Get a msgraph access token using another access token

0
votes

I created an Azure app for which I created custom scopes through the "Expose API" screen. I have a single page application that uses the code flow to login into the application requesting these custom scopes. On my ASP.NET Core web application, I added the authentication layer to use JWT as bearer. Works pretty well and I can secure my web APIs as expected.

Now, I also added API permissions for msgraph because I want to be able to create online meetings with it. The flow would be:

  • The user logs in using my custom scope audience
  • He sends a call to a secure web api to create something
  • Something is added to the database
  • An online meeting is created on behalf of the user

The "issue" is that the access token received by my web API is not valid for msgraph, I need to get one, on behalf of the user related to the access_token. However, I have no idea how to get a msgraph token using another access_token. I don't even know if that's possible.

However, if it's not possible, how am I supposed to create the online meeting from the .NET Core part of my application ?

1
azureazure-active-directoryazure-ad-graph-api

1 Answers

1
votes

Take a look at the On Behalf Flow, specifically the example "First case: Access token request with a shared secret". You can use your existing access token as the assertion parameter.

The following HTTP POST requests an access token and refresh token with user.read scope for the https://graph.microsoft.com web API.

//line breaks for legibility only

POST /oauth2/v2.0/token HTTP/1.1
Host: login.microsoftonline.com
Content-Type: application/x-www-form-urlencoded

grant_type=urn:ietf:params:oauth:grant-type:jwt-bearer
&client_id=2846f71b-a7a4-4987-bab3-760035b2f389
&client_secret=BYyVnAt56JpLwUcyo47XODd
&assertion=eyJ0eXAiOiJKV1QiLCJhbGciOiJSUzI1NiIsImtpZCI6InowMzl6ZHNGdWl6cEJmQlZLMVRuMjVRSFlPMCJ9.eyJhdWQiOiIyODQ2ZjcxYi1hN2E0LTQ5ODctYmFiMy03NjAwMzViMmYzODkiLCJpc3MiOiJodHRwczovL2xvZ2luLm1pY3Jvc29mdG9ubGluZS5jb20vNzJmOTg4YmYtODZmMS00MWFmLTkxYWItMmQ3Y2QwMTFkYjQ3L3YyLjAiLCJpYXQiOjE0OTM5MjA5MTYsIm5iZiI6MTQ5MzkyMDkxNiwiZXhwIjoxNDkzOTI0ODE2LCJhaW8iOiJBU1FBMi84REFBQUFnZm8vNk9CR0NaaFV2NjJ6MFFYSEZKR0VVYUIwRUlIV3NhcGducndMMnVrPSIsIm5hbWUiOiJOYXZ5YSBDYW51bWFsbGEiLCJvaWQiOiJkNWU5NzljNy0zZDJkLTQyYWYtOGYzMC03MjdkZDRjMmQzODMiLCJwcmVmZXJyZWRfdXNlcm5hbWUiOiJuYWNhbnVtYUBtaWNyb3NvZnQuY29tIiwic3ViIjoiZ1Q5a1FMN2hXRUpUUGg1OWJlX1l5dVZNRDFOTEdiREJFWFRhbEQzU3FZYyIsInRpZCI6IjcyZjk4OGJmLTg2ZjEtNDFhZi05MWFiLTJkN2NkMDExZGI0NyIsInV0aSI6IjN5U3F4UHJweUVPd0ZsTWFFMU1PQUEiLCJ2ZXIiOiIyLjAifQ.TPPJSvpNCSCyUeIiKQoLMixN1-M-Y5U0QxtxVkpepjyoWNG0i49YFAJC6ADdCs5nJXr6f-ozIRuaiPzy29yRUOdSz_8KqG42luCyC1c951HyeDgqUJSz91Ku150D9kP5B9-2R-jgCerD_VVuxXUdkuPFEl3VEADC_1qkGBiIg0AyLLbz7DTMp5DvmbC09DhrQQiouHQGFSk2TPmksqHm3-b3RgeNM1rJmpLThis2ZWBEIPx662pjxL6NJDmV08cPVIcGX4KkFo54Z3rfwiYg4YssiUc4w-w3NJUBQhnzfTl4_Mtq2d7cVlul9uDzras091vFy32tWkrpa970UvdVfQ
&scope=https://graph.microsoft.com/user.read+offline_access
&requested_token_use=on_behalf_of