Authentication

This guide is about authenticating users on incoming HTTP requests. This is done by authentication middlewares setting the req.user property which is then used in authorization enforcement decisions.

• cds. User
  • .is (<role>)
  • . id
  • . attr
  • . tokenInfo
• cds.User.Privileged
• cds.User.Anonymous
• cds.User.default
• Authorization Enforcement
• Authentication Strategies
  • Dummy Authentication
  • Mocked Authentication
  • Basic Authentication
  • JWT-based Authentication
  • XSUAA-based Authentication
  • IAS-based Authentication
  • Custom Authentication
• Authentication Enforced in Production
• XSUAA in Hybrid Setup
  • Prepare Local Environment
  • Configure the Application
  • Set Up the Roles for the Application
  • Running App Router

cds. User

Represents the currently logged-in user as filled into req.user by authentication middlewares. Simply create instances of cds.User or of subclasses thereof in custom middlewares. For example:

const cds = require('@sap/cds')
const DummyUser = new class extends cds.User { is:()=>true }
module.exports = (req,res,next) => {
  req.user = new DummyUser('dummy')
  next()
}

Or you can call the constructor of cds.User with specific arguments, to create a user instance. For example:

const cds = require('@sap/cds')
// with user ID as string
const user = new cds.User('userId')
// a user instance
const anotherUser = new cds.User(user)
// a user instance like object
const yetAnotherUser = new cds.User({id: user.id, roles: user.roles, attr: user.attr})

.is (<role>)

Checks if user has assigned the given role. Example usage:

if (req.user.is('admin')) ...

The role names correspond to the values of @requires and the @restrict.grants.to annotations in your CDS models.

. id

A user's unique ID. It corresponds to $user in @restrict annotations of your CDS models (Also in JavaScript, user can act as a shortcut for user.id in comparisons.)

. attr

User-related attributes, for example, from JWT tokens These correspond to $user.<x> in @restrict annotations of your CDS models

. tokenInfo

Parsed JWT token info provided by @sap/xssec.

Note: This API is only available for authentication kinds based on @sap/xssec.

cds.User.Privileged

In some cases, you might need to bypass authorization checks while consuming a local service. For this, you can create a transaction with a privileged user as follows:

this.before('*', function (req) {
  const user = new cds.User.Privileged
  return this.tx({ user }, tx => tx.run(
    INSERT.into('RequestLog').entries({
      url: req._.req.url,
      user: req.user.id
    })
  )
})

Alternatively, you can also use the ready-to-use instance cds.User.privileged directly, that is, const user = cds.User.privileged.

cds.User.Anonymous

Class cds.User.Anonymous allows you to instantiate an anonymous user (const user = new cds.User.Anonymous), for example in a custom authentication implementation.

Alternatively, you can also use the ready-to-use instance cds.User.anonymous directly, that is, const user = cds.User.anonymous.

cds.User.default

If a request couldn't be authenticated, for example due to a missing authorization header, the framework will use cds.User.default as fallback.

By default, cds.User.default points to cds.User.Anonymous. However, you can override this, for example to be cds.User.Privileged in tests, or to be any other class that returns an instance of cds.User.

Authorization Enforcement

Applications can use the req.user APIs to do programmatic enforcement. For example, the authorization of the following CDS service:

service CustomerService @(requires: 'authenticated-user'){
  entity Orders @(restrict: [
    { grant: ['READ','WRITE'], to: 'admin' },
  ]){/*...*/}
  entity Approval @(restrict: [
    { grant: 'WRITE', where: '$user.level > 2' }
  ]){/*...*/}
}

can be programmatically enforced by means of the API as follows:

const cds = require('@sap/cds')
cds.serve ('CustomerService') .with (function(){
  this.before ('*', req =>
   req.user.is('authenticated') || req.reject(403)
  )
  this.before (['READ', 'CREATE'], 'Orders', req =>
    req.user.is('admin') || req.reject(403)
  )
  this.before ('*', 'Approval', req =>
    req.user.attr.level > 2 || req.reject(403)
  )
})

Authentication Strategies

CAP ships with a few prebuilt authentication strategies, used by default: mocked during development and jwt in production. You can override these defaults and configure the authentication strategy to be used through the cds.requires.auth config option in cds.env, for example:

package.json

"cds": {
  "requires": {
    "auth": "jwt"
  }
}

Inspect effective configuration

Run cds env get requires.auth in your project root to find out the effective config for your current environment.

