Bring back the notepad

1 files changed, 251 insertions, 2 deletions

diff --git a/roseh.moe.go b/roseh.moe.go
index bf0a90b..78c0625 100644
--- a/roseh.moe.go
+++ b/roseh.moe.go
@@ -1,8 +1,13 @@
 package main
 
 import (
+	"bytes"
+	"crypto/hmac"
 	"crypto/rand"
+	"crypto/sha256"
+	"crypto/subtle"
 	"embed"
+	"encoding/base64"
 	"encoding/binary"
 	"flag"
 	"fmt"
@@ -10,18 +15,45 @@ import (
 	"io"
 	"log"
 	"net/http"
+	"os"
 	"strings"
 	"sync"
 	"time"
+
+	"gitlab.com/rhogenson/roseh.moe/internal/pwhash"
 )
 
 var (
-	port    = flag.Int("port", 42069, "port to listen on")
-	selfURL = flag.String("self-url", "http://localhost:42069", "base URL of the server")
+	port        = flag.Int("port", 42069, "port to listen on")
+	selfURL     = flag.String("self-url", "http://localhost:42069", "base URL of the server")
+	secretsFile = flag.String("secrets", "secrets", "secrets file")
 
 	serverStartTime = time.Now()
 )
 
+var notepadPassword, secretKey []byte
+
+func loadSecrets() error {
+	secrets, err := os.ReadFile(*secretsFile)
+	if err != nil {
+		return err
+	}
+	for _, line := range bytes.Split(bytes.TrimSuffix(secrets, []byte("\n")), []byte("\n")) {
+		if pw, ok := bytes.CutPrefix(line, []byte("notepad-password=")); ok {
+			notepadPassword, err = base64.RawURLEncoding.AppendDecode(nil, pw)
+			if err != nil {
+				return err
+			}
+		} else if key, ok := bytes.CutPrefix(line, []byte("secret-key=")); ok {
+			secretKey, err = base64.RawURLEncoding.AppendDecode(nil, key)
+			if err != nil {
+				return err
+			}
+		}
+	}
+	return nil
+}
+
 var (
 	//go:embed templates/404.html.template
 	notFoundString   string
@@ -215,14 +247,231 @@ func wormholeReady(w http.ResponseWriter, r *http.Request) {
 	fmt.Fprintf(w, "event: ready\ndata:\n\n")
 }
 
