We have built a desktop app that import/exports SharePoint lists into/from Office 365 sites. The app works perfectly, and we were able to do the import/export of Office 365 site pages for many clients so far.

but on a particular site, when I try to import some pages, I get the following error:

System.Net.WebException: The remote server returned an error: (403) Forbidden.
   at System.Net.HttpWebRequest.GetResponse()
   at Microsoft.SharePoint.Client.Idcrl.SharePointOnlineAuthenticationProvider.GetCookie(Uri url, String endpoint, String ticket)
   at Microsoft.SharePoint.Client.Idcrl.SharePointOnlineAuthenticationProvider.GetAuthenticationCookie(Uri url, String username, SecureString password)
   at Microsoft.SharePoint.Client.SharePointOnlineCredentials.GetAuthenticationCookie(Uri url, Boolean refresh)
   at Microsoft.SharePoint.Client.ClientRuntimeContext.SetupRequestCredential(ClientRuntimeContext context, HttpWebRequest request)
   at Microsoft.SharePoint.Client.SPWebRequestExecutor.GetRequestStream()
   at Microsoft.SharePoint.Client.ClientContext.GetFormDigestInfoPrivate()
   at Microsoft.SharePoint.Client.ClientContext.EnsureFormDigest()
   at Microsoft.SharePoint.Client.ClientContext.ExecuteQuery()

Note that the account used for the authentication, has a Full Control permission on the site ( I can create sub-sites, lists, ...etc if logged in through a web browser )

I have also checked this answer, and we're already using SharePointOnlineCredentials for authentication ( you can see that from the stack trace above )

So what is preventing me from doing the import through our desktop App ?

Note: I did not paste any code since the app is already battle tested and worked so many times before, and I do believe that the case here is some kind of settings on the client's site.


After some investigation, and thanks to @Evariste, It seems that authentication is failing this time because the site is not using the classic Office 365 authentication model, and instead they're using the MAPI protocol.

  • 2
    Do they use the same authentification mechasnim? Maybe they're going with ADFS identities... – Evariste Dec 22 '15 at 13:58
  • @Evariste yes same authentication, what do you mean by "they're going with ADFS identities", can you explain more ? what are they doing exactly, and how using ADFS will block external API calls access ? – Anas Nakawa Dec 22 '15 at 14:27
  • 2
    I see your error raises while trying to authenticate your API calls. In Office 365, you may have 2 different authentication modes: the "classic" one with an Office 365 user address/password, and the federated. mixed mode one when Customer sync AD accounts with the accounts stored in Office 365. He uses ADFS for this. Authentication mechanism is then a little bit different I think. – Evariste Dec 22 '15 at 14:31
  • @Evariste you're right, they're not using the classic authentication model, they are using MAPI protocol, how that would affect our situation here, thanks ? – Anas Nakawa Dec 23 '15 at 8:35
  • 2
    Never heard about a "MAPI protocol" to authenticate against SP. :( MAPI is a messaging protocol used by Outlook and Exchange to access email stores and communicate. – Evariste Dec 23 '15 at 9:01

This happened to me one fine day where a program that used to collect metrics from SP Online site suddenly stopped working (it has worked for 1 month till them). No passwords were changed and the user was still active.

Finally found the issue. Classic MS System Restart fixed everything.

In my system I access a lot of tenants and MS websites which at some point messed up my cookies and cache I believe.

After restart, the program started working fine without any changes.

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