MySQL - Add username customization (#10834)

plugins/database/mysql/connection_producer.go

@@ -37,7 +37,6 @@ type mySQLConnectionProducer struct {
 
 	RawConfig             map[string]interface{}
 	maxConnectionLifetime time.Duration
-	Legacy                bool
 	Initialized           bool
 	db                    *sql.DB
 	sync.Mutex

plugins/database/mysql/connection_producer_test.go

@@ -124,7 +124,7 @@ ssl-key=/etc/mysql/server-key.pem`
 
 	// //////////////////////////////////////////////////////
 	// Test
-	mysql := newMySQL(MetadataLen, MetadataLen, UsernameLen)
+	mysql := newMySQL(DefaultUserNameTemplate)
 
 	conf := map[string]interface{}{
 		"connection_url":      retURL,

plugins/database/mysql/mysql-database-plugin/main.go

@@ -19,7 +19,7 @@ func main() {
 // Run instantiates a MySQL object, and runs the RPC server for the plugin
 func Run() error {
 	var f func() (interface{}, error)
-	f = mysql.New(mysql.MetadataLen, mysql.MetadataLen, mysql.UsernameLen)
+	f = mysql.New(mysql.DefaultUserNameTemplate)
 	dbType, err := f()
 	if err != nil {
 		return err

plugins/database/mysql/mysql-legacy-database-plugin/main.go

@@ -6,7 +6,6 @@ import (
 
 	"github.com/hashicorp/vault/plugins/database/mysql"
 	dbplugin "github.com/hashicorp/vault/sdk/database/dbplugin/v5"
-	"github.com/hashicorp/vault/sdk/database/helper/credsutil"
 )
 
 func main() {
@@ -20,7 +19,7 @@ func main() {
 // Run instantiates a MySQL object, and runs the RPC server for the plugin
 func Run() error {
 	var f func() (interface{}, error)
-	f = mysql.New(credsutil.NoneLength, mysql.LegacyMetadataLen, mysql.LegacyUsernameLen)
+	f = mysql.New(mysql.DefaultLegacyUserNameTemplate)
 	dbType, err := f()
 	if err != nil {
 		return err

plugins/database/mysql/mysql.go

@@ -8,11 +8,10 @@ import (
 	"strings"
 
 	stdmysql "github.com/go-sql-driver/mysql"
-	"github.com/hashicorp/errwrap"
 	dbplugin "github.com/hashicorp/vault/sdk/database/dbplugin/v5"
-	"github.com/hashicorp/vault/sdk/database/helper/credsutil"
 	"github.com/hashicorp/vault/sdk/database/helper/dbutil"
 	"github.com/hashicorp/vault/sdk/helper/strutil"
+	"github.com/hashicorp/vault/sdk/helper/template"
 )
 
 const (
@@ -26,13 +25,9 @@ const (
 	`
 
 	mySQLTypeName = "mysql"
-)
 
-var (
-	MetadataLen       int = 10
-	LegacyMetadataLen int = 4
-	UsernameLen       int = 32
-	LegacyUsernameLen int = 16
+	DefaultUserNameTemplate       = `{{ printf "v-%s-%s-%s-%s" (.DisplayName | truncate 10) (.RoleName | truncate 10) (random 20) (unix_time) | truncate 32 }}`
+	DefaultLegacyUserNameTemplate = `{{ printf "v-%s-%s-%s" (.RoleName | truncate 4) (random 20) | truncate 16 }}`
 )
 
 var _ dbplugin.Database = (*MySQL)(nil)
@@ -40,15 +35,17 @@ var _ dbplugin.Database = (*MySQL)(nil)
 type MySQL struct {
 	*mySQLConnectionProducer
 
-	displayNameLen int
-	roleNameLen    int
-	maxUsernameLen int
+	usernameProducer        template.StringTemplate
+	defaultUsernameTemplate string
 }
 
 // New implements builtinplugins.BuiltinFactory
-func New(displayNameLen int, roleNameLen int, maxUsernameLen int) func() (interface{}, error) {
+func New(defaultUsernameTemplate string) func() (interface{}, error) {
 	return func() (interface{}, error) {
-		db := newMySQL(displayNameLen, roleNameLen, maxUsernameLen)
+		if defaultUsernameTemplate == "" {
+			return nil, fmt.Errorf("missing default username template")
+		}
+		db := newMySQL(defaultUsernameTemplate)
 		// Wrap the plugin with middleware to sanitize errors
 		dbType := dbplugin.NewDatabaseErrorSanitizerMiddleware(db, db.SecretValues)
 
