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COS 80011 Web Application Architectures Lecture 10 Access Control

COS 80011 Web Application Architectures Lecture 10 Access Control. What is Access Control? Access Control Matrix and Access Control List Role-Based Access Control User-Role Assignment Role-Permission Assignment Attribute-Based Access Control Context-Aware Access Control

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COS 80011 Web Application Architectures Lecture 10 Access Control

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  1. COS 80011Web Application ArchitecturesLecture 10Access Control

  2. What is Access Control? Access Control Matrix and Access Control List Role-Based Access Control User-Role Assignment Role-Permission Assignment Attribute-Based Access Control Context-Aware Access Control Context-Aware User-Role Assignment Context-Aware Role-Permission Assignment Outline

  3. What is Access Control? Access Control Matrix and Access Control List Role-Based Access Control User-Role Assignment Role-Permission Assignment Attribute-Based Access Control Context-Aware Access Control Context-Aware User-Role Assignment Context-Aware Role-Permission Assignment Outline

  4. Access control is one of the fundamental security mechanisms needed to protect computer resources (and/or services) against unauthorized access according to a security policy policy – is a rule (who can access what) verifying whether a subject (user) is allowed to carry out a specific action (operation) on an object (resource) it is a mechanism to determine whether a request from a user to access resources in a system should be permitted or denied Access Control (I)

  5. It has three major components subjects– represent the users in a system performing actions on an object objects– represent the resources that are being protected by the system operations– represent all the actions that the subjects can perform on the objects Access Control (II)

  6. Access Control Models/Technologies Access Control Matrix or Access Matrix (AM) Access Control List (ACL) Role-Based Access Control (RBAC) Attribute-Based Access Control (ABAC) Context-Aware Access Control (CAAC) Extended RBAC Models: TMAC (team), OrBAC (organization), … ABAC Models: XACML, … … Access Control (III)

  7. Traditional forms of Access Control AM, ACL, RBAC, … file systems, operating systems, database systems, … Access Control on the Web XACML (OASIS standard Web-based AC), XACML for RBAC, … Domain-specific inputs converted to the XACML Request Context.xml (PEP) XACML core policy framework or XACML RBAC implementation using (J2SE, CORBA, etc.), resources are exposed as Web services (PDP, PIP, PAP) XACML Response Context.xml is converted to the domain-specific outputs (PEP) Access Control (IV)

  8. What is Access Control? Access Control Matrix and Access Control List Role-Based Access Control User-Role Assignment Role-Permission Assignment Attribute-Based Access Control Context-Aware Access Control Context-Aware User-Role Assignment Context-Aware Role-Permission Assignment Outline

  9. Access Control Matrix or Access Matrix (AM) access control technology has a long history that started in the late 60s it was first introduced by Lampsonin 1971, who introduced a formal, mathematical description of a basic access control model named Access Control Matrix <Lampson, Butler W. (1971), Protection, Proceedings of the 5th Princeton Conference on Information Sciences and Systems> Access Control Matrix (I)

  10. Access Control Matrix or Access Matrix (AM) the first basic model of access control is the AM a formal security model in computer systems characterizes the rights of the subjects with respect to the objects describes the relationships between subjects and objects in a system <Lampson, Butler W. (1971), Protection, Proceedings of the 5th Princeton Conference on Information Sciences and Systems> Access Control Matrix (II)

  11. Access Control Matrix: It has three components a set of Objects O, a set of Subjects S, and an Access functionA an Object is an entity in the system which has to be protected aSubject is an entity that has access to the Object which Subjects can access which Objects is determined by the Access function Access Control Matrix (III)

  12. Access Control Matrix the rows of the Access function are labelled with the Subject names and its columns by the Object names. element Ai,j specifies the access which Subjecti has to Objectj each element or cell of the matrix consists of a set of strings called access attributes, such as read and write, which are typical access attributes Access Control Matrix (IV)

  13. AM Implementations operating systems database systems Access Control Matrix (V)

  14. AM Implementations a rectangular array of cells, with one row per subject and one column per object Access Control Matrix (VI) Table: A rectangular array

  15. Access control list (ACL) each column in an Access Control Matrix (AM) is translated to an Access Control List (ACL) the ACL contains entries for each subject defining the operations that the subject can execute on the given object Access Control List (I)

  16. Access control list (ACL): it specifies which users or system processes are granted access to objects what operations are allowed on given objects <Access Control List: Google patents, http://www.google.com/patents/US20130145028> Access Control List (II)

  17. ACL Implementations File System ACL: Afile system ACL is a data structure (table) containing entries that specify individual user or group rights to specific system resources. resources - programs, files, etc. entries – access control entries (ACEs). Access Control List (III)

  18. ACL Implementations File System ACL - used to administrate file permissions for example, a file has an ACL that contains (Bob, delete) this gives Bob permission to delete the file. <MS Windows, Unix/Linux Operating Systems> Access Control List (IV)

