33 1434 4/13/86
53715 603-00-1444 Heart 2/28/76 Disease
53715 412-22-1111 412 22 1111 Hepatitis p 1/21/76
53703 210-12-2222 Bronchitis 4/13/86
53703 450-45-6666 Broken 2/28/76 Arm
53706 Flu
53706 Hang Nail
Male 53715 Heart Disease
Name DOB Sex Zip p
FFemale l 53715 HHepatitis
Code
Male
Andre
53703
1/21/76
Bronchitis
Male 53715
Male
BBethh 53703
1/10/81
Broken
FFemale l
Arm
55410
Female
Carol
53706
10/1/44
Flu
Female 90210
Female
Dan
53706
2/21/84
Hang
Male
Nail
02174
Ellen 4/19/72 Female 02237
Voter Registration Data
Rl Released d Medical Md l Data
D

Cryptography Overview

Cryptography
� Basic assumptions
◦ Message to be encrypted
◦ Algorithms (publicly known) to encrypt/decrypt message
◦ Key y( (known only yto sender/recipient) p )
◦ Given only algorithms and encrypted message, nobody knows a
method to decrypt that is significantly faster than trying all keys
� Types of attacks
◦ Ciphertext only
◦ Known plaintext
◦ Chosen plaintext
� Real attacks generally don’t break cryptography!
◦ Don’t pick the lock, tunnel into the vault

Symmetric Cryptography
�� The secret key that seals also unseals
◦ M’ = f(M,key) encryption or sealing
◦ M = f’(M’ f’(M’,key) k ) ddecryption p i or unsealing li
� Uses:
◦ Prevent eavesdropping
� Must be secure channel for key exchange
◦ Secure storage
� I have to remember my key
◦ Authentication
� Challenge/response
◦ Integrity Check
� Checksum on the message
� Encrypt the checksum

Public Key ( (Assymetric ( (Assymetric Assymetric) ) Cryptography
�� First published in 1976 (Diffie (Diffie-Hellman) Hellman)
◦ More common today: RSA
� Matched pair of keys
◦ Public key (e) to encrypt
◦ Private key (d) to decrypt
� F For iintegrity, i encrypt checksum h k with i h
sender’s private key
◦ Only sender’s public key will decrypt properly

Public Key ( (Assymetric ( (Assymetric Assymetric) ) Cryptography
�� Uses:
◦ Prevent eavesdropping
◦ Authentication
◦ Integrity g y
� Problem: public key algorithms slow
◦ SSolution: l ti Use U t to share h secret t key
k

Public Key Cryptography:
Non Non-repudiation repudiation
�� Message Integrity Checksum (MAC) can
convince Recipient that Sender created message
◦ Message correct, from right source
� But can’t convince anyone else!
◦ Sender, recipient share key
◦ Either could generate message
� Public key solves this problem
◦ Private key required to encrypt
◦ Only y
known to sender

Public Key Cryptography
�� Public key d d, private key e
◦ m = e(d(m)) = d(e(m))
� Given d, d(m), hard to find m
◦ same for e, e(m)
� Given d, hard to find e
◦ same for e, d
� Most based on modular arithmetic
◦ Modular exponentiation

Algorithms: Diffie Diffie-Hellman Hellman
�� Goal: Two parties agree on common
number
◦ E E.g., l learn shared h d key k
� Initial: large prime p, g < p
◦ publicly known
� Each chooses secret
� T = g s mod p
� Exchange and repeat
� Exchange and repeat
◦ Result is the same

Algorithms: Diffie Diffie-Hellman Hellman (Problems)
�� Authentication
◦ Am I talking to the right person?
� Man in the middle
◦ Sets up session with either end

Algorithms: RSA
(Rivest, Shamir, Adleman)
�� Key generation
◦ Choose primes p,q
◦ Ch Choose e relatively l ti l prime i t to ( (p-1)(q-1) 1)( 1)
◦ Public key
◦ PPrivate i key k d where h d = 1/(e 1/( mod d ( (p-1)(q-1)) 1)( 1))
� Encrypt: c = me mod n
◦ Decrypt: m = c d mod n
� de = 1 mod (p-1)(q-1), so m = (m e ) d mod n
� Breakable if we can factor (why?)

Hash Algorithms
�� Transform arbitrarily long message m into (short)
fixed-length message h(m)
◦ Must be easy to compute h(m)
◦ Given h(m), hard to find (an) m
◦ Hard to find m 1 and m 2 such that h(m ( 1)=h(m 1) ( 2) 2)
� Goal: h(m) should appear random
◦ Non-trivial to define “appear pp random”
� Uses
◦ Password storage g (easy ( y to verify y that it is probably p y
correct)
◦ Integrity: Send m, h(m|s)
◦ Storage integrity

Changing one input bit should
change ~50% of the output bits.
Message MD5
“this is a test” ff22941336956098ae9a564289d1bf1b
“this is c test” c5e530b91f5f324b1e64d3ee7a21d573
“this is a test ” 6df4c47dba4b01ccf4b5e0d9a7b8d925

128 ? 128 ?
How big is 2 2128 How big is 2 2128 �� MD5 is 128 bits long
� 2 128 =
340,282,366,920,938,463,463,374,607,431,7
68,211,456 , ,
� If you could try a billion 2 combinations a
second, d it would ld take t k 10,790 10 790 billion billi years

Message Digest Algorithms
�� Rivest Functions:
◦ MD2 (128 bits)
◦ MD4 (128 bits)
◦ MD5 (128 ( bits) )
� NIST Functions:
◦ SHA (160 bits) bit ) SHA SHA-1 1 (160 bit bits) )
◦ SHA-512, SHA-1024
� Other Functions:
◦ Snerfu, N-Hash, N Hash, RIPE-MD, RIPE MD, HAVAL

(Strange) Hash Uses
�� Authentication
◦ A sends challenge rA ◦ B responds with h(k|r h(k|rA) A) and r B
◦ A responds with h(k|rB) � Integrity / Message Authentication Code
◦ h(m | k)
�� Generate a one-time one time pad
◦ h(k | r) gives first block, then h(k | bi-1) gives bi �� Can also generate a hash using symmetric
encryption
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