Building a multi-tenant app for SharePoint Online O365

Question

I am attempting to build a multi-tenant application for Office 365 which focuses on SharePoint Online and authenticates through Azure using OAuth2. The problem is specific to Sh

Answer 1

I want to add detail to the solution mentioned briefly in my comment above - This will be important to anyone developing multi-tenant applications in Office 365, especially if the application will ever access SharePoint sites including OneDrive.

The procedure here is a little non-standard from the OAuth 2.0 perspective, but makes some sense in the multi-tenant world. The key is re-using the first CODE returned from Azure. Follow me here:

First we follow the standard OAuth authentication steps:

GET /common/oauth2/authorize?client_id=5cb5e93b-57f5-4e09-97c5-e0d20661c59a
&redirect_uri=https://myappdomain.com/v1/oauth2_redirect/
&response_type=code&prompt=login&state=D79E5777 HTTP/1.1
Host: login.windows.net
Cache-Control: no-cache

This redirects to the Azure login page where the user logs in. If successful, Azure then calls back to your endpoint with a code:

https://myappdomain.com/v1/oauth2_redirect/?code=AAABAAAA...{ONE-CODE-To-RULE-THEM-ALL}xyz

Now we POST back to the /token endpoint to acquire the actual Bearer token to be used in subsequent REST calls. Again, this is just classic OAuth2... but watch how we use the /Discovery endpoint as the resource - instead of any of the endpoints we will actually be using to gather data. Also, we ask for UserProfile.Read scope.

POST /common/oauth2/token HTTP/1.1
Host: login.windows.net
Accept: text/json
Cache-Control: no-cache

----WebKitFormBoundaryE19zNvXGzXaLvS5C
Content-Disposition: form-data; name="grant_type"

authorization_code
----WebKitFormBoundaryE19zNvXGzXaLvS5C
Content-Disposition: form-data; name="code"

AAABAAAA...{ONE-CODE-To-RULE-THEM-ALL}xyz
----WebKitFormBoundaryE19zNvXGzXaLvS5C
Content-Disposition: form-data; name="client_id"

5cb5e93b-57f5-4e09-97c5-e0d20661c59a
----WebKitFormBoundaryE19zNvXGzXaLvS5C
Content-Disposition: form-data; name="client_secret"

02{my little secret}I=
----WebKitFormBoundaryE19zNvXGzXaLvS5C
Content-Disposition: form-data; name="redirect_uri"

https://myappdomain.com/v1/oauth2_redirect/
----WebKitFormBoundaryE19zNvXGzXaLvS5C
Content-Disposition: form-data; name="scope"

UserProfile.Read
----WebKitFormBoundaryE19zNvXGzXaLvS5C
Content-Disposition: form-data; name="resource"

https://api.office.com/discovery/
----WebKitFormBoundaryE19zNvXGzXaLvS5C

The response to this POST will contain an access-token that can be used to make REST calls to the /discovery endpoint.

{
    "refresh-token":  "AAABsvRw-mAAWHr8XOY2lVOKZNLJ{BAR}xkSAA", 
    "resource": "https://api.office.com/discovery/", 
    "pwd_exp": "3062796", 
    "pwd_url": "https://portal.microsoftonline.com/ChangePassword.aspx", 
    "expires_in": "3599", 
    "access-token": "ey_0_J0eXAiOiJjsp6PpUhSjpXlm0{F00}-j0aLiFg", 
    "scope": "Contacts.Read", 
    "token-type": "Bearer", 
    "not_before": "1422385173", 
    "expires_on": "1422389073"
}

Now, using this access-token, query the /Services endpoint to find out what else is available in Office 365 for this user.

GET /discovery/v1.0/me/services HTTP/1.1
Host: api.office.com
Cache-Control: no-cache

----WebKitFormBoundaryE19zNvXGzXaLvS5D
Content-Disposition: form-data; name="Authorization"

Bearer ey_0_J0eXAiOiJjsp6PpUhSjpXlm0{F00}-j0aLiFg
----WebKitFormBoundaryE19zNvXGzXaLvS5D

The result will include an array of Service structures, describing the various endpoints and capabilities of each endpoint.

