I have the following scenario:
1.- A web api project in Azure, that I want to secure using Azure AD (I don't mind Token, cookie, whatever, as far as it meets the entire scenario)
2.- An Azure web site in asp.net MVC, also secured by Azure AD. This website has to call the web api controller with SSO (I'm using same Azure AD in the entire scenario)
3.- Some JavaScript code running in a page in SharePoint Online, also calling the web api controller in any secure way (The Office 365 tenant is also using same Azure AD). If you don't know about SharePoint, let's say I have an SPA project where I can only use Javascript and html (no server side code).
Following some of the MS Azure AD samples and some blogs from Vittorio Bertocci I'm able to get the points 1 and 2 working fine, using OWIN and Oppen ID connect. However, seems impossible to achieve point 3. As I'm inside a page in SharePoint Online, I can only use javascript, and not any server side code. I'd like to get a valid token for the current user, that is already logged in SP, and remember that SP uses same Azure AD that web api site. Can I call the Azure AD and get a valid token, just from client code?
I'm open to any possible solution. I can do whatever in the web api project. If you are thinking in a SharePoint app with an appPart, and the appPart calls the web api from server side code, I agree that will work, but it's an option that is not allowed at the moment :(
Many thanks.
UPDATE 2018: This is now supported by SharePoint Online and the SPFx development model, and officially documented, for instance here
Consume enterprise APIs secured with Azure AD in SharePoint Framework
Being said that the work done meanwhile by Vittorio, Kirk, and their teams, but extending that also to Andrew that has delivered great samples, is awesome; that doesn't really fully reply the original question because one of the requirements is to don't run the component as Add-in Part.
If you try to use ADAL JS (which starts its own OAuth flow) hosting that directly in a SP page, that's not going to work, or anyway you can expect a weird behavior for the user (cause of client redirects happening on the browser).
The solution proposed by Peter Karpinski is interesting, and will work matching the requirements in the original question, but requires quite some complexity and additional management/resources.
This recent article provides an alternative solution similar to Peter's one, but requiring less 'extras' and somewhat simpler, also reusing user's SP identity.
Consuming Azure Hosted Web API from SharePoint Online using JavaScript and Office 365 identities
and doesn't either require the use of ADAL on the client side and the implementation of custom security provider / token issuer on the server side.
The identity (cookie) will be passed via properly handling CORS (documentation) on both sides.
However, as you can read in my comments to that blog, this won't work normally with IE due to its security zone implementation. You'll have to be sure you have control on IE security zones on the clients, or have an alternative solution specific for IE.