Why is the browser not setting cookies after an AJAX request returns?

OK, so I finally figured out the problem. It turns out that setting the Path option is important when sending cookies in an AJAX request. If you set Path=/, e.g.:

Set-Cookie:SessionId=foo; Path=/; HttpOnly

...then the browser will set the cookie when you navigate to a different page. Without setting Path, the browser uses the "default" path. Apparently, the default path for a cookie set by an AJAX request is different from the default path used when you navigate to a page directly. I'm using Go/Martini, so on the server-side I do this:

session.Options(session.Options{HttpOnly: true, Path:"/"})

I'd guess that Python/Ruby/etc. have a similar mechanism for setting Path.

See also: cookies problem in PHP and AJAX

@atomkirk's answer didn't apply to me because

1. I don't use the fetch API
2. I was making cross-site requests (i.e. CORS)

NOTE: If your server is using Access-Control-Allow-Origins:* (aka "all origins"/"wildcard origins"), you may not be able to send credentials (see below).

As for the fetch API; CORS requests will need {credentials:'include'} for both sending & receiving cookies

For CORS requests, use the "include" value to allow sendingcredentials to other domains:

fetch('https://example.com:1234/users', {               credentials: 'include' })

... To opt into accepting cookies from the server, you must use the credentials option.

{credentials:'include'} just sets xhr.withCredentials=true

Check fetch code

if (request.credentials === 'include') {      xhr.withCredentials = true } 

So plain Javascript/XHR.withCredentials is the important part.

If you're using jQuery, you can set withCredentials using $.ajaxSetup(...)

$.ajaxSetup({             crossDomain: true,             xhrFields: {                 withCredentials: true             }         });

If you're using AngularJS, the $http service config arg accepts a withCredentials property:

$http({    withCredentials: true});

If you're using Angular (Angular IO), the common.http.HttpRequest service options arg accepts a withCredentials property:

this.http.post<Hero>(this.heroesUrl, hero, {    withCredentials: true});

As for the request, when xhr.withCredentials=true; the Cookie header is sent

Before I changed xhr.withCredentials=true

1. I could see Set-Cookie name & value in the response, but Chrome's "Application" tab in the Developer Tools showed me the name and an empty value
2. Subsequent requests did not send a Cookie request header.

After the change xhr.withCredentials=true

1. I could see the cookie's name and the cookie's value in the Chrome's "Application" tab (a value consistent with the Set-Cookie header).
2. Subsequent requests did send a Cookie request header with the same value, so my server treated me as "authenticated"

As for the response: the server may need certain Access-Control... headers

For example, I configured my server to return these headers:

• Access-Control-Allow-Credentials:true
• Access-Control-Allow-Origin:https://{your-origin}:{your-port}

EDIT: this approach won't work if you allow all origins/wildcard origins, as described here (thanks to @ChandanBhattad) :

The CORS request was attempted with the credentials flag set, but the server is configured using the wildcard ("*") as the value of Access-Control-Allow-Origin, which doesn't allow the use of credentials.

Until I made this server-side change to the response headers, Chrome logged errors in the console like

Failed to load https://{saml-domain}/saml-authn: Redirect from https://{saml-domain}/saml-redirect has been blocked by CORS policy:

The value of the 'Access-Control-Allow-Credentials' header in the response is '' which must be 'true' when the request's credentials mode is 'include'. Origin https://{your-domain} is therefore not allowed access.

The credentials mode of requests initiated by the XMLHttpRequest is controlled by the withCredentials attribute.

After making this Access-* header change, Chrome did not log errors; the browser let me check the authenticated responses for all subsequent requests.

If you're using the new fetch API, you can try including credentials:

fetch('/users', {  credentials: 'same-origin'})

That's what fixed it for me.

In particular, using the polyfill: https://github.com/github/fetch#sending-cookies