CAIP-217: Authorization Scopes

Simple Summary

This CAIP defines a simple syntax for scopes of authorization between applications (e.g. dapps) and user-agents (e.g. “wallets” or signers). These are expressed as JSON objects as a building block across multiple protocols and mechanisms, for example:

• A JSON-RPC protocol for persisting and synchronizing authorized sessions (CAIP-25)
• Routing individual RPC commands to an authorized network (CAIP-27)

Motivation

The layering of today’s cryptographic and decentralized systems favors loosely-coupled combinations of protocols (representated in the CAIPs model as namespaces), instances or consensus-communities within those protocols (addressed in the CAIPs model as [CAIP-2][] URNs), and sets of supported RPC methods and notifications used in those namespaces. Bundling all of these into an object facilitates unambiguous authorization schemes, including progressive authorization patterns, feature discovery, authority negotiation (See CAIP-211) and delegations.

Specification

An authorization scope is represented in JSON as an object which is keyed to a string that expresses its target network and contains arrays of strings expressing the various capabilities authorized there. When embedded in any other JSON context (including the params of a JSON-RPC message), the object MUST be expressed as the value of a property named by the scope string.

Language

The key words “MUST”, “MUST NOT”, “REQUIRED”, “SHALL”, “SHALL NOT”, “SHOULD”, “SHOULD NOT”, “RECOMMENDED”, “NOT RECOMMENDED”, “MAY”, and “OPTIONAL” written in uppercase in this document are to be interpreted as described in RFC 2119

Definition

The syntax of a scopeObject is as follows:

[scopeString]: {
   *scopes: [(chainId)+],
   methods: [(method_name)+],
   notifications: [(notification_name)+],
   *accounts: [(account_id)+]
   *rpcDocuments: [(rpcDocument)+],
   *rpcEndpoints: [(rpcEndpoint)+]
}

Where:

• {scopeString} (conditional) = EITHER a namespace identifier string registered in the CASA namespaces registry to authorize multiple chains with identical properties OR a single, valid [CAIP-2][] identifier, i.e., a specific chain_id within a namespace.
• scopes (conditional) = An array of 0 or more [CAIP-2][] chainIds. For each entry in scopes, all the other properties of the scopeObject apply, but in some cases, such as when members of accounts are specific to 1 or more chains in scopes, they may be ignored or filtered where inapplicable; namespace-specific rules for organizing or interpreting properties in multi-scope MAY be specified in a namespace-specific profile of this specification.
  • This property MUST NOT be present if the object is already scoped to a single chainId in the string value above.
  • This property MUST NOT be present if the scope is an entire namespace in which chainIds are not defined.
  • This property MAY be present if the scope is an entire namespace in which chainIds are defined.
• methods = An array of 0 or more JSON-RPC methods that an application can call on the agent and/or an agent can call on an application.
• notifications = An array of 0 or more JSON-RPC notifications that an application send to or expect from the agent.
• accounts (optional) = An array of 0 or more CAIP-10 identifiers, each valid within the scope of authorization.
• rpcDocuments (optional) = An array of URIs that each dereference to an RPC document specifying methods and notifications applicable in this scope.
  • These are ordered from most authoritative to least, i.e. methods defined more than once by the union of entries should be defined by their earliest definition only.
• rpcEndpoints (optional) = An array of URLs that each dereference to an RPC endpoints for routing requests within this scope.
  • These are ordered from most authoritative to least, i.e. priority SHOULD be given to endpoints in the order given, as per the CAIP-211 profile for that namespace, if one has been specified.

Additional constraints MAY be imposed by the usage of scopeObjects in protocols such as CAIP-25, and specific namespaces may have implicit values or validity constraints for these properties.

Whenever another CAIP uses the name scopeObject and has this CAIP in the required front-matter property, it SHALL be interpreted as reference to this specification.

References

Copyright

Copyright and related rights waived via CC0.

Citation

Please cite this document as:

Pedro Gomes, Hassan Malik, Juan Caballero, "CAIP-217: Authorization Scopes [DRAFT]," Chain Agnostic Improvement Proposals, no. 217, November 2022. [Online serial]. Available: https://github.com/ChainAgnostic/CAIPs/blob/master/CAIPs/caip-217.md