Fence

A fence separates protected resources from the outside world and allows only trusted entities to enter.

Fence is a core service of the Gen3 stack that has multiple capabilities:

1. Act as an auth broker to integrate with one or more IdPs and provide downstream authentication and authorization for Gen3 services.
2. Manage tokens.
3. Act as an OIDC provider to support external applications to use Gen3 services.
4. Issue short lived, cloud native credentials to access data in various cloud storage services

Contents

1. API Documentation
2. Terminologies
3. Identity Providers
4. OIDC & OAuth2
5. Accessing Data
6. Setup
7. Token management
8. fence-create
9. Default expiration times

API Documentation

OpenAPI documentation available here.

YAML file for the OpenAPI documentation is found in the openapis folder (in the root directory); see the README in that folder for more details.

Terminologies

AuthN

Authentication - establishes "who you are" with the application through communication with an Identity Provider.

AuthZ

Authorization - establishes "what you can do" and "which resources you have access to" within the application.

IdP

Identity Provider - the service that lets a user login and provides the identity of the user to downstream services. Examples: Google login, University login, NIH Login.

Auth broker

An interface which enables a user to authenticate using any of multiple IdPs.

OAuth2

A widely used AuthZ protocol for delegating access to an application to use resources on behalf of a user.

https://tools.ietf.org/html/rfc6749

https://oauth.net/2/

Client

OAuth 2.0 Client - An application which makes requests for protected resources (on a resource server) on behalf of a resource owner (end-user) and with the resource owner's authorization.

Auth Server

OAuth 2.0 Authorization Server - A server which issues access tokens to the client after successfully authenticating the resource owner and obtaining authorization.

Access Token

A string, issued by the auth server to the client, representing authorization credentials used to access protected resources (on a resource server).

OIDC

OpenID Connect - an extension of OAuth2 which provides an AuthN layer on top of the OAuth 2.0 AuthZ layer. It introduced a new type of token, the id token, that is specifically designed to be consumed by clients to get the identity information of the user.

http://openid.net/specs/openid-connect-core-1_0.html

OP

OpenID Provider - an OAuth 2.0 Authentication Server which also implements OpenID Connect.

RP

Relying Party - an OAuth 2.0 Client which uses (requests) OpenID Connect.

Identity Providers

Fence can be configured to support different Identity Providers (IdPs) for AuthN. At the moment, supported IDPs include:

• Google
• Shibboleth
  • NIH iTrust
  • InCommon
  • eduGAIN
• CILogon
• Cognito
• Synapse
• Microsoft
• ORCID
• RAS

OIDC & OAuth2

Fence acts as a central broker that supports multiple IdPs. At the same time, it acts as an IdP itself. In that sense, fence is both an RP and an OP.

Fence as RP

Example:

• Google IAM is the OpenID Provider (OP)
• Fence is the Relying Party (RP)
• Google Calendar API is the resource provider

Fence as OP

• Fence is the OpenID Provider (OP)
• A third-party application is the Relying Party (RP)
• Gen3 microservices (e.g. sheepdog) are resource providers

Example Flows

Note that the 3rd Party App acts as the RP in these examples.

Flow: Client Registration

Flow: OpenID Connect

In the following flow, Fence and the IdP together constitute an OP. Fence, by itself, acts as an OAuth 2.0 Auth Server; the IdP enables the additional implementation of OIDC (by providing AuthN). From an OIDC viewpoint, therefore, Fence and the IdP can be abstracted into one OP.

If the third-party application doesn't need to use any Gen3 resources (and just wants to authenticate the user), they can just get needed information in the ID token after the handshake is finished .

Flow: Using Tokens for Access

If a third-party application wants to use Gen3 resources like fence/sheepdog/peregrine, they call those services with an Access Token passed in an Authorization header.

In the following flow, 3rd Party App is the RP; Protected Endpoint is an endpoint of a Gen3 Resource (the microservice), and both of these are part of a resource server; and Fence is the OP. Here, importantly, Fence may be interfacing with another IdP or with another Fence instance in order to implement the OIDC layer. Either way, note that the Fence blob in this diagram actually abstracts Fence in concert with some IdP, which may or may not also be (a different instance of) Fence.

