Attribute-based access control: Difference between revisions

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{{Short description|Access control paradigm}}

'''Attribute-based access control''' ('''ABAC'''), also known as '''policy-based access control''', defines an [[access control]] paradigm whereby access rights are granted to users through the use of [[Policy|policies]] which combine attributes together. The policies can use any type of [[Attribute (computing)|attributes]] (user attributes, resource attributes, object, environment attributes etc.). This model supports [[Boolean Logic|Boolean logic]], in which rules contain "IF, THEN" statements about who is making the request, the resource, and the action. For example: IF the requestor is a manager, THEN allow [[File system permissions|read/write access]] to sensitive data.

'''Attribute-based access control''' ('''ABAC'''), also known as '''policy-based access control''' for [[Identity management|IAM]], defines an access control paradigm whereby a subject's authorization to perform a set of operations is determined by evaluating attributes associated with the subject, object, requested operations, and, in some cases, environment attributes.<ref>{{Cite web|last=Computer Security Division|first=Information Technology Laboratory|date=2016-05-24|title=Attribute Based Access Control {{!}} CSRC {{!}} CSRC|url=https://csrc.nist.gov/Projects/Attribute-Based-Access-Control|access-date=2021-11-25|website=CSRC {{!}} NIST|language=EN-US}}</ref>

ABAC is a method of implementing access control policies that is highly adaptable and can be customized using a wide range of attributes, making it suitable for use in distributed or rapidly changing environments. The only limitations on the policies that can be implemented with ABAC are the capabilities of the computational language and the availability of relevant attributes.<ref>{{Cite journal |last1=Hu |first1=Vincent C. |last2=Kuhn |first2=D. Richard |last3=Ferraiolo |first3=David F. |last4=Voas |first4=Jeffrey |date=February 2015 |title=Attribute-Based Access Control |journal=Computer |volume=48 |issue=2 |pages=85–88 |doi=10.1109/MC.2015.33 |bibcode=2015Compr..48b..85H |s2cid=54967881 |issn=1558-0814}}</ref> ABAC policy rules are generated as Boolean functions of the subject's attributes, the object's attributes, and the environment attributes.<ref>{{Cite web |title=Guide to Secure Web Services: Recommendations of the National Institute of Standards and Technology |url=https://nvlpubs.nist.gov/nistpubs/Legacy/SP/nistspecialpublication800-95.pdf}}</ref>

Unlike [[Role-based access control|role-based access control (RBAC)]], which employs pre-defined roles that carry a specific set of [[Privilege (computing)|privileges]] associated with them and to which subjects are assigned, the key difference with ABAC is the concept of policies that express a complex Boolean rule set that can evaluate many different attributes.<ref>{{Cite web |date=2014 |url=http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-162.pdf |title=SP 800-162, Guide to Attribute Based Access Control (ABAC) Definition and Considerations |publisher=NIST |accessdate=2015-12-08 |archive-url=https://web.archive.org/web/20160305222004/http://nvlpubs.nist.gov/nistpubs/specialpublications/NIST.sp.800-162.pdf |archive-date=2016-03-05 |url-status=dead }}</ref> Attribute values can be set-valued or atomic-valued. Set-valued attributes contain more than one atomic value. Examples are ''role'' and ''project''. Atomic-valued attributes contain only one atomic value. Examples are [[Classified information#Clearance|clearance]] and [[Information sensitivity|sensitivity]]. Attributes can be compared to static [[Value (computer science)|values]] or to one another, thus enabling relation-based access control.

Unlike [[role-based access control]] (RBAC), which defines roles that carry a specific set of privileges associated with them and to which subjects are assigned, ABAC can express complex rule sets that can evaluate many different attributes. Through defining consistent subject and object attributes into security policies, ABAC eliminates the need for explicit authorizations to individuals’ subjects needed in a non-ABAC access method, reducing the complexity of managing access lists and groups.