@@ -56,14 +53,12 @@ func New(displayNameLen int, roleNameLen int, maxUsernameLen int) func() (interf
 	}
 }
 
-func newMySQL(displayNameLen int, roleNameLen int, maxUsernameLen int) *MySQL {
+func newMySQL(defaultUsernameTemplate string) *MySQL {
 	connProducer := &mySQLConnectionProducer{}
 
 	return &MySQL{
 		mySQLConnectionProducer: connProducer,
-		displayNameLen:          displayNameLen,
-		roleNameLen:             roleNameLen,
-		maxUsernameLen:          maxUsernameLen,
+		defaultUsernameTemplate: defaultUsernameTemplate,
 	}
 }
 
@@ -81,13 +76,36 @@ func (m *MySQL) getConnection(ctx context.Context) (*sql.DB, error) {
 }
 
 func (m *MySQL) Initialize(ctx context.Context, req dbplugin.InitializeRequest) (dbplugin.InitializeResponse, error) {
-	err := m.mySQLConnectionProducer.Initialize(ctx, req.Config, req.VerifyConnection)
+	usernameTemplate, err := strutil.GetString(req.Config, "username_template")
 	if err != nil {
 		return dbplugin.InitializeResponse{}, err
 	}
+
+	if usernameTemplate == "" {
+		usernameTemplate = m.defaultUsernameTemplate
+	}
+
+	up, err := template.NewTemplate(template.Template(usernameTemplate))
+	if err != nil {
+		return dbplugin.InitializeResponse{}, fmt.Errorf("unable to initialize username template: %w", err)
+	}
+
+	m.usernameProducer = up
+
+	_, err = m.usernameProducer.Generate(dbplugin.UsernameMetadata{})
+	if err != nil {
+		return dbplugin.InitializeResponse{}, fmt.Errorf("invalid username template: %w", err)
+	}
+
+	err = m.mySQLConnectionProducer.Initialize(ctx, req.Config, req.VerifyConnection)
+	if err != nil {
+		return dbplugin.InitializeResponse{}, err
+	}
+
 	resp := dbplugin.InitializeResponse{
 		Config: req.Config,
 	}
+
 	return resp, nil
 }
 
@@ -96,7 +114,7 @@ func (m *MySQL) NewUser(ctx context.Context, req dbplugin.NewUserRequest) (dbplu
 		return dbplugin.NewUserResponse{}, dbutil.ErrEmptyCreationStatement
 	}
 
-	username, err := m.generateUsername(req)
+	username, err := m.usernameProducer.Generate(req.UsernameConfig)
 	if err != nil {
 		return dbplugin.NewUserResponse{}, err
 	}
@@ -122,19 +140,6 @@ func (m *MySQL) NewUser(ctx context.Context, req dbplugin.NewUserRequest) (dbplu
 	return resp, nil
 }
 
-func (m *MySQL) generateUsername(req dbplugin.NewUserRequest) (string, error) {
-	username, err := credsutil.GenerateUsername(
-		credsutil.DisplayName(req.UsernameConfig.DisplayName, m.displayNameLen),
-		credsutil.RoleName(req.UsernameConfig.RoleName, m.roleNameLen),
-		credsutil.MaxLength(m.maxUsernameLen),
-	)
-	if err != nil {
-		return "", errwrap.Wrapf("error generating username: {{err}}", err)
-	}
-
-	return username, nil
-}
-
 func (m *MySQL) DeleteUser(ctx context.Context, req dbplugin.DeleteUserRequest) (dbplugin.DeleteUserResponse, error) {
 	// Grab the read lock
 	m.Lock()

plugins/database/mysql/mysql_test.go

@@ -3,6 +3,7 @@ package mysql
 import (
 	"context"
 	"database/sql"
+	"fmt"
 	"strings"
 	"testing"
 	"time"
@@ -10,213 +11,465 @@ import (
 	stdmysql "github.com/go-sql-driver/mysql"
 	mysqlhelper "github.com/hashicorp/vault/helper/testhelpers/mysql"
 	dbplugin "github.com/hashicorp/vault/sdk/database/dbplugin/v5"
+	dbtesting "github.com/hashicorp/vault/sdk/database/dbplugin/v5/testing"
 	"github.com/hashicorp/vault/sdk/database/helper/credsutil"
 	"github.com/hashicorp/vault/sdk/database/helper/dbutil"
 	"github.com/hashicorp/vault/sdk/helper/strutil"
+	"github.com/stretchr/testify/require"
 )
 