Flow: Refresh Token Use

Flow: Refresh Token Use (Token is Expired)

Flow: Multi-Tenant Fence

The following diagram illustrates the case in which one fence instance uses another fence instance as its identity provider.

A use case for this is when we setup a fence instance that uses NIH login as the IdP. Here, we go through a detailed approval process in NIH. Therefore we would like to do it only once for a single lead Fence instance, and then allow other fence instances to simply redirect to use the lead Fence as an IdP for logging in via NIH.

In the following flow, Fence (Client Instance) is an OP relative to OAuth Client, but an RP relative to Fence (IDP).

Notes

See the OIDC specification for more details. Additionally, see the OAuth2 specification.

Access Control / Authz

Currently fence works with another Gen3 service named arborist to implement attribute-based access control for commons users. The YAML file of access control information (see #create-user-access-file) contains a section authz which are data sent to arborist in order to set up the access control model.

Accessing Data

Fence has multiple options that provide a mechanism to access data. The access to data can be moderated through authorization information in a User Access File.

Users can be provided specific privilege's on projects in the User Access File. A project is identified by a unique authorization identifier AKA auth_id.

A project can be associated with various storage backends that store object data for that given project. You can assign read-storage and write-storage privileges to users who should have access to that stored object data. read and write allow access to the data stored in a graph database.

Depending on the backend, Fence can be configured to provide users access to the data in different ways.

Signed URLS

Temporary signed URLs are supported in all major commercial clouds. Signed URLs are the most 'cloud agnostic' way to allow users to access data located in different platforms.

Fence has the ability to request a specific file by its GUID (globally unique identifier) and retrieve a temporary signed URL for object data in AWS or GCP that will provide direct access to that object.

Google Cloud Storage

Whereas pre-signed URL is a cloud agnostic solution, services and tools on Google Cloud Platform prefer to use Google's concept of a "Service Account". Because of that, Fence provides a few more methods to access data in Google.

See Fence and Google for more details on data access methods specific to Google.

Setup

Install Requirements and Fence

Install Poetry.

# Install Fence and dependencies
poetry install

Create Configuration File

Fence requires a configuration file to run. We have a command line utility to help you create one based on a default configuration.

The configuration file itself will live outside of this repo (to prevent accidentally checking in sensitive information like database passwords).

To create a new configuration file from the default configuration:

python cfg_help.py create

This file will be placed in one of the default search directories for Fence.

To get the exact path where the new configuration file was created, use:

python cfg_help.py get

The file should have detailed information about each of the configuration variables. Remember to fill out the new configuration file!

Other Configuration Notes

• Fence will look for configuration files from a list of search directories ( which are currently defined in fence/settings.py.)
• For more configuration options (such as having multiple different config files for development), see the cfg_help.py file.

Set Up Databases

The tests clear out the database every time they are run. If you want to keep a persistent database for manual testing and general local usage, create a second test database with a different name:

NOTE: Requires a minimum of Postgres v9.4 (because of JSONB types used)

# Create test database(s).
# This one is for automated tests, which clear the database after running;
# `tests/test_settings.py` should have `fence_test_tmp` in the `DB` variable.
psql -U test postgres -c 'create database fence_test_tmp'
userdatamodel-init --db fence_test_tmp
# This one is for manual testing/general local usage; Your config
# should have `fence_test` in the `DB` variable.
psql -U test postgres -c 'create database fence_test'
userdatamodel-init --db fence_test --username test --password test

Keypair Configuration

Fence uses RSA keypairs to sign and allow verification of JWTs that it issues. When the application is initialized, Fence loads in keypair files from the keys directory. To store keypair files, use the following procedure: - Create a subdirectory in the fence/keys directory, named with a unique identifier, preferably a timestamp in ISO 8601 format of when the keys are created. The name of the directory is used for the kid (key ID) for those keys; the default (assuming the directory is named with an ISO timestamp) looks like this:

       fence_key_2018-05-01T14:00:00Z

 - Generate a private and public keypair following the RSA 256 algorithm
   and store those in that directory. The key files must be named
   `jwt_public_key.pem` and `jwt_private_key.pem`.

