Bug: http://curl.haxx.se/bug/view.cgi?id=1414
Reported-by: teo8976

Problem: if CURLOPT_FORBID_REUSE is set, requests using NTLM failed
since NTLM requires multiple requests that re-use the same connection
for the authentication to work

Solution: Ignore the forbid reuse flag in case the NTLM authentication
handshake is in progress, according to the NTLM state flag.

Fixed known bug #77.

Updated "FTP 4.6 GSSAPI via Windows SSPI" and "SASL 14.1 Other
authentication mechanisms" following recent additions.

Added SASL 14.2 GSSAPI via GSS-API libraries.

This repeats what has already been documented in both the curl manpage
and CURLOPT_USERPWD documentation but is provided here for completeness
as someone may not especially read the latter when using libcurl.

Added information about Kerberos V5 requiring the domain part in the
user name.

Mentioned that the user name can be specified in UPN format, and not
just in Down-Level Logon Name format, following the information
added in commit 7679cb3f reworking the exisitng information in the
process.

Bug: http://curl.haxx.se/mail/lib-2014-07/0335.html
Reported-by: David Shaw

Reflect recent changes in SPNEGO and GSS-API code in the docs.
Update them with appropriate namings and remove visible spots for
GSS-Negotiate.

... and has been so since 2005

Each backend now defines CURL_SSL_BACKEND accordingly. Added the *AXTLS
one which was missing previously.

... with permission from David Shaw

1 - fixes the warnings when built without http2 support

2 - adds CURLE_HTTP2, a new error code for errors detected by nghttp2
basically when they are about http2 specific things.

This is just fundamentally broken. SPNEGO (RFC4178) is a protocol which
allows client and server to negotiate the underlying mechanism which will
actually be used to authenticate. This is *often* Kerberos, and can also
be NTLM and other things. And to complicate matters, there are various
different OIDs which can be used to specify the Kerberos mechanism too.

A SPNEGO exchange will identify *which* GSSAPI mechanism is being used,
and will exchange GSSAPI tokens which are appropriate for that mechanism.

But this SPNEGO implementation just strips the incoming SPNEGO packet
and extracts the token, if any. And completely discards the information
about *which* mechanism is being used. Then we *assume* it was Kerberos,
and feed the token into gss_init_sec_context() with the default
mechanism (GSS_S_NO_OID for the mech_type argument).

Furthermore... broken as this code is, it was never even *used* for input
tokens anyway, because higher layers of curl would just bail out if the
server actually said anything *back* to us in the negotiation. We assume
that we send a single token to the server, and it accepts it. If the server
wants to continue the exchange (as is required for NTLM and for SPNEGO
to do anything useful), then curl was broken anyway.

So the only bit which actually did anything was the bit in
Curl_output_negotiate(), which always generates an *initial* SPNEGO
token saying "Hey, I support only the Kerberos mechanism and this is its
token".

You could have done that by manually just prefixing the Kerberos token
with the appropriate bytes, if you weren't going to do any proper SPNEGO
handling. There's no need for the FBOpenSSL library at all.

The sane way to do SPNEGO is just to *ask* the GSSAPI library to do
SPNEGO. That's what the 'mech_type' argument to gss_init_sec_context()
is for. And then it should all Just Work™.

That 'sane way' will be added in a subsequent patch, as will bug fixes
for our failure to handle any exchange other than a single outbound
token to the server which results in immediate success.

... with a mention of *NOSIGNAL, based on talk in bug #1386

Bug: http://curl.haxx.se/mail/archive-2014-07/0006.html