Duct buddy-auth.jwt-oidc

A Duct library that provides Integrant keys and associated code implementing a :duct.middleware.buddy/authentication compatible JWT token validation function for OpenID Connect ID Tokens.

See OpenID Connect Core 1.0 Terminology for additional details on the meaning of the OpenID Connect terms used below.

Installation

To use this library you also need to add the following dependency to your project (use the most recent version of it):

[duct/middleware.buddy "0.1.0"]

Caching

The library caches both the OpenID Provider signing keys and a configurable amount of ID Token validation results, to speed up repeated token validation. The signing keys are cached for a configurable amount of time (see below). The ID Token validation results are cached until ID Token expiration time in case the token is successfully validated, or for an hour if it is not valid.

Caveat with respect to JWT signatures

The library only supports asymmetric signatures for ID Tokens, and marks any ID Token signed with a symmetric signature as invalid (regardless of its actual validity!). The rationale for this decision is that regarding symmetric signatures OpenID Connect Core 1.0 specification states that.:

"Symmetric signatures MUST NOT be used by public (non-confidential) Clients because of their inability to keep secrets."

Web applications are non-confidential by their very nature, so the library refuses to validate symmetric signatures.

Usage

The library currently supports a single Integrant key: :magnet.buddy-auth/jwt-oidc. To initialize it, the following keys are mandatory and their values must not be nil:

• :claims key which is a map with the set of OpenID Connect claims that the ID Token should satisfy. At least the following mandatory keys should be specified:
  • :iss is the URL, using the https scheme with no query or fragment component, that the ID Token OpenID Provider (OP) asserts as its Issuer Identifier. This also must be identical to the iss Claim value in ID Tokens issued by this OP.
  • :aud are the audience(s) that ID Tokens issued by the <issuer-identifier-url> are intended for. It contains the OAuth 2.0 client_id of the Relying Party as an audience value. It may also contain identifiers for other audiences. In the general case, the <aud-values> value is an array of case-sensitive strings. In the common special case when there is just one audience, the aud value MAY be a single case-sensitive string.
• :jwks-uri is the URL of the OpenID Provider's JSON Web Key Set [JWK] document. This contains the signing key(s) the Relaying Party uses to validate signatures from the OpenID Provider. It must be a string or a java.net.URL value.

You can also use the following optional configuration keys:

• :pubkeys-expire-in which is the time to live for the cached OpenID Provider signing keys. It has to be specified in an integral number of seconds greater than zero. If not specified the default value is 86400 (one day).
• :max-cached-tokens which is the maximum amount of cached ID Token validation results. It has to be an integer value greater than zero. If not specified, the default value is 50.
• :jwks-retrieval-timeout which specifies the connection timeout (in milli-seconds) for JWKS retrieval. It has to be an integer value greater than zero. If not specified, the default value is 500 milli-seconds.
• :jwks-retrieval-retries which specifies the number of additional retries in case of connection failure for JWKS retrieval. It has to be an integer value greater than zero. If not specified, the default value is 3 retries.
• :logger a value that implements the duct.logger/Logger protocol. If not nil, the library will log any relevant issues that may prevent tokens from being validated (e.g., inability to get the JWKS URL, getting invalid keys in the JWKS document, etc.)

Example (using all optional configuration keys with their default values):

{:magnet.buddy-auth/jwt-oidc
 {:claims {:iss #duct/env ["ISSUER_URL" Str]
           :aud #duct/env ["AUDIENCE" Str]}
  :jwks-uri #duct/env ["JWKS_URI" Str]
  :pubkeys-expire-in 86400
  :max-cached-tokens 50
  :jwks-retrieval-timeout 500
  :jwks-retrieval-retries 3
  :logger #ig/ref :duct/logger}}

Initializing the key returns an authfn function that can be used in conjunction with :duct.middleware.buddy/authentication. Example:

{:magnet.buddy-auth/jwt-oidc
 {:claims {:iss #duct/env ["ISSUER_URL" Str]
           :aud #duct/env ["AUDIENCE" Str]}
  :jwks-uri #duct/env ["JWKS_URI" Str]
  :logger #ig/ref :duct/logger}

 :duct.middleware.buddy/authentication
 {:backend    :token
  :token-name "Bearer"
  :authfn     #ig/ref :magnet.buddy-auth/jwt-oidc}}

The authfn function does all the OpenID Connect ID Token validation process and returns the value of the sub claim if the ID Token was successfully validated. Otherwise, it returns nil. The function throws AssertionError if any of the following conditions occur:

• :jwks-uri is not a string or a valid java.net.URL value.
• :iss is nil
• :aud is nil

Testing

The library includes self-contained units tests, and an integration test that depends on AWS Cognito User Pools. That test is named magnet.buddy-auth.jwt-oidc-test.test-cognito-token-validation and has the ^:integration metadata keyword associated to it, so you can exclude it from your unit tests runs.

If you want to run the integration test, the following set of environment variables are needed (the first three are the standard AWS credentials environment variables):

• AWS_ACCESS_KEY_ID: The Access key ID of an AWS IAM user. That user must have permission to perform the InitiateAuth action, on the AWS cognito-idp resource that points to a particular AWS Cognito User Pool.
• AWS_SECRET_ACCESS_KEY: The Secret Access key associated to the previous Access key ID.
• AWS_DEFAULT_REGION: The region where the User Pool is located at.
• COGNITO_TESTS_USER_POOL_CLIENT_ID: The ID of an "App client" that is allowed to interact with the User Pool.
• COGNITO_TESTS_ISSUER_URL: The Issuer URL (iss claim, in OpenID Connect terminology) used by the User Pool when minting OpenID Connect ID Tokens. See ID Token Payload for additional details.
• COGNITO_TESTS_AUDIENCE: This is the Audience (aud, in OpenID Connect terminology), that contains the User Pool client_id used for the user authenticated. See the previous link for additional details.
• COGNITO_TESTS_JWKS_URI: The URI of the JSON Web Key Set (JWKS) for the User Pool. See step 2.a in Step 2: Validate the JWT Signature for additional details.
• COGNITO_TESTS_USERNAME: The "sign in" value of an existing user in the User Pool (note that depending on the User Pool configuration, the "sign in" value can be a username, an email address, or other values).
• COGNITO_TESTS_PASSWORD: The password for the previous user name.
• COGNITO_TESTS_SUB: The subject value (sub claim, in OpenID Connect terminology) assigned to the previous user in the User Pool.

License

Copyright (c) 2018, 2019 Magnet S Coop.

This Source Code Form is subject to the terms of the Mozilla Public License, v. 2.0. If a copy of the MPL was not distributed with this file, You can obtain one at https://mozilla.org/MPL/2.0/