 var _ dbplugin.Database = (*MySQL)(nil)
 
 func TestMySQL_Initialize(t *testing.T) {
-	cleanup, connURL := mysqlhelper.PrepareTestContainer(t, false, "secret")
-	defer cleanup()
-
-	connectionDetails := map[string]interface{}{
-		"connection_url": connURL,
-	}
-
-	initReq := dbplugin.InitializeRequest{
-		Config:           connectionDetails,
-		VerifyConnection: true,
-	}
-
-	db := newMySQL(MetadataLen, MetadataLen, UsernameLen)
-	_, err := db.Initialize(context.Background(), initReq)
-	if err != nil {
-		t.Fatalf("err: %s", err)
-	}
-
-	if !db.Initialized {
-		t.Fatal("Database should be initialized")
-	}
-
-	err = db.Close()
-	if err != nil {
-		t.Fatalf("err: %s", err)
-	}
-
-	// Test decoding a string value for max_open_connections
-	connectionDetails = map[string]interface{}{
-		"connection_url":       connURL,
-		"max_open_connections": "5",
-	}
-
-	initReq = dbplugin.InitializeRequest{
-		Config:           connectionDetails,
-		VerifyConnection: true,
-	}
-
-	db = newMySQL(MetadataLen, MetadataLen, UsernameLen)
-	_, err = db.Initialize(context.Background(), initReq)
-	if err != nil {
-		t.Fatalf("err: %s", err)
-	}
-}
-
-func TestMySQL_CreateUser(t *testing.T) {
-	t.Run("missing creation statements", func(t *testing.T) {
-		db := newMySQL(MetadataLen, MetadataLen, UsernameLen)
-
-		password, err := credsutil.RandomAlphaNumeric(32, false)
-		if err != nil {
-			t.Fatalf("unable to generate password: %s", err)
-		}
-
-		createReq := dbplugin.NewUserRequest{
-			UsernameConfig: dbplugin.UsernameMetadata{
-				DisplayName: "test",
-				RoleName:    "test",
-			},
-			Statements: dbplugin.Statements{
-				Commands: []string{},
-			},
-			Password:   password,
-			Expiration: time.Now().Add(time.Minute),
-		}
-
-		userResp, err := db.NewUser(context.Background(), createReq)
-		if err == nil {
-			t.Fatalf("expected err, got nil")
-		}
-		if userResp.Username != "" {
-			t.Fatalf("expected empty username, got [%s]", userResp.Username)
-		}
-	})
-
-	t.Run("non-legacy", func(t *testing.T) {
-		// Shared test container for speed - there should not be any overlap between the tests
-		cleanup, connURL := mysqlhelper.PrepareTestContainer(t, false, "secret")
-		defer cleanup()
-
-		connectionDetails := map[string]interface{}{
-			"connection_url": connURL,
-		}
-
-		initReq := dbplugin.InitializeRequest{
-			Config:           connectionDetails,
-			VerifyConnection: true,
-		}
-
-		db := newMySQL(MetadataLen, MetadataLen, UsernameLen)
-		_, err := db.Initialize(context.Background(), initReq)
-		if err != nil {
-			t.Fatalf("err: %s", err)
-		}
-
-		testCreateUser(t, db, connURL)
-	})
-
-	t.Run("legacy", func(t *testing.T) {
-		// Shared test container for speed - there should not be any overlap between the tests
-		cleanup, connURL := mysqlhelper.PrepareTestContainer(t, true, "secret")
-		defer cleanup()
-
-		connectionDetails := map[string]interface{}{
-			"connection_url": connURL,
-		}
-
-		initReq := dbplugin.InitializeRequest{
-			Config:           connectionDetails,
-			VerifyConnection: true,
-		}
-
-		db := newMySQL(credsutil.NoneLength, LegacyMetadataLen, LegacyUsernameLen)
-		_, err := db.Initialize(context.Background(), initReq)
-		if err != nil {
-			t.Fatalf("err: %s", err)
-		}
-
-		testCreateUser(t, db, connURL)
-	})
-}
-
-func testCreateUser(t *testing.T, db *MySQL, connURL string) {
 	type testCase struct {
-		createStmts []string
+		rootPassword string
 	}
 
