Gateway: add support for HTTP OPTIONS request type

core/corehttp/gateway_handler.go

@@ -82,6 +82,11 @@ func (i *gatewayHandler) ServeHTTP(w http.ResponseWriter, r *http.Request) {
 		return
 	}
 
+	if r.Method == "OPTIONS" {
+		i.optionsHandler(w, r)
+		return
+	}
+
 	errmsg := "Method " + r.Method + " not allowed: "
 	if !i.config.Writable {
 		w.WriteHeader(http.StatusMethodNotAllowed)
@@ -94,6 +99,15 @@ func (i *gatewayHandler) ServeHTTP(w http.ResponseWriter, r *http.Request) {
 	log.Error(errmsg) // TODO(cryptix): log errors until we have a better way to expose these (counter metrics maybe)
 }
 
+func (i *gatewayHandler) optionsHandler(w http.ResponseWriter, r *http.Request) {
+	/*
+		OPTIONS is a noop request that is used by the browsers to check
+		if server accepts cross-site XMLHttpRequest (indicated by the presence of CORS headers)
+		https://developer.mozilla.org/en-US/docs/Web/HTTP/Access_control_CORS#Preflighted_requests
+	*/
+	i.addUserHeaders(w) // return all custom headers (including CORS ones, if set)
+}
+
 func (i *gatewayHandler) getOrHeadHandler(w http.ResponseWriter, r *http.Request) {
 	ctx, cancel := context.WithTimeout(i.node.Context(), time.Hour)
 	// the hour is a hard fallback, we don't expect it to happen, but just in case

test/sharness/t0112-gateway-cors.sh

@@ -0,0 +1,78 @@
+#!/bin/sh
+#
+# Copyright (c) 2016 Marcin Rataj
+# MIT Licensed; see the LICENSE file in this repository.
+#
+
+test_description="Test HTTP Gateway CORS Support"
+
+test_config_ipfs_cors_headers() {
+    ipfs config --json Gateway.HTTPHeaders.Access-Control-Allow-Origin '["*"]'
+    ipfs config --json Gateway.HTTPHeaders.Access-Control-Allow-Methods '["PUT", "GET", "POST"]'
+    ipfs config --json Gateway.HTTPHeaders.Access-Control-Allow-Headers '["X-Requested-With"]'
+
+    ipfs config --json API.HTTPHeaders.Access-Control-Allow-Origin '["*"]'
+    ipfs config --json API.HTTPHeaders.Access-Control-Allow-Methods '["PUT", "GET", "POST"]'
+    ipfs config --json API.HTTPHeaders.Access-Control-Allow-Headers '["X-Requested-With"]'
+}
+
+. lib/test-lib.sh
+
+test_init_ipfs
+test_config_ipfs_gateway_readonly $ADDR_GWAY
+test_config_ipfs_cors_headers
+test_launch_ipfs_daemon
+
+gwport=$PORT_GWAY
+apiport=$PORT_API
+thash='QmUNLLsPACCz1vLxQVkXqqLX5R1X345qqfHbsf67hvA3Nn'
+
+# Gateway
+
+# HTTP GET Request
+test_expect_success "GET to Gateway succeeds" '
+    curl -svX GET "http://127.0.0.1:$gwport/ipfs/$thash" 2>curl_output
+'
+# GET Response from Gateway should contain CORS headers
+test_expect_success "GET response for Gateway resource looks good" '
+    grep "Access-Control-Allow-Origin:" curl_output &&
+    grep "Access-Control-Allow-Methods:" curl_output &&
+    grep "Access-Control-Allow-Headers:" curl_output
+'
+
+# HTTP OPTIONS Request
+test_expect_success "OPTIONS to Gateway succeeds" '
+    curl -svX OPTIONS "http://127.0.0.1:$gwport/ipfs/$thash" 2>curl_output
+'
+# OPTION Response from Gateway should contain CORS headers
+test_expect_success "OPTIONS response for Gateway resource looks good" '
+    grep "Access-Control-Allow-Origin:" curl_output &&
+    grep "Access-Control-Allow-Methods:" curl_output &&
+    grep "Access-Control-Allow-Headers:" curl_output
+'
+
+# Read-Only API (at the Gateway Port)
+
+# HTTP GET Request
+test_expect_success "GET to API succeeds" '
+    curl -svX GET "http://127.0.0.1:$gwport/api/v0/cat?arg=$thash" 2>curl_output
+'
+# GET Response from the API should NOT contain CORS headers
+# Blacklisting: https://git.io/vzaj2
+# Rationale: https://git.io/vzajX
+test_expect_success "OPTIONS response for API looks good" '
+    grep -q "Access-Control-Allow-" curl_output && false || true
+'
+
+# HTTP OPTIONS Request
+test_expect_success "OPTIONS to API succeeds" '
+    curl -svX OPTIONS "http://127.0.0.1:$gwport/api/v0/cat?arg=$thash" 2>curl_output
+'
+# OPTIONS Response from the API should NOT contain CORS headers
+test_expect_success "OPTIONS response for API looks good" '
+    grep -q "Access-Control-Allow-" curl_output && false || true
+'
+
+test_kill_ipfs_daemon
+
+test_done