Database Security and Authorization

1. Database Security and Authorization By Yazmin Escoto Rodriguez Christine Tannuwidjaja

2. Main Types of Security: Enforce security of portions of a database against unauthorized access - Database Security and Authorization Subsystem Prevent unauthorized persons from accessing the system itself - Access Control Control the access to statistical databases - Statistical Database Security Protect sensitive data that is being transmitted via some type of communications - Data Encryption

3. Database Security and Authorization Subsystem Discretionary Security Mechanisms - concerned with defining, modeling, and enforcing access to information Mandatory Security Mechanisms for Multilevel Security - requires that data items and users are assigned to certain security labels

4. Mandatory Access Control Elements: OBJECTS CLASSIFICATIONS --class(o)-- SUBJECTS CLEARANCE --clear(s)-- Levels: Top Secret, Secret, Confidential, Unclassified

5. Mandatory Access Control Rules: Simple Property: subject s is allowed to read data item d if clear(s) ≥ class(d) *-property: subject s is allowed to write data item d if clear(s) ≤ class(d) • Simple Property protects information from unauthorized access • *-property protects data from contamination or unauthorized modification

6. Set up: we have: - subject x with clear(x) = TS - subject y with clear(y) = S - subject z with clear(z) = U Multilevel Security Databases- example

7. Multilevel Security Databases- example

8. Multilevel Security Databases- example

9. Multilevel Security Databases- example • subject z wants to insert the next tuple < Silver, LP, Omaha> Polyinstantiation : the existence of multiple data objects with the same key

10. Multilevel Security Databases- example • subject z wants to replace the null values with certain data items < Markov Chain, New Jersey>

11. Security Relevant Knowledge Data Flow Diagram -- represents the functions the system should perform Entity Relationship -- describes the structural part of the database • Classification Constraints • To assign to security classifications concepts of schemas: • ones that classify items • ones that classify query results

12. System Object In security it is the target of protection • Entity type • Specialization type • Relationship type What is it? O(A1..,An) - Ai (i=1..N) is an attribute and is defined over domain Di Has an identity property (key attributes) A ⊆ (A1,..,An) Notation

13. Multilevel Secure Application MAJOR QUESTION: Which way should the attributes and occurrences of O be assigned to proper security classifications? CLASSIFICATION RESULT: Security object O  multilevel security object Om Performed by means of security constraints

14. Graphical Extensions to the ER Secrecy Levels Ranges of Secrecy Levels Aggregation leading to TS (N..constant) Inference leading to Co Evaluation of predicate P Security dependency (U) (Co) (S) (TS) [U..S] [Co..TS] N X P

15. ER Diagram SSN Date Function Title Name Is Assigned to Subject Employee (0,N) (0,M) Project Dep Client Salary SSN Title

16. Object Classification Constraints – Simple Constraints • Let X be a set of attributes of security object O (X ⊆ {A1,…,An}) • SiC (O(X))=C, (C ∈ SL) • Results in a multilevel object Om(A1, C1,…, An, Cn,TC) where Ci=C ∀ Ai ∈ X, Ci left unchanged for Ai ∉ X • Application to ER: - SiC(Is Assigned to,{Function},S) - assigns property Function of relationship “Is Assigned to” to a classification of secret.

17. ER Diagram – classifying properties of security objects SSN Date Function Title Name Is Assigned to Subject Employee (0,N) (0,M) Project Dep Client Salary SSN Title

18. Object Classification Constraints – Content-based Constraints • Let Ai be an attribute of security object O with domain Di, let P be a predicate defined on Ai and let X ⊆ {Ai,…,An} • CbC (O(X), P: Aiθ a) = C or CbC (O(X), P: Aiθ Aj) = C (θ ∈ {=,≠,<,>,≤,≥}, a∈ Di, i ≠ j, C ∈ SL) • For any instance o of security object O(A1,…,An) for which a predicate evaluates into true the transformation into o(a1,c1,…,an,cn,tc) is performed • Classifications are assigned in a way that ci = C in the case Ai ∈ X, ci left unchanged otherwise • Application to ER: - CbC (Employee, {SSN, Name}, Salary, ‘≥’, ‘100’, Co)) - represents the semantic that properties SSN and Name of employees with a salary ≥ 100 are treated as confidential information

19. ER Diagram – classifying properties of security objects SSN Date Function Title Name Is Assigned to Subject Employee (0,N) (0,M) Project P Dep Client Salary SSN Title