 	tests := map[string]testCase{
-		"create name": {
-			createStmts: []string{`
-				CREATE USER '{{name}}'@'%' IDENTIFIED BY '{{password}}';
-				GRANT SELECT ON *.* TO '{{name}}'@'%';`,
-			},
+		"non-special characters in root password": {
+			rootPassword: "B44a30c4C04D0aAaE140",
 		},
-		"create username": {
-			createStmts: []string{`
-				CREATE USER '{{username}}'@'%' IDENTIFIED BY '{{password}}';
-				GRANT SELECT ON *.* TO '{{username}}'@'%';`,
-			},
-		},
-		"prepared statement name": {
-			createStmts: []string{`
-				CREATE USER '{{name}}'@'%' IDENTIFIED BY '{{password}}';
-				set @grants=CONCAT("GRANT SELECT ON ", "*", ".* TO '{{name}}'@'%'");
-				PREPARE grantStmt from @grants;
-				EXECUTE grantStmt;
-				DEALLOCATE PREPARE grantStmt;
-				`,
-			},
-		},
-		"prepared statement username": {
-			createStmts: []string{`
-				CREATE USER '{{username}}'@'%' IDENTIFIED BY '{{password}}';
-				set @grants=CONCAT("GRANT SELECT ON ", "*", ".* TO '{{username}}'@'%'");
-				PREPARE grantStmt from @grants;
-				EXECUTE grantStmt;
-				DEALLOCATE PREPARE grantStmt;
-				`,
-			},
+		"special characters in root password": {
+			rootPassword: "#secret!%25#{@}",
 		},
 	}
 
 	for name, test := range tests {
 		t.Run(name, func(t *testing.T) {
-			password, err := credsutil.RandomAlphaNumeric(32, false)
-			if err != nil {
-				t.Fatalf("unable to generate password: %s", err)
-			}
+			testInitialize(t, test.rootPassword)
+		})
+	}
+}
 
