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LionShare & USHER

LionShare is an academic peer-to-peer file sharing system emphasizing strong identity management. Users are required to prove their identity to share files, using digitally signed protocol messages and XML fragments. Authentication is managed through short-term certificates obtained from the SASL-CA. The system supports attribute-based access controls and integrates with Shibboleth for authorization, allowing flexible user permissions. Moving forward, LionShare aims to expand its functionalities with pluggable certificate types while ensuring a secure sharing environment.

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LionShare & USHER

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  1. LionShare & USHER Derek Morr Spring ’06 MM

  2. Overview • LionShare is an academic peer-to-peer filesharing system. • Strong emphasis on on identity management: Users must be identified to share files. • Optional attribute-based authorization.

  3. Authentication • To identify themselves, users digitally sign certain protocol messages and XML fragments. • Users obtain short-term certs from an online CA, called the SASL-CA. • Think kx509, but with SASL and in Java.

  4. Certificate Types • Identity: CN=DEREK VAUGHAN MORR(dvm105@psu.edu)/dvm105@psu.edu, OU=ACADEMIC SERV & EMERGING TECH, O=Pennsylvania State University, L=UNIVERSITY PARK, ST=Pennsylvania, C=US • Opaque: CN=6ZYEBU6OPVQSCQLEKEM463QVLLQXTUU2PTCSYDLK2VHZA3FJR27UJFUJXB5ZSEVUL3US2FZ5O4LZWIR3737THCFTX4B2RJMWC27LB2DMQFL7ZQAXMD4Q

  5. Authorization • Users can create attribute-based ACLs. • LS 1.1 supports a subset of eduPerson; this may be expanded in a later release. • We use a custom SAML profile to obtain and exchange attributes. This requires a plugin to Shib 1.3.

  6. Split Roots • AuthN (the SASL-CA) is rooted in USHER. • AuthZ (Shib) is rooted in InCommon. • Fortunately, the two CAs have similar policies.

  7. Bridging the Roots • Users obtain an USHER-rooted opaque cert from the SASL-CA with a CryptoShibHandle in the DN: CN=6ZYEBU6OPVQSCQLEKEM463QVLLQXTUU2PTCSYDLK2VHZA3FJR27UJFUJXB5ZSEVUL3US2FZ5O4LZWIR3737THCFTX4B2RJMWC27LB2DMQFL7ZQAXMD4Q • This is a symmetrically encrypted identifier that the IdP can interpret.

  8. Bridging the Roots • Open a mutually authenticated SSL tunnel to IdP with the opaque cert to obtain an InCommon-rooted SAML AttributeAssertion. • The AttributeAssertion is bound to the USHER-rooted opaque cert via Holder-of-Key Confirmation

  9. Holder-of-Key Confirmation <SubjectConfirmation> <ConfirmationMethod> urn:lionshare-test:holder-of-key </ConfirmationMethod> <SubjectConfirmationData> <ds:KeyInfo xmlns:ds="http://www.w3.org/2000/09/xmldsig#"> <ds:X509Data> <ds:X509Certificate> Base64-encoded opaque cert here… </ds:X509Certificate> </ds:X509Data> </ds:KeyInfo> </SubjectConfirmationData> </SubjectConfirmation>

  10. Security Model USHER Foundation

  11. “Friendly Trust” • AuthZ (Shib) has extensive metadata about each node that supplements PKIX. • AuthN (SASL-CA) does not. Anything from USHER is trusted. • No one wants to run a LS-specific federation.

  12. Deployment • 1.0 - Sept ’05 • 1.1 - April/May ’06 • Penn State got its USHER CA cert last week. • In last stages of testing, should go live “soon.”

  13. SASL-CA Future • Version 0.4 almost ready (rc5 is being prepped). • Version 0.5: • Pluggable cert types, possibly based on HEPKI-TAG certprofiles • May introduce backwards-incompatible protocol changes

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