(Objective-C) Office365 IMAP OAuth2 with Shared Mailbox

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Demonstrates how to authenticate using OAuth2 with shared mailboxes in outlook.office365.com. (SASL XOAUTH2 authentication for shared mailboxes in Office 365)

For more information, see https://docs.microsoft.com/en-us/exchange/client-developer/legacy-protocols/how-to-authenticate-an-imap-pop-smtp-application-by-using-oauth#sasl-xoauth2-authentication-for-shared-mailboxes-in-office-365

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#import <CkoJsonObject.h>
#import <CkoImap.h>

// An Office365 OAuth2 access token must first be obtained prior
// to running this code.

// Getting the OAuth2 access token for the 1st time requires the O365 account owner's 
// interactive authorizaition via a web browser.  Afterwards, the access token
// can be repeatedly refreshed automatically.

// See the following examples for getting and refreshing an OAuth2 access token

// Get Office365 SMTP/IMAP/POP3 OAuth2 Access Token
// Refresh Office365 SMTP/IMAP/POP3 OAuth2 Access Token

// First get our previously obtained OAuth2 access token.
CkoJsonObject *jsonToken = [[CkoJsonObject alloc] init];
BOOL success = [jsonToken LoadFile: @"qa_data/tokens/office365.json"];
if (success == NO) {
    NSLog(@"%@",@"Failed to open the office365 OAuth JSON file.");
    return;
}

CkoImap *imap = [[CkoImap alloc] init];

imap.Ssl = YES;
imap.Port = [NSNumber numberWithInt:993];

// Connect to the Office365 IMAP server.
success = [imap Connect: @"outlook.office365.com"];
if (success != YES) {
    NSLog(@"%@",imap.LastErrorText);
    return;
}

// Use OAuth2 authentication.
imap.AuthMethod = @"XOAUTH2";

// In case of shared mailbox access using OAuth, application needs to obtain the access token on behalf of a user
// but replace the userName field in the SASL XOAUTH2 encoded string with the email address of the shared mailbox.

// Login using the shared mailbox email address for the username, and the access token for the password.
// This will cause the SASL XOAUTH2 format to be used, as described at Office 365 SASL XOAUTH2 format 

success = [imap Login: @"SHARED_MAILBOX_EMAIL_ADDRESS" password: [jsonToken StringOf: @"access_token"]];
if (success != YES) {
    NSLog(@"%@",imap.LastErrorText);
    return;
}

NSLog(@"%@",@"O365 OAuth2 shared mailbox authentication is successful.");

// Do something...
success = [imap SelectMailbox: @"Inbox"];
if (success != YES) {
    NSLog(@"%@",imap.LastErrorText);
    return;
}

// Your application can continue to do other things in the IMAP session....

// When finished, logout and close the connection.
success = [imap Logout];
success = [imap Disconnect];

NSLog(@"%@",@"Finished.");