Office 365 Authentication for site collection only - ios

Question

I want to login Sharepoint Online with Claim Based Authentication(Office 365 Authentication) from ios application.
I used the SOAP Method as the following.
<s:Envelope xmlns:s="http://www.w3.org/2003/05/soap-envelope"
xmlns:a="http://www.w3.org/2005/08/addressing"
xmlns:u="http://docs.oasis-open.org/wss/2004/01/oasis-200401-wss-wssecurity-utility-1.0.xsd">
<s:Header>
<a:Action s:mustUnderstand="1">http://schemas.xmlsoap.org/ws/2005/02/trust/RST/Issue</a:Action>
<a:ReplyTo>
<a:Address>http://www.w3.org/2005/08/addressing/anonymous</a:Address>
</a:ReplyTo>
<a:To s:mustUnderstand="1">https://login.microsoftonline.com/extSTS.srf</a:To>
<o:Security s:mustUnderstand="1"
xmlns:o="http://docs.oasis-open.org/wss/2004/01/oasis-200401-wss-wssecurity-secext-1.0.xsd">
<o:UsernameToken>
<o:Username>$username</o:Username>
<o:Password>$password</o:Password>
</o:UsernameToken>
</o:Security>
</s:Header>
<s:Body>
<t:RequestSecurityToken xmlns:t="http://schemas.xmlsoap.org/ws/2005/02/trust">
<wsp:AppliesTo xmlns:wsp="http://schemas.xmlsoap.org/ws/2004/09/policy">
<a:EndpointReference>
<a:Address>$endpoint</a:Address>
</a:EndpointReference>
</wsp:AppliesTo>
<t:KeyType>http://schemas.xmlsoap.org/ws/2005/05/identity/NoProofKey</t:KeyType>
<t:RequestType>http://schemas.xmlsoap.org/ws/2005/02/trust/Issue</t:RequestType>
<t:TokenType>urn:oasis:names:tc:SAML:1.0:assertion</t:TokenType>
</t:RequestSecurityToken>
</s:Body>
</s:Envelope>
At Endpoint Address,will need to set sharepoint root site URL.
The problem is that when the login user cannot authenticate to root site
but can authenticate to site collection only, this user cannot login to
office 365.
How can I work around for this?
If the other way to login method with Office 365 authentication(claim based authentication),
please advice me.

Answer 1

You may want to checkout the iOS SDK for the Office 365 APIs. Here is a link to a sample application on GitHub that shows how to authenticate to Office 365 and get the access token. Once you have a valid token, you can make a REST call to SharePoint Online passing the token in Authorization Bearer header.
https://github.com/OfficeDev/Office-365-SDK-for-iOS