  19. ACL Implementations File System ACL – access ACL and default ACL (Red Hat Linux) an access ACL is the access control list for a specific file or directory. adefault ACL can only be associated with a directory; if a file within the directory does not have an access ACL. default ACL uses the rules of the default ACL for the directory. ACLs can be configured per user or per group. <https://access.redhat.com/site/documentation/en-US/Red_Hat_Enterprise_Linux/6/html/Storage_Administration_Guide/ch-acls.html> Access Control List (V)

  20. ACL Implementations File System ACL – access ACL and default ACL (Red Hat Linux) thesetfacl utility sets ACLs for files and directories. # setfacl-m rulesfiles use the -m option to add/modify the ACL of a file/directory rule formats u:uid:perms, g:gid:perms # setfacl-m u:bob:rw/cos80011/waa <https://access.redhat.com/site/documentation/en-US/Red_Hat_Enterprise_Linux/6/html/Storage_Administration_Guide/ch-acls.html> Access Control List (VI)

  21. ACL Implementations SQL-based systems relational database systems networking ACLs Access Control List (VII)

  22. Advantages easy to implement, simplicity and flexibility are the keys effective in closed and relatively unchangeable systems Disadvantages do not allow modelling the global policy rules by which permissions can change in any particular system they do not have adequate functionalities to maintain the users and objects in the large-scale systems, where more than one user need same object AM and ACL (VIII)

  23. What is Access Control? Access Control Matrix and Access Control List Role-Based Access Control User-Role Assignment Role-Permission Assignment Attribute-Based Access Control Context-Aware Access Control Context-Aware User-Role Assignment Context-Aware Role-Permission Assignment Outline

  24. Role-Based Access Control (RBAC) awell accepted access control model based on the role of the user is Role-based Access Control (RBAC) was introduced to tackle the problems: global policy rules, large-scale systems first RBAC, Ferraiolo et al (RBAC92) the RBAC92 model has been subsequently extended by Sandhu et al (RBAC96) <Sandhu et al (RBAC96): http://dl.acm.org/citation.cfm?id=226710> <Ferraioloet al (RBAC92): http://csrc.nist.gov/rbac/ferraiolo-kuhn-92.pdf> Role-Based Access Control (I)

  25. Role-Based Access Control (RBAC) in RBAC, it is not important to identify the individual who makes the access request, but to know his position in the structure of an organization this concept is known as a rolein RBAC the authorizations are not assigned directly to a particular user, but to the user’s role Role-Based Access Control (II)

  26. Role-Based Access Control (RBAC) usergroupand userrole–roles are closely related to the concept of user groups in access control however, a role brings together a set of users on one side and a set of permissions on the other whereas user groups are typically defined as a set of users only Role-Based Access Control (III)

  27. Role-Based Access Control (RBAC): three main concepts RBAC ensures that only an authorized user is given access to a certain resource, and is based on a user’s role in an organization users, roles, and permissions in a simple/basic RBAC model users – subjects are typically represented by users, who are assigned to roles and are granted membership into the roles based on their credentials and responsibilities in an organization roles – roles represent a job function, describing the authority and responsibility conferred on a user assigned to that role, within an organization permissions – permissions are assigned to roles, permissions contain resources and operations (the operations are allowed on the objects/resources) Role-Based Access Control (IV)

  28. Role-Based Access Control (RBAC) Model Role-Based Access Control (V) User Assignment UA Permission Assignment PA P Permi-ssion U User R Role Figure: Basic RBAC Model

  29. Role-Based Access Control (RBAC) Model U, R and P are the users, roles and permissions respectively UA is a many-to-many user to role assignment relation PAis a many-to-many permission to role assignment relation Role-Based Access Control (VI) U P

  30. Role-Based Access Control (RBAC): ESP Submissions (Assignments) user-role and role-permission assignments (policies) Role-Based Access Control (VII) Table: Relationships among users, roles and permissions

  31. Role-Based Access Control (RBAC): Role Hierarchy also called role inheritance for structuring roles to reflect an organization’s lines of authority and responsibility the senior roles can inherit all permissions from the junior roles the senior roles can have permissions in addition to those inherited from the junior roles Role-Based Access Control (VIII)

  32. Role-Based Access Control (RBAC): Role Hierarchy Example The lecturer role (senior role) can inherits all permissions from the staff role (junior role) The lecturer role can have own permissions also Role-Based Access Control (IX) University User Student Staff UGS Lecturer PGS Tutor Figure: Role Hierarchy

  33. Role-Based Access Control (RBAC): Other RBAC Concepts RBAC Session (users can create and terminate sessions, to activate/deactivate roles) RBAC Constraints (predicates that can apply to the UA and PA relations) Role-Based Access Control (X) <Sandhu et al (RBAC96): http://dl.acm.org/citation.cfm?id=226710>

  34. Role-Based Access Control (RBAC): Patient Medical Records Management user-role assignments Role-Based Access Control (XI)

