Fix the auth code to enable us to i.e set DIGEST and then find out that the

server doesn't require any auth at all and then we just continue nicely. We
now have an extra bit in the connection struct named 'authprobe' that is TRUE
when doing pure "HTTP authentication probing".

lib/http.c

@@ -168,29 +168,25 @@ static CURLcode Curl_output_basic(struct connectdata *conn, bool proxy)
 static bool pickoneauth(struct auth *pick)
 {
   bool picked;
-  if(pick->avail) {
-    /* only deal with authentication we want */
-    long avail = pick->avail & pick->want;
-    picked = TRUE;
+  /* only deal with authentication we want */
+  long avail = pick->avail & pick->want;
+  picked = TRUE;
 
-    /* The order of these checks is highly relevant, as this will be the order
-       of preference in case of the existance of multiple accepted types. */
-    if(avail & CURLAUTH_GSSNEGOTIATE)
-      pick->picked = CURLAUTH_GSSNEGOTIATE;
-    else if(avail & CURLAUTH_DIGEST)
-      pick->picked = CURLAUTH_DIGEST;
-    else if(avail & CURLAUTH_NTLM)
-      pick->picked = CURLAUTH_NTLM;
-    else if(avail & CURLAUTH_BASIC)
-      pick->picked = CURLAUTH_BASIC;
-    else {
-      pick->picked = CURLAUTH_NONE; /* none was picked clear it */
-      picked = FALSE;
-    }
-    pick->avail = CURLAUTH_NONE; /* clear it here */
+  /* The order of these checks is highly relevant, as this will be the order
+     of preference in case of the existance of multiple accepted types. */
+  if(avail & CURLAUTH_GSSNEGOTIATE)
+    pick->picked = CURLAUTH_GSSNEGOTIATE;
+  else if(avail & CURLAUTH_DIGEST)
+    pick->picked = CURLAUTH_DIGEST;
+  else if(avail & CURLAUTH_NTLM)
+    pick->picked = CURLAUTH_NTLM;
+  else if(avail & CURLAUTH_BASIC)
+    pick->picked = CURLAUTH_BASIC;
+  else {
+    pick->picked = CURLAUTH_PICKNONE; /* we select to use nothing */
+    picked = FALSE;
   }
-  else
-    return FALSE;
+  pick->avail = CURLAUTH_NONE; /* clear it here */
 
   return picked;
 }
@@ -212,14 +208,16 @@ CURLcode Curl_http_auth_act(struct connectdata *conn)
   if(data->state.authproblem)
     return data->set.http_fail_on_error?CURLE_HTTP_RETURNED_ERROR:CURLE_OK;
 
-  if(conn->bits.user_passwd) {
+  if(conn->bits.user_passwd &&
+     ((conn->keep.httpcode == 401) || conn->bits.authprobe)) {
     pickhost = pickoneauth(&data->state.authhost);
-    if(!pickhost && (conn->keep.httpcode == 401))
+    if(!pickhost)
       data->state.authproblem = TRUE;
   }
-  if(conn->bits.proxy_user_passwd) {
+  if(conn->bits.proxy_user_passwd &&
+     ((conn->keep.httpcode == 407) || conn->bits.authprobe) ) {
     pickproxy = pickoneauth(&data->state.authproxy);
-    if(!pickproxy && (conn->keep.httpcode == 407))
+    if(!pickproxy)
       data->state.authproblem = TRUE;
   }
 
@@ -283,21 +281,17 @@ Curl_http_output_auth(struct connectdata *conn,
     return CURLE_OK; /* no authentication with no user or password */
   }
 
-  if(data->state.authhost.want &&
-     !data->state.authhost.picked) {
+  if(data->state.authhost.want && !data->state.authhost.picked)
     /* The app has selected one or more methods, but none has been picked
        so far by a server round-trip. Then we set the picked one to the
        want one, and if this is one single bit it'll be used instantly. */
     data->state.authhost.picked = data->state.authhost.want;
-  }
 
-  if(data->state.authproxy.want &&
-     !data->state.authproxy.picked) {
-    /* The app has selected one or more methods, but none has been picked
-       so far by a server round-trip. Then we set the picked one to the
-       want one, and if this is one single bit it'll be used instantly. */
+  if(data->state.authproxy.want && !data->state.authproxy.picked)
+    /* The app has selected one or more methods, but none has been picked so
+       far by a proxy round-trip. Then we set the picked one to the want one,
+       and if this is one single bit it'll be used instantly. */
     data->state.authproxy.picked = data->state.authproxy.want;
-  }
 
   /* To prevent the user+password to get sent to other than the original
      host due to a location-follow, we do some weirdo checks here */
@@ -1313,7 +1307,11 @@ CURLcode Curl_http(struct connectdata *conn)
     httpreq = HTTPREQ_HEAD;
     request = (char *)"HEAD";
     conn->bits.no_body = TRUE;
+    conn->bits.authprobe = TRUE; /* this is a request done to probe for
+                                    authentication methods */
   }
+  else
+    conn->bits.authprobe = FALSE;
 
   Curl_safefree(conn->allocptr.ref);
   if(data->change.referer && !checkheaders(data, "Referer:"))

lib/http.h

@@ -50,5 +50,12 @@ CURLcode Curl_http_input_auth(struct connectdata *conn,
 CURLcode Curl_http_auth_act(struct connectdata *conn);
 
 int Curl_http_should_fail(struct connectdata *conn);
+
+/* If only the PICKNONE bit is set, there has been a round-trip and we
+   selected to use no auth at all. Ie, we actively select no auth, as opposed
+   to not having one selected. The other CURLAUTH_* defines are present in the
+   public curl/curl.h header. */
+#define CURLAUTH_PICKNONE (1<<30) /* don't use auth */
+
 #endif
 #endif

lib/urldata.h

@@ -319,6 +319,9 @@ struct ConnectBits {
                          This is implicit when SSL-protocols are used through
                          proxies, but can also be enabled explicitly by
                          apps */
+  bool authprobe;     /* set TRUE when this transfer is done to probe for auth
+                         types, as when asking for "any" type when speaking
+                         HTTP */
 };
 
 struct hostname {