To generate a keypair using openssl:

# Generate the private key.
openssl genpkey -algorithm RSA -out jwt_private_key.pem -pkeyopt rsa_keygen_bits:2048

# Generate the public key.
openssl rsa -pubout -in jwt_private_key.pem -out jwt_public_key.pem

# Depending on the `openssl` distribution, you may find these work instead:
#
#     openssl rsa -out private_key.pem 2048
#     openssl rsa -in private_key.pem -pubout -out public_key.pem

It's not a bad idea to confirm that the files actually say RSA PRIVATE KEY and PUBLIC KEY (and in fact Fence will require that the private key files it uses actually say "PRIVATE KEY" and that the public keys do not).

Files containing public/private keys should have this format (the format used by openssl for generating RSA keys):

-----BEGIN PUBLIC KEY-----
... [key is here] ...
-----END PUBLIC KEY-----

If a key is not in this format, then PyJWT will raise errors about not being able to read the key.

Fence will use the first keypair in the list to sign the tokens it issues through OAuth.

Create User Access File

You can setup user access via admin fence script providing a user yaml file Example user yaml:

cloud_providers: {}
groups: {}
users:
  [email protected]:
    projects:
    - auth_id: project_a
      privilege: [read, update, create, delete]
    - auth_id: project_b
      privilege: [read]
  [email protected]:
    projects:
    - auth_id: project_b
      privilege: [read]

Example sync command:

fence-create sync --yaml user.yaml

Register OAuth Client

When you want to build an application that uses Gen3 resources on behalf of a user, you should register an OAuth client for this app. Fence right now exposes client registration via admin CLI, because the Oauth2 client for a Gen3 commons needs approval from the sponsor of the commons. If you are an external developer, you should submit a support ticket.

As a Gen3 commons administrator, you can run following command for an approved client:

fence-create client-create --client CLIENT_NAME --urls OAUTH_REDIRECT_URL --username USERNAME

This command should output a tuple of (client_id, client_secret) which must be saved by the OAuth client to use with fence.

Token management

Fence utilizes OpenID Connect to generate tokens for clients. It can also provide tokens directly to a user.

Clients and users may then use those tokens with other Gen3 Data Commons services to access protected endpoints that require specific permissions.

We use JSON Web Tokens (JWTs) as the format for all tokens of the following types:

• OIDC ID token: this token is used by the OIDC client to get a user's identity from the token content
• OIDC access token: this token can be sent to Gen3 services via bearer header and get protected resources.
• OIDC refresh token: this token can be sent to fence to request a new access / id token.

JWT Information

Example ID Token

{
  "sub": "7",
  "azp": "test-client",
  "pur": "id",
  "aud": [
    "openid",
    "user",
    "test-client"
  ],
  "context": {
    "user": {
      "is_admin": false,
      "name": "test",
      "projects": {
        "phs000178": [
          "read",
          "update",
          "create",
          "delete",
          "read-storage"
        ]
      },
      "google": {
          "linked_google_account": "[email protected]"
      }
    }
  },
  "iss": "https://bionimbus-pdc.opensciencedatacloud.org",
  "jti": "3ae2910b-0294-43dc-af2a-03fd60082aef",
  "exp": 1516983302,
  "iat": 1516982102,
  "auth_time": 1516982102
}

Example Access Token

{
  "sub": "7",
  "azp": "test-client",
  "pur": "access",
  "aud": [
    "openid",
    "user",
    "test-client"
  ],
  "context": {
    "user": {
      "is_admin": false,
      "name": "test",
      "projects": {
        "phs000178": [
          "read",
          "update",
          "create",
          "delete",
          "read-storage"
        ]
      },
      "google": {
          "proxy_group": "abcdefgh123456",
          "linked_google_account": "[email protected]"
      }
    }
  },
  "iss": "https://bionimbus-pdc.opensciencedatacloud.org",
  "jti": "2e6ade06-5afb-4ce7-9ab5-e206225ce291",
  "exp": 1516983302,
  "iat": 1516982102
}

