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SIPPING IETF51 3GPP Security and Authentication

Explore the authentication principles and security aspects of 3GPP IP Multimedia Subsystem (IMS) domain, including session key distribution, SIP signaling protection, and network domain security. Learn about access security features and the integration of authentication protocol into DIAMETER and SIP. The document outlines concrete authentication examples in SIP and discusses access security documentation. Discover relevant 3GPP dependencies on IETF in relation to security protocols and specifications.

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SIPPING IETF51 3GPP Security and Authentication

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  1. SIPPING IETF513GPP Security and Authentication Peter Howard 3GPP SA3 (Security) delegate peter.howard@vodafone.com

  2. Home S-CSCF I-CSCF Visited GGSN SGSN RAN 3GPP IP Multimedia Subsystem (Release 5) Cx interface based on Diameter SIP proxies get authorisation and authentication information HSS REGISTER/INVITE REGISTER/INVITE P-CSCF UA REGISTER/INVITE SIP-based interfaces SIP proxy servers PS domain

  3. 3GPP Release 5 Security • Packet Switched (PS) domain • access security features retained from 3GPP Release 99 specifications • IP Multimedia Subsystem (IMS) domain • new access security features to be specified • to protect the access link to the IMS domain • independent of underlying PS domain security features • network domain security features to protect signalling links between network elements with the IMS domain

  4. Home S-CSCF I-CSCF Visited GGSN SGSN RAN IP Multimedia Subsystem: Access Security 1. Distribution of authentication information Draft 3GPP TS 33.203 4. Protection of SIP signalling using agreed session key HSS REGISTER/INVITE REGISTER/INVITE P-CSCF UA REGISTER/INVITE 3. Session key distribution 2. Mutual authentication and session key agreement

  5. Home S-CSCF I-CSCF Visited GGSN SGSN RAN IP Multimedia Subsystem: Network Domain Security Draft 3GPP TS 33.210 HSS REGISTER/INVITE REGISTER/INVITE P-CSCF UA REGISTER/INVITE Per-hop protection of signalling using IPsec/IKE

  6. Access Security: Authentication Principles • 3GPP authentication protocol (3GPP AKA) • based on secret key stored in UA’s tamper-proof subscriber identity module (SIM) and in the HSS • Authentication check located in S-CSCF • Working assumption is to authenticate only at SIP registrations with on-demand re-authentication requiring re-registration • Use SIP authentication rather than an outer layer protocol such as TLS or IKE in order to minimise roundtrips

  7. Integration of Authentication Protocol into DIAMETER and SIP • Distribution of authentication information to S-CSCF using DIAMETER • distribution of authentication vectors for 3GPP AKA • Integration of authentication protocol into SIP registration • 3GPP AKA protocol between UA and S-CSCF • distribution of session key to P-CSCF

  8. Possible Information Flow for Authentication and Session Key Establishment (from draft 3GPP TS 33.203) Changed to 407 Proxy Authentication Required Cx-Put Cx-Pull

  9. Use of Extensible Authentication Protocol (EAP) • There is a desire to minimise impact on protocols and equipment if 3GPP AKA is updated or if other schemes are used • a generic/extensible scheme to carry the authentication messages is desirable • candidates include SASL, EAP, GSS_API • current working assumption is EAP which has much of the necessary machinery in place

  10. EAP AKA in SIP SIP HTTP Authentication PGP HTTP Basic HTTP Digest HTTP EAP EAP Token Card EAP TLS EAP GSM EAP AKA EAP ...

  11. Concrete Authentication Example in SIP 1.  REGISTER sip:… SIP/2.0 Authorization: eapbase64_eap_identity_response ... 2.  SIP/2.0 407 Proxy Authentication Required WWW-Authenticate: eapbase64_eap_aka_challenge_request … 3.  REGISTER sip:… SIP/2.0 Authorization: eapbase64_eap_aka_challenge_response … 4.  SIP/2.0 200 OK WWW-Authenticate: eapbase64_eap_aka_success ...

  12. EAP AKA in DIAMETER DIAMETER base EAP Extensions EAP Token Card EAP TLS EAP GSM EAP AKA EAP ...

  13. Access Security: Security Mode Establishment between UA and P-CSCF • Determines when to start applying protection and which algorithm to use • includes secure algorithm negotiation • Uses session key derived during authentication • Integration into SIP registration with no new roundtrips

  14. Access security: Protection of SIP signalling between UA and P-CSCF • Integrity protection of SIP signalling between UA and P-CSCF • Uses session key derived during authentication • Symmetric scheme because of efficiency concerns • Candidate mechanisms include modified CMS and ESP

  15. IP Multimedia Subsystem: Access Security Documentation 3GPP IETF High level architecture TS 23.228 (SA2) TS 33.203 (SA3) Other specs (e.g. AKA) (SA3) SIPPING WG TS 24.228 (CN1) TS 29.228 (CN4) TS 24.229 (CN1) TS 29.229 (CN4) AAA, PPPEXT, IPsec, … Protocol detail

  16. Summary of 3GPP dependencies on IETF relating to security • 3GPP AKA in EAP • draft-arkko-pppext-aka-00.txt • EAP and session key transport in SIP • draft-torvinen-http-eap-00.txt (to appear) • EAP and session key transport in DIAMETER • SIP extensions to support security mode establishment

  17. References • Draft 3GPP TS 33.203, Access security for IP-based services (Release 5). • Draft 3GPP TS 33.210, Network domain security; IP network layer security (Release 5). • J. Arkko and H. Haverinen, “EAP AKA Authentication” draft-arkko-pppext-aka-00.txt. • V. Torvinen, J. Arkko, A. Niemi, “HTTP Authentication with EAP”, draft-torvinen-http-eap-00.txt (to appear). • L. Blunk, J. Vollbrecht, “PPP Extensible Authentication Protocol (EAP)”, RFC 2284. • P. Calhoun et al. “DIAMETER NASREQ Extensions”, draft-ietf-aaa-diameter-nasreq-06.txt.

  18. Questions? Peter Howard peter.howard@vodafone.com

  19. Authentication and Key Agreement Protocol (3GPP AKA) S-CSCF ISIM/UA HSS Authentication vector request Authentication vector response • Three party protocol • Two-pass mutual authentication protocol between UA and S-CSCF • Each authentication vector is good for one authentication • Authentication vectors can be distributed in batches to minimise signalling/load on HSS Authentication request Authentication response Distribution of session key to P-CSCF P-CSCF

  20. Other IP Multimedia Subsystem Security Issues (1) • Hide caller’s public ID from called party • by encrypting remote party ID header at caller’s S-CSCF and decrypting by same S-CSCF • is there a requirement to hide caller’s IP addresses that are dynamically assigned? • Network configuration hiding • mechanism being developed to hide host domain name of CSCFs and number of CSCFs within one operator’s network

  21. Other IP Multimedia Subsystem Security Issues (2) • Session transfer • guidance on security aspects based on GSM call transfer feature • authorisation and accounting of transferred leg needs to involve transferring party who has dropped out of session • should there be a limit to the number of transferred sessions? • should final destination be hidden from calling party? • Security aspects of other IP multimedia subsystem services? • End-to-end security

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