minio/cmd/crossdomain-xml-handler.go

/*
 * Minio Cloud Storage, (C) 2016 Minio, Inc.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package cmd

import "net/http"

// Standard cross domain policy information located at https://s3.amazonaws.com/crossdomain.xml
const crossDomainXML = `<?xml version="1.0"?><!DOCTYPE cross-domain-policy SYSTEM "http://www.adobe.com/xml/dtds/cross-domain-policy.dtd"><cross-domain-policy><allow-access-from domain="*" secure="false" /></cross-domain-policy>`

// Standard path where an app would find cross domain policy information.
const crossDomainXMLEntity = "/crossdomain.xml"

// Cross domain policy implements http.Handler interface, implementing a custom ServerHTTP.
type crossDomainPolicy struct {
	handler http.Handler
}

// A cross-domain policy file is an XML document that grants a web client, such as Adobe Flash Player
// or Adobe Acrobat (though not necessarily limited to these), permission to handle data across domains.
// When clients request content hosted on a particular source domain and that content make requests
// directed towards a domain other than its own, the remote domain needs to host a cross-domain
// policy file that grants access to the source domain, allowing the client to continue the transaction.
func setCrossDomainPolicy(h http.Handler) http.Handler {
	return crossDomainPolicy{handler: h}
}

func (c crossDomainPolicy) ServeHTTP(w http.ResponseWriter, r *http.Request) {
	// Look for 'crossdomain.xml' in the incoming request.
	switch r.URL.Path {
	case crossDomainXMLEntity:
		// Write the standard cross domain policy xml.
		w.Write([]byte(crossDomainXML))
		// Request completed, no need to serve to other handlers.
		return
	}
	// Continue to serve the request further.
	c.handler.ServeHTTP(w, r)
}