Although the concept itself existed for many years, ABAC is considered<ref>{{Cite web |url=http://www.axiomatics.com/attribute-based-access-control.html |title=Attribute Based Access Control (ABAC), ''axiomatics.com'' |accessdate=2016-07-05}}</ref> a "next generation" authorization model because it provides dynamic, context-aware and risk-intelligent access control to resources allowing access control policies that include specific attributes from many different information systems to be defined to resolve an authorization and achieve an efficient regulatory compliance, allowing enterprises flexibility in their implementations based on their existing infrastructures.

Attribute values can be set-valued or atomic-valued. Set-valued attributes contain more than one atomic value. Examples are ''role'' and ''project''. Atomic-valued attributes contain only one atomic value. Examples are ''clearance'' and ''sensitivity''. Attributes can be compared to static values or to one another, thus enabling relation-based access control.{{Citation needed|date=September 2023}}

Attribute-based access control is sometimes referred to as '''policy-based access control''' ('''PBAC''')<ref>{{Cite web|url=https://www.webfarmr.eu/2019/11/what-is-policy-based-access-control/|title=What is Policy-Based Access Control?|date=2019-11-20|website=Harvesting web technologies|language=en-US|access-date=2019-11-20}}</ref> or '''claims-based access control''' ('''CBAC'''),<ref>[http://genericiam.blogspot.co.uk/2015/10/rbac-first-abac-next-or-what.html RBAC first – ABAC next, or what?, 2015, Horst Walther, ''GenericIAM Blog'']. Retrieved on 2016-08-30.</ref> which is a Microsoft-specific term.<ref>[http://www.hpl.hp.com/techreports/2009/HPL-2009-30.pdf Karp, Alan, Harry Haury, and Michael Davis. "From ABAC to ZBAC: the evolution of access control models." ''International Conference on Information Warfare and Security''. Academic Conferences International Limited, 2010]. Retrieved on 2016-08-30.</ref> The key standards that implement ABAC are [[XACML]] and [[ALFA (XACML)]].

Although the concept itself existed for many years, ABAC is considered<ref>{{Cite web |url=http://www.axiomatics.com/attribute-based-access-control.html |title=Attribute Based Access Control (ABAC), ''axiomatics.com'' |accessdate=2016-07-05}}</ref> a "next generation" authorization model because it provides dynamic, context-aware and risk-intelligent access control to resources allowing access control policies that include specific attributes from many different information systems to be defined to resolve an authorization and achieve an efficient regulatory compliance, allowing enterprises flexibility in their implementations based on their existing infrastructures.

Attribute-based access control is sometimes referred to as '''policy-based access control''' ('''PBAC''') or '''claims-based access control''' ('''CBAC'''), which is a Microsoft-specific term. The key standards that implement ABAC are [[XACML]] and [[ALFA (XACML)]].<ref>{{Cite journal|last1=Silva|first1=Edelberto Franco|last2=Muchaluat-Saade|first2=Débora Christina|last3=Fernandes|first3=Natalia Castro|date=2018-01-01|title=ACROSS: A generic framework for attribute-based access control with distributed policies for virtual organizations|url=http://www.sciencedirect.com/science/article/pii/S0167739X17316060|journal=Future Generation Computer Systems|language=en|volume=78|pages=1–17|doi=10.1016/j.future.2017.07.049|issn=0167-739X|url-access=subscription}}</ref>

== Dimensions of attribute-based access control ==

ABAC can be seen as:

* Externalized authorization management<ref>{{Cite web|url=https://www.gartner.com/doc/2358815/technology-overview-externalized-authorization-management|title=Technology Overview for Externalized Authorization Management|website=www.gartner.com|access-date=2017-05-31}}</ref>

* Dynamic authorization management<ref>{{Cite web|url=https://wwwplus.kuppingercole.com/reportarticle/mc71144/dynamic-authorization-management/lc70966|title=Leadership Compass: Dynamic Authorization Management - 7096671144|website=KuppingerCole|date=14 July 2020 |access-date=20172020-0507-3114}}</ref>

* Policy-based access control

* Fine-grained authorization

== Components ==

=== Architecture ===

ABAC comes with a recommended architecture which is as follows:

# The PEP or Policy Enforcement Point: it is responsible for protecting the apps & data you want to apply ABAC to. The PEP inspects the request and generates an authorization request from it which it sends to the PDP.

