Make bcrypt cost configurable (#1793)

cmd/create-account/main.go

@@ -24,6 +24,7 @@ import (
 	"github.com/matrix-org/dendrite/setup/config"
 	"github.com/matrix-org/dendrite/userapi/storage/accounts"
 	"github.com/sirupsen/logrus"
+	"golang.org/x/crypto/bcrypt"
 )
 
 const usage = `Usage: %s
@@ -57,7 +58,7 @@ func main() {
 
 	accountDB, err := accounts.NewDatabase(&config.DatabaseOptions{
 		ConnectionString: cfg.UserAPI.AccountDatabase.ConnectionString,
-	}, cfg.Global.ServerName)
+	}, cfg.Global.ServerName, bcrypt.DefaultCost)
 	if err != nil {
 		logrus.Fatalln("Failed to connect to the database:", err.Error())
 	}

cmd/generate-config/main.go

@@ -5,6 +5,7 @@ import (
 	"fmt"
 
 	"github.com/matrix-org/dendrite/setup/config"
+	"golang.org/x/crypto/bcrypt"
 	"gopkg.in/yaml.v2"
 )
 
@@ -68,6 +69,7 @@ func main() {
 		cfg.Logging[0].Level = "trace"
 		// don't hit matrix.org when running tests!!!
 		cfg.SigningKeyServer.KeyPerspectives = config.KeyPerspectives{}
+		cfg.UserAPI.BCryptCost = bcrypt.MinCost
 	}
 
 	j, err := yaml.Marshal(cfg)

dendrite-config.yaml

@@ -340,6 +340,13 @@ sync_api:
 
 # Configuration for the User API.
 user_api:
+  # The cost when hashing passwords on registration/login. Default: 10. Min: 4, Max: 31
+  # See https://pkg.go.dev/golang.org/x/crypto/bcrypt for more information.
+  # Setting this lower makes registration/login consume less CPU resources at the cost of security
+  # should the database be compromised. Setting this higher makes registration/login consume more
+  # CPU resources but makes it harder to brute force password hashes.
+  # This value can be low if performing tests or on embedded Dendrite instances (e.g WASM builds)
+  # bcrypt_cost: 10
   internal_api:
     listen: http://localhost:7781
     connect: http://localhost:7781

setup/base.go

@@ -263,7 +263,7 @@ func (b *BaseDendrite) KeyServerHTTPClient() keyserverAPI.KeyInternalAPI {
 // CreateAccountsDB creates a new instance of the accounts database. Should only
 // be called once per component.
 func (b *BaseDendrite) CreateAccountsDB() accounts.Database {
-	db, err := accounts.NewDatabase(&b.Cfg.UserAPI.AccountDatabase, b.Cfg.Global.ServerName)
+	db, err := accounts.NewDatabase(&b.Cfg.UserAPI.AccountDatabase, b.Cfg.Global.ServerName, b.Cfg.UserAPI.BCryptCost)
 	if err != nil {
 		logrus.WithError(err).Panicf("failed to connect to accounts db")
 	}

setup/config/config_userapi.go

@@ -1,10 +1,15 @@
 package config
 
+import "golang.org/x/crypto/bcrypt"
+
 type UserAPI struct {
 	Matrix *Global `yaml:"-"`
 
 	InternalAPI InternalAPIOptions `yaml:"internal_api"`
 
+	// The cost when hashing passwords.
+	BCryptCost int `yaml:"bcrypt_cost"`
+
 	// The Account database stores the login details and account information
 	// for local users. It is accessed by the UserAPI.
 	AccountDatabase DatabaseOptions `yaml:"account_database"`
@@ -20,6 +25,7 @@ func (c *UserAPI) Defaults() {
 	c.DeviceDatabase.Defaults(10)
 	c.AccountDatabase.ConnectionString = "file:userapi_accounts.db"
 	c.DeviceDatabase.ConnectionString = "file:userapi_devices.db"
+	c.BCryptCost = bcrypt.DefaultCost
 }
 
 func (c *UserAPI) Verify(configErrs *ConfigErrors, isMonolith bool) {

userapi/storage/accounts/postgres/storage.go

@@ -44,10 +44,11 @@ type Database struct {
 	accountDatas accountDataStatements
 	threepids    threepidStatements
 	serverName   gomatrixserverlib.ServerName
+	bcryptCost   int
 }
 
