1 files changed, 116 insertions, 0 deletions
diff --git a/auth.go b/auth.go
new file mode 100644
index 0000000..601f28a
--- /dev/null
+++ b/auth.go
@@ -0,0 +1,116 @@
+package main
+
+import (
+	"context"
+	"database/sql"
+	"errors"
+	"log"
+	"net/http"
+	"net/url"
+
+	"golang.org/x/crypto/bcrypt"
+)
+
+const (
+	userContextKey   = "_user"
+	sessionDuration  = 86400 * 7 // 7 days
+	loginQueryMarker = "next"
+)
+
+func RequireAuth(next http.Handler) http.Handler {
+	return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		s := session(r)
+
+		if !s.s.IsNew && s.Authenticated {
+			u, err := Q.GetUserById(r.Context(), s.UserID)
+			if err == nil {
+				// authenticated --> done
+				ctx := context.WithValue(r.Context(), userContextKey, u.ID)
+				next.ServeHTTP(w, r.WithContext(ctx))
+				return
+			}
+
+			s.Invalidate()
+			s.Save(w, r)
+		}
+
+		// redirect to login with next-param
+		v := url.Values{}
+		v.Set(loginQueryMarker, r.URL.Path)
+		redirPath := "/login?" + v.Encode()
+		http.Redirect(w, r, redirPath, http.StatusFound)
+	})
+}
+
+func checkLogin(ctx context.Context, user User) (bool, int64) {
+	dbUser, err := Q.GetUserByName(ctx, user.Name)
+	if err == nil {
+		hash := []byte(dbUser.Pwd)
+		pwd := []byte(user.Password)
+
+		if bcrypt.CompareHashAndPassword(hash, pwd) != nil {
+			return false, 0
+		}
+	} else if errors.Is(err, sql.ErrNoRows) {
+		return false, 0
+	} else {
+		log.Panicf("Could not load user '%s': %v", user.Name, err)
+	}
+
+	return true, dbUser.ID
+}
+
+func handleLogin(w http.ResponseWriter, r *http.Request) {
+	u := User{}
+	parseForm(r, &u)
+
+	ok, userId := checkLogin(r.Context(), u)
+
+	if !ok {
+		u.Errors = []error{fieldError{"Password", "Invalid"}}
+		showLoginPage(w, u)
+		return
+	}
+
+	s := session(r)
+	if u.RememberMe {
+		s.MaxAge(sessionDuration) // 1 week
+	} else {
+		s.MaxAge(0)
+	}
+
+	s.UserID = userId
+	s.Authenticated = true
+	s.Save(w, r)
+
+	// redirect
+	next := r.URL.Query().Get(loginQueryMarker)
+	if next == "" {
+		next = "/"
+	}
+	http.Redirect(w, r, next, http.StatusFound)
+}
+
+func handleLogout() http.HandlerFunc {
+	return func(w http.ResponseWriter, r *http.Request) {
+		s := session(r)
+		s.Invalidate()
+		s.Save(w, r)
+
+		http.Redirect(w, r, "/", http.StatusFound)
+	}
+}
+
+func showLoginPage(w http.ResponseWriter, u User) {
+	showTemplate(w, "login", u)
+}
+
+func loginPage() http.HandlerFunc {
+	return func(w http.ResponseWriter, r *http.Request) {
+		showLoginPage(w, User{})
+	}
+}
+
+func userId(r *http.Request) int64 {
+	return r.Context().Value(userContextKey).(int64)
+}