There are authentication backends such as Shibboleth that do send no Basic Auth credentials for DAV requests. This means that the ownCloud DAV backend would consider these requests coming from an untrusted source and require higher levels of security checks. (e.g. a CSRF check)
While an elegant solution would rely on authenticating via token (so that one can properly ensure that the request came indeed from a trusted client) this is a okay'ish workaround for this problem until we have something more reliable in the authentication code.
This makes sure that whenever a Webdav call is done through Ajax, if the
session has expired, it will not send back a challenge but a simple 401
response. Without this fix, the default code would send back a challenge
and trigger the browser's basic auth dialog.
Lukas Reschke
Arthur Schiwon
Thomas Müller
Roeland Jago Douma
Vincent Petry
Scrutinizer Auto-Fixer