+func sign(msg []byte, info string) []byte {
+	mac := hmac.New(sha256.New, secretKey)
+	mac.Write(binary.AppendVarint(nil, int64(len(info))))
+	io.WriteString(mac, info)
+	mac.Write(msg)
+	return mac.Sum(msg)
+}
+
+func verify(msg []byte, info string) ([]byte, bool) {
+	if len(msg) < sha256.Size {
+		return nil, false
+	}
+	msg, messageMAC := msg[:len(msg)-sha256.Size], msg[len(msg)-sha256.Size:]
+	mac := hmac.New(sha256.New, secretKey)
+	mac.Write(binary.AppendVarint(nil, int64(len(info))))
+	io.WriteString(mac, info)
+	mac.Write(msg)
+	expectedMAC := mac.Sum(nil)
+	if !hmac.Equal(messageMAC, expectedMAC) {
+		return nil, false
+	}
+	return msg, true
+}
+
+func makeToken() (string, error) {
+	b, err := time.Now().MarshalBinary()
+	if err != nil {
+		return "", err
+	}
+	return base64.RawURLEncoding.EncodeToString(sign(b, "auth")), nil
+}
+
+const cookieExpiration = 180 * 24 * time.Hour
+
+func checkToken(token string) bool {
+	authCookie, err := base64.RawURLEncoding.DecodeString(token)
+	if err != nil {
+		return false
+	}
+	msg, ok := verify(authCookie, "auth")
+	if !ok {
+		return false
+	}
+	var t time.Time
+	if err := t.UnmarshalBinary(msg); err != nil {
+		return false
+	}
+	return time.Since(t) < cookieExpiration
+}
+
+func attachCookie(w http.ResponseWriter) error {
+	token, err := makeToken()
+	if err != nil {
+		return err
+	}
+	http.SetCookie(w, &http.Cookie{
+		Name:        "auth",
+		Value:       token,
+		Path:        "/",
+		Expires:     time.Now().Add(cookieExpiration),
+		Secure:      true,
+		HttpOnly:    true,
+		SameSite:    http.SameSiteStrictMode,
+		Partitioned: true,
+	})
+	return nil
+}
+
+func cookieAuth(w http.ResponseWriter, r *http.Request) (string, bool) {
+	const csrfTokenLen = 32
+	var csrfToken string
+	if csrfCookie, err := r.Cookie("csrf-token"); err == nil {
+		csrfToken = csrfCookie.Value
+	} else {
+		buf := make([]byte, csrfTokenLen)
+		rand.Read(buf)
+		csrfToken = base64.RawURLEncoding.EncodeToString(buf)
+		http.SetCookie(w, &http.Cookie{
+			Name:        "csrf-token",
+			Value:       csrfToken,
+			Path:        "/",
+			Secure:      true,
+			HttpOnly:    true,
+			SameSite:    http.SameSiteStrictMode,
+			Partitioned: true,
+		})
+	}
+
+	cookie, err := r.Cookie("auth")
+	if err != nil {
+		return csrfToken, false
+	}
+	if !checkToken(cookie.Value) {
+		return csrfToken, false
+	}
+	attachCookie(w)
+	return csrfToken, true
+}
+
+func checkCSRFToken(r *http.Request) error {
+	cookie, err := r.Cookie("csrf-token")
+	if err != nil {
+		return err
+	}
+	cookieHash := sha256.Sum256([]byte(cookie.Value))
+	formValueHash := sha256.Sum256([]byte(r.FormValue("csrf-token")))
+	if subtle.ConstantTimeCompare(cookieHash[:], formValueHash[:]) == 0 {
+		return fmt.Errorf("bad CSRF token")
+	}
+	return nil
+}
+
+var (
+	//go:embed templates/login.html.template
+	loginTemplateString string
+	loginTemplate       = template.Must(template.Must(outlineTemplate.Clone()).New("body").Parse(loginTemplateString)).Lookup("outline")
+)
+
+type loginTemplateArgs struct {
+	CSRFToken string
+	Redirect  string
+	Error     bool
+}
+
+func executeLoginTemplate(w io.Writer, csrfToken, redirect string) {
+	if err := loginTemplate.Execute(w, loginTemplateArgs{
+		Redirect:  base64.RawURLEncoding.EncodeToString(sign([]byte(redirect), "redirect")),
+		CSRFToken: csrfToken,
+	}); err != nil {
+		log.Printf("Warning: login: %s", err)
+	}
+}
+
+func login(w http.ResponseWriter, r *http.Request) {
+	if err := checkCSRFToken(r); err != nil {
+		http.Error(w, "bad CSRF token", http.StatusBadRequest)
+		return
+	}
+	if err := pwhash.Check(notepadPassword, r.FormValue("password")); err != nil {
+		if err := loginTemplate.Execute(w, loginTemplateArgs{
+			Error:     true,
+			Redirect:  r.FormValue("redirect"),
+			CSRFToken: r.FormValue("csrf-token"),
+		}); err != nil {
+			log.Printf("Warning: login: %s", err)
+		}
+		return
+	}
+	attachCookie(w)
+	redirect := "/"
+	if b, err := base64.RawURLEncoding.DecodeString(r.FormValue("redirect")); err == nil {
+		if r, ok := verify(b, "redirect"); ok {
+			redirect = string(r)
+		}
+	}
+	http.Redirect(w, r, redirect, http.StatusSeeOther)
+}
+
+var (
+	//go:embed templates/note.html.template
+	notepadString   string
+	notepadTemplate = template.Must(template.Must(outlineTemplate.Clone()).New("body").Parse(notepadString)).Lookup("outline")
+
+	notepadContentsMu sync.Mutex
+	notepadContents   string
+)
+
+type notepadTemplateArgs struct {
+	Content   string
+	CSRFToken string
+}
+
+func notepad(w http.ResponseWriter, r *http.Request) {
+	csrfToken, ok := cookieAuth(w, r)
+	if !ok {
+		executeLoginTemplate(w, csrfToken, "/notepad")
+		return
+	}
+	notepadContentsMu.Lock()
+	currentContent := notepadContents
+	notepadContentsMu.Unlock()
+	if err := notepadTemplate.Execute(w, notepadTemplateArgs{Content: currentContent, CSRFToken: csrfToken}); err != nil {
+		log.Printf("Warning: notepad: %s", err)
+	}
+}
+
+func saveNote(w http.ResponseWriter, r *http.Request) error {
+	if err := checkCSRFToken(r); err != nil {
+		return err
+	}
+	if _, ok := cookieAuth(w, r); !ok {
+		return fmt.Errorf("not logged in")
+	}
+	newContent := r.FormValue("content")
+	notepadContentsMu.Lock()
+	notepadContents = newContent
+	notepadContentsMu.Unlock()
+	return nil
+}
+
+func autosave(w http.ResponseWriter, r *http.Request) {
+	msg := "Saved ✓"
+	if err := saveNote(w, r); err != nil {
+		msg = fmt.Sprintf("Failed to save: %s", err)
+	}
+	if err := notepadTemplate.ExecuteTemplate(w, "saveIndicator", msg); err != nil {
+		log.Printf("Warning: autosave: %s", err)
+	}
+}
+
 func main() {
 	flag.Parse()
 
+	if err := loadSecrets(); err != nil {
+		log.Fatal(err)
+	}
+
 	http.HandleFunc("GET /pong", pong)
 	http.HandleFunc("GET /wormhole", wormhole)
 	http.HandleFunc("POST /wormhole/{hole}", wormholeSend)
 	http.HandleFunc("GET /wormhole/{hole}", wormholeRecv)
 	http.HandleFunc("GET /wormhole/{hole}/ready", wormholeReady)
+	http.HandleFunc("POST /login", login)
+	http.HandleFunc("GET /notepad", notepad)
+	http.HandleFunc("POST /notepad", autosave)
 	http.HandleFunc("GET /static/", static)
 	http.HandleFunc("GET /favicon.ico", favicon)
 	http.HandleFunc("GET /{$}", index)