Broken access controls

 Akansha Kesharwani
 Sr. Security Consultant @ Payatu Software Labs LLP
 Works on Web Application Pentesting and Mobile application Pentesting
 Member @ Null Pune chapter
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 Introduction
 Insecure Direct Object References
 Missing Functional Level of Access Controls
 Potential Impact
 Example
 Remediation
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 Access Control aka Authorization is how a application grant access to content and
functions to some users and not others.
 As a attacker if the user is able to perform an action or access the content and
functions of some other user which the attacker should not have been authorized,
then we term it as Broken Access Control.
 In OWASP 2017, Insecure Direct Object Reference and Missing Functional Level of
Access Control where merged and a new category Broken Access Control was
formed.
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Courtesy: https://www.owasp.org/index.php/Broken_Access_Control

 A direct object reference occurs when a developer exposes a reference to an
internal implementation object, such as a file, directory, or database key.Without
an access control check or other protection, attackers can manipulate these
references to access unauthorized data.
 Occurs when developer uses HTTP parameter to refer an internal object
 Ex: https://demo.com?id=1
 Can access to other accounts
 Ex: https://example.com/profile=123
6Courtesy: https://www.owasp.org/index.php/Top_10_2013-Top_10

 HTTP GET parameters
 Tampering reference in the URL
 Ex: https://example.com?profile=123
 Changing profile parameter to “456”
 https://example.com?profile=456
 It will give access to profile referred by “456”.
 HTTP POST parameters
 In the body of POST parameters.
 HTTP Headers
 Cookies
 Languages (Accept-Language)
 User-Agent
7Courtesy: https://www.owasp.org/index.php/Top_10_2013-Top_10

 It occurs when the web application fails to verify the functional level access right
before making the functionality accessible to the user. So the user not having
proper authorization will be able to access the functionality which they do not have
right to access.
 Occurs when an authorization check is missing in a particular functionality.
 Ex: Admin functionality missing authorization check in a web application.
 https://www.example.com/admin.jsp
 https://www.example.com/phpinfo
 If the user roles are not in place, then user of least privilege might be able to
access the functionality of user having highest privilege.
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 HTTP GET and POST parameters
 Tampering reference in the URL
 Ex: https://example.com?admin=false
 Changing admin parameter to “true”
 https://example.com?admin=true
 It will give access to functionality available to admin user.
 In the body of POST parameters.
 HTTP Headers
 Cookies
 Forced Browsing
 Accessing admin functionality when user is authenticated as normal user.
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 The potential impact of Broken Access Control greatly depends on what kind of
information or features the attacker can gain access to.
 This can be anything from seemingly useless information to a full system takeover.
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 Avoid exposing reference of internal object to user.
 Validate internal object reference at server side.
 Verify authorization to all referenced objects.
 The enforcement mechanism(s) should deny all access by default, requiring explicit
grants to specific roles for access to every function.
 If the function is involved in a workflow, check to make sure the conditions are in the
proper state to allow access.
 Disable web server directory listing and ensure file metadata (e.g. .git) and backup
files are not present within web roots.
 Log access control failures, alert admins when appropriate (e.g. repeated failures).
 Rate limit API and controller access to minimize the harm from automated attack
tooling.
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 https://www.owasp.org/index.php/Top_10-2017_A5-Broken_Access_Control
 https://www.owasp.org/index.php/Top_10_2013-A7-
Missing_Function_Level_Access_Control
 https://www.owasp.org/index.php/Top_10_2010-A4-
Insecure_Direct_Object_References
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