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How to Think about OAuth Security - Disclosure ...

Aaron Parecki
September 02, 2020

How to Think about OAuth Security - Disclosure 2020

Slides from my talk at Disclosure Conference

https://disclosureconference.com/

Aaron Parecki

September 02, 2020
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  1. @aaronpk so... how can I let an app access my

    data without giving it my password?
  2. @aaronpk September 2020 OAuth 2.0 RFC6749 OAuth Core Authorization Code

    Implicit Password Client Credentials Grant Types
  3. User: I’d like to use this great app App: Please

    go to the authorization server to grant me access User: I’d like to log in to “Yelp”, it wants to access my contacts AS: Here is a temporary code the app can use App: Here is the temporary code, and my secret, please give me a token User: Here is the temporary code, please use this to get a token AS: Here is an access token! App: Please let me access this user’s data with this access token! User Agent App OAuth Server API ?
  4. @aaronpk September 2020 OAuth 2.0 RFC6749 OAuth Core Authorization Code

    Implicit Password Client Credentials Grant Types RFC6750 Bearer Tokens Token Usage Tokens in HTTP Header Tokens in POST Form Body Tokens in GET Query String
  5. @aaronpk September 2020 OAuth 2.0 RFC6749 OAuth Core Authorization Code

    Implicit Password Client Credentials RFC6750 Bearer Tokens RFC7636 +PKCE Tokens in HTTP Header Tokens in POST Form Body Tokens in GET Query String
  6. @aaronpk September 2020 OAuth 2.0 RFC6749 OAuth Core Authorization Code

    Implicit Password Client Credentials RFC6750 Bearer Tokens RFC7636 +PKCE RFC8252 PKCE for mobile Tokens in HTTP Header Tokens in POST Form Body Tokens in GET Query String
  7. User: I’d like to use this great app App: Please

    go to the authorization server to grant me access User: I’d like to log in to “Yelp”, it wants to access my contacts AS: Here is a temporary code the app can use App: Here is the temporary code, and my secret, please give me a token User: Here is the temporary code, please use this to get a token AS: Here is an access token! App: Please let me access this user’s data with this access token! User Agent App OAuth Server API ?
  8. Front Channel Back Channel https://accounts.google.com/?... Passing data via the browser's

    address bar The user, or malicious software, can modify the requests and responses Sent from client to server HTTPS request from client to server, so requests cannot be tampered with
  9. @aaronpk September 2020 OAuth Server OAuth Client Passing Data via

    the Front Channel Did they catch 
 it? Did someone else 
 steal it? Is this really 
 from the real 
 OAuth server?
  10. @aaronpk September 2020 OAuth 2.0 RFC6749 OAuth Core Authorization Code

    Implicit Password Client Credentials RFC6750 Bearer Tokens RFC7636 +PKCE RFC8252 PKCE for mobile Tokens in HTTP Header Tokens in POST Form Body Tokens in GET Query String
  11. @aaronpk September 2020 OAuth 2.0 RFC6749 OAuth Core Authorization Code

    Implicit Password Client Credentials RFC6750 Bearer Tokens RFC7636 +PKCE RFC8252 PKCE for mobile Browser App BCP PKCE for SPAs Tokens in HTTP Header Tokens in POST Form Body Tokens in GET Query String
  12. @aaronpk September 2020 OAuth 2.0 RFC6749 OAuth Core Authorization Code