-			createReq := dbplugin.NewUserRequest{
+func testInitialize(t *testing.T, rootPassword string) {
+	cleanup, connURL := mysqlhelper.PrepareTestContainer(t, false, rootPassword)
+	defer cleanup()
+
+	mySQLConfig, err := stdmysql.ParseDSN(connURL)
+	if err != nil {
+		panic(fmt.Sprintf("Test failure: connection URL is invalid: %s", err))
+	}
+	rootUser := mySQLConfig.User
+	mySQLConfig.User = "{{username}}"
+	mySQLConfig.Passwd = "{{password}}"
+	tmplConnURL := mySQLConfig.FormatDSN()
+
+	type testCase struct {
+		initRequest  dbplugin.InitializeRequest
+		expectedResp dbplugin.InitializeResponse
+
+		expectErr         bool
+		expectInitialized bool
+	}
+
+	tests := map[string]testCase{
+		"missing connection_url": {
+			initRequest: dbplugin.InitializeRequest{
+				Config:           map[string]interface{}{},
+				VerifyConnection: true,
+			},
+			expectedResp:      dbplugin.InitializeResponse{},
+			expectErr:         true,
+			expectInitialized: false,
+		},
+		"basic config": {
+			initRequest: dbplugin.InitializeRequest{
+				Config: map[string]interface{}{
+					"connection_url": connURL,
+				},
+				VerifyConnection: true,
+			},
+			expectedResp: dbplugin.InitializeResponse{
+				Config: map[string]interface{}{
+					"connection_url": connURL,
+				},
+			},
+			expectErr:         false,
+			expectInitialized: true,
+		},
+		"username and password replacement in connection_url": {
+			initRequest: dbplugin.InitializeRequest{
+				Config: map[string]interface{}{
+					"connection_url": tmplConnURL,
+					"username":       rootUser,
+					"password":       rootPassword,
+				},
+				VerifyConnection: true,
+			},
+			expectedResp: dbplugin.InitializeResponse{
+				Config: map[string]interface{}{
+					"connection_url": tmplConnURL,
+					"username":       rootUser,
+					"password":       rootPassword,
+				},
+			},
+			expectErr:         false,
+			expectInitialized: true,
+		},
+		"invalid username template": {
+			initRequest: dbplugin.InitializeRequest{
+				Config: map[string]interface{}{
+					"connection_url":    connURL,
+					"username_template": "{{.FieldThatDoesNotExist}}",
+				},
+				VerifyConnection: true,
+			},
+			expectedResp:      dbplugin.InitializeResponse{},
+			expectErr:         true,
+			expectInitialized: false,
+		},
+		"bad username template": {
+			initRequest: dbplugin.InitializeRequest{
+				Config: map[string]interface{}{
+					"connection_url":    connURL,
+					"username_template": "{{ .DisplayName", // Explicitly bad template
+				},
+				VerifyConnection: true,
+			},
+			expectedResp:      dbplugin.InitializeResponse{},
+			expectErr:         true,
+			expectInitialized: false,
+		},
+		"custom username template": {
+			initRequest: dbplugin.InitializeRequest{
+				Config: map[string]interface{}{
+					"connection_url":    connURL,
+					"username_template": "foo-{{random 10}}-{{.DisplayName}}",
+				},
+				VerifyConnection: true,
+			},
+			expectedResp: dbplugin.InitializeResponse{
+				Config: map[string]interface{}{
+					"connection_url":    connURL,
+					"username_template": "foo-{{random 10}}-{{.DisplayName}}",
+				},
+			},
+			expectErr:         false,
+			expectInitialized: true,
+		},
+	}
+
+	for name, test := range tests {
+		t.Run(name, func(t *testing.T) {
+			db := newMySQL(DefaultUserNameTemplate)
+			defer dbtesting.AssertClose(t, db)
+			initResp, err := db.Initialize(context.Background(), test.initRequest)
+			if test.expectErr && err == nil {
+				t.Fatalf("err expected, got nil")
+			}
+			if !test.expectErr && err != nil {
+				t.Fatalf("no error expected, got: %s", err)
+			}
+			require.Equal(t, test.expectedResp, initResp)
+			require.Equal(t, test.expectInitialized, db.Initialized, "Initialized variable not set correctly")
+		})
+	}
+}
+
+func TestMySQL_NewUser_nonLegacy(t *testing.T) {
+	displayName := "token"
+	roleName := "testrole"
