OAuth 2.0 SecurityIETF OAuth WG Conference Call, 14th December 2012

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Agenda

• Discuss security requirements and use cases in order to get a better understanding of the design space outlined in <draft-tschofenig-oauth-security>

Use Case #1: Load Balancer

User Agent &

Resource Owner

Client (C)

Authorization Server (AS)

Resource Server (RS)

Load Balancer

TLS

Access Token

Keys & Meta Data

AS-C

AS-RS

Access Token

AS-RS

AuthenticatorC-RS

TLS

Notes for Use Case 1

• To prevent a load balancer from being used channel bindings can be deployed.

• The operator of the resource server may decide to “terminate” application security also at the load balancer.

Use Case #2: “Unprotected” Resource

User Agent &

Resource Owner

Client (C)

Authorization Server (AS)

Resource Server (RS)

Access Token

Keys & Meta Data

AS-C

AS-RS

Access Token

AS-RS

AuthenticatorC-RS

TLS

Notes for Use Case 2

• This use case only assumes that TLS is not used by the resource server.

• OAuth 2.0 requires TLS to be used with the authorization server.

• Hence, a TLS-incapable OAuth 2.0 client requires more changes.

Use Case #3: Prevent Access Token Re-Use

Access Token

User Agent &

Resource Owner

Client (C)

Authorization Server (AS)

Resource Server 1 (RS1)

Access Token

Keys & Meta Data

AS-C

AS

Access Token

AS

AuthenticatorC-RS1

TLS

Resource Server 2 (RS1)

AS

AuthenticatorC’-RS2

Notes for Use Case 3

• Assumption: – RS cannot re-generate Authenticator.

• Alternative solutions: 1. AS puts intended recipient (RS1) into the

access token.

2. AS encrypts token with key known to RS1 only.

Use Case #4: AS-to-RS Relationship Anonymity

• Idea: AS should not know with whom a resource owner is talking to.

• Implications:– No RS info made available to the AS by the

client– RS does not interact with the AS (in the

backend).– AS signs access token

Open Issue: Client Instance

• Client authentication allow authentication to the AS.– Same credentials may be re-use by a number

of different client instances

• Suggestion was made to offer authentication of a client instance.

• By whom would this identification be used and for what purpose?

• What identifier could be used?

Open Issue: Key Lifetime & Context

• The client obtains keying material from the AS.• Questions:

– Does it change when a new access token is requested?

– Is it valid only for a specific RS?– When an access token with a new scope is requested

does the keying material change?– Who contributes to the keying material: client, AS, or

both?– Is there an explicit lifetime associated?