# The PDP or Policy Decision Point is the brain of the architecture. This is the piece which evaluates incoming requests against policies it has been configured with. The PDP returns a Permit / Deny decision. The PDP may also use PIPs to retrieve missing metadata

# The PEP or Policy Enforcement Point: it is responsible for protecting the apps & data you want to apply ABAC to. The PEP inspects the request and generates an authorization request from it which it sends to the PDP.

# The PDP or Policy Decision Point is the brain of the architecture. This is the piece which evaluates incoming requests against policies it has been configured with. The PDP returns a Permit / Deny decision. The PDP may also use PIPs to retrieve missing metadata

# The PIP or Policy Information Point bridges the PDP to external sources of attributes e.g. LDAP or databases.

=== Attributes ===

Attributes can be about anything and anyone. They tend to fall into 4 different categories or functions (as in grammatical function):

# Subject attributes: attributes that describe the user attempting the access e.g. age, clearance, department, role, job title...

# Action attributes: attributes that describe the action being attempted e.g. read, delete, view, approve...

# Object attributes: attributes that describe the object (or resource) being accessed e.g. the object type (medical record, bank account...), the department, the classification or sensitivity, the ___location...

# Contextual (environment) attributes: attributes that deal with time, ___location or dynamic aspects of the access control scenario<ref name="stackoverflow.com">{{cite web|url=http://stackoverflow.com/questions/36705901/alternatives-for-roles-claims-access-control-systems|title=Alternatives for Roles/Claims Access Control Systems|website=stackoverflow.com}}</ref>

=== Policies ===

Policies are statements that bring together attributes to express what can happen and is not allowed. Policies in ABAC can be granting or denying policies. Policies can also be local or global and can be written in a way that they override other policies. Examples include:

# A user can view a document if the document is in the same department as the user

# A user can edit a document if they are the owner and if the document is in draft mode

# Deny access before 9am9 AM

With ABAC you can have asan manyunlimited policiesnumber asof you likepolicies that cater to many different scenarios and technologies.<ref name="stackoverflow.com"/>

== Other models ==

Historically, access control models have included [[mandatory access control]] (MAC), [[discretionary access control]] (DAC), and more recently [[role-based access control]] (RBAC). These access control models are user-centric and do not take into account additional parameters such as resource information, the relationship between the user (the requesting entity) and the resource, and dynamic information, e.g. time of the day or user IP.

ABAC tries to address this by defining access control based on attributes which describe the requesting entity (the user), the targeted object or resource, the desired action (view, edit, delete...), and environmental or contextual information. This is why access control is said to be attribute-based.

ABAC tries to address this by defining access control based on attributes which describe the requesting entity (the user), the targeted object or resource, the desired action (view, edit, delete...), and environmental or contextual information. This is why access control is said to be attribute-based.

==Implementations==

One standard that implements attribute- and policy-based access control is [[XACML]], the eXtensible Access Control Markup Language. XACML defines an architecture, a policy language, and a request / response scheme. It does not handle attribute management (user attribute assignment, object attribute assignment, environment attribute assignment) which is left to traditional [[Identity_management|IAM]] tools, databases, and directories.

== Implementations==

Companies, including every branch in the United States military, have started using ABAC. At its basic level, ABAC uses an ‘IF/THEN/AND’ model to protect the data itself rather than assigning data to a user who can take that information anywhere they please or give a hacker the ability to swipe{{Definition needed|date=June 2019}} the file. The US Department of Commerce has made this a mandatory practice and the adoption is spreading throughout several governmental and military agencies.[https://community.plm.automation.siemens.com/t5/Digital-Transformations/Attribute-Based-Access-Control-ABAC-Encryption-on-Steroids/ba-p/580836]<ref>{{Cite web|url=https://community.plm.automation.siemens.com/t5/Digital-Transformations/Attribute-Based-Access-Control-ABAC-Encryption-on-Steroids/ba-p/580836|title=Attribute Based Access Control (ABAC) – Encryption on Steroids|last=Coffey|first=Alisa|date=2019-03-28|website=Siemens PLM Community|language=en|access-date=2019-04-01}}</ref>

There are three main implementations of ABAC:

* [https://www.oasis-open.org/committees/tc_home.php?wg_abbrev=xacml#CURRENT OASIS XACML]

* [[Abbreviated Language for Authorization|Abbreviated Language for Authorization (ALFA)]].

