X-RequestDigest in Modal Dialog (without masterpage)

Question

I'm trying to post a REST query to SP.Utilities.Utility.Sendmail so I can send a mail from my sharepoint hosted app. For this I have the following function:

function sendEmail(from, to, body, subject, success, fail) {

appweburl = decodeURIComponent(getQueryStringParameter('SPAppWebUrl'));
hostweburl = decodeURIComponent(getQueryStringParameter('SPHostUrl'));
var urlTemplate = appweburl + "/_api/SP.Utilities.Utility.SendEmail";
$.ajax({
    contentType: 'application/json',
    url: urlTemplate,
    type: "POST",
    data: JSON.stringify({
        'properties': {
            '__metadata': { 'type': 'SP.Utilities.EmailProperties' },
            'From': from,
            'To': { 'results': [to] },
            'Body': body,
            'Subject': subject
        }
    }
  ),
    headers: {
        "Accept": "application/json;odata=verbose",
        "content-type": "application/json;odata=verbose",
        "X-RequestDigest": $("#__REQUESTDIGEST").val()
    },
    success: function (data) {
        success();
    },
    error: function (err) {
        fail(err);
    }
});

This code has worked for me in the past, so I know it's correct. For this project however, I'm trying to send a mail from a modal dialog inside my appweb. This modal dialog page has no masterpage.

Because this page has no masterpage, it's missing the $("#__REQUESTDIGEST").val() and I get a 403 forbidden error. I tried to fix this by passing the REQUESTDIGEST of my parent page, and use this one, however, this gives me a 400 bad request error.

Adding <SharePoint:FormDigest ID="FormDigest1" runat="server"></SharePoint:FormDigest> doesn't work either since IIS doesn't process it obviously.

Does anybody have any idea what the correct approach is to getting a REQUESTDIGEST in a page without a masterpage?

Answer 1

You have to make a POST to _api/contextinfo to get a form digest. Scot Hillier has a library to help.

http://www.shillier.com/archive/2013/09/08/managing-sharepoint-2013-app-context.aspx

Answer 2

When using the JavaScript cross-domain library, SP.RequestExecutor handles getting and sending the form digest value for you, so you don't need to use $("#__REQUESTDIGEST").val()

executor = new SP.RequestExecutor(oWeb) ;
executor.executeAsync({your POST object})

source: https://msdn.microsoft.com/en-us/library/office/jj164022.aspx#WritingData