 // NewDatabase creates a new accounts and profiles database
-func NewDatabase(dbProperties *config.DatabaseOptions, serverName gomatrixserverlib.ServerName) (*Database, error) {
+func NewDatabase(dbProperties *config.DatabaseOptions, serverName gomatrixserverlib.ServerName, bcryptCost int) (*Database, error) {
 	db, err := sqlutil.Open(dbProperties)
 	if err != nil {
 		return nil, err
@@ -56,6 +57,7 @@ func NewDatabase(dbProperties *config.DatabaseOptions, serverName gomatrixserver
 		serverName: serverName,
 		db:         db,
 		writer:     sqlutil.NewDummyWriter(),
+		bcryptCost: bcryptCost,
 	}
 
 	// Create tables before executing migrations so we don't fail if the table is missing,
@@ -131,7 +133,7 @@ func (d *Database) SetDisplayName(
 func (d *Database) SetPassword(
 	ctx context.Context, localpart, plaintextPassword string,
 ) error {
-	hash, err := hashPassword(plaintextPassword)
+	hash, err := d.hashPassword(plaintextPassword)
 	if err != nil {
 		return err
 	}
@@ -175,7 +177,7 @@ func (d *Database) createAccount(
 	// Generate a password hash if this is not a password-less user
 	hash := ""
 	if plaintextPassword != "" {
-		hash, err = hashPassword(plaintextPassword)
+		hash, err = d.hashPassword(plaintextPassword)
 		if err != nil {
 			return nil, err
 		}
@@ -246,8 +248,8 @@ func (d *Database) GetNewNumericLocalpart(
 	return d.accounts.selectNewNumericLocalpart(ctx, nil)
 }
 
-func hashPassword(plaintext string) (hash string, err error) {
+func (d *Database) hashPassword(plaintext string) (hash string, err error) {
-	hashBytes, err := bcrypt.GenerateFromPassword([]byte(plaintext), bcrypt.DefaultCost)
+	hashBytes, err := bcrypt.GenerateFromPassword([]byte(plaintext), d.bcryptCost)
 	return string(hashBytes), err
 }
 

userapi/storage/accounts/sqlite3/storage.go

@@ -42,6 +42,7 @@ type Database struct {
 	accountDatas accountDataStatements
 	threepids    threepidStatements
 	serverName   gomatrixserverlib.ServerName
+	bcryptCost   int
 
 	accountsMu     sync.Mutex
 	profilesMu     sync.Mutex
@@ -50,7 +51,7 @@ type Database struct {
 }
 
 // NewDatabase creates a new accounts and profiles database
-func NewDatabase(dbProperties *config.DatabaseOptions, serverName gomatrixserverlib.ServerName) (*Database, error) {
+func NewDatabase(dbProperties *config.DatabaseOptions, serverName gomatrixserverlib.ServerName, bcryptCost int) (*Database, error) {
 	db, err := sqlutil.Open(dbProperties)
 	if err != nil {
 		return nil, err
@@ -59,6 +60,7 @@ func NewDatabase(dbProperties *config.DatabaseOptions, serverName gomatrixserver
 		serverName: serverName,
 		db:         db,
 		writer:     sqlutil.NewExclusiveWriter(),
+		bcryptCost: bcryptCost,
 	}
 