Example Refresh Token

{
  "sub": "7",
  "azp": "test-client",
  "pur": "refresh",
  "aud": [
    "openid",
    "user",
    "test-client"
  ],
  "iss": "https://bionimbus-pdc.opensciencedatacloud.org",
  "jti": "c72e5573-39fa-4391-a445-191e370b7cc5",
  "exp": 1517010902,
  "iat": 1516982102
}

fence-create: Automating common tasks with a command line interface

fence-create is a command line utility that is bundled with fence and allows you to automate some commons tasks within fence. For the latest and greatest run the command fence-create --help.

WARNING: fence-create directly modifies the database in some cases and may circumvent security checks (most of these utilities are used for testing). BE CAREFUL when you're running these commands and make sure you know what they're doing.

Register Internal Oauth Client

As a Gen3 commons administrator, if you want to create an oauth client that skips user consent step, use the following command:

fence-create client-create --client CLIENT_NAME --urls OAUTH_REDIRECT_URL --username USERNAME --auto-approve

Register an Implicit Oauth Client

As a Gen3 commons administrator, if you want to create an implicit oauth client for a webapp:

fence-create client-create --client fancywebappname --urls 'https://betawebapp.example/fence
https://webapp.example/fence' --public --username fancyapp --grant-types authorization_code refresh_token implicit

If there are more than one URL to add, use space to delimit them like this:

fence-create client-create --urls 'https://url1/' 'https://url2/' --client ...

To specify allowed scopes, use the allowed-scopes argument:

fence-create client-create ...  --allowed-scopes openid user data

Modify OAuth Client

fence-create client-modify --client CLIENT_NAME --urls http://localhost/api/v0/oauth2/authorize

That command should output any modifications to the client. Similarly, multiple URLs are allowed here too.

Delete OAuth Client

fence-create client-delete --client CLIENT_NAME

That command should output the result of the deletion attempt.

List OAuth Clients

fence-create client-list

That command should output the full records for any registered OAuth clients.

Set up for External Buckets on Google

fence-create link-external-bucket --bucket-name demo-bucket
fence-create link-bucket-to-project --bucket_id demo-bucket --bucket_provider google --project_auth_id test-project

The link-external-bucket returns an email for a Google group which needs to be added to access to the bucket demo-bucket.

Notify users who are blocking service account registration

fence-create notify-problem-users --emails [email protected] [email protected] --auth_ids test --google_project_id test-google

notify-problem-users emails users in the provided list (can be fence user email or linked google email) who do not have access to any of the auth_ids provided. Also accepts a check_linking flag to check that each user has linked their google account.

Default Expiration Times in Fence

Table contains various artifacts in fence that have temporary lifetimes and their default values.

NOTE: "SA" in the below table stands for Service Account

Name	Lifetime	Extendable?	Maximum Lifetime	Details
Access Token	20 minutes	TRUE	Life of Refresh Token
Refresh Token	30 days	FALSE	N/A
User's SA Account Access	7 days	TRUE	N/A	Access to data (e.g. length it stays in the proxy group). Can optionally provide an expiration less than 7 days
User's Google Account Access	1 day	TRUE	N/A	After AuthN, how long we associate a Google email with the given user. Can optionally provide an expiration less than 1 day
User's Google Account Linkage	Indefinite	N/A	N/A	Can optionally provide an expiration less than 1 hour
Google Signed URL	Up to 1 hour	FALSE	N/A	Can optionally provide an expiration less than 1 hour
AWS Signed URL	Up to 1 hour	FALSE	N/A	Obtained by an oauth client through /credentials/google
Client SA (for User) Key	10 days	FALSE	N/A	Obtained by the user themselves for temp access. Can optionally provide an expiration less than 10 days
User Primary SA Key	10 days	FALSE	N/A	Used for Google URL signing
User Primary SA Key for URL Signing	30 days	FALSE	N/A
Sliding Session Window	30 minutes	TRUE	8 hours	access_token cookies get generated automatically when expired if session is still active