{
    "@odata.context": "https://api.office.com/discovery/v1.0/me/$metadata#allServices",
    "value": [
        {
            "capability": "MyFiles",
            "entityKey": "MyFiles@O365_SHAREPOINT",
            "providerId": "72f988bf-86f1-41af-91ab-2d7cd011db47",
            "serviceEndpointUri": "https://contoso-my.sharepoint.com/_api/v1.0/me",
            "serviceId": "O365_SHAREPOINT",
            "serviceName": "Office 365 SharePoint",
            "serviceResourceId": "https://contoso-my.sharepoint.com/"
        },
        {
            "capability": "RootSite",
            "entityKey": "RootSite@O365_SHAREPOINT",
            "providerId": "72f988bf-86f1-41af-91ab-2d7cd011db47",
            "serviceEndpointUri": "https://contoso.sharepoint.com/_api",
            "serviceId": "O365_SHAREPOINT",
            "serviceName": "Office 365 SharePoint",
            "serviceResourceId": "https://contoso.sharepoint.com/"
        },
        {
            "capability": "Contacts",
            "entityKey": "Contacts@O365_EXCHANGE",
            "providerId": "72f988bf-86f1-41af-91ab-2d7cd011db47",
            "serviceEndpointUri": "https://outlook.office365.com/api/v1.0",
            "serviceId": "O365_EXCHANGE",
            "serviceName": "Office 365 Exchange",
            "serviceResourceId": "https://outlook.office365.com/"
        }
    ]
}

Now comes the tricky part... At this point, we know the endpoints that we really want to authenticate to - some of which are tenant-specific. Normally you'd think we need to play the OAuth2 dance all over again with each of these endpoints. But in this case, we can cheat a little - and simply POST the same CODE that we originally received from Azure - using the same HTTP request above, only altering the resource and the scope fields using the serviceResourceId and capability from the Service structure above. Like this:

POST /common/oauth2/token HTTP/1.1
Host: login.windows.net
Accept: text/json
Cache-Control: no-cache

----WebKitFormBoundaryE19zNvXGzXaLvS5C
Content-Disposition: form-data; name="grant_type"

authorization_code
----WebKitFormBoundaryE19zNvXGzXaLvS5C
Content-Disposition: form-data; name="code"

AAABAAAA...{ONE-CODE-To-RULE-THEM-ALL}xyz
----WebKitFormBoundaryE19zNvXGzXaLvS5C
Content-Disposition: form-data; name="client_id"

5cb5e93b-57f5-4e09-97c5-e0d20661c59a
----WebKitFormBoundaryE19zNvXGzXaLvS5C
Content-Disposition: form-data; name="client_secret"

02{my little secret}I=
----WebKitFormBoundaryE19zNvXGzXaLvS5C
Content-Disposition: form-data; name="redirect_uri"

https://myappdomain.com/v1/oauth2_redirect/
----WebKitFormBoundaryE19zNvXGzXaLvS5C
Content-Disposition: form-data; name="scope"

MyFiles.Read
----WebKitFormBoundaryE19zNvXGzXaLvS5C
Content-Disposition: form-data; name="resource"

https://contoso-my.sharepoint.com/
----WebKitFormBoundaryE19zNvXGzXaLvS5C

then do the same for the other two:

...
----WebKitFormBoundaryE19zNvXGzXaLvS5C
Content-Disposition: form-data; name="scope"

RootSite.Read
----WebKitFormBoundaryE19zNvXGzXaLvS5C
Content-Disposition: form-data; name="resource"

https://contoso.sharepoint.com/
----WebKitFormBoundaryE19zNvXGzXaLvS5C

and

...
----WebKitFormBoundaryE19zNvXGzXaLvS5C
Content-Disposition: form-data; name="scope"

Contacts.Read
----WebKitFormBoundaryE19zNvXGzXaLvS5C
Content-Disposition: form-data; name="resource"

https://outlook.office365.com/
----WebKitFormBoundaryE19zNvXGzXaLvS5C

All three of these calls will result in a response like the first POST above, providing you with a refresh-token and an access-token for each of the respective endpoints. All of this for the price of only a single user authentication. :)

Viola! Mystery solved - you CAN write multi-tenant applications for O365. :)