94 lines
2.4 KiB
Go
94 lines
2.4 KiB
Go
/*
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Copyright 2013 CoreOS Inc.
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Licensed under the Apache License, Version 2.0 (the "License");
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you may not use this file except in compliance with the License.
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You may obtain a copy of the License at
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http://www.apache.org/licenses/LICENSE-2.0
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Unless required by applicable law or agreed to in writing, software
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distributed under the License is distributed on an "AS IS" BASIS,
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WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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See the License for the specific language governing permissions and
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limitations under the License.
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*/
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package main
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import (
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"fmt"
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"net/http"
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"net/url"
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"strings"
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)
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type CORSInfo map[string]bool
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// CORSInfo implements the flag.Value interface to allow users to define a list of CORS origins
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func (ci *CORSInfo) Set(s string) error {
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m := make(map[string]bool)
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for _, v := range strings.Split(s, ",") {
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v = strings.TrimSpace(v)
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if v == "" {
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continue
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}
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if v != "*" {
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if _, err := url.Parse(v); err != nil {
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return fmt.Errorf("Invalid CORS origin: %s", err)
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}
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}
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m[v] = true
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}
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*ci = CORSInfo(m)
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return nil
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}
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func (ci *CORSInfo) String() string {
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o := make([]string, 0)
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for k, _ := range *ci {
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o = append(o, k)
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}
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return strings.Join(o, ",")
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}
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// OriginAllowed determines whether the server will allow a given CORS origin.
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func (c CORSInfo) OriginAllowed(origin string) bool {
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return c["*"] || c[origin]
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}
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type CORSHandler struct {
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Handler http.Handler
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Info *CORSInfo
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}
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// addHeader adds the correct cors headers given an origin
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func (h *CORSHandler) addHeader(w http.ResponseWriter, origin string) {
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w.Header().Add("Access-Control-Allow-Methods", "POST, GET, OPTIONS, PUT, DELETE")
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w.Header().Add("Access-Control-Allow-Origin", origin)
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w.Header().Add("Access-Control-Allow-Headers", "accept, content-type")
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}
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// ServeHTTP adds the correct CORS headers based on the origin and returns immediately
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// with a 200 OK if the method is OPTIONS.
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func (h *CORSHandler) ServeHTTP(w http.ResponseWriter, req *http.Request) {
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// It is important to flush before leaving the goroutine.
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// Or it may miss the latest info written.
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defer w.(http.Flusher).Flush()
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// Write CORS header.
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if h.Info.OriginAllowed("*") {
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h.addHeader(w, "*")
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} else if origin := req.Header.Get("Origin"); h.Info.OriginAllowed(origin) {
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h.addHeader(w, origin)
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}
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if req.Method == "OPTIONS" {
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w.WriteHeader(http.StatusOK)
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return
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}
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h.Handler.ServeHTTP(w, req)
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}
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