Putting this information here for future readers' benefit.
401 (Unauthorized) response header -> Request authentication header
Here are several WWW-Authenticate
response headers. (The full list is at IANA: HTTP Authentication Schemes.)
WWW-Authenticate: Basic
-> Authorization: Basic + token - Use for basic authentication WWW-Authenticate: NTLM
-> Authorization: NTLM + token (2 challenges)WWW-Authenticate: Negotiate
-> Authorization: Negotiate + token - used for Kerberos authentication
Negotiate
: This authentication scheme violates both HTTP semantics (being connection-oriented) and syntax (use of syntax incompatible with the WWW-Authenticate and Authorization header field syntax).You can set the Authorization: Basic
header only when you also have the WWW-Authenticate: Basic
header on your 401 challenge.
But since you have WWW-Authenticate: Negotiate
this should be the case for Kerberos based authentication.