diff --git a/Documentation/proposals/token-revocation.md b/Documentation/proposals/token-revocation.md new file mode 100644 index 00000000..b4a50eb0 --- /dev/null +++ b/Documentation/proposals/token-revocation.md @@ -0,0 +1,82 @@ +# Proposal: design for revoking refresh tokens. + +Refresh tokens are issued to the client by the authorization server and are used +to request a new access token when the current access token becomes invalid or expires. +It is a common usecase for the end users to revoke client access to their identity. +This proposal defines the changes needed in Dex v2 to support refresh token revocation. + +## Motivation + +1. Currently refresh tokens are not associated with the user. Need a new "session object" for this. +2. Need an API to list refresh tokens based on the UserID. +3. We need a way for users to login to dex and revoke a client. +4. Limit the number refresh tokens for each user-client pair to 1. + +## Details + +Currently in Dex when an end user successfully logs in via a connector and has the OfflineAccess +scope set to true, a refresh token is created and stored in the backing datastore. There is no +association between the end user and the refresh token. Hence if we want to support the functionality +of users being able to revoke refresh tokens, the first step is to have a structure in place that allows +us retrieve a list of refresh tokens depending on the authenticated user. + +```go +// Reference object for RefreshToken containing only metadata. +type RefreshTokenRef struct { + // ID of the RefreshToken + ID string + CreatedAt time.Time + LastUsed time.Time +} + +// Session objects pertaining to users with refresh tokens. +// +// Will have to handle garbage collection i.e. if no refresh token exists for a user, +// this object must be cleaned up. +type OfflineSession struct { + // UserID of an end user who has logged in to the server. + UserID string + // The ID of the connector used to login the user. + ConnID string + // List of pointers to RefreshTokens issued for SessionID + Refresh []*RefreshTokenRef +} + +// Retrieve OfflineSession obj for given userId and connID +func getOfflineSession (userId string, connID string) + +``` + +### Changes in Dex CodeFlows + +1. Client requests a refresh token: + Try to retrieve the `OfflineSession` object for the User with the given `UserID + ConnID`. + This leads to two possibilities: + * Object exists: This means a Refresh token already exists for the user. + Update the existing `OffilineSession` object with the newly received token as follows: + * CreateRefresh() will create a new `RefreshToken` obj in the storage. + * Update the `Refresh` list with the new `RefreshToken` pointer. + * Delete the old refresh token in storage. + + * No object found: This implies that this will be the first refresh token for the user. + * CreateRefresh() will create a new `RefreshToken` obj in the storage. + * Create an OfflineSession for the user and add the new `RefreshToken` pointer to + the `Refresh` list. + +2. Refresh token rotation: + There will be no change to this codeflow. When the client refreshes a refresh token, the `TokenID` + still remains intact and only the `RefreshToken` obj gets updated with a new nonce. We do not need + any additional checks in the OfflineSession objects as the `RefreshToken` pointers still remain intact. + +3. User revokes a refresh token (New functionality): + A user that has been authenticated externally will have the ability to revoke their refresh tokens. + Please note that Dex's API does not perform the authentication, this will have to be done by an + external app. + Steps involved: + * Get `OfflineSession` obj with given UserID + ConnID. + * If a refresh token exists in `Refresh`, delete the `RefreshToken` (handle this in storage) + and its pointer value in `Refresh`. Clean up the OfflineSession object. + * If there is no refresh token found, handle error case. + +NOTE: To avoid race conditions between “requesting a refresh token” and “revoking a refresh token”, use +locking mechanism when updating an `OfflineSession` object.