2019-04-13 22:50:08 +02:00
|
|
|
package main
|
|
|
|
|
|
|
|
import (
|
|
|
|
"context"
|
|
|
|
"encoding/hex"
|
|
|
|
"math/rand"
|
|
|
|
"net/http"
|
|
|
|
"net/url"
|
|
|
|
)
|
|
|
|
|
|
|
|
// session storage indexed by a random UUID
|
|
|
|
var sessions = map[string]*Session{}
|
|
|
|
|
|
|
|
type Session struct {
|
|
|
|
LoggedIn bool // may access the DB
|
|
|
|
}
|
|
|
|
|
|
|
|
type sessionContextKey struct{}
|
|
|
|
|
|
|
|
func sessionGenId() string {
|
|
|
|
u := make([]byte, 16)
|
|
|
|
if _, err := rand.Read(u); err != nil {
|
|
|
|
panic("cannot generate random bytes")
|
|
|
|
}
|
|
|
|
return hex.EncodeToString(u)
|
|
|
|
}
|
|
|
|
|
|
|
|
// TODO: We don't want to keep an unlimited amount of cookies in the storage.
|
|
|
|
// - The essential question is: how do we avoid DoS?
|
|
|
|
// - Which cookies are worth keeping?
|
|
|
|
// - Definitely logged-in users, only one person should know the password.
|
|
|
|
// - Evict by FIFO? LRU?
|
|
|
|
func sessionGet(w http.ResponseWriter, r *http.Request) (session *Session) {
|
|
|
|
if c, _ := r.Cookie("sessionid"); c != nil {
|
|
|
|
session, _ = sessions[c.Value]
|
|
|
|
}
|
|
|
|
if session == nil {
|
|
|
|
id := sessionGenId()
|
|
|
|
session = &Session{LoggedIn: false}
|
|
|
|
sessions[id] = session
|
|
|
|
http.SetCookie(w, &http.Cookie{Name: "sessionid", Value: id})
|
|
|
|
}
|
|
|
|
return
|
|
|
|
}
|
|
|
|
|
|
|
|
func sessionWrap(inner func(http.ResponseWriter, *http.Request)) func(
|
|
|
|
http.ResponseWriter, *http.Request) {
|
|
|
|
return func(w http.ResponseWriter, r *http.Request) {
|
|
|
|
// We might also try no-cache with an ETag for the whole database,
|
|
|
|
// though I don't expect any substantial improvements of anything.
|
|
|
|
w.Header().Set("Cache-Control", "no-store")
|
|
|
|
|
2019-04-15 03:16:19 +02:00
|
|
|
redirect := "login"
|
2019-04-14 21:25:55 +02:00
|
|
|
if r.RequestURI != "/" && r.Method == http.MethodGet {
|
2019-04-13 22:50:08 +02:00
|
|
|
redirect += "?redirect=" + url.QueryEscape(r.RequestURI)
|
|
|
|
}
|
|
|
|
|
|
|
|
session := sessionGet(w, r)
|
|
|
|
if !session.LoggedIn {
|
|
|
|
http.Redirect(w, r, redirect, http.StatusSeeOther)
|
|
|
|
return
|
|
|
|
}
|
|
|
|
inner(w, r.WithContext(
|
|
|
|
context.WithValue(r.Context(), sessionContextKey{}, session)))
|
|
|
|
}
|
|
|
|
}
|