 	// Create tables before executing migrations so we don't fail if the table is missing,
@@ -143,7 +145,7 @@ func (d *Database) SetDisplayName(
 func (d *Database) SetPassword(
 	ctx context.Context, localpart, plaintextPassword string,
 ) error {
-	hash, err := hashPassword(plaintextPassword)
+	hash, err := d.hashPassword(plaintextPassword)
 	if err != nil {
 		return err
 	}
@@ -208,7 +210,7 @@ func (d *Database) createAccount(
 	// Generate a password hash if this is not a password-less user
 	hash := ""
 	if plaintextPassword != "" {
-		hash, err = hashPassword(plaintextPassword)
+		hash, err = d.hashPassword(plaintextPassword)
 		if err != nil {
 			return nil, err
 		}
@@ -278,8 +280,8 @@ func (d *Database) GetNewNumericLocalpart(
 	return d.accounts.selectNewNumericLocalpart(ctx, nil)
 }
 
-func hashPassword(plaintext string) (hash string, err error) {
+func (d *Database) hashPassword(plaintext string) (hash string, err error) {
-	hashBytes, err := bcrypt.GenerateFromPassword([]byte(plaintext), bcrypt.DefaultCost)
+	hashBytes, err := bcrypt.GenerateFromPassword([]byte(plaintext), d.bcryptCost)
 	return string(hashBytes), err
 }
 

userapi/storage/accounts/storage.go

@@ -27,12 +27,12 @@ import (
 
 // NewDatabase opens a new Postgres or Sqlite database (based on dataSourceName scheme)
 // and sets postgres connection parameters
-func NewDatabase(dbProperties *config.DatabaseOptions, serverName gomatrixserverlib.ServerName) (Database, error) {
+func NewDatabase(dbProperties *config.DatabaseOptions, serverName gomatrixserverlib.ServerName, bcryptCost int) (Database, error) {
 	switch {
 	case dbProperties.ConnectionString.IsSQLite():
-		return sqlite3.NewDatabase(dbProperties, serverName)
+		return sqlite3.NewDatabase(dbProperties, serverName, bcryptCost)
 	case dbProperties.ConnectionString.IsPostgres():
-		return postgres.NewDatabase(dbProperties, serverName)
+		return postgres.NewDatabase(dbProperties, serverName, bcryptCost)
 	default:
 		return nil, fmt.Errorf("unexpected database type")
 	}

userapi/storage/accounts/storage_wasm.go

@@ -25,10 +25,11 @@ import (
 func NewDatabase(
 	dbProperties *config.DatabaseOptions,
 	serverName gomatrixserverlib.ServerName,
+	bcryptCost int,
 ) (Database, error) {
 	switch {
 	case dbProperties.ConnectionString.IsSQLite():
-		return sqlite3.NewDatabase(dbProperties, serverName)
+		return sqlite3.NewDatabase(dbProperties, serverName, bcryptCost)
 	case dbProperties.ConnectionString.IsPostgres():
 		return nil, fmt.Errorf("can't use Postgres implementation")
 	default:

userapi/userapi.go

@@ -37,7 +37,6 @@ func AddInternalRoutes(router *mux.Router, intAPI api.UserInternalAPI) {
 func NewInternalAPI(
 	accountDB accounts.Database, cfg *config.UserAPI, appServices []config.ApplicationService, keyAPI keyapi.KeyInternalAPI,
 ) api.UserInternalAPI {
-
 	deviceDB, err := devices.NewDatabase(&cfg.DeviceDatabase, cfg.Matrix.ServerName)
 	if err != nil {
 		logrus.WithError(err).Panicf("failed to connect to device db")

userapi/userapi_test.go

@@ -16,6 +16,7 @@ import (
 	"github.com/matrix-org/dendrite/userapi/inthttp"
 	"github.com/matrix-org/dendrite/userapi/storage/accounts"
 	"github.com/matrix-org/gomatrixserverlib"
+	"golang.org/x/crypto/bcrypt"
 )
 
 const (
@@ -25,7 +26,7 @@ const (
 func MustMakeInternalAPI(t *testing.T) (api.UserInternalAPI, accounts.Database) {
 	accountDB, err := accounts.NewDatabase(&config.DatabaseOptions{
 		ConnectionString: "file::memory:",
-	}, serverName)
+	}, serverName, bcrypt.MinCost)
 	if err != nil {
 		t.Fatalf("failed to create account DB: %s", err)
 	}