Dummy Authentication

This strategy creates a user that passes all authorization checks. It's meant for temporarily disabling the @requires and @restrict annotations at development time.

Configuration: Choose this strategy as follows:

package.json

"cds": {
  "requires": {
    "auth": "dummy"
  }
}

Mocked Authentication

This authentication strategy uses basic authentication with pre-defined mock users during development.

Note: When testing different users in the browser, it's best to use an incognito window, because logon information might otherwise be reused.

Configuration: Choose this strategy as follows:

package.json

"cds": {
  "requires": {
    "auth": "mocked"
  }
}

You can optionally configure users as follows:

package.json

"cds": {
  "requires": {
    "auth": {
      "kind": "mocked",
      "users": {
        "<user.id>": {
          "password": "<password>",
          "roles": [ "<role-name>", ... ],
          "attr": { ... }
        }
      }
    }
  }
}

Pre-defined Mock Users

The default configuration shipped with @sap/cds specifies these users:

  "users": {
    "alice": { "tenant": "t1", "roles": [ "admin" ] },
    "bob":   { "tenant": "t1", "roles": [ "cds.ExtensionDeveloper" ] },
    "carol": { "tenant": "t1", "roles": [ "admin", "cds.ExtensionDeveloper", "cds.UIFlexDeveloper" ] },
    "dave":  { "tenant": "t1", "roles": [ "admin" ], "features": [] },
    "erin":  { "tenant": "t2", "roles": [ "admin", "cds.ExtensionDeveloper", "cds.UIFlexDeveloper" ] },
    "fred":  { "tenant": "t2", "features": [ "isbn" ] },
    "me":    { "tenant": "t1", "features": [ "*" ] },
    "yves":  { "roles": [ "internal-user" ] }
    "*":     true //> all other logins are allowed as well
  }

This default configuration is merged with your custom configuration such that, by default, logins by alice, bob, ... and others (*) are allowed.

If you want to restrict these additional logins, you need to overwrite the defaults:

  "users": {
    "alice": { "roles": [] },
    "bob": { "roles": [] },
    "*": false //> do not allow other users than the ones specified
  }

Basic Authentication

This authentication strategy uses basic authentication to use mock users during development.

Note: When testing different users in the browser, it's best to use an incognito window, because logon information might otherwise be reused.

Configuration: Choose this strategy as follows:

package.json

"cds": {
  "requires": {
    "auth": "basic"
  }
}

You can optionally configure users as follows:

package.json

"cds": {
  "requires": {
    "auth": {
      "kind": "basic",
      "users": {
        "<user.id>": {
          "password": "<password>",
          "roles": [ "<role-name>", ... ],
          "attr": { ... }
        }
      }
    }
  }
}

In contrast to mocked authentication, no default users are automatically added to the configuration.

JWT-based Authentication

This is the default strategy used in production. User identity, as well as assigned roles and user attributes, are provided at runtime, by a bound instance of the 'User Account and Authentication' service (UAA). This is done in form of a JWT token in the Authorization header of incoming HTTP requests.

This authentication strategy also adds req.user.tokenInfo.

Prerequisites: You need to add @sap/xssec to your project:

npm add @sap/xssec

Configuration: Choose this strategy as follows:

package.json

"cds": {
  "requires": {
    "auth": "jwt"
  }
}

Learn more about testing JWT-based authentication in XSUAA in Hybrid Setup.