+
+	type testCase struct {
+		usernameTemplate string
+
+		newUserReq dbplugin.NewUserRequest
+
+		expectedUsernameRegex string
+		expectErr             bool
+	}
+
+	tests := map[string]testCase{
+		"name statements": {
+			newUserReq: dbplugin.NewUserRequest{
 				UsernameConfig: dbplugin.UsernameMetadata{
-					DisplayName: "test",
-					RoleName:    "test",
+					DisplayName: displayName,
+					RoleName:    roleName,
 				},
 				Statements: dbplugin.Statements{
-					Commands: test.createStmts,
+					Commands: []string{
+						`CREATE USER '{{name}}'@'%' IDENTIFIED BY '{{password}}';
+						GRANT SELECT ON *.* TO '{{name}}'@'%';`,
+					},
 				},
-				Password:   password,
+				Password:   "09g8hanbdfkVSM",
 				Expiration: time.Now().Add(time.Minute),
+			},
+
+			expectedUsernameRegex: `^v-token-testrole-[a-zA-Z0-9]{15}$`,
+			expectErr:             false,
+		},
+		"username statements": {
+			newUserReq: dbplugin.NewUserRequest{
+				UsernameConfig: dbplugin.UsernameMetadata{
+					DisplayName: displayName,
+					RoleName:    roleName,
+				},
+				Statements: dbplugin.Statements{
+					Commands: []string{
+						`CREATE USER '{{username}}'@'%' IDENTIFIED BY '{{password}}';
+						GRANT SELECT ON *.* TO '{{username}}'@'%';`,
+					},
+				},
+				Password:   "09g8hanbdfkVSM",
+				Expiration: time.Now().Add(time.Minute),
+			},
+
+			expectedUsernameRegex: `^v-token-testrole-[a-zA-Z0-9]{15}$`,
+			expectErr:             false,
+		},
+		"prepared name statements": {
+			newUserReq: dbplugin.NewUserRequest{
+				UsernameConfig: dbplugin.UsernameMetadata{
+					DisplayName: displayName,
+					RoleName:    roleName,
+				},
+				Statements: dbplugin.Statements{
+					Commands: []string{
+						`CREATE USER '{{name}}'@'%' IDENTIFIED BY '{{password}}';
+						set @grants=CONCAT("GRANT SELECT ON ", "*", ".* TO '{{name}}'@'%'");
+						PREPARE grantStmt from @grants;
+						EXECUTE grantStmt;
+						DEALLOCATE PREPARE grantStmt;`,
+					},
+				},
+				Password:   "09g8hanbdfkVSM",
+				Expiration: time.Now().Add(time.Minute),
+			},
+
+			expectedUsernameRegex: `^v-token-testrole-[a-zA-Z0-9]{15}$`,
+			expectErr:             false,
+		},
+		"prepared username statements": {
+			newUserReq: dbplugin.NewUserRequest{
+				UsernameConfig: dbplugin.UsernameMetadata{
+					DisplayName: displayName,
+					RoleName:    roleName,
+				},
+				Statements: dbplugin.Statements{
+					Commands: []string{
+						`CREATE USER '{{username}}'@'%' IDENTIFIED BY '{{password}}';
+						set @grants=CONCAT("GRANT SELECT ON ", "*", ".* TO '{{username}}'@'%'");
+						PREPARE grantStmt from @grants;
+						EXECUTE grantStmt;
+						DEALLOCATE PREPARE grantStmt;`,
+					},
+				},
+				Password:   "09g8hanbdfkVSM",
+				Expiration: time.Now().Add(time.Minute),
+			},
+
+			expectedUsernameRegex: `^v-token-testrole-[a-zA-Z0-9]{15}$`,
+			expectErr:             false,
+		},
+		"custom username template": {
+			usernameTemplate: "foo-{{random 10}}-{{.RoleName | uppercase}}",
+
+			newUserReq: dbplugin.NewUserRequest{
+				UsernameConfig: dbplugin.UsernameMetadata{
+					DisplayName: displayName,
+					RoleName:    roleName,
+				},
+				Statements: dbplugin.Statements{
+					Commands: []string{
+						`CREATE USER '{{username}}'@'%' IDENTIFIED BY '{{password}}';
+						GRANT SELECT ON *.* TO '{{username}}'@'%';`,
+					},
+				},
+				Password:   "09g8hanbdfkVSM",
+				Expiration: time.Now().Add(time.Minute),
+			},
+
+			expectedUsernameRegex: `^foo-[a-zA-Z0-9]{10}-TESTROLE$`,
+			expectErr:             false,
+		},
+	}
+
+	for name, test := range tests {
+		t.Run(name, func(t *testing.T) {
+			cleanup, connURL := mysqlhelper.PrepareTestContainer(t, false, "secret")
+			defer cleanup()
+
+			connectionDetails := map[string]interface{}{
+				"connection_url":    connURL,
+				"username_template": test.usernameTemplate,
 			}
 
