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@astaxie @yunkai
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// Copyright 2014 beego Author. All Rights Reserved.
//
// 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 cors provides handlers to enable CORS support.
// Usage
// import (
// "github.com/astaxie/beego"
// "github.com/astaxie/beego/plugins/cors"
// )
//
// func main() {
// // CORS for https://foo.* origins, allowing:
// // - PUT and PATCH methods
// // - Origin header
// // - Credentials share
// beego.InsertFilter("*", beego.BeforeRouter, cors.Allow(&cors.Options{
// AllowOrigins: []string{"https://*.foo.com"},
// AllowMethods: []string{"PUT", "PATCH"},
// AllowHeaders: []string{"Origin"},
// ExposeHeaders: []string{"Content-Length"},
// AllowCredentials: true,
// }))
// beego.Run()
// }
package cors
import (
"net/http"
"regexp"
"strconv"
"strings"
"time"
"github.com/astaxie/beego"
"github.com/astaxie/beego/context"
)
const (
headerAllowOrigin = "Access-Control-Allow-Origin"
headerAllowCredentials = "Access-Control-Allow-Credentials"
headerAllowHeaders = "Access-Control-Allow-Headers"
headerAllowMethods = "Access-Control-Allow-Methods"
headerExposeHeaders = "Access-Control-Expose-Headers"
headerMaxAge = "Access-Control-Max-Age"
headerOrigin = "Origin"
headerRequestMethod = "Access-Control-Request-Method"
headerRequestHeaders = "Access-Control-Request-Headers"
)
var (
defaultAllowHeaders = []string{"Origin", "Accept", "Content-Type", "Authorization"}
// Regex patterns are generated from AllowOrigins. These are used and generated internally.
allowOriginPatterns = []string{}
)
// Options represents Access Control options.
type Options struct {
// If set, all origins are allowed.
AllowAllOrigins bool
// A list of allowed origins. Wild cards and FQDNs are supported.
AllowOrigins []string
// If set, allows to share auth credentials such as cookies.
AllowCredentials bool
// A list of allowed HTTP methods.
AllowMethods []string
// A list of allowed HTTP headers.
AllowHeaders []string
// A list of exposed HTTP headers.
ExposeHeaders []string
// Max age of the CORS headers.
MaxAge time.Duration
}
// Header converts options into CORS headers.
func (o *Options) Header(origin string) (headers map[string]string) {
headers = make(map[string]string)
// if origin is not allowed, don't extend the headers
// with CORS headers.
if !o.AllowAllOrigins && !o.IsOriginAllowed(origin) {
return
}
// add allow origin
if o.AllowAllOrigins {
headers[headerAllowOrigin] = "*"
} else {
headers[headerAllowOrigin] = origin
}
// add allow credentials
headers[headerAllowCredentials] = strconv.FormatBool(o.AllowCredentials)
// add allow methods
if len(o.AllowMethods) > 0 {
headers[headerAllowMethods] = strings.Join(o.AllowMethods, ",")
}
// add allow headers
if len(o.AllowHeaders) > 0 {
headers[headerAllowHeaders] = strings.Join(o.AllowHeaders, ",")
}
// add exposed header
if len(o.ExposeHeaders) > 0 {
headers[headerExposeHeaders] = strings.Join(o.ExposeHeaders, ",")
}
// add a max age header
if o.MaxAge > time.Duration(0) {
headers[headerMaxAge] = strconv.FormatInt(int64(o.MaxAge/time.Second), 10)
}
return
}
// PreflightHeader converts options into CORS headers for a preflight response.
func (o *Options) PreflightHeader(origin, rMethod, rHeaders string) (headers map[string]string) {
headers = make(map[string]string)
if !o.AllowAllOrigins && !o.IsOriginAllowed(origin) {
return
}
// verify if requested method is allowed
for _, method := range o.AllowMethods {
if method == rMethod {
headers[headerAllowMethods] = strings.Join(o.AllowMethods, ",")
break
}
}
// verify if requested headers are allowed
var allowed []string
for _, rHeader := range strings.Split(rHeaders, ",") {
rHeader = strings.TrimSpace(rHeader)
lookupLoop:
for _, allowedHeader := range o.AllowHeaders {
if strings.ToLower(rHeader) == strings.ToLower(allowedHeader) {
allowed = append(allowed, rHeader)
break lookupLoop
}
}
}
headers[headerAllowCredentials] = strconv.FormatBool(o.AllowCredentials)
// add allow origin
if o.AllowAllOrigins {
headers[headerAllowOrigin] = "*"
} else {
headers[headerAllowOrigin] = origin
}
// add allowed headers
if len(allowed) > 0 {
headers[headerAllowHeaders] = strings.Join(allowed, ",")
}
// add exposed headers
if len(o.ExposeHeaders) > 0 {
headers[headerExposeHeaders] = strings.Join(o.ExposeHeaders, ",")
}
// add a max age header
if o.MaxAge > time.Duration(0) {
headers[headerMaxAge] = strconv.FormatInt(int64(o.MaxAge/time.Second), 10)
}
return
}
// IsOriginAllowed looks up if the origin matches one of the patterns
// generated from Options.AllowOrigins patterns.
func (o *Options) IsOriginAllowed(origin string) (allowed bool) {
for _, pattern := range allowOriginPatterns {
allowed, _ = regexp.MatchString(pattern, origin)
if allowed {
return
}
}
return
}
// Allow enables CORS for requests those match the provided options.
func Allow(opts *Options) beego.FilterFunc {
// Allow default headers if nothing is specified.
if len(opts.AllowHeaders) == 0 {
opts.AllowHeaders = defaultAllowHeaders
}
for _, origin := range opts.AllowOrigins {
pattern := regexp.QuoteMeta(origin)
pattern = strings.Replace(pattern, "\\*", ".*", -1)
pattern = strings.Replace(pattern, "\\?", ".", -1)
allowOriginPatterns = append(allowOriginPatterns, "^"+pattern+"$")
}
return func(ctx *context.Context) {
var (
origin = ctx.Input.Header(headerOrigin)
requestedMethod = ctx.Input.Header(headerRequestMethod)
requestedHeaders = ctx.Input.Header(headerRequestHeaders)
// additional headers to be added
// to the response.
headers map[string]string
)
if ctx.Input.Method() == "OPTIONS" &&
(requestedMethod != "" || requestedHeaders != "") {
headers = opts.PreflightHeader(origin, requestedMethod, requestedHeaders)
for key, value := range headers {
ctx.Output.Header(key, value)
}
ctx.ResponseWriter.WriteHeader(http.StatusOK)
return
}
headers = opts.Header(origin)
for key, value := range headers {
ctx.Output.Header(key, value)
}
}
}
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