1// Copyright 2013 The Prometheus Authors
2// Licensed under the Apache License, Version 2.0 (the "License");
3// you may not use this file except in compliance with the License.
4// You may obtain a copy of the License at
5//
6// http://www.apache.org/licenses/LICENSE-2.0
7//
8// Unless required by applicable law or agreed to in writing, software
9// distributed under the License is distributed on an "AS IS" BASIS,
10// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
11// See the License for the specific language governing permissions and
12// limitations under the License.
13
14package httputil
15
16import (
17	"net/http"
18	"regexp"
19)
20
21var corsHeaders = map[string]string{
22	"Access-Control-Allow-Headers":  "Accept, Authorization, Content-Type, Origin",
23	"Access-Control-Allow-Methods":  "GET, POST, OPTIONS",
24	"Access-Control-Expose-Headers": "Date",
25	"Vary":                          "Origin",
26}
27
28// Enables cross-site script calls.
29func SetCORS(w http.ResponseWriter, o *regexp.Regexp, r *http.Request) {
30	origin := r.Header.Get("Origin")
31	if origin == "" {
32		return
33	}
34
35	for k, v := range corsHeaders {
36		w.Header().Set(k, v)
37	}
38
39	if o.String() == "^(?:.*)$" {
40		w.Header().Set("Access-Control-Allow-Origin", "*")
41		return
42	}
43
44	if o.MatchString(origin) {
45		w.Header().Set("Access-Control-Allow-Origin", origin)
46	}
47}
48