-			userResp, err := db.NewUser(context.Background(), createReq)
-			if err != nil {
-				t.Fatalf("err: %s", err)
+			initReq := dbplugin.InitializeRequest{
+				Config:           connectionDetails,
+				VerifyConnection: true,
 			}
 
-			if err := mysqlhelper.TestCredsExist(t, connURL, userResp.Username, password); err != nil {
-				t.Fatalf("Could not connect with new credentials: %s", err)
+			db := newMySQL(DefaultUserNameTemplate)
+			defer db.Close()
+			_, err := db.Initialize(context.Background(), initReq)
+			require.NoError(t, err)
+
+			userResp, err := db.NewUser(context.Background(), test.newUserReq)
+			if test.expectErr && err == nil {
+				t.Fatalf("err expected, got nil")
+			}
+			if !test.expectErr && err != nil {
+				t.Fatalf("no error expected, got: %s", err)
+			}
+			require.Regexp(t, test.expectedUsernameRegex, userResp.Username)
+
+			err = mysqlhelper.TestCredsExist(t, connURL, userResp.Username, test.newUserReq.Password)
+			require.NoError(t, err, "Failed to connect with credentials")
+		})
+	}
+}
+
+func TestMySQL_NewUser_legacy(t *testing.T) {
+	displayName := "token"
+	roleName := "testrole"
+
+	type testCase struct {
+		usernameTemplate string
+
+		newUserReq dbplugin.NewUserRequest
+
+		expectedUsernameRegex string
+		expectErr             bool
+	}
+
+	tests := map[string]testCase{
+		"name statements": {
+			newUserReq: dbplugin.NewUserRequest{
+				UsernameConfig: dbplugin.UsernameMetadata{
+					DisplayName: displayName,
+					RoleName:    roleName,
+				},
+				Statements: dbplugin.Statements{
+					Commands: []string{
+						`CREATE USER '{{name}}'@'%' IDENTIFIED BY '{{password}}';
+						GRANT SELECT ON *.* TO '{{name}}'@'%';`,
+					},
+				},
+				Password:   "09g8hanbdfkVSM",
+				Expiration: time.Now().Add(time.Minute),
+			},
+
+			expectedUsernameRegex: `^v-test-[a-zA-Z0-9]{9}$`,
+			expectErr:             false,
+		},
+		"username statements": {
+			newUserReq: dbplugin.NewUserRequest{
+				UsernameConfig: dbplugin.UsernameMetadata{
+					DisplayName: displayName,
+					RoleName:    roleName,
+				},
+				Statements: dbplugin.Statements{
+					Commands: []string{
+						`CREATE USER '{{username}}'@'%' IDENTIFIED BY '{{password}}';
+						GRANT SELECT ON *.* TO '{{username}}'@'%';`,
+					},
+				},
+				Password:   "09g8hanbdfkVSM",
+				Expiration: time.Now().Add(time.Minute),
+			},
+
+			expectedUsernameRegex: `^v-test-[a-zA-Z0-9]{9}$`,
+			expectErr:             false,
+		},
+		"prepared name statements": {
+			newUserReq: dbplugin.NewUserRequest{
+				UsernameConfig: dbplugin.UsernameMetadata{
+					DisplayName: displayName,
+					RoleName:    roleName,
+				},
+				Statements: dbplugin.Statements{
+					Commands: []string{
+						`CREATE USER '{{name}}'@'%' IDENTIFIED BY '{{password}}';
+						set @grants=CONCAT("GRANT SELECT ON ", "*", ".* TO '{{name}}'@'%'");
+						PREPARE grantStmt from @grants;
+						EXECUTE grantStmt;
+						DEALLOCATE PREPARE grantStmt;`,
+					},
+				},
+				Password:   "09g8hanbdfkVSM",
+				Expiration: time.Now().Add(time.Minute),
+			},
+
+			expectedUsernameRegex: `^v-test-[a-zA-Z0-9]{9}$`,
+			expectErr:             false,
+		},
+		"prepared username statements": {
+			newUserReq: dbplugin.NewUserRequest{
+				UsernameConfig: dbplugin.UsernameMetadata{
+					DisplayName: displayName,
+					RoleName:    roleName,
+				},
+				Statements: dbplugin.Statements{
+					Commands: []string{
+						`CREATE USER '{{username}}'@'%' IDENTIFIED BY '{{password}}';
+						set @grants=CONCAT("GRANT SELECT ON ", "*", ".* TO '{{username}}'@'%'");
+						PREPARE grantStmt from @grants;
+						EXECUTE grantStmt;
+						DEALLOCATE PREPARE grantStmt;`,
+					},
+				},
+				Password:   "09g8hanbdfkVSM",
+				Expiration: time.Now().Add(time.Minute),
+			},
+
+			expectedUsernameRegex: `^v-test-[a-zA-Z0-9]{9}$`,
+			expectErr:             false,
+		},
+		"custom username template": {
+			usernameTemplate: `{{printf "foo-%s-%s" (random 5) (.RoleName | uppercase) | truncate 16}}`,
+
+			newUserReq: dbplugin.NewUserRequest{
+				UsernameConfig: dbplugin.UsernameMetadata{
+					DisplayName: displayName,
+					RoleName:    roleName,
+				},
+				Statements: dbplugin.Statements{
+					Commands: []string{
+						`CREATE USER '{{username}}'@'%' IDENTIFIED BY '{{password}}';
+						GRANT SELECT ON *.* TO '{{username}}'@'%';`,
+					},
+				},
+				Password:   "09g8hanbdfkVSM",
+				Expiration: time.Now().Add(time.Minute),
+			},
+
+			expectedUsernameRegex: `^foo-[a-zA-Z0-9]{5}-TESTRO$`,
+			expectErr:             false,
+		},
+	}
+
+	for name, test := range tests {
+		t.Run(name, func(t *testing.T) {
+			cleanup, connURL := mysqlhelper.PrepareTestContainer(t, false, "secret")
+			defer cleanup()
+
+			connectionDetails := map[string]interface{}{
+				"connection_url":    connURL,
+				"username_template": test.usernameTemplate,
 			}
 
