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Security “ Negotiation ” Open Issues - and draft-arkko-sip-sec-agree-01.txt

Security “ Negotiation ” Open Issues - and draft-arkko-sip-sec-agree-01.txt. Jari Arkko jari.arkko@ericsson.com Co-authored with Vesa Torvinen (Ericsson), Tao Haukka (Nokia), Sanjoy Sen, Lee Valerius (Nortel). An example network. Client 1: TLS, Dig. TLS. Server: TLS, Dig. Client 2:

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Security “ Negotiation ” Open Issues - and draft-arkko-sip-sec-agree-01.txt

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  1. Security “Negotiation”Open Issues- and draft-arkko-sip-sec-agree-01.txt Jari Arkko jari.arkko@ericsson.com Co-authored with Vesa Torvinen (Ericsson), Tao Haukka (Nokia), Sanjoy Sen, Lee Valerius (Nortel)

  2. An example network Client 1: TLS, Dig TLS Server: TLS, Dig Client 2: Digest Digest TLS Client 3: TLS, Dig • Multiple security mechanisms • No network-wide policy control • Different software versions

  3. An example network – Attack Client 1: TLS, Dig Digest Server: TLS, Dig Attacker Client 2: Digest Digest Digest Client 3: TLS, Dig

  4. Potential Solutions • (1) TLS, IKE have internal protection • Limited only to the case where we have already decided to use them • (2) Enhanced HTTP Digest has bidding down protection • Again limited in the same manner • (3) Sips: makes sure TLS is used • Assumes URLs have learned securely • Either (a) limits users to talking to TLS-capable nodes or (b) allows a bidding down attack • Can ensure complete path secured, but hop-by-hop • (4) Draft-arkko-sip-sec-agree-01 • Server lists its mechanisms, client picks one • Once security is on, client repeats the list => modifications detected • Full solution, but assumes at least integrity protection is used from day one

  5. Issues • Is the bidding down attack a problem? • Yes • There are realistic upgrade cases where this would be useful • Internal protection in TLS etc enough? • Not if we have multiple mechanisms • Sips: doesn’t help either unless we only use TLS • Proposal? • We should do something about this! • Sip-sec-agree sufficient? • Integrity protection required from day one, but can we do any better? • Lowest acceptable integrity protection must not be vulnerable • Any attacks that we haven’t thought of?

  6. Detailed Solution Issues • Stateless vs. stateful approach? • => Stateless! • Possible to use Support/Require? • Seem to have different semantics, not good match • => New header • Target identified e2e (OPTIONS) or along-the-path (header) • => Include along-the-path negotiation for less RTT’s • SIP layer response when the list was modified?

  7. Way forward • Do something! • Proposal: new small RFC by SIP WG • Needed for 3GPP • Time pressure

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