* [[National Institute of Standards and Technology|NIST]]'s [https://www.nist.gov/identity-access-management/policy-machine-and-next-generation-access-control Next-generation Access Control] (NGAC)

One standard that implements attribute- and policy-based access control is [[XACML]], the eXtensible Access Control Markup Language. XACML, defines an architecture (shared with ALFA and NGAC), a policy language, and a request / response scheme. It does not handle attribute management (user attribute assignment, object attribute assignment, environment attribute assignment) which is left to traditional [[Identity_managementIdentity management|IAM]] tools, databases, and directories.

==Applications==

The concept of ABAC can be applied at any level of the technology stack and an enterprise infrastructure. For example, ABAC can be used at the firewall, server, application, database, and data layer. The use of attributes bring additional context to evaluate the legitimacy of any request for access and inform the decision to grant or deny access.

Companies, including every branch in the United States military, have started using ABAC. At a basic level, ABAC protects data with 'IF/THEN/AND' rules rather than assign data to users. The US Department of Commerce has made this a mandatory practice and the adoption is spreading throughout several governmental and military agencies.<ref>{{cite web |last1=Sanford |first1=Jim |title=Encryption on Steroids – Attribute Based Access Control (ABAC) |url=https://blogs.sw.siemens.com/thought-leadership/2019/03/28/attribute-based-access-control-abac-encryption-on-steroids/ |website=Siemens |date=28 March 2019 |access-date=13 October 2023}}</ref>

An important consideration when evaluating ABAC solutions is to understand its potential overhead on performance and its impact on the user experience. It is expected that the more granular the controls, the higher the overhead.

== Applications ==

=== API and micro services security ===

The concept of ABAC can be applied at any level of the technology stack and an enterprise infrastructure. For example, ABAC can be used at the firewall, server, application, database, and data layer. The use of attributes bring additional context to evaluate the legitimacy of any request for access and inform the decision to grant or deny access.

ABAC can be used to apply attribute-based, fine-grained authorization to the API methods or functions. For instance, a banking API may expose an approveTransaction(transId) method. ABAC can be used to secure the call. With ABAC, a policy author can write the following:

An important consideration when evaluating ABAC solutions is to understand its potential overhead on performance and its impact on the user experience. It is expected that the more granular the controls, the higher the overhead.

=== API and micro servicesmicroservices security ===

ABAC can be used to apply attribute-based, fine-grained authorization to the API methods or functions. For instance, a banking API may expose an {{Code|approveTransaction(transId)}} method. ABAC can be used to secure the call. With ABAC, a policy author can write the following:

* '''Policy''': managers can approve transactions up to their approval limit

* '''Attributes used''': role, action IDidentifier, object type, amount, approval limit.

The flow would be as follows:

# The user, Alice, calls the API method {{Code|approveTransaction(123)}}

# The user, Alice, calls the API method approveTransaction(123)

# The API receives the call and authenticates the user.

# An interceptor in the API calls out to the authorization engine (typically called a Policy Decision Point or PDP) and asks: ''Can Alice approve transaction 123?''

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=== Application security ===

One of the key benefits to ABAC is that the authorization policies and attributes can be defined in a technology neutral way. This means policies defined for APIs or databases can be reused in the application space. Common applications that can benefit from ABAC are:

# Content management systems (CMS)

# contentEnterprise managementresource planning (ERP) systems

# webHome-grown applications

# ERPs

# home-grownWeb applications

# web applications

The same process and flow as the one described in the API section applies here too.

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=== Database security ===

Security for databases has long been specific to the database vendors: Oracle VPD, IBM FGAC, and Microsoft RLS are all means to achieve fine-grained ABAC-like security.