20. Object Classification Constraints – Complex Constraints • Let O, O’ be two security objects and the existence of an instance o of O is dependent on the existence of a corresponding occurrence o’ of O’ where the k values of the identifying property K’ of o’ are identical to k values of attributes of o (foreign key) • Let P(O’) be a valid predicate defined on o’ and let X ⊆ {A1,…,An} be an attribute set of O • CoC (O(X), P(O’)) = C (C ∈ SL) • For every instance o of security object O(A1,…,An) for which a predicate evaluates into true in the related object o’ of O’ the transformation into o(a1,c1,…,an,cn,tc) is performed • Classifications are assigned in a way that ci = C in the case Ai ∈ X, ci left unchanged otherwise

21. Object Classification Constraints – Complex Constraints (con’t) • Application to ER: • - CoC (Is Assigned to, {SSN}, Project, Subject, ‘=‘, ‘Research’, S) • - individual assignment data (SSN) is regarded as secret information in the case the assignment refers to a project with Subject = ‘Research’

22. ER Diagram – classifying properties of security objects SSN Date Function Title Name Is Assigned to Subject Employee (0,N) (0,M) Project P Dep Client Salary SSN Title P

23. Object Classification Constraints – Level-based Constraints • Let level (Ai) be a function that returns the classification ci of the value of attribute Ai in object o(a1,c1,…,an,cn,tc) of a multilevel security object Om • Let X be a set of attributes of Om such that X ⊆ {A1,…,An} • LbC (O(X)) = level (Ai) • Result for every object o(a1,c1,…,an,cn,tc) to the assignment cj = ci in the case Aj ∈ X • Application to ER: • - LbC (Project, {Client}, Subject) • - states that property Client of security object Project must always have the same classification as the property Subject of the Project

24. ER Diagram – classifying properties of security objects SSN Date Function Title Name Is Assigned to Subject Employee (0,N) (0,M) Project P Dep Client Salary SSN Title P

25. Query Result Classification Constraints – Association-based Constraints • Let O (A1,…An) be a security object with identifying property K • Let X (X ⊆ {A1,…,An} (K ⋂ X = {}) be a set of attributes of O • AbC (O (K,X)) = C (C ∈ SL) • Results in the assignment of security level C to the retrieval result of each query that takes X together with identifying property K • Application to ER: • - AbC (Employee, {Salary}, Co) • - the salary of an individual person is confidential • - the value of salaries without the information which employee gets what salary is unclassified

26. ER Diagram – classifying query results SSN Date Function Title Name Is Assigned to Subject Employee (0,N) (0,M) Project Dep Client [Co] Salary SSN Title

27. Query Result Classification Constraints – Aggregation Constraints • Let count(O) be a function that returns the number of instances referenced by a particular query and belonging to security object O (A1,…,An) • Let X (X ⊆ {A1,…,An}) be sensitive attributes of O • AgC (O, (X, count(O) > n = C (C ∈ SL, n ∈ N) • Result into the classification C for the retrieval result of a query in the case count(O) > n, i.e. the number of instances of O referenced by a query accessing properties X exceeds the value n

28. Query Result Classification Constraints – Aggregation Constraints (con’t) • Application to ER: • - AgC (Is Assigned to, {Title}, ‘3’, S) • - the information which employee is assigned to what projects is regarded as unclassified • - aggregating all assignments for a certain project and thereby inferring which team is responsible for what project is considered secret

29. ER Diagram – classifying query results SSN Date Function Title Name Is Assigned to Subject Employee (0,N) (0,M) Project Dep Client [Co] Salary SSN Title 3

30. Query Result Classification Constraints – Inference Constraints • Let PO be the set of multilevel objects involved in a potential logical inference • Let O, O’ be two particular objects from PO with corresponding multilevel representation O (A1,C1,…,An,Cn,TC) and O’ (A’1,C’1,…,A’n,C’n,TC’) • Let X ⊆ {A1,…,An} and Y⊆ {A’1,…,A’n}) • IfC (O(X), O’(Y)) = C • Results into the assignment of security level C to the retrieval result of each query that takes Y together with the properties in X

31. Query Result Classification Constraints – Inference Constraints (con’t) • Application to ER: • - IfC (Employee, {Dep}, Project, {Subject}, Co) • - consider the situation where the information which employee is assigned to what projects is considered as confidential • - from having access to the department an employee works for and to the subject of a project, users may infer which department may be responsible for the project and thus may conclude which employee are involved

32. ER Diagram – classifying query results SSN Date Function Title Name Is Assigned to Subject Employee (0,N) (0,M) Project Dep Client [Co] Salary SSN Title 3 X

33. QUESTION?