Difference between revisions of "OpenID Connect"

Revision as of 10:42, 11 September 2020

Full Title or Meme

An extension of OAuth 2.0 to give a Relying Party access to User Information for Identification. (Other uses of this protocol are possible, but not of interest for Identity Management).

Context

• The OAuth 2.0 protocol gave access to User Resources, but without authentication, it was fraught with may vulnerabilities.
• The OpenID Connect protocol is always among three parties: the User (called subject), the Relying Party (called client for OAuth compatibility) and the Identifier or Attribute Provider (called OpenID Provider).
  • An exception is for Self-issued Identifiers where the user (sub) and the issuer (OP) are the same entity.
• There are always three Identifiers: the subject id (sub), the client id (client_id), and a URL pointing to an authoritative set of configuration parameters of the OpenID Provider (OP).

To be integrated

Note that in the Open ID document the RP is called a client and the IdP is called an Open ID provider (OP). It is a long-term goal for the IDEF to create an OpenID Connect profile that shows which options to use. In the meantime the Compliant Implementation of RP on ASP.NET provides a working model of a compliant OpenID Connect implementation. The following items might be included in a IDEF profile:

1. The RP and not the user has the ability to determine how the unprotected flow of access tokens are handled. IDEF could require the use of the "Authorization Code Flow", as shown above, which places all access tokens in protected flows between the RP and the IdP. That presumes that the RP is able to protect secrets like the User Private Information from disclosure.
2. The RP determines which User Private Information it wishes to receive and leaves it up to the IdP to determine whether the user has any choice as to which information to disclose. Some IdPs are very diligent and allow the user to select based on the claims profiles provided by the RP. It is more common for IdPs to offer the list of requested claims profiles to the user on a "take-it-or-leave-it" basis. the IDEF could require IdPs to give the user more granular control.
3. The Subject Identifier (sub in OpenID) is provided from the IdP to the RP during authentication. It is not a requirement that the IdP avoid reuse the same "sub" between two RP's to prevent linking between User Objects in those two RPs unless "pairwise" is specified. Any IDEF profile should require Pairwise Identifiers for subject as it is not in the interest of any digital entity to enable it. See the wiki page on Pairwise Identifier for the pros and cons of this approach.

Features that are not available in OpenID Connect that would improve the user experience include:

1. The ability to mark scope value by whether they were mandatory so that the consent form could let the user know which were optional. Please see this paper for more details on this issue. This might be solved by eliminating all values from the scope other than "openid". The use of the claims parameter might solve this problem as it does have an appropriate modifier.
2. There is not a complete protocol for passing information between the various identity providers in the OpenID Connect specifications. The Token Introspection RFC does provide data exchange, but does not describe the endpoint discovery mechanism. That would be needed at the point where the use case (or implementation guide) for the separation of the Attribute Provider from the other OpenID Providers (OP) was described.

Problems

• The great advantage of OpenID Connect is that it is simple and easy to implement.
• The great disadvantage of OpenID Connect is that it is simple and easy to implement.

Some of the problems that arise when the solution is not sufficiently simple to use OpenID Connect as it is written.

1. UK Open banking has found problems, like Bearer tokens, that resulted in the Financial-grade API of FAPI profile for OpenID Connect.
2. The Issuer is defined in different ways even the the body of the document and other restrictions are found in the conditions near the end of the document.
3. The dependence on the transport layer security (TLS) means that the legal entity and the URL need to be tightly bound, which is not always desirable.

These are issues that the OpenID Connect core specification leaves up the the implementer to choices that create Security or Privacy problems.

1. The Subject ID may be ephemeral. The following quote is from Draft profile FAPI Pt 2 " While the name ID Token suggests that it is something that provides the identity of the resource owner (subject), it is not necessarily so. While it does identify the authorization server by including the issuer identifier, it is perfectly fine to have ephemeral subject identifier. In this case, the ID Token acts as a detached signature of the issuer to the authorization response and it was an explicit design decision of OpenID Connect Core to make the ID Token act as a detached signature. "
2. The Subject ID (sub) may be shared among all of the clients that use the same OP unless pair-wise sub is included in the meta-data.
3. The Identifier or Attribute Provider may optionally ask for User Consent and may provide any set of claims they deem appropriate.

Solutions

These are additional limitations that need to be provided to the OpenID Connect implementation to meet existing legislation for the 3 party problem.

• Security Profile:

1. The Subject ID (sub) must be persistent and not used for different users for at least one year after it use is no longer used for its most recent Subject.
2. The Subject ID (sub) must not be shared with different clients by implementing pair-wise identifiers in the OP.
3. The Identifier or Attribute Provider must not provide any claims to the Relying Party that have not been part of an User Consent approval process.

References

1. OpenID specifications (use this if you want to be sure you have the latest version): http://openid.net/developers/specs/
2. OpenID connect core specification with Errata Set 1 (2014-11-08): http://openid.net/specs/openid-connect-core-1_0.html