Using ABAC, it is possible to define policies that apply across multiple databases. This is called [[Data_masking#Dynamic_data_masking|dynamic data masking]].

An example would be:

* Policy: managers can view transactions in their region

* Reworked policy in a data-centric way: users with <tt>{{code|code=role == manager</tt>}} can do the action <tt>{{code|code== SELECT}} on {{code|code=table == TRANSACTIONS}} if {{code|code=user.region == transaction.region</tt>}}

=== Data security ===

Data security typically goes one step further than database security and applies control directly to the data element. This is often referred to as [[data-centric security]]. On traditional relational databases, ABAC policies can control access to data at the table, column, field, cell and sub-cell using logical controls with filtering conditions and masking based on attributes. Attributes can be data, user, session or tools based to deliver the greatest level of flexibility in dynamically granting/denying access to a specific data element. On [[big data]], and distributed file systems such as Hadoop, ABAC applied at the data layer control access to folder, sub-folder, file, sub-file and other granular.

=== Big data security ===

Attribute-based access control can also be applied to Big Data systems like Hadoop. Policies similar to those used previously can be applied when retrieving data from data lakes.<ref>{{cite web|url=httphttps://www.prweb.com/releases/2016/10dynamic_fine_grained_authorization_secures_big_data/prweb13771686.htm|title=Dynamic, Fine-Grained Authorization Secures Big Data|publisher=}}</ref><ref>{{Cite web |title=First Fine-grained Data Access Control On Hadoop |url=http://bluetalon.com/bluetalon-unveils-industry-first-fine-grained-data-access-control-on-hadoop-distributed-file-system-hdfs-with-filtering-and-dynamic-data-masking-capabilities/ |titlearchive-url=First Finehttps://web.archive.org/web/20160323174613/http://bluetalon.com/bluetalon-unveils-industry-first-fine-grained-data-access-control-on-hadoop-distributed-file-system-hdfs-with-filtering-and-dynamic-data-masking-capabilities/ Data Access Control On Hadoop|archive-date=2016-03-23}}</ref>

=== File server security ===

As of Windows Server 2012, Microsoft has implemented an ABAC approach to controlling access to files and folders. This is achieved through dynamic access control lists(DAC)<ref>{{Cite web|url=https://docs.microsoft.com/en-us/windows/security/identity-protection/access-control/dynamic-access-control|title = Dynamic Access Control Overview (DACLWindows 10) - Windows security| date=13 February 2024 }}</ref> and Security Descriptor Definition Language ([[SDDL]]). SDDL can be seen as an ABAC language as it uses metadata of the user (claims) and of the file / folder to control access.

== See also ==

{{columns-list|colwidth=30em|

* [[Access control list]]

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* [[Organisation-based access control]] (OrBAC)

* [[Role-based access control]] (RBAC)

* [[Relationship-based access control]] (ReBAC)

* [[RSBAC|Rule-set-based access control (RSBAC)]]

* [[Capability-based security]]

* [[Location-based authentication]]

* [[Risk-based authentication]]

* [[Classified information]]

* [[Federated identity]]

* [[grsecurity]]

* [[Identity driven networking]]

* [[Identity management]]

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== References ==

{{Reflistreflist}}

Gartner - improving-runtime-authorization-maturity

== External links ==

* [http://www.axiomatics.com/attribute-based-access-control.html What is attribute-based access control?]

* [http://csrc.nist.gov/projects/abac/ ATTRIBUTE BASED ACCESS CONTROL (ABAC) - OVERVIEW]

* [https://link.springer.com/chapter/10.1007%2F978-3-642-31540-4_4 Unified Attribute Based Access Control Model (ABAC) covering DAC, MAC and RBAC]

* [httphttps://profsandhu.com/dissert/Dissertation_Xin_Jin.pdf Attribute Based Access Control Models (ABAC) and Implementation in Cloud Infrastructure as a Service]

* [https://f5.com/about-us/blog/articles/abac-not-rbac-welcome-to-the-iot-world-of-contextual-security ABAC not RBAC: Welcome to the (IoT) World of Contextual Security, 2015, Lori MacVittie]

[[Category:Access control]]