// Package dataprovider provides data access.
// It abstracts different data providers and exposes a common API.
package dataprovider

import (
	"bufio"
	"bytes"
	"context"
	"crypto/sha1"
	"crypto/sha256"
	"crypto/sha512"
	"crypto/subtle"
	"crypto/x509"
	"encoding/base64"
	"encoding/json"
	"errors"
	"fmt"
	"hash"
	"io"
	"net"
	"net/http"
	"net/url"
	"os"
	"os/exec"
	"path"
	"path/filepath"
	"regexp"
	"runtime"
	"strconv"
	"strings"
	"sync"
	"time"

	"github.com/GehirnInc/crypt"
	"github.com/GehirnInc/crypt/apr1_crypt"
	"github.com/GehirnInc/crypt/md5_crypt"
	"github.com/GehirnInc/crypt/sha512_crypt"
	"github.com/alexedwards/argon2id"
	"github.com/go-chi/render"
	"github.com/rs/xid"
	"golang.org/x/crypto/bcrypt"
	"golang.org/x/crypto/pbkdf2"
	"golang.org/x/crypto/ssh"

	"github.com/drakkan/sftpgo/httpclient"
	"github.com/drakkan/sftpgo/kms"
	"github.com/drakkan/sftpgo/logger"
	"github.com/drakkan/sftpgo/metrics"
	"github.com/drakkan/sftpgo/utils"
	"github.com/drakkan/sftpgo/vfs"
)

const (
	// SQLiteDataProviderName defines the name for SQLite database provider
	SQLiteDataProviderName = "sqlite"
	// PGSQLDataProviderName defines the name for PostgreSQL database provider
	PGSQLDataProviderName = "postgresql"
	// MySQLDataProviderName defines the name for MySQL database provider
	MySQLDataProviderName = "mysql"
	// BoltDataProviderName defines the name for bbolt key/value store provider
	BoltDataProviderName = "bolt"
	// MemoryDataProviderName defines the name for memory provider
	MemoryDataProviderName = "memory"
	// CockroachDataProviderName defines the for CockroachDB provider
	CockroachDataProviderName = "cockroach"
	// DumpVersion defines the version for the dump.
	// For restore/load we support the current version and the previous one
	DumpVersion = 7

	argonPwdPrefix            = "$argon2id$"
	bcryptPwdPrefix           = "$2a$"
	pbkdf2SHA1Prefix          = "$pbkdf2-sha1$"
	pbkdf2SHA256Prefix        = "$pbkdf2-sha256$"
	pbkdf2SHA512Prefix        = "$pbkdf2-sha512$"
	pbkdf2SHA256B64SaltPrefix = "$pbkdf2-b64salt-sha256$"
	md5cryptPwdPrefix         = "$1$"
	md5cryptApr1PwdPrefix     = "$apr1$"
	sha512cryptPwdPrefix      = "$6$"
	trackQuotaDisabledError   = "please enable track_quota in your configuration to use this method"
	operationAdd              = "add"
	operationUpdate           = "update"
	operationDelete           = "delete"
	sqlPrefixValidChars       = "abcdefghijklmnopqrstuvwxyz_"
)

// ordering constants
const (
	OrderASC  = "ASC"
	OrderDESC = "DESC"
)

