Extensions to TLS

Simon Blake-Wilson

Certicom

David Hopwood

Independent Consultant

Jan Mikkelsen

Transactionware

Magnus Nystrom

RSA Security

Tim Wright

Vodafone

Content

• Updates from “wireless extensions”

• Issues raised

• The way forward?

DNS name extension

• New to the draft

• Allows a single “machine” to host multiple “servers”

• Client tells server DNS name of server being contacted

• Server may use info to help produce response

Other Extensions

• Clarified session resumption - extensions ignored during session resumption

• Short session IDs - removed

• Client cert urls - client supplies a list, one url = one cert

• Client cert urls - both cert hash and url supplied

• Truncated MACs - restricted to HMAC with MD5 and SHA-1

• Trusted root indication - cert hash option added

New Error Alerts

• Be careful when new error alerts get sent!

• Unsupported extension

• Bad extension order

• Unrecognized domain

• Certificate unobtainable

• Bad OCSP response

Issues

• How serious is “certificate unobtainable” alert?

• Do we need to require client driven extensions?

• How/where do DNS names get canonicalized?

• Generalize OCSP status request?

• Tie extensions with TLS version rev?

The Way Forward?

• Update based on comments and known issues

• WG last call?