    Implicit Password Client Credentials RFC6750 Bearer Tokens Tokens in HTTP Header Tokens in POST Form Body Tokens in GET Query String RFC7636 +PKCE RFC8252 PKCE for mobile Browser App BCP PKCE for SPAs PKCE for confidential clients Security BCP
  13. @aaronpk September 2020 OAuth 2.0 Security BCP • All OAuth

    clients MUST use PKCE with the authorization code flow • Password grant MUST NOT be used • Use exact string matching for redirect URIs • No access tokens in query strings • Refresh tokens for single page apps must be 
 sender-constrained or one-time use oauth.net/2/oauth-best-practice
  14. @aaronpk September 2020 OAuth 2.0 Security BCP • All OAuth

    clients MUST use PKCE with the authorization code flow • Password grant MUST NOT be used • Use exact string matching for redirect URIs • No access tokens in query strings • Refresh tokens for single page apps must be 
 sender-constrained or one-time use oauth.net/2/oauth-best-practice
  15. @aaronpk September 2020 Password oauth.net/2/oauth-best-practice • Added to OAuth to

    enable migrating applications from HTTP Basic Auth or using a stored password to OAuth
  16. @aaronpk September 2020 Password • Exposes the username and password

    to the application • Even for first-party / trusted clients, this increases the attack surface • Trains users that it's okay to enter their password in more than one place • Difficult or impossible to extend to support multifactor or passwordless authentication (WebCrypto, WebAuthn)
  17. @aaronpk September 2020 OAuth 2.0 Security BCP • All OAuth

    clients MUST use PKCE with the authorization code flow • Password grant MUST NOT be used • Use exact string matching for redirect URIs • No access tokens in query strings • Refresh tokens for single page apps must be 
 sender-constrained or one-time use oauth.net/2/oauth-best-practice
  18. RFC6749 RFC6750 CLIENT TYPE AUTH METHOD GRANT TYPE RFC6819 RFC7009

    RFC7592 RFC7662 RFC7636 RFC7591 RFC7519 BUILDING YOUR APPLICATION RFC8252 OIDC RFC8414 STATE PARAM TLS CSRF UMA 2 FAPI RFC7515 RFC7516 RFC7517 RFC7518 TOKEN BINDING POP SECURITY BCP CIBA HTTP SIGNING MUTUAL TLS SPA BCP JARM JAR TOKEN EXCHANGE DPOP
  19. @aaronpk September 2020 OAuth 2.0 RFC6749 OAuth Core Authorization Code

    Implicit Password Client Credentials RFC6750 Bearer Tokens Tokens in HTTP Header Tokens in POST Form Body Tokens in GET Query String RFC7636 +PKCE RFC8252 PKCE for mobile Browser App BCP PKCE for SPAs PKCE for confidential clients Security BCP
  20. @aaronpk September 2020 OAuth 2.1 Consolidate the OAuth 2.0 specs,


    adding best practices, 
 removing deprecated features Capture current best practices in OAuth 2.0 under a single name Add references to extensions that didn't exist when OAuth 2.0 was published
  21. @aaronpk September 2020 OAuth 2.1 No new behavior defined by

    OAuth 2.1 Non-Goals: Don't include anything experimental, 
 in progress or not widely implemented
  22. @aaronpk September 2020 OAuth 2.1 Authors: Dick Hardt, Aaron Parecki,

    Torsten Lodderstedt • OAuth 2.1 is a consolidation of: 
 OAuth 2.0 (RFC6749), Native Apps BCP (RFC8252), PKCE (RFC7636), Browser-Based Apps BCP (draft), Security BCP (draft), 
 Bearer Tokens (RFC6750) • Grant types defined: Authorization Code with PKCE, Client Credentials • Exact redirect URI matching • No Bearer tokens in query strings • Refresh tokens for SPAs must be sender-constrained or one-time use • Implicit and password grants are omitted
  23. @aaronpk September 2020 Credentialed Client This distinction already exists in

    OAuth 2.0! OAuth 2.0: If the client type is confidential or the client was issued client credentials, the client MUST authenticate... OAuth 2.1: Confidential or credentialed clients MUST authenticate...
  24. @aaronpk September 2020 Credentialed Client • A client that has

    credentials, but whose identity is not confirmed • e.g. a client that obtains a client secret via dynamic client registration
  25. @aaronpk September 2020 OAuth 2.1 Client Types Public Confidential Credentialed

    Confirmed Identity Can Authenticate Confirmed Identity Can Authenticate Confirmed Identity Can Authenticate