SIP Security Issues : The SIP Authentication Procedure and its Processing Load Speaker: Lin-Yi Wu Advisor : Prof. Yi-Bing Lin Date : 2003/04/09

Main Reference  Salsano, S.; Veltri, L.; Papalilo, D, “ SIP security issues: the SIP authentication procedure and its processing load “, IEEE Network, Volume: 16 Issue: 6, Nov/Dec 2002  J. Rosenberg et al., “ SIP: Session Initiation Protocol “ IETF RFC 3261, June 2002

Outline  Motivation  Classification of security End-to-End Hop-by-Hop  Security Support in SIP Authentication Encryption  Evaluation of Processing Cost  Proposed solution Requirements Limitation of current SIP security mechanism Design concept

Motivation  Achieve the same security level in PSTN High service availability  Prevent DOS, IDS, fault tolerance … etc. Protection of user-to-network and user- to-user traffic  Authentication  Data Integrity  Encryption

Classification of security mechanism  End-to-End mechanism Secure association between caller and callee user agent Protect any confidential information besides route information  Hop-by-Hop mechanism Secure association between two successive SIP entities in the path Protect route information

Security Support in SIP  End-to-End mechanism Defined in SIP protocol  Authentication Proxy-Authenticate, Proxy-Authorization, WWW- Authenticate, Authorization  Encryption S/MIME  Hop-by-Hop mechanism Rely on Network level or Transport Level security  IPSec  TLS

Evaluation of Authentication Processing Cost

Analysis : SIP Authentication Requirements  Requirements Authentication  Mutual Authentication  Key Distribution  Roaming agreement Integrity Cipher Key exchange Prevention of replay attack  Limitation of current Authentication mechanism Authentication  Mutual Authentication : NO  Key Distribution : Predefine secret  Roaming agreement : NO Integrity : achieve by S/MIME Cipher Key exchange : NO Prevention of replay attack : achieve by nonce

Concept of Design : Public/Private key based Authentication  The public key /private key of A : Pub_A/Pri_A  The public key /private key of B : Pub_B/Pri_B  A knows B ’ s public key Pub_B  B knows A ’ s public key Pub_A

Concept of Design : Certificate-based authentication (1/2)  Only CA ’ s public key has to be known.

 Roaming agreement Concept of Design : Certificate-based authentication (2/2)

 Roaming agreement Concept of Design : Certificate-based authentication (2/2)

Examine the Requirements  Authentication Mutual Authentication : YES Key Distribution : base on Certificate verification Roaming agreement : solved by PKI architecture  Integrity : S/MIME  Cipher Key exchange : can be achieved by public key & private key system  Prevention of replay attack : achieve by nonce New type of Headers have to be specified. Concept of Design: Examine the requirements

The End

Authentication Procedure

S/MIME INVITE SIP/2.0 Via: SIP/2.0/UDP pc33.atlanta.com;branch=z9hG4bKnashds8 To: Bob From: Alice ;tag= Call-ID: a84b4c76e66710 CSeq: INVITE Max-Forwards: 70 Contact: Content-Type: application/pkcs7-mime; smime-type=enveloped-data; name=smime.p7m Content-Disposition: attachment; filename=smime.p7m handling=required Content-Type: application/sdp v=0 o=alice IN IP4 pc33.atlanta.com s=- t=0 0 c=IN IP4 pc33.atlanta.com m=audio 3456 RTP/AVP a=rtpmap:0 PCMU/8000

SIP Header Privacy and Integrity using S/MIME : Tunneling SIP INVITE SIP/2.0 Via: SIP/2.0/UDP pc33.atlanta.com; branch=z9hG4bKnashds8 To: Bob From: Alice ;tag= Call-ID: a84b4c76e66710 CSeq: INVITE Max-Forwards: 70 Date: Thu, 21 Feb :02:03 GMT Contact: Content-Type: multipart/signed; protocol="application/pkcs7-signature"; micalg=sha1; boundary=boundary42 Content-Length: boundary42 Content-Type: message/sip INVITE SIP/2.0 Via: SIP/2.0/UDP pc33.atlanta.com; branch=z9hG4bKnashds8 To: Bob From: Alice ;tag= Call-ID: a84b4c76e66710 CSeq: INVITE Max-Forwards: 70 Date: Thu, 21 Feb :02:03 GMT Contact: Content-Type: application/sdp Content-Length: 147 v=0 o=UserA IN IP4 here.com s=Session SDP c=IN IP4 pc33.atlanta.com t=0 0 m=audio RTP/AVP 0 a=rtpmap:0 PCMU/ boundary42 Content-Type: application/pkcs7- signature; name=smime.p7s Content-Transfer-Encoding: base64 Content-Disposition: attachment; filename=smime.p7s; handling=required ghyHhHUujhJhjH77n8HHGTrfvbnj756tbB9HG4 VQpfyF467GhIGfHfYT6 4VQpfyF467GhIGfHfYT6jH77n8HHGghyHhHUu jhJh756tbB9HGTrfvbnj n8HHGTrfvhJhjH776tbB9HG4VQbnj7567GhIGf HfYT6ghyHhHUujpfyF4 7GhIGfHfYT64VQbnj756 --boundary42-

SIP Header Privacy and Integrity using S/MIME : Tunneling SIP INVITE SIP/2.0 Via: SIP/2.0/UDP pc33.atlanta.com;branch=z9hG4bKnashds8 To: Bob From: Anonymous ;tag= Call-ID: a84b4c76e66710 CSeq: INVITE Max-Forwards: 70 Date: Thu, 21 Feb :02:03 GMT Contact: Content-Type: multipart/signed; protocol="application/pkcs7-signature"; micalg=sha1; boundary=boundary42 Content-Length: boundary42 Content-Type: application/pkcs7-mime; smime-type=enveloped-data; name=smime.p7m Content-Transfer-Encoding: base64 Content-Disposition: attachment; filename=smime.p7m handling=required Content-Length: 231 ********************************************************* * Content-Type: message/sip * * INVITE SIP/2.0 * Via: SIP/2.0/UDP pc33.atlanta.com;branch=z9hG4bKnashds8 * To: Bob * From: Alice ;tag= * Call-ID: a84b4c76e66710 * CSeq: INVITE * Max-Forwards: 70 * Date: Thu, 21 Feb :02:03 GMT * Contact: * Content-Type: application/sdp * v=0 * o=alice IN IP4 pc33.atlanta.com * s=Session SDP * t=0 0 * c=IN IP4 pc33.atlanta.com * m=audio 3456 RTP/AVP * a=rtpmap:0 PCMU/8000 **********************************************

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