icloud caldav returning 401 unauthorized

Was using caldav to access icloud calendar, it was working fine. Today, all the requests in my postman collection started to get 401 from caldav.icloud.com I am accessing my own personal account to test, double checked my password hundred times, still not working.

Request:

PROPFIND / HTTP/1.1
Host: caldav.icloud.com
Authorization: Basic xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
Content-Type: application/xml
Cache-Control: no-cache
Postman-Token: 39b27b44-0a6f-b351-540f-f9446df618d0

<propfind xmlns='DAV:'>
    <prop>
        <current-user-principal/>
    </prop>
</propfind>

Response was:

401 unauthorized

Header:

Connection →keep-alive
Content-Length →141
Content-Type →text/html;charset=utf-8
Date →Fri, 30 Jun 2017 14:23:34 GMT
Server →AppleHttpServer/2f080fc0
Strict-Transport-Security →max-age=31536000; includeSubDomains
WWW-Authenticate →x-mobileme-authtoken realm="MMCalDav", basic realm="MMCalDav"
X-Apple-Request-UUID →95e3a459-10b1-4d0a-a3ae-73f29b569481
X-Responding-Server →caldav:44101701:pv38p41ic-ztdg01080801:8001:17D70:375f9f89bf
X-Transaction-Id →95e3a459-10b1-4d0a-a3ae-73f29b569481
access-control-expose-headers →X-Apple-Request-UUID, Via
via →icloudedge:br30p01ic-zteu01122201:7401:17D30:Berlin

Body:

<html>
    <head>
        <title>Unauthorized</title>
    </head>
    <body>
        <h1>Unauthorized</h1>
        <p>You are not authorized to access this resource.</p>
    </body>
</html>

Any ideas?

Solution

You cannot do a 3rd party login into iCloud with your regular login/password anymore (DAV, IMAP, etc). Since June 15, 2017 you need an "App specific password".

This page describes how to generate one: Using app-specific passwords. From that page:

Sign in to your Apple ID account page.
In the Security section, click Generate Password below App-Specific Passwords.
Follow the steps on your screen.