var (
	// SupportedProviders defines the supported data providers
	SupportedProviders = []string{SQLiteDataProviderName, PGSQLDataProviderName, MySQLDataProviderName,
		BoltDataProviderName, MemoryDataProviderName, CockroachDataProviderName}
	// ValidPerms defines all the valid permissions for a user
	ValidPerms = []string{PermAny, PermListItems, PermDownload, PermUpload, PermOverwrite, PermRename, PermDelete,
		PermCreateDirs, PermCreateSymlinks, PermChmod, PermChown, PermChtimes}
	// ValidLoginMethods defines all the valid login methods
	ValidLoginMethods = []string{SSHLoginMethodPublicKey, LoginMethodPassword, SSHLoginMethodKeyboardInteractive,
		SSHLoginMethodKeyAndPassword, SSHLoginMethodKeyAndKeyboardInt, LoginMethodTLSCertificate,
		LoginMethodTLSCertificateAndPwd}
	// SSHMultiStepsLoginMethods defines the supported Multi-Step Authentications
	SSHMultiStepsLoginMethods = []string{SSHLoginMethodKeyAndPassword, SSHLoginMethodKeyAndKeyboardInt}
	// ErrNoAuthTryed defines the error for connection closed before authentication
	ErrNoAuthTryed = errors.New("no auth tryed")
	// ValidProtocols defines all the valid protcols
	ValidProtocols = []string{"SSH", "FTP", "DAV"}
	// ErrNoInitRequired defines the error returned by InitProvider if no inizialization/update is required
	ErrNoInitRequired = errors.New("the data provider is up to date")
	// ErrInvalidCredentials defines the error to return if the supplied credentials are invalid
	ErrInvalidCredentials = errors.New("invalid credentials")
	validTLSUsernames     = []string{string(TLSUsernameNone), string(TLSUsernameCN)}
	webDAVUsersCache      sync.Map
	config                Config
	provider              Provider
	sqlPlaceholders       []string
	hashPwdPrefixes       = []string{argonPwdPrefix, bcryptPwdPrefix, pbkdf2SHA1Prefix, pbkdf2SHA256Prefix,
		pbkdf2SHA512Prefix, pbkdf2SHA256B64SaltPrefix, md5cryptPwdPrefix, md5cryptApr1PwdPrefix, sha512cryptPwdPrefix}
	pbkdfPwdPrefixes        = []string{pbkdf2SHA1Prefix, pbkdf2SHA256Prefix, pbkdf2SHA512Prefix, pbkdf2SHA256B64SaltPrefix}
	pbkdfPwdB64SaltPrefixes = []string{pbkdf2SHA256B64SaltPrefix}
	unixPwdPrefixes         = []string{md5cryptPwdPrefix, md5cryptApr1PwdPrefix, sha512cryptPwdPrefix}
	logSender               = "dataProvider"
	availabilityTicker      *time.Ticker
	availabilityTickerDone  chan bool
	credentialsDirPath      string
	sqlTableUsers           = "users"
	sqlTableFolders         = "folders"
	sqlTableFoldersMapping  = "folders_mapping"
	sqlTableAdmins          = "admins"
	sqlTableSchemaVersion   = "schema_version"
	argon2Params            *argon2id.Params
	lastLoginMinDelay       = 10 * time.Minute
	usernameRegex           = regexp.MustCompile("^[a-zA-Z0-9-_.~]+$")
)

type schemaVersion struct {
	Version int
}

// Argon2Options defines the options for argon2 password hashing
type Argon2Options struct {
	Memory      uint32 `json:"memory" mapstructure:"memory"`
	Iterations  uint32 `json:"iterations" mapstructure:"iterations"`
	Parallelism uint8  `json:"parallelism" mapstructure:"parallelism"`
}

// PasswordHashing defines the configuration for password hashing
type PasswordHashing struct {
	Argon2Options Argon2Options `json:"argon2_options" mapstructure:"argon2_options"`
}

// UserActions defines the action to execute on user create, update, delete.
type UserActions struct {
	// Valid values are add, update, delete. Empty slice to disable
	ExecuteOn []string `json:"execute_on" mapstructure:"execute_on"`
	// Absolute path to an external program or an HTTP URL
	Hook string `json:"hook" mapstructure:"hook"`
}

// ProviderStatus defines the provider status
type ProviderStatus struct {
	Driver   string `json:"driver"`
	IsActive bool   `json:"is_active"`
	Error    string `json:"error"`
}