XSUAA-based Authentication

Authentication kind xsuaa is a logical extension of kind jwt that additionally offers access to SAML attributes through req.user.attr (for example, req.user.attr.familyName).

Prerequisites: You need to add @sap/xssec to your project:

npm add @sap/xssec

Configuration: Choose this strategy as follows:

package.json

"cds": {
  "requires": {
    "auth": "xsuaa"
  }
}

See XSUAA in Hybrid Setup below for additional information of how to test this

WARNING

It's recommended to only use this authentication kind if it's necessary for your use case, as it denotes a lock-in to SAP BTP.

IAS-based Authentication

This is an additional authentication strategy using the Identity Authentication Service (IAS) that can be used in production. User identity and user attributes are provided at runtime, by a bound instance of the IAS service. This is done in form of a JWT token in the Authorization header of incoming HTTP requests.

This authentication strategy also adds req.user.tokenInfo.

To allow forwarding to remote services, JWT tokens issued by IAS service don't contain authorization information. In particular, no scopes are included. Closing this gap is up to you as application developer.

Prerequisites: You need to add @sap/xssec to your project:

npm add @sap/xssec

Configuration: Choose this strategy as follows:

package.json

"cds": {
  "requires": {
    "auth": "ias"
  }
}

Custom Authentication

You can configure an own implementation by specifying an own impl as follows:

"requires": {
  "auth": {
    "impl": "srv/custom-auth.js" // > relative path from project root
  }
}

Essentially, custom authentication middlewares must do two things:

First, they must fulfill the req.user contract by assigning an instance of cds.User or a look-alike to the incoming request at req.user.

Second, if running in a multitenant environment, req.tenant must be set to a string identifying the tenant that is addressed by the incoming request.

module.exports = function custom_auth (req, res, next) {
  // do your custom authentication
  req.user = new cds.User({
    id: '<user-id>',
    roles: ['<role-a>', '<role-b>'],
    attr: {
      <user-attribute-a>: '<value>',
      <user-attribute-b>: '<value>'
    }
  })
  req.tenant = '<tenant>'
}

The TypeScript equivalent has to use the default export.

import cds from "@sap/cds";
import {Request, Response, NextFunction} from "express";
type Req = Request & { user: cds.User, tenant: string };

export default function custom_auth(req: Req, res: Response, next: NextFunction) {
  // do your custom authentication ...
}

If you want to customize the user ID, please also have a look at this example.

Authentication Enforced in Production

In a productive scenario with an authentication strategy configured, for example the default jwt, all CAP service endpoints are authenticated by default, regardless of the authorization model. That is, all services without @restrict or @requires implicitely get @requires: 'authenticated-user'.

This can be disabled via feature flag cds.requires.auth.restrict_all_services: false, or by using mocked authentication explicitly in production.

XSUAA in Hybrid Setup

Prepare Local Environment

The following steps assume you've set up the Cloud Foundry Command Line Interface.

1. Log in to Cloud Foundry:

cf l -a <api-endpoint>

If you don't know the API endpoint, have a look at section Regions and API Endpoints Available for the Cloud Foundry Environment.

2. Go to the project you have created in Getting started in a Nutshell.

3. Configure your app for XSUAA-based authentication if not done yet:

   cds add xsuaa --for hybrid

This command creates the XSUAA configuration file xs-security.json and adds the service and required dependencies to your package.json file.

4. Make sure xsappname is configured and tenant-mode is set to dedicated in xs-security.json file:

{
  "xsappname": "bookshop-hybrid",
  "tenant-mode": "dedicated",
  ...
  }

5. Configure the redirect URI:

   Add the following OAuth configuration to the xs-security.json file:

   "oauth2-configuration": {
     "redirect-uris": [
       "http://localhost:5000/"
     ]
   }

6. Create an XSUAA service instance with this configuration:

   cf create-service xsuaa application bookshop-uaa -c xs-security.json

   Later on, if you've changed the scopes, you can use cf update-service bookshop-uaa -c xs-security.json to update the configuration.

