CVE-2024-2698

A vulnerability was found in FreeIPA in how the initial implementation of MS-SFU by MIT Kerberos was missing a condition for granting the forwardable flag on S4U2Self tickets. Fixing this mistake required adding a special case for the check_allowed_to_delegate() function: If the target service argument is NULL, then it means the KDC is probing for general constrained delegation rules and not checking a specific S4U2Proxy request.

In FreeIPA 4.11.0, the behavior of ipadb_match_acl() was modified to match the changes from upstream MIT Kerberos 1.20. However, a mistake resulting in this mechanism applies in cases where the target service argument is set AND where it is unset. This results in S4U2Proxy requests being accepted regardless of whether or not there is a matching service delegation rule.

Weakness

The product performs an authorization check when an actor attempts to access a resource or perform an action, but it does not correctly perform the check.

Affected Software

Name	Vendor	Start Version	End Version
Freeipa	Freeipa	4.11.0 (including)	4.11.2 (excluding)
Freeipa	Freeipa	4.12.0 (including)	4.12.0 (including)
Red Hat Enterprise Linux 8	RedHat	idm:DL1-8100020240528133707.823393f5	*
Red Hat Enterprise Linux 8.8 Extended Update Support	RedHat	idm:DL1-8080020240530051744.b0a6ceea	*
Red Hat Enterprise Linux 9	RedHat	ipa-0:4.11.0-15.el9_4	*
Red Hat Enterprise Linux 9.2 Extended Update Support	RedHat	ipa-0:4.10.1-12.el9_2.2	*
Freeipa	Ubuntu	focal	*
Freeipa	Ubuntu	mantic	*
Freeipa	Ubuntu	oracular	*
Freeipa	Ubuntu	plucky	*
Freeipa	Ubuntu	trusty/esm	*

Potential Mitigations

Divide the product into anonymous, normal, privileged, and administrative areas. Reduce the attack surface by carefully mapping roles with data and functionality. Use role-based access control (RBAC) [REF-229] to enforce the roles at the appropriate boundaries.
Note that this approach may not protect against horizontal authorization, i.e., it will not protect a user from attacking others with the same role.
Use a vetted library or framework that does not allow this weakness to occur or provides constructs that make this weakness easier to avoid.
For example, consider using authorization frameworks such as the JAAS Authorization Framework [REF-233] and the OWASP ESAPI Access Control feature [REF-45].
For web applications, make sure that the access control mechanism is enforced correctly at the server side on every page. Users should not be able to access any unauthorized functionality or information by simply requesting direct access to that page.
One way to do this is to ensure that all pages containing sensitive information are not cached, and that all such pages restrict access to requests that are accompanied by an active and authenticated session token associated with a user who has the required permissions to access that page.

NVD	https://nvd.nist.gov/vuln/detail/CVE-2024-2698
CWE	https://cwe.mitre.org/data/definitions/863.html

Incorrect Authorization

Weakness

Affected Software

Potential Mitigations

References