Is it possible to request a token on behalf of a user from Web API in Node.js using adal-node?

In a C# API it is possible to request a token on behalf of another client by providing a 'UserAssertion' token provider. How can this be achieved in a Nodejs application using adal-node?

Solution

ADAL Node does not support the on-behalf-of flow. There's an active request to support this in ADAL Node, I'd recommend adding more information about the scenario you're trying to implement to that request.

There's nothing preventing it from being technically possible, and the token service endpoints are well-documented. You'll need to take the incoming access token, and post it to the service, here's an example.

>  POST /oauth2/token HTTP/1.1 Host: login.microsoftonline.com
> Content-Type: application/x-www-form-urlencoded
> 
> grant_type=urn%3Aietf%3Aparams%3Aoauth%3Agrant-type%3Ajwt-bearer
> &client_id=625391af-c675-43e5-8e44-edd3e30ceb15
> &client_secret=0Y1W%2BY3yYb3d9N8vSjvm8WrGzVZaAaHbHHcGbcgG%2BoI%3D
> &resource=https%3A%2F%2Fgraph.windows.net
> &assertion=eyJ0eXAiOiJKV1QiLCJhbGciOiJSUzI1NiIsIng1dCI6InowMzl6ZHNGdWl6cEJmQlZLMVRuMjVRSFlPMCIsImtpZCI6InowMzl6ZHNGdWl6cEJmQlZLMVRuMjVRSFlPMCJ9.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.R-Ke-XO7lK0r5uLwxB8g5CrcPAwRln5SccJCfEjU6IUqpqcjWcDzeDdNOySiVPDU_ZU5knJmzRCF8fcjFtPsaA4R7vdIEbDuOur15FXSvE8FvVSjP_49OH6hBYqoSUAslN3FMfbO6Z8YfCIY4tSOB2I6ahQ_x4ZWFWglC3w5mK-_4iX81bqi95eV4RUKefUuHhQDXtWhrSgIEC0YiluMvA4TnaJdLq_tWXIc4_Tq_KfpkvI004ONKgU7EAMEr1wZ4aDcJV2yf22gQ1sCSig6EGSTmmzDuEPsYiyd4NhidRZJP4HiiQh-hePBQsgcSgYGvz9wC6n57ufYKh2wm_Ti3Q
> &requested_token_use=on_behalf_of &scope=openid

The app will then (on success) receive the following info back.

{
    "token_type":"Bearer",
    "scope":"User.Read",
    "expires_in":"43482",
    "ext_expires_in":"302683",
    "expires_on":"1493466951",
    "not_before":"1493423168",
    "resource":"https://graph.windows.net",
    "access_token":"eyJ0eXAiOiJKV1QiLCJhbGciOiJSUzI1NiIsIng1dCI6InowMzl6ZHNGdWl6cEJmQlZLMVRuMjVRSFlPMCIsImtpZCI6InowMzl6ZHNGdWl6cEJmQlZLMVRuMjVRSFlPMCJ9.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.cqmUVjfVbqWsxJLUI1Z4FRx1mNQAHP-L0F4EMN09r8FY9bIKeO-0q1eTdP11Nkj_k4BmtaZsTcK_mUygdMqEp9AfyVyA1HYvokcgGCW_Z6DMlVGqlIU4ssEkL9abgl1REHElPhpwBFFBBenOk9iHddD1GddTn6vJbKC3qAaNM5VarjSPu50bVvCrqKNvFixTb5bbdnSz-Qr6n6ACiEimiI1aNOPR2DeKUyWBPaQcU5EAK0ef5IsVJC1yaYDlAcUYIILMDLCD9ebjsy0t9pj_7lvjzUSrbMdSCCdzCqez_MSNxrk1Nu9AecugkBYp3UVUZOIyythVrj6-sVvLZKUutQ",
    "refresh_token":"AQABAAAAAABnfiG-mA6NTae7CdWW7QfdjKGu9-t1scy_TDEmLi4eLQMjJGt_nAoVu6A4oSu1KsRiz8XyQIPKQxSGfbf2FoSK-hm2K8TYzbJuswYusQpJaHUQnSqEvdaCeFuqXHBv84wjFhuanzF9dQZB_Ng5za9xKlUENrNtlq9XuLNVKzxEyeUM7JyxzdY7JiEphWImwgOYf6II316d0Z6-H3oYsFezf4Xsjz-MOBYEov0P64UaB5nJMvDyApV-NWpgklLASfNoSPGb67Bc02aFRZrm4kLk-xTl6eKE6hSo0XU2z2t70stFJDxvNQobnvNHrAmBaHWPAcC3FGwFnBOojpZB2tzG1gLEbmdROVDp8kHEYAwnRK947Py12fJNKExUdN0njmXrKxNZ_fEM33LHW1Tf4kMX_GvNmbWHtBnIyG0w5emb-b54ef5AwV5_tGUeivTCCysgucEc-S7G8Cz0xNJ_BOiM_4bAv9iFmrm9STkltpz0-Tftg8WKmaJiC0xXj6uTf4ZkX79mJJIuuM7XP4ARIcLpkktyg2Iym9jcZqymRkGH2Rm9sxBwC4eeZXM7M5a7TJ-5CqOdfuE3sBPq40RdEWMFLcrAzFvP0VDR8NKHIrPR1AcUruat9DETmTNJukdlJN3O41nWdZOVoJM-uKN3uz2wQ2Ld1z0Mb9_6YfMox9KTJNzRzcL52r4V_y3kB6ekaOZ9wQ3HxGBQ4zFt-2U0mSszIAA",
    "id_token":"eyJ0eXAiOiJKV1QiLCJhbGciOiJub25lIn0.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."
}

You can then extract the access_token and use it against resource in a bearer request. You'll also want to track the access_token expiration so you can use the refresh_token for renewal.

If you do want to implement in manually, here's the on-behalf-of reference documentation. I recommend checking out the possible errors as well so the app can handle multi-factor auth and conditional access challenges.