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-----BEGIN PGP SIGNED MESSAGE----- Hash: SHA256 =========================================================================== AUSCERT External Security Bulletin Redistribution ESB-2018.3937 Shibboleth Identity Provider Security Advisory 20 December 2018 =========================================================================== AusCERT Security Bulletin Summary --------------------------------- Product: Shibboleth Identity Provider Publisher: Shibboleth Operating System: Linux variants OS X Windows Impact/Access: Unauthorised Access -- Remote/Unauthenticated Resolution: Patch/Upgrade Original Bulletin: https://shibboleth.net/community/advisories/secadv_20181219.txt - --------------------------BEGIN INCLUDED TEXT-------------------- Shibboleth Identity Provider Security Advisory [19 December 2018] Shibboleth IdP Vulnerable to Untrusted Relying Party Access Via CAS Proxy ========================================================================= The CAS protocol specification [1] strictly defines the conditions under which a relying party is granted the privilege to proxy: 1. Proxy callback endpoint must present a trusted X.509 certificate over HTTPS. 2. HTTP response code must be 200. The Shibboleth IdP uses an application-specific facility, a Trust Engine, to configure trusted certificates. A software bug, however, causes the Java system trust store to be consulted as a fallback when a certificate fails the Trust Engine validation process. Since the default system trust store contains common commercial CAs, the consequence for most deployers is that the scope of trusted certificates is far broader than intended. The increase in trusted certificate scope risks granting an untrusted relying party the privilege to proxy. Affected Versions ================= All 3.x versions of the IdP software prior to V3.4.2 are affected. Mitigating Factors ================== There are a couple notable requirements that must be met in order to exploit the vulnerability: 1. A malicious service is authorized to proxy in the CAS service registry. 2. An authenticated user visits a malicious service such that it receives a proxy-granting ticket. The first point depends on the kinds of expressions commonly used to register CAS service endpoints. While regular expression wildcards are commonplace, they tend to be scoped within organizational DNS boundaries. Further, the wildcards tend to be in the path part of URLs. Recommendations =============== The Shibboleth Project recommends upgrading to Shibboleth IdP V3.4.2, which contains a fix for the CAS proxy vulnerability. For deployers upgrading from versions prior to 3.4.0, please consult the documentation [2] to port your CAS proxy trust configuration. If upgrading is not possible, the IdP should be configured to use a minimized system trust store containing the smallest set of trusted certificates required for proper function. Please consult the documentation [3] for detailed instructions. References ========== [1] https://bit.ly/2UBrMV8 [2] https://wiki.shibboleth.net/confluence/x/oIEYAw [3] https://wiki.shibboleth.net/confluence/x/HwE1Aw Credits ======= Paul B. Henson, Cal Poly Pomona Marvin S Addison, Virginia Tech URL for this Security Advisory: https://shibboleth.net/community/advisories/secadv_20181219.txt - --------------------------END INCLUDED TEXT-------------------- You have received this e-mail bulletin as a result of your organisation's registration with AusCERT. The mailing list you are subscribed to is maintained within your organisation, so if you do not wish to continue receiving these bulletins you should contact your local IT manager. If you do not know who that is, please send an email to auscert@auscert.org.au and we will forward your request to the appropriate person. NOTE: Third Party Rights This security bulletin is provided as a service to AusCERT's members. As AusCERT did not write the document quoted above, AusCERT has had no control over its content. The decision to follow or act on information or advice contained in this security bulletin is the responsibility of each user or organisation, and should be considered in accordance with your organisation's site policies and procedures. AusCERT takes no responsibility for consequences which may arise from following or acting on information or advice contained in this security bulletin. NOTE: This is only the original release of the security bulletin. It may not be updated when updates to the original are made. If downloading at a later date, it is recommended that the bulletin is retrieved directly from the author's website to ensure that the information is still current. Contact information for the authors of the original document is included in the Security Bulletin above. If you have any questions or need further information, please contact them directly. Previous advisories and external security bulletins can be retrieved from: https://www.auscert.org.au/bulletins/ =========================================================================== Australian Computer Emergency Response Team The University of Queensland Brisbane Qld 4072 Internet Email: auscert@auscert.org.au Facsimile: (07) 3365 7031 Telephone: (07) 3365 4417 (International: +61 7 3365 4417) AusCERT personnel answer during Queensland business hours which are GMT+10:00 (AEST). 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