Check user credentials before adding user

cmd/data/db.go

@@ -35,23 +35,28 @@ func OpenDB(dbName string) (*DB, error) {
 }
 
 func (db *DB) AddUser(user, pass, first, last string, writer, editor, admin bool) error {
-	hashedPass, err := bcrypt.GenerateFromPassword([]byte(pass), bcrypt.DefaultCost)
-	if err != nil {
-		return fmt.Errorf("error creating password hash: %v", err)
+	userString, stringLen, ok := checkUserStrings(user, first, last)
+	if !ok {
+		return fmt.Errorf("error: %v is longer than %v characters", userString, stringLen)
 	}
 
 	if !permissionsOK(writer, editor, admin) {
-		return fmt.Errorf("error with mutually exclusive permissions: writer = %v, editor = %v, admin = %v",
+		return fmt.Errorf("error: permissions must be mutually exclusive: writer = %v, editor = %v, admin = %v",
 			writer, editor, admin)
 	}
 
+	hashedPass, err := bcrypt.GenerateFromPassword([]byte(pass), bcrypt.DefaultCost)
+	if err != nil {
+		return fmt.Errorf("error creating password hash: %v", err)
+	}
+
 	query := `
     INSERT INTO users
         (username, password, first_name, last_name, writer, editor, admin)
     VALUES
         (?, ?, ?, ?, ?, ?)
     `
-	_, err = db.Exec(query, user, hashedPass, first, last, writer, editor, admin)
+	_, err = db.Exec(query, user, string(hashedPass), first, last, writer, editor, admin)
 	if err != nil {
 		return fmt.Errorf("error inserting user into DB: %v", err)
 	}
@@ -87,7 +92,7 @@ func (db *DB) ChangePassword(id int64, oldPass, newPass string) error {
     SET password = ?
     WHERE id = ?
     `
-	_, err = db.Exec(updateQuery, newHashedPass, id)
+	_, err = db.Exec(updateQuery, string(newHashedPass), id)
 	if err != nil {
 		return fmt.Errorf("error updating password in DB: %v", err)
 	}

cmd/data/helpers.go

@@ -51,6 +51,21 @@ func getCredentials() (string, string, error) {
 	return user, pass, nil
 }
 
+func checkUserStrings(user, first, last string) (string, int, bool) {
+	userLen := 15
+	nameLen := 50
+
+	if len(user) > userLen {
+		return user, userLen, false
+	} else if len(first) > nameLen {
+		return first, nameLen, false
+	} else if len(last) > nameLen {
+		return last, nameLen, false
+	} else {
+		return "", 0, true
+	}
+}
+
 func permissionsOK(writer, editor, admin bool) bool {
 	return writer && !editor && !admin ||
 		!writer && editor && !admin ||