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Federated identity » History » Revision 6

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Tom Clegg, 06/19/2017 07:45 PM


Federated identity

A person should be able to create an account and get a token from a single identity provider, and use that token to access private/protected resources on multiple Arvados clusters.

Motivating use cases:
  • A user on cluster B shares a project with a user on cluster A.
  • A container running on cluster A reads and writes data on cluster B.
  • A user logged in to Workbench A can search/view/download/upload collections at cluster B.
Configuration examples:
  • An organization has 5 clusters, but only one of them has user accounts and roles in its database.
  • An on-premise cluster runs containers that use public data stored in the cloud (without mirroring the data locally).

Design sketch

Each Arvados client must be able to prove to cluster B that it is authorized by cluster A to act on behalf of a user account which is controlled by cluster A. This must not involve giving enough information to cluster B to act on behalf of the user account: for example, the client cannot simply give cluster B its cluster A token for the purpose of doing a canary query.

Protocol idea

"Salted tokens": instead of passing its literal token, the client passes the token UUID and HMAC(token, "bbbbb") when sending a request to cluster B (where "bbbbb" is cluster B's cluster ID / UUID prefix). Cluster B validates the request by passing those two parameters untouched to a "verify request" ("no-op") endpoint at cluster A.
  • Cluster B figures out cluster A's API endpoint by looking at the "site ID prefix" of the token UUID.
  • Cluster B can be configured with a lookup table (clusterID→apiHost) to override the implicit {id}.arvadosapi.com
  • Cluster B can be configured to only use the lookup table, i.e., to never use implicit {id}.arvadosapi.com endpoints

(PA) an even simpler approach would be be to contact cluster A to get a scoped token which only allows "GET /users/current" on cluster A but is accepted by cluster B as an [all] token for that user.

Adding permissions

There are a few permission-granting cases to consider.

grantor grantee object notes
user on site A user on site A object on site A (existing permission system)
user on site A group on site A object on site A (existing permission system)
user on site A user or group on site A object on site B Client creates a link at site B. Site B asks site A whether the grantee user/group is visible to user A.
user on site A user or group on site B object on site B Client creates a link at site B. Site B asks site A for a list of groups user A can see, then checks whether (possibly via one of those groups) user A can read the grantee user/group according to site B's local database.
user on site A user or group on site B object on site A Client creates a link at site A. Site A generates a salted token and uses it to ask site B whether user A can read the grantee user/group.

TODO

Things to address
  • how to sync groups
  • diagrams
  • mnemonic cluster names / more concrete examples (including who is reachable on the internet)
  • [how] do you get a list of users/groups you can share stuff with?
  • clarify what UUIDs look like (some people have A uuids, some have B uuids)

Updated by Tom Clegg about 5 years ago · 6 revisions