Security - PowerPoint Presentation

Slide1

Security

Hannes

TschofenigSlide2

Goal for this Meeting

Use the next 2 hours to determine what the security consideration section of the OAuth

draft(s) should contain.Currently, the security consideration section of draft-ietf-oauth-v2-10 is empty. Note: No time to actually write text today. The next couple of slides are an introduction to get the discussion started. Approaches the topic based on NIST SP 800-63 Slide3

Abstract View on OAuth

,-. (* *) `+' User ' :------------ ---|--- ~~~~~~~~~~:

: Service / \ : Management

: Interaction / \ : of Resources

: : Consent :

: : :

: : :

: +---:-+ Carol :

: 1. |Carol| as :

: Obtain .'>| | Asserting :

: Access .' +-----+ Party :

: Token.' :

: .' :

: .' :

:

v

' :

+-:---+ +--:--+ Bob

|Alice|<------------------------->|Bob | as

| | 2. Authenticated | | Relying

+-----+ Request + +-----+ Party

Access TokenSlide4

Status: draft-ietf-oauth-v2-10

(with relevance for security)

Token: Token Format not specifiedToken Content not specifiedProtection of token unspecified.HTTP Basic Authentication used for interaction with the authorization server, see (1)No HTTP-level authentication for authenticated request (2) specified. TLS not mandatory to use for (2) either. Slide5

Example Instantiation:

Web Server FlowSlide6
Slide7

Security Threats

(based on NIST SP 800-63)

Token manufacture/modificationAn attacker may generate a bogus token or modify the token content of an existing token, causing Bob to grant inappropriate access to the Alice.Token disclosureTokens may contain authentication and attribute statements that include sensitive information.

Token redirect

An attacker uses the token generated for consumption by Bob to obtain access to a second Relying Party.

Token reuse

An attacker attempts to use a token that has already been used once with Bob. Slide8

Threat Mitigation

(based on NIST SP 800-63)

Token modification: Protect the content, or use a reference instead!Token redirect: Carol must include the identity of the token consumer, Bob.Token disclosure:Variant (a): Do not include sensitive informationVariant (b

): Offer confidentiality protectionSlide9

Dealing with Token Reuse

Approach #1: Confidentiality Protection & extra condition*

*: Alice has to make sure it does not distribute the token to entities other than Bob

TLS

TLS

Carol

Alice

BobSlide10

Dealing with Token Reuse (2)

Approach #2: Sender Constraint Token contains information about the legitimate presenter (Alice).

Bob has to authenticate Alice first to verify whether the token constraint matches the authenticated identitySlide11

Dealing with Token Reuse (3)

Approach #3: Key Confirmation

Req

Token, {

Request}SK

,

{

SK}Bob

Carol

Alice

Bob

Token,SK

,

{

SK}Bob

TLSSlide12

Mandatory to implement?

Challenge: draft-ietf-oauth-v2-10 does not provide a completely interoperable solution since many aspects are left for bi-lateral agreements between Alice & Bob.

So, what should be mandatory to implement? Key Confirmation ApproachExperience in deployment available from Kerberos. Other approaches suffer from operational considerationsEnsuring that Alice only provides token to BobEstablishing authentication infrastructurePutting proper constraints in the token.

MUST implement and use TLS between Alice and Carol (exchange #1)Slide13

Additional Security Considerations

This slide set focuses on the token exchange. Security for the exchange between Alice and Carol isn’t described in great detail.

Main document can only provide requirements for token protection Will have to be postponed to documents covering the details. Example: Additional security considerations based on properties of individual flows. Relate to properties provided by operating systems, libraries/application frameworks, and browsers.