// Config provider configuration
type Config struct {
	// Driver name, must be one of the SupportedProviders
	Driver string `json:"driver" mapstructure:"driver"`
	// Database name. For driver sqlite this can be the database name relative to the config dir
	// or the absolute path to the SQLite database.
	Name string `json:"name" mapstructure:"name"`
	// Database host
	Host string `json:"host" mapstructure:"host"`
	// Database port
	Port int `json:"port" mapstructure:"port"`
	// Database username
	Username string `json:"username" mapstructure:"username"`
	// Database password
	Password string `json:"password" mapstructure:"password"`
	// Used for drivers mysql and postgresql.
	// 0 disable SSL/TLS connections.
	// 1 require ssl.
	// 2 set ssl mode to verify-ca for driver postgresql and skip-verify for driver mysql.
	// 3 set ssl mode to verify-full for driver postgresql and preferred for driver mysql.
	SSLMode int `json:"sslmode" mapstructure:"sslmode"`
	// Custom database connection string.
	// If not empty this connection string will be used instead of build one using the previous parameters
	ConnectionString string `json:"connection_string" mapstructure:"connection_string"`
	// prefix for SQL tables
	SQLTablesPrefix string `json:"sql_tables_prefix" mapstructure:"sql_tables_prefix"`
	// Set the preferred way to track users quota between the following choices:
	// 0, disable quota tracking. REST API to scan user dir and update quota will do nothing
	// 1, quota is updated each time a user upload or delete a file even if the user has no quota restrictions
	// 2, quota is updated each time a user upload or delete a file but only for users with quota restrictions
	//    and for virtual folders.
	//    With this configuration the "quota scan" REST API can still be used to periodically update space usage
	//    for users without quota restrictions
	TrackQuota int `json:"track_quota" mapstructure:"track_quota"`
	// Sets the maximum number of open connections for mysql and postgresql driver.
	// Default 0 (unlimited)
	PoolSize int `json:"pool_size" mapstructure:"pool_size"`
	// Users default base directory.
	// If no home dir is defined while adding a new user, and this value is
	// a valid absolute path, then the user home dir will be automatically
	// defined as the path obtained joining the base dir and the username
	UsersBaseDir string `json:"users_base_dir" mapstructure:"users_base_dir"`
	// Actions to execute on user add, update, delete.
	// Update action will not be fired for internal updates such as the last login or the user quota fields.
	Actions UserActions `json:"actions" mapstructure:"actions"`
	// Absolute path to an external program or an HTTP URL to invoke for users authentication.
	// Leave empty to use builtin authentication.
	// If the authentication succeed the user will be automatically added/updated inside the defined data provider.
	// Actions defined for user added/updated will not be executed in this case.
	// This method is slower than built-in authentication methods, but it's very flexible as anyone can
	// easily write his own authentication hooks.
	ExternalAuthHook string `json:"external_auth_hook" mapstructure:"external_auth_hook"`
	// ExternalAuthScope defines the scope for the external authentication hook.
	// - 0 means all supported authentication scopes, the external hook will be executed for password,
	//     public key, keyboard interactive authentication and TLS certificates
	// - 1 means passwords only
	// - 2 means public keys only
	// - 4 means keyboard interactive only
	// - 8 means TLS certificates only
	// you can combine the scopes, for example 3 means password and public key, 5 password and keyboard
	// interactive and so on
	ExternalAuthScope int `json:"external_auth_scope" mapstructure:"external_auth_scope"`
	// CredentialsPath defines the directory for storing user provided credential files such as
	// Google Cloud Storage credentials. It can be a path relative to the config dir or an
	// absolute path
	CredentialsPath string `json:"credentials_path" mapstructure:"credentials_path"`
	// Absolute path to an external program or an HTTP URL to invoke just before the user login.
	// This program/URL allows to modify or create the user trying to login.
	// It is useful if you have users with dynamic fields to update just before the login.
	// Please note that if you want to create a new user, the pre-login hook response must
	// include all the mandatory user fields.
	//
	// The pre-login hook must finish within 30 seconds.
	//
	// If an error happens while executing the "PreLoginHook" then login will be denied.
	// PreLoginHook and ExternalAuthHook are mutally exclusive.
	// Leave empty to disable.
	PreLoginHook string `json:"pre_login_hook" mapstructure:"pre_login_hook"`
	// Absolute path to an external program or an HTTP URL to invoke after the user login.
	// Based on the configured scope you can choose if notify failed or successful logins
	// or both
	PostLoginHook string `json:"post_login_hook" mapstructure:"post_login_hook"`
	// PostLoginScope defines the scope for the post-login hook.
	// - 0 means notify both failed and successful logins
	// - 1 means notify failed logins
	// - 2 means notify successful logins
	PostLoginScope int `json:"post_login_scope" mapstructure:"post_login_scope"`
	// Absolute path to an external program or an HTTP URL to invoke just before password
	// authentication. This hook allows you to externally check the provided password,
	// its main use case is to allow to easily support things like password+OTP for protocols
	// without keyboard interactive support such as FTP and WebDAV. You can ask your users
	// to login using a string consisting of a fixed password and a One Time Token, you
	// can verify the token inside the hook and ask to SFTPGo to verify the fixed part.
	CheckPasswordHook string `json:"check_password_hook" mapstructure:"check_password_hook"`
	// CheckPasswordScope defines the scope for the check password hook.
	// - 0 means all protocols
	// - 1 means SSH
	// - 2 means FTP
	// - 4 means WebDAV
	// you can combine the scopes, for example 6 means FTP and WebDAV
	CheckPasswordScope int `json:"check_password_scope" mapstructure:"check_password_scope"`
	// Defines how the database will be initialized/updated:
	// - 0 means automatically
	// - 1 means manually using the initprovider sub-command
	UpdateMode int `json:"update_mode" mapstructure:"update_mode"`
	// PasswordHashing defines the configuration for password hashing
	PasswordHashing PasswordHashing `json:"password_hashing" mapstructure:"password_hashing"`
	// PreferDatabaseCredentials indicates whether credential files (currently used for Google
	// Cloud Storage) should be stored in the database instead of in the directory specified by
	// CredentialsPath.
	PreferDatabaseCredentials bool `json:"prefer_database_credentials" mapstructure:"prefer_database_credentials"`
	// SkipNaturalKeysValidation allows to use any UTF-8 character for natural keys as username, admin name,
	// folder name. These keys are used in URIs for REST API and Web admin. By default only unreserved URI
	// characters are allowed: ALPHA / DIGIT / "-" / "." / "_" / "~".
	SkipNaturalKeysValidation bool `json:"skip_natural_keys_validation" mapstructure:"skip_natural_keys_validation"`
}