   TIP

   This step is necessary for locally running apps and for apps deployed on Cloud Foundry.

Configure the Application

1. Create a service key:

   cf create-service-key bookshop-uaa bookshop-uaa-key

   This lets you gain access to the XSUAA credentials from your local application.

2. Bind to the new service key:

   cds bind -2 bookshop-uaa

   This adds an auth section containing the binding and the kind xsuaa to the .cdsrc-private.json file. This file is created if it doesn't exist and keeps the local and private settings of your app:

   {
     "requires": {
       "[hybrid]": {
         "auth": {
           "kind": "xsuaa",
           "binding": { ... }
         }
       }
     }
   }

   If your running in BAS, you can alternatively create a new run configuration, connecting the auth to your XSUAA service instance.

   In that case you need to add the environment variable cds_requires_auth_kind=xsuaa to the run configuration.

3. Check authentication configuration:

cds env list requires.auth --resolve-bindings --profile hybrid

This prints the full auth configuration including the credentials.

Set Up the Roles for the Application

By creating a service instance of the xsuaa service, all the roles from the xs-security.json file are added to your subaccount. Next, you create a role collection that assigns these roles to your users.

1. Open the SAP BTP Cockpit.

   For your trial account, this is: https://cockpit.hanatrial.ondemand.com

2. Navigate to your subaccount and then choose Security > Role Collections.

3. Choose Create New Role Collection:

   

4. Enter a Name for the role collection, for example BookshopAdmin, and choose Create.

5. Choose your new role collection to open it and switch to Edit mode.

6. Add the admin role for your bookshop application (application id bookshop!a<XXXX>) to the Roles list.

7. Add the email addresses for your users to the Users list.

8. Choose Save

Running App Router

The App Router component implements the necessary authentication flow with XSUAA to let the user log in interactively. The resulting JWT token is sent to the application where it's used to enforce authorization and check the user's roles.

1. Add App Router to the app folder of your project:

   cds add approuter

2. Install npm packages for App Router:

   npm install --prefix app/router

3. In your project folder run:

   Mac/Linux

   cds bind --exec -- npm start --prefix app/router

   Windows

   cds bind --exec -- npm start --prefix app/router

   Powershell

   cds bind --exec '--' npm start --prefix app/router

   Learn more about cds bind --exec.

   This starts an App Router instance on http://localhost:5000 with the credentials for the XSUAA service that you have bound using cds bind.

   Usually the App Router is started using npm start in the app folder. But you need to provide the VCAP_SERVICES variable with the XSUAA credentials. With the cds bind --exec command you can launch an arbitrary command with the VCAP_SERVICES variable filled with your cds bind service bindings.

   Since it only serves static files or delegates to the backend service, you can keep the server running. It doesn't need to be restarted after you have changed files.

4. Make sure that your CAP application is running as well with the hybrid profile:

   cds watch --profile hybrid

   If you are using BAS Run Configurations, you need to configure cds watch with profile hybrid:

   1. Right click on your run configuration
   2. Choose Show in File
   3. Change the command args:

   "args": [
      "cds",
      "watch",
      "--profile",
      "hybrid"
   ],

5. After the App Router and CAP application are started, log in at http://localhost:5000 and verify that the routes are protected as expected.

   In our example, if you assigned the admin scope to your user in SAP BTP cockpit, you can now access the admin service at http://localhost:5000/admin.

   
   

   To test UIs w/o a running UAA service, just add this to app/router/xs-app.json: "authenticationMethod": "none"

SAP Business Application Studio:

The login fails pointing to the correct OAuth configuration URL that is expected.

1. Replace the URL http://localhost:5000/ in your xs-security.json file with the full URL from the error message:

   "oauth2-configuration": {
       "redirect-uris": [
         "<url from error message>"
     ]
   }

   WARNING

   This is a specific configuration for your dev space and should not be submitted or shared.

2. Update the XSUAA service:

   cf update-service bookshop-uaa -c xs-security.json

3. Retry