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main.go
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main.go
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package main
import (
"bufio"
"crypto/hmac"
"crypto/sha256"
"crypto/subtle"
"embed"
"encoding/base64"
"flag"
"fmt"
"html/template"
"io"
"log"
"net"
"net/http"
"net/url"
"os"
"strings"
"github.com/coreos/go-systemd/v22/activation"
"github.com/portier/portier-go"
)
//go:embed *.html
var fs embed.FS
var tmpl = template.Must(template.ParseFS(fs, "*.html"))
const defaultRemember = 14 * 24 * 60 * 60 // 2 weeks
type authPage struct{}
func (p authPage) render(w io.Writer) {
err := tmpl.ExecuteTemplate(w, "auth.html", p)
if err != nil {
log.Fatal("auth.html render error:", err)
}
}
type errorPage struct {
Message string
}
func (p errorPage) render(w io.Writer) {
err := tmpl.ExecuteTemplate(w, "error.html", p)
if err != nil {
log.Fatal("error.html render error:", err)
}
}
func main() {
listen := flag.String("listen", "localhost:8081", "listen address")
authURL := flag.String("url", "", "base URL proxied here")
cookieName := flag.String("cookie", "AuthSession", "cookie name")
secret := flag.String("secret", "", "cookie signing secret")
remember := flag.Int("remember", defaultRemember, "session duration in seconds")
secure := flag.Bool("secure", false, "set the cookie secure flag")
broker := flag.String("broker", portier.DefaultBroker, "Portier broker to use")
optional := flag.Bool("optional", false, "make login optional")
allowListFile := flag.String("allowlist", "", "file of emails (one per line) to limit access to")
flag.Parse()
if *authURL == "" {
log.Fatal("The -url flag is required")
}
if *secret == "" {
log.Fatal("The -secret flag is required")
}
parsedURL, err := url.Parse(*authURL)
if err != nil {
log.Fatal("invalid -url:", err)
}
if !parsedURL.IsAbs() {
log.Fatal("invalid -url: not an absolute URL")
}
client, err := portier.NewClient(&portier.Config{
Broker: *broker,
RedirectURI: fmt.Sprintf("%s/verify", *authURL),
})
if err != nil {
log.Fatal("portier.NewClient error:", err)
}
var allowList map[string]struct{}
if *allowListFile != "" {
file, err := os.Open(*allowListFile)
if err != nil {
log.Fatal("invalid -allowlist:", err)
}
defer file.Close()
allowList = make(map[string]struct{})
scanner := bufio.NewScanner(file)
for scanner.Scan() {
line := strings.TrimSpace(scanner.Text())
if line != "" && !strings.HasPrefix(line, "#") {
allowList[line] = struct{}{}
}
}
if err := scanner.Err(); err != nil {
log.Fatal(err)
}
}
authPath := parsedURL.Path
verifyPath := fmt.Sprintf("%s/verify", parsedURL.Path)
sigName := fmt.Sprintf("%s.sig", *cookieName)
signValue := func(val string) string {
hasher := hmac.New(sha256.New, []byte(*secret))
hasher.Write([]byte(val))
return base64.StdEncoding.EncodeToString(hasher.Sum(nil))
}
http.HandleFunc("/check", func(rw http.ResponseWriter, req *http.Request) {
var email string
cookie, _ := req.Cookie(*cookieName)
sig, _ := req.Cookie(sigName)
if cookie != nil && sig != nil && cookie.Value != "" && sig.Value != "" {
expected := signValue(cookie.Value)
if subtle.ConstantTimeCompare([]byte(sig.Value), []byte(expected)) == 1 {
email = cookie.Value
}
}
rw.Header().Set("X-Portier-Email", email)
if email != "" && allowList != nil {
if _, ok := allowList[email]; !ok {
rw.WriteHeader(403)
return
}
}
if email != "" || *optional {
rw.WriteHeader(204)
} else {
rw.WriteHeader(403)
}
})
http.HandleFunc(authPath, func(rw http.ResponseWriter, req *http.Request) {
switch req.Method {
case "GET":
authPage{}.render(rw)
case "POST":
email := req.PostFormValue("email")
if email == "" {
authPage{}.render(rw)
return
}
authURL, err := client.StartAuth(email)
if err != nil {
log.Print("portier.Client.StartAuth error:", err)
rw.WriteHeader(500)
errorPage{Message: err.Error()}.render(rw)
return
}
rw.Header().Set("Location", authURL)
rw.WriteHeader(303)
case "DELETE":
http.SetCookie(rw, &http.Cookie{
Name: *cookieName,
Path: "/",
MaxAge: -1,
Secure: *secure,
HttpOnly: true,
SameSite: http.SameSiteLaxMode,
})
http.SetCookie(rw, &http.Cookie{
Name: sigName,
Path: "/",
MaxAge: -1,
Secure: *secure,
HttpOnly: true,
SameSite: http.SameSiteLaxMode,
})
rw.WriteHeader(204)
default:
rw.WriteHeader(405)
errorPage{Message: "invalid request method"}.render(rw)
}
})
http.HandleFunc(verifyPath, func(rw http.ResponseWriter, req *http.Request) {
if req.Method != "POST" {
rw.WriteHeader(405)
errorPage{Message: "invalid request method"}.render(rw)
return
}
token := req.PostFormValue("id_token")
if token == "" {
msg := req.PostFormValue("error_description")
if msg == "" {
msg = "missing id_token"
}
rw.WriteHeader(400)
errorPage{Message: msg}.render(rw)
return
}
email, err := client.Verify(token)
if err != nil {
rw.WriteHeader(400)
errorPage{Message: err.Error()}.render(rw)
return
}
if allowList != nil {
if _, ok := allowList[email]; !ok {
rw.WriteHeader(403)
errorPage{Message: "your email address is not allowed to access this site"}.render(rw)
return
}
}
http.SetCookie(rw, &http.Cookie{
Name: *cookieName,
Value: email,
Path: "/",
MaxAge: *remember,
Secure: *secure,
HttpOnly: true,
SameSite: http.SameSiteLaxMode,
})
http.SetCookie(rw, &http.Cookie{
Name: sigName,
Value: signValue(email),
Path: "/",
MaxAge: *remember,
Secure: *secure,
HttpOnly: true,
SameSite: http.SameSiteLaxMode,
})
rw.Header().Set("Location", "/")
rw.WriteHeader(303)
})
var listener net.Listener
listeners, _ := activation.Listeners()
if len(listeners) == 1 {
listener = listeners[0]
log.Print("Listening with socket activation")
} else if len(listeners) > 1 {
log.Fatal("Socket activation did not pass exactly 1 socket")
} else {
listener, err = net.Listen("tcp", *listen)
if err != nil {
log.Fatal("net.Listen error:", err)
} else {
log.Print("Listening on ", *listen)
}
}
log.Fatal(http.Serve(listener, nil))
}