  35. Role-Based Access Control (RBAC): Patient Medical Records Management role-permission assignments Role-Based Access Control (XII)

  36. Role-Based Access Control (RBAC): Patient Medical Records Management The specialist physician role (senior role) can inherits all permissions from the physician role (junior role) Role-Based Access Control (XIII) Healthcare User Nurse Physician Specialist Physician Registered Nurse Nurse Manager Emergency Doctor Primary-care Physician Figure: An Excerpt of Healthcare Role Hierarchy

  37. Role-Based Access Control (RBAC): Patient Medical Records Management Role-Based Access Control (XIV) Physician Emergency Doctor Specialist Physician Primary-care Physician

  38. Role-Based Access Control (RBAC): main part Role-Based Access Control (XV) Organization Resource Role Operation

  39. Advantages simplifies management of permissions effective/useful model in large-scale systems/domains Disadvantages the user-role and role-permission assignments are static without taking into account the dynamic attributes, such as the location of users this makes a less effective solution in today’s open and dynamic environments Role-Based Access Control (XVI)

  40. What is Access Control? Access Control Matrix and Access Control List Role-Based Access Control User-Role Assignment Role-Permission Assignment Attribute-Based Access Control Context-Aware Access Control Context-Aware User-Role Assignment Context-Aware Role-Permission Assignment Outline

  41. Attribute-Based Access Control (ABAC) a new access control paradigm where access rights are granted to users through the use of policies which combine attributes together the policies can use any type of attributes (user attributes, resource attribute, etc.) it is a rule-based approach to access control, it does not use the concept of a role the building blocks in the ABAC model are the attributes an ABAC policy specifies which constraints need to be satisfied based on the attributes (e.g., user age is greater than 20) in order to grant access to an object Attribute-Based Access Control (I)

  42. Attribute-Based Access Control (ABAC) the formal definition of basic ABAC is composed of four parts: access control related entities, attributes of entities, policy representation, and policy evaluation entities – requestor (Req), resource (Res), action (Act), environment (Env) attributes of entities (e.g., attributes of environment (Attr(Env)) – the current date or time) policy specification – the definition of access control policies policy evaluation– the process of making an access decision based on the security policy <ABAC, http://www.mcs.anl.gov/uploads/cels/papers/P1367.pdf> Attribute-Based Access Control (II)

  43. Attribute-Based Access Control (ABAC): policy evaluation an access control decision is made by the evaluation function (), access control decision function, ADF it takes the attributes of the requestor, the resource, the action, the environment as parameters Attribute-Based Access Control (III)

  44. eXtensibleAccess Control Markup Language (XACML) is the standard that implements attribute-based access control a standard XML-based protocol for access control policies suitable for a variety of application environments (e.g., Web-based) uses the attributes of subject, resource, action, and environment this framework contains PEP, PDP, PIP, and PAP <OASIS XACML 3.0 (2013), http://docs.oasis-open.org/xacml/3.0/xacml-3.0-core-spec-os-en.pdf> Attribute-Based Access Control (IV)

  45. eXtensibleAccess Control Markup Language (XACML): four main components Policy Enforcement Point (PEP) Policy Decision Point (PDP) Policy Administration Point (PAP) Policy Information Point (PIP) <OASIS XACML 3.0 (2013), http://docs.oasis-open.org/xacml/3.0/xacml-3.0-core-spec-os-en.pdf> Attribute-Based Access Control (V)

  46. XACMLData Authorization Framework Attribute-Based Access Control (VI) <OASIS XACML 3.0 (2013), http://docs.oasis-open.org/xacml/3.0/xacml-3.0-core-spec-os-en.pdf> Figure: XACML Data Flow Diagram

  47. XACMLData Authorization Framework: when access request comes from the access requesters (users) the PEP intercepts the access requests from users and sends the requests to the PDP (through the context handler) the PDP makes access decisions according to the security policy (policy set) written by the PAP the PDP uses the attributes of the subjects, the resources, and the environment obtained by querying the PIP (via the context handler) the access decision given by the PDP is sent to the PEP(through the context handler) the PEP sends either permitted or denied request to the users according to the decision of PDP Attribute-Based Access Control (VII)

  48. XACML Implementation Domain-specific Inputs (from the requesters) converted to XACML Request Context (.xml) XACML Policy (.xml) XACML Response Context (.xml) converted to Domain-specific Outputs (back to the requesters) Attribute-Based Access Control (VIII)

  49. Language Model of XACML Attribute-Based Access Control (IX) Figure: XACML Context and Policy <OASIS XACML 3.0 (2013), http://docs.oasis-open.org/xacml/3.0/xacml-3.0-core-spec-os-en.pdf>

  50. Advantages easy to implement/setup very useful model in small-scale systems/domains Disadvantages when the number of users is high, the number of authorizations can become extremely large, which complicates the administration tasks this brings high complexity of security administration and significant cost of management of growing large-scale systems it does not provide adequate functionalities for dynamic access permissions Attribute-Based Access Control (X)

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