-			// Test a second time to make sure usernames don't collide
-			userResp, err = db.NewUser(context.Background(), createReq)
-			if err != nil {
-				t.Fatalf("err: %s", err)
+			initReq := dbplugin.InitializeRequest{
+				Config:           connectionDetails,
+				VerifyConnection: true,
 			}
 
-			if err := mysqlhelper.TestCredsExist(t, connURL, userResp.Username, password); err != nil {
-				t.Fatalf("Could not connect with new credentials: %s", err)
+			db := newMySQL(DefaultLegacyUserNameTemplate)
+			defer db.Close()
+			_, err := db.Initialize(context.Background(), initReq)
+			require.NoError(t, err)
+
+			userResp, err := db.NewUser(context.Background(), test.newUserReq)
+			if test.expectErr && err == nil {
+				t.Fatalf("err expected, got nil")
 			}
+			if !test.expectErr && err != nil {
+				t.Fatalf("no error expected, got: %s", err)
+			}
+			require.Regexp(t, test.expectedUsernameRegex, userResp.Username)
+
+			err = mysqlhelper.TestCredsExist(t, connURL, userResp.Username, test.newUserReq.Password)
+			require.NoError(t, err, "Failed to connect with credentials")
 		})
 	}
 }
@@ -260,7 +513,8 @@ func TestMySQL_RotateRootCredentials(t *testing.T) {
 				VerifyConnection: true,
 			}
 
-			db := newMySQL(MetadataLen, MetadataLen, UsernameLen)
+			db := newMySQL(DefaultUserNameTemplate)
+			defer db.Close()
 			_, err := db.Initialize(context.Background(), initReq)
 			if err != nil {
 				t.Fatalf("err: %s", err)
@@ -335,7 +589,8 @@ func TestMySQL_DeleteUser(t *testing.T) {
 		VerifyConnection: true,
 	}
 
-	db := newMySQL(MetadataLen, MetadataLen, UsernameLen)
+	db := newMySQL(DefaultUserNameTemplate)
+	defer db.Close()
 	_, err := db.Initialize(context.Background(), initReq)
 	if err != nil {
 		t.Fatalf("err: %s", err)
@@ -444,7 +699,8 @@ func TestMySQL_UpdateUser(t *testing.T) {
 			ctx, cancel := context.WithTimeout(context.Background(), 30*time.Second)
 			defer cancel()
 
-			db := newMySQL(MetadataLen, MetadataLen, UsernameLen)
+			db := newMySQL(DefaultUserNameTemplate)
+			defer db.Close()
 			_, err := db.Initialize(context.Background(), initReq)
 			if err != nil {
 				t.Fatalf("err: %s", err)
@@ -483,35 +739,6 @@ func TestMySQL_UpdateUser(t *testing.T) {
 	}
 }
 
-func TestMySQL_Initialize_ReservedChars(t *testing.T) {
-	pw := "#secret!%25#{@}"
-	cleanup, connURL := mysqlhelper.PrepareTestContainer(t, false, pw)
-	defer cleanup()
-
-	// Revert password set to test replacement by db.Init
-	connURL = strings.ReplaceAll(connURL, pw, "{{password}}")
-
-	connectionDetails := map[string]interface{}{
-		"connection_url": connURL,
-		"password":       pw,
-	}
-
-	db := newMySQL(MetadataLen, MetadataLen, UsernameLen)
-	_, err := db.Init(context.Background(), connectionDetails, true)
-	if err != nil {
-		t.Fatalf("err: %s", err)
-	}
-
-	if !db.Initialized {
-		t.Fatal("Database should be initialized")
-	}
-
-	err = db.Close()
-	if err != nil {
-		t.Fatalf("err: %s", err)
-	}
-}
-
 func createTestMySQLUser(t *testing.T, connURL, username, password, query string) {
 	t.Helper()
 	db, err := sql.Open("mysql", connURL)