Office365 authentication without login redirection - authentication

Question

I'm trying to load data from Office365 email without need for user interaction. I've created Azure App and I have Client ID and Client secret.
I also have user information (email + password).
I need to call Office365 API to download emails from mailbox. But I need application to download them in background without user interaction (redirecting to MS/Office365 login page) to get authenticated/logged into mailbox.
Is there any way how to do this only through Office API, without need of redirection?
Thanks for any info.

Answer 1

Yes, you are able to create a daemon service app using the Client Credential flow to authenticate the app.
Here is a code sample to retrieve the mails using Microsoft Graph SDK with this flow:
string clientId = "";
string clientsecret = "";
string tenant = "";
string resourceURL = "https://graph.microsoft.com";
string authority = "https://login.microsoftonline.com/" + tenant + "/oauth2/token";
string userMail = "user1#yourdomain.onmicrosoft.com";
var credential = new ClientCredential(clientId, clientsecret);
AuthenticationContext authContext =new AuthenticationContext(authority);
var authResult = await authContext.AcquireTokenAsync(resourceURL, credential);
var graphserviceClient = new GraphServiceClient(
new DelegateAuthenticationProvider(
(requestMessage) =>
{
requestMessage.Headers.Authorization = new AuthenticationHeaderValue("bearer", authResult.AccessToken);
return Task.FromResult(0);
}));
var items = await graphserviceClient.Users[userMail].Messages.Request().OrderBy("receivedDateTime desc").GetAsync();
foreach (var item in items)
{
Console.WriteLine(item.Subject);
}
And we need to register the app on the Azure AD portal and grant the app Mail.Read scope like figure below:
Refer to here for more detail about calling Microsoft Graph in a service or daemon app