Bearer Token

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Revision as of 15:49, 9 September 2018 by Tom (talk | contribs) (Problem)

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Full Title or Meme

A data structure that passes Anonymous Authorization grants to a Resource server.

Context

RFC 6750 "The OAuth 2.0 Authorization Framework: Bearer Token Usage" defines the Bearer Token.

Problem

  • Any party in possession of a Bearer Token can use it to get access to the associated Resources (without demonstrating possession of a cryptographic key). To prevent misuse, bearer tokens need to be protected from disclosure in storage and in transport.
  • Bearer Tokens are valid only for as short time as possible. These tokens work like passwords, and if intercepted can be used immediately by an attacker. Therefore the OAuth2 (with bearer token) specification requires that all communication takes place over SSL - since no cryptography is built into the specification. Typically access tokens have a short validity, which can be refreshed with a "refresh token" which has longer validity but is only transferred when the initial bearer token is received by the consumer, and when a bearer token is refreshed.
  • Token reuse: OAuth 2.0 or OpenID Connect use of bearer tokens raises the risk of token theft. For years architects have been waiting for Token Binding to get ratified so there would be transparent mechanism to close this gap. If this feature gets dropped from Chrome, this enterprise use case doesn't go away and only Microsoft Browsers support the feature.
  • Sarah Squire on Token Binding]

Solution

  • Don't use Bearer Tokens without modifying them to include an Identifier to the owner of the token.
  • Microsoft introduced EAP and Channel Binding
  • Protection from the secure channel endpoint to a front end server

Reference