From 6ed9c0c34cd5f98b5769288d36b7c654e7ebb513 Mon Sep 17 00:00:00 2001
From: Jakob Borg <jakob@kastelo.net>
Date: Sun, 24 Sep 2023 19:23:49 +0200
Subject: [PATCH] lib/config: Accept pre-hashed password (fixes #9123) (#9124)

---
 cmd/syncthing/generate/generate.go |  4 ++--
 lib/api/api_auth_test.go           |  2 +-
 lib/api/confighandler.go           |  4 ++--
 lib/config/config_test.go          | 14 +++++++++++++-
 lib/config/guiconfiguration.go     | 17 ++++++++++++++---
 5 files changed, 32 insertions(+), 9 deletions(-)

diff --git a/cmd/syncthing/generate/generate.go b/cmd/syncthing/generate/generate.go
index 6b3d0b369..5446cb3ba 100644
--- a/cmd/syncthing/generate/generate.go
+++ b/cmd/syncthing/generate/generate.go
@@ -69,7 +69,7 @@ func Generate(l logger.Logger, confDir, guiUser, guiPassword string, noDefaultFo
 		return err
 	}
 
-	if err := syncthing.EnsureDir(dir, 0700); err != nil {
+	if err := syncthing.EnsureDir(dir, 0o700); err != nil {
 		return err
 	}
 	locations.SetBaseDir(locations.ConfigBaseDir, dir)
@@ -127,7 +127,7 @@ func updateGUIAuthentication(l logger.Logger, guiCfg *config.GUIConfiguration, g
 	}
 
 	if guiPassword != "" && guiCfg.Password != guiPassword {
-		if err := guiCfg.HashAndSetPassword(guiPassword); err != nil {
+		if err := guiCfg.SetPassword(guiPassword); err != nil {
 			return fmt.Errorf("failed to set GUI authentication password: %w", err)
 		}
 		l.Infoln("Updated GUI authentication password.")
diff --git a/lib/api/api_auth_test.go b/lib/api/api_auth_test.go
index be6a0c3a8..ed3677eeb 100644
--- a/lib/api/api_auth_test.go
+++ b/lib/api/api_auth_test.go
@@ -16,7 +16,7 @@ var guiCfg config.GUIConfiguration
 
 func init() {
 	guiCfg.User = "user"
-	guiCfg.HashAndSetPassword("pass")
+	guiCfg.SetPassword("pass")
 }
 
 func TestStaticAuthOK(t *testing.T) {
diff --git a/lib/api/confighandler.go b/lib/api/confighandler.go
index 5abc1f055..fc3e73a59 100644
--- a/lib/api/confighandler.go
+++ b/lib/api/confighandler.go
@@ -319,7 +319,7 @@ func (c *configMuxBuilder) adjustConfig(w http.ResponseWriter, r *http.Request)
 	var status int
 	waiter, err := c.cfg.Modify(func(cfg *config.Configuration) {
 		if to.GUI.Password != cfg.GUI.Password {
-			if err := to.GUI.HashAndSetPassword(to.GUI.Password); err != nil {
+			if err := to.GUI.SetPassword(to.GUI.Password); err != nil {
 				l.Warnln("hashing password:", err)
 				errMsg = err.Error()
 				status = http.StatusInternalServerError
@@ -401,7 +401,7 @@ func (c *configMuxBuilder) adjustGUI(w http.ResponseWriter, r *http.Request, gui
 	var status int
 	waiter, err := c.cfg.Modify(func(cfg *config.Configuration) {
 		if gui.Password != oldPassword {
-			if err := gui.HashAndSetPassword(gui.Password); err != nil {
+			if err := gui.SetPassword(gui.Password); err != nil {
 				l.Warnln("hashing password:", err)
 				errMsg = err.Error()
 				status = http.StatusInternalServerError
diff --git a/lib/config/config_test.go b/lib/config/config_test.go
index 241cc2b59..d90e01fb9 100644
--- a/lib/config/config_test.go
+++ b/lib/config/config_test.go
@@ -22,6 +22,7 @@ import (
 	"testing"
 
 	"github.com/d4l3k/messagediff"
+	"golang.org/x/crypto/bcrypt"
 
 	"github.com/syncthing/syncthing/lib/build"
 	"github.com/syncthing/syncthing/lib/events"
@@ -773,8 +774,9 @@ func TestGUIConfigURL(t *testing.T) {
 func TestGUIPasswordHash(t *testing.T) {
 	var c GUIConfiguration
 
+	// Setting a plaintext password should work
 	testPass := "pass"
-	if err := c.HashAndSetPassword(testPass); err != nil {
+	if err := c.SetPassword(testPass); err != nil {
 		t.Fatal(err)
 	}
 	if c.Password == testPass {
@@ -789,6 +791,16 @@ func TestGUIPasswordHash(t *testing.T) {
 	if err := c.CompareHashedPassword(failPass); err == nil {
 		t.Errorf("Match on different password: %v", err)
 	}
+
+	// Setting a bcrypt hash directly should also work
+	hash, err := bcrypt.GenerateFromPassword([]byte("test"), bcrypt.MinCost)
+	if err != nil {
+		t.Fatal(err)
+	}
+	c.SetPassword(string(hash))
+	if err := c.CompareHashedPassword("test"); err != nil {
+		t.Errorf("No match on hashed password: %v", err)
+	}
 }
 
 func TestDuplicateDevices(t *testing.T) {
diff --git a/lib/config/guiconfiguration.go b/lib/config/guiconfiguration.go
index cbedfffcb..9f5df227f 100644
--- a/lib/config/guiconfiguration.go
+++ b/lib/config/guiconfiguration.go
@@ -9,6 +9,7 @@ package config
 import (
 	"net/url"
 	"os"
+	"regexp"
 	"strconv"
 	"strings"
 
@@ -115,9 +116,19 @@ func (c GUIConfiguration) URL() string {
 	return u.String()
 }
 
-// SetHashedPassword hashes the given plaintext password and stores the new hash.
-func (c *GUIConfiguration) HashAndSetPassword(password string) error {
-	hash, err := bcrypt.GenerateFromPassword([]byte(password), 0)
+// matches a bcrypt hash and not too much else
+var bcryptExpr = regexp.MustCompile(`^\$2[aby]\$\d+\$.{50,}`)
+
+// SetPassword takes a bcrypt hash or a plaintext password and stores it.
+// Plaintext passwords are hashed. Returns an error if the password is not
+// valid.
+func (c *GUIConfiguration) SetPassword(password string) error {
+	if bcryptExpr.MatchString(password) {
+		// Already hashed
+		c.Password = password
+		return nil
+	}
+	hash, err := bcrypt.GenerateFromPassword([]byte(password), bcrypt.DefaultCost)
 	if err != nil {
 		return err
 	}