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// Copyright (c) Microsoft Corporation.
// Licensed under the MIT license.
// Package local contains a local HTTP server used with interactive authentication.
package local
import (
"context"
"fmt"
"net"
"net/http"
"strconv"
"strings"
"time"
)
var okPage = []byte(`
<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8" />
<title>Authentication Complete</title>
</head>
<body>
<p>Authentication complete. You can return to the application. Feel free to close this browser tab.</p>
</body>
</html>
`)
const failPage = `
<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8" />
<title>Authentication Failed</title>
</head>
<body>
<p>Authentication failed. You can return to the application. Feel free to close this browser tab.</p>
<p>Error details: error %s error_description: %s</p>
</body>
</html>
`
// Result is the result from the redirect.
type Result struct {
// Code is the code sent by the authority server.
Code string
// Err is set if there was an error.
Err error
}
// Server is an HTTP server.
type Server struct {
// Addr is the address the server is listening on.
Addr string
resultCh chan Result
s *http.Server
reqState string
}
// New creates a local HTTP server and starts it.
func New(reqState string, port int) (*Server, error) {
var l net.Listener
var err error
var portStr string
if port > 0 {
// use port provided by caller
l, err = net.Listen("tcp", fmt.Sprintf("localhost:%d", port))
portStr = strconv.FormatInt(int64(port), 10)
} else {
// find a free port
for i := 0; i < 10; i++ {
l, err = net.Listen("tcp", "localhost:0")
if err != nil {
continue
}
addr := l.Addr().String()
portStr = addr[strings.LastIndex(addr, ":")+1:]
break
}
}
if err != nil {
return nil, err
}
serv := &Server{
Addr: fmt.Sprintf("http://localhost:%s", portStr),
s: &http.Server{Addr: "localhost:0", ReadHeaderTimeout: time.Second},
reqState: reqState,
resultCh: make(chan Result, 1),
}
serv.s.Handler = http.HandlerFunc(serv.handler)
if err := serv.start(l); err != nil {
return nil, err
}
return serv, nil
}
func (s *Server) start(l net.Listener) error {
go func() {
err := s.s.Serve(l)
if err != nil {
select {
case s.resultCh <- Result{Err: err}:
default:
}
}
}()
return nil
}
// Result gets the result of the redirect operation. Once a single result is returned, the server
// is shutdown. ctx deadline will be honored.
func (s *Server) Result(ctx context.Context) Result {
select {
case <-ctx.Done():
return Result{Err: ctx.Err()}
case r := <-s.resultCh:
return r
}
}
// Shutdown shuts down the server.
func (s *Server) Shutdown() {
// Note: You might get clever and think you can do this in handler() as a defer, you can't.
_ = s.s.Shutdown(context.Background())
}
func (s *Server) putResult(r Result) {
select {
case s.resultCh <- r:
default:
}
}
func (s *Server) handler(w http.ResponseWriter, r *http.Request) {
q := r.URL.Query()
headerErr := q.Get("error")
if headerErr != "" {
desc := q.Get("error_description")
// Note: It is a little weird we handle some errors by not going to the failPage. If they all should,
// change this to s.error() and make s.error() write the failPage instead of an error code.
_, _ = w.Write([]byte(fmt.Sprintf(failPage, headerErr, desc)))
s.putResult(Result{Err: fmt.Errorf(desc)})
return
}
respState := q.Get("state")
switch respState {
case s.reqState:
case "":
s.error(w, http.StatusInternalServerError, "server didn't send OAuth state")
return
default:
s.error(w, http.StatusInternalServerError, "mismatched OAuth state, req(%s), resp(%s)", s.reqState, respState)
return
}
code := q.Get("code")
if code == "" {
s.error(w, http.StatusInternalServerError, "authorization code missing in query string")
return
}
_, _ = w.Write(okPage)
s.putResult(Result{Code: code})
}
func (s *Server) error(w http.ResponseWriter, code int, str string, i ...interface{}) {
err := fmt.Errorf(str, i...)
http.Error(w, err.Error(), code)
s.putResult(Result{Err: err})
}
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