Merge branch 'emptyauth-auto'

An earlier attempt to support NTLM authentication better (by setting
http.emptyauth=true always) failed to take into account that some
servers that support only Basic authentication may be very unhappy
about those "empty credentials".

Jeff King came up with a beautiful fix; this topic branch reverts our
earlier attempt at fixing the problem and applies those patches
instead.

Signed-off-by: Johannes Schindelin <[email protected]>

http.c

@@ -109,7 +109,7 @@ static int curl_save_cookies;
 struct credential http_auth = CREDENTIAL_INIT;
 static int http_proactive_auth;
 static const char *user_agent;
-static int curl_empty_auth = 1;
+static int curl_empty_auth = -1;
 
 enum http_follow_config http_follow_config = HTTP_FOLLOW_INITIAL;
 
@@ -125,6 +125,7 @@ static struct credential cert_auth = CREDENTIAL_INIT;
 static int ssl_cert_password_required;
 #ifdef LIBCURL_CAN_HANDLE_AUTH_ANY
 static unsigned long http_auth_methods = CURLAUTH_ANY;
+static int http_auth_methods_restricted;
 #endif
 
 static struct curl_slist *pragma_header;
@@ -333,7 +334,10 @@ static int http_options(const char *var, const char *value, void *cb)
 		return git_config_string(&user_agent, var, value);
 
 	if (!strcmp("http.emptyauth", var)) {
-		curl_empty_auth = git_config_bool(var, value);
+		if (value && !strcmp("auto", value))
+			curl_empty_auth = -1;
+		else
+			curl_empty_auth = git_config_bool(var, value);
 		return 0;
 	}
 
@@ -382,10 +386,45 @@ static int http_options(const char *var, const char *value, void *cb)
 	return git_default_config(var, value, cb);
 }
 
+static int curl_empty_auth_enabled(void)
+{
+	if (curl_empty_auth >= 0)
+		return curl_empty_auth;
+
+#ifndef LIBCURL_CAN_HANDLE_AUTH_ANY
+	/*
+	 * Our libcurl is too old to do AUTH_ANY in the first place;
+	 * just default to turning the feature off.
+	 */
+#else
+	/*
+	 * In the automatic case, kick in the empty-auth
+	 * hack as long as we would potentially try some
+	 * method more exotic than "Basic".
+	 *
+	 * But only do this when this is our second or
+	 * subsequent * request, as by then we know what
+	 * methods are available.
+	 */
+	if (http_auth_methods_restricted)
+		switch (http_auth_methods) {
+		case CURLAUTH_BASIC:
+		case CURLAUTH_DIGEST:
+#ifdef CURLAUTH_DIGEST_IE
+		case CURLAUTH_DIGEST_IE:
+#endif
+			return 0;
+		default:
+			return 1;
+		}
+#endif
+	return 0;
+}
+
 static void init_curl_http_auth(CURL *result)
 {
 	if (!http_auth.username || !*http_auth.username) {
-		if (curl_empty_auth)
+		if (curl_empty_auth_enabled())
 			curl_easy_setopt(result, CURLOPT_USERPWD, ":");
 		return;
 	}
@@ -1079,7 +1118,7 @@ struct active_request_slot *get_active_slot(void)
 #ifdef LIBCURL_CAN_HANDLE_AUTH_ANY
 	curl_easy_setopt(slot->curl, CURLOPT_HTTPAUTH, http_auth_methods);
 #endif
-	if (http_auth.password || curl_empty_auth)
+	if (http_auth.password || curl_empty_auth_enabled())
 		init_curl_http_auth(slot->curl);
 
 	return slot;
@@ -1347,6 +1386,10 @@ static int handle_curl_result(struct slot_results *results)
 		} else {
 #ifdef LIBCURL_CAN_HANDLE_AUTH_ANY
 			http_auth_methods &= ~CURLAUTH_GSSNEGOTIATE;
+			if (results->auth_avail) {
+				http_auth_methods &= results->auth_avail;
+				http_auth_methods_restricted = 1;
+			}
 #endif
 			return HTTP_REAUTH;
 		}