// BackupData defines the structure for the backup/restore files
type BackupData struct {
	Users   []User                  `json:"users"`
	Folders []vfs.BaseVirtualFolder `json:"folders"`
	Admins  []Admin                 `json:"admins"`
	Version int                     `json:"version"`
}

// HasFolder returns true if the folder with the given name is included
func (d *BackupData) HasFolder(name string) bool {
	for _, folder := range d.Folders {
		if folder.Name == name {
			return true
		}
	}
	return false
}

type keyboardAuthHookRequest struct {
	RequestID string   `json:"request_id"`
	Username  string   `json:"username,omitempty"`
	IP        string   `json:"ip,omitempty"`
	Password  string   `json:"password,omitempty"`
	Answers   []string `json:"answers,omitempty"`
	Questions []string `json:"questions,omitempty"`
}

type keyboardAuthHookResponse struct {
	Instruction string   `json:"instruction"`
	Questions   []string `json:"questions"`
	Echos       []bool   `json:"echos"`
	AuthResult  int      `json:"auth_result"`
	CheckPwd    int      `json:"check_password"`
}

type checkPasswordRequest struct {
	Username string `json:"username"`
	IP       string `json:"ip"`
	Password string `json:"password"`
	Protocol string `json:"protocol"`
}

type checkPasswordResponse struct {
	// 0 KO, 1 OK, 2 partial success, -1 not executed
	Status int `json:"status"`
	// for status = 2 this is the password to check against the one stored
	// inside the SFTPGo data provider
	ToVerify string `json:"to_verify"`
}

// ValidationError raised if input data is not valid
type ValidationError struct {
	err string
}

// Validation error details
func (e *ValidationError) Error() string {
	return fmt.Sprintf("Validation error: %s", e.err)
}

// NewValidationError returns a validation errors
func NewValidationError(error string) *ValidationError {
	return &ValidationError{
		err: error,
	}
}

// MethodDisabledError raised if a method is disabled in config file.
// For example, if user management is disabled, this error is raised
// every time a user operation is done using the REST API
type MethodDisabledError struct {
	err string
}

// Method disabled error details
func (e *MethodDisabledError) Error() string {
	return fmt.Sprintf("Method disabled error: %s", e.err)
}

// RecordNotFoundError raised if a requested user is not found
type RecordNotFoundError struct {
	err string
}

func (e *RecordNotFoundError) Error() string {
	return fmt.Sprintf("not found: %s", e.err)
}

// GetQuotaTracking returns the configured mode for user's quota tracking
func GetQuotaTracking() int {
	return config.TrackQuota
}

// Provider defines the interface that data providers must implement.
type Provider interface {
	validateUserAndPass(username, password, ip, protocol string) (User, error)
	validateUserAndPubKey(username string, pubKey []byte) (User, string, error)
	validateUserAndTLSCert(username, protocol string, tlsCert *x509.Certificate) (User, error)
	updateQuota(username string, filesAdd int, sizeAdd int64, reset bool) error
	getUsedQuota(username string) (int, int64, error)
	userExists(username string) (User, error)
	addUser(user *User) error
	updateUser(user *User) error
	deleteUser(user *User) error
	getUsers(limit int, offset int, order string) ([]User, error)
	dumpUsers() ([]User, error)
	updateLastLogin(username string) error
	getFolders(limit, offset int, order string) ([]vfs.BaseVirtualFolder, error)
	getFolderByName(name string) (vfs.BaseVirtualFolder, error)
	addFolder(folder *vfs.BaseVirtualFolder) error
	updateFolder(folder *vfs.BaseVirtualFolder) error
	deleteFolder(folder *vfs.BaseVirtualFolder) error
	updateFolderQuota(name string, filesAdd int, sizeAdd int64, reset bool) error
	getUsedFolderQuota(name string) (int, int64, error)
	dumpFolders() ([]vfs.BaseVirtualFolder, error)
	adminExists(username string) (Admin, error)
	addAdmin(admin *Admin) error
	updateAdmin(admin *Admin) error
	deleteAdmin(admin *Admin) error
	getAdmins(limit int, offset int, order string) ([]Admin, error)
	dumpAdmins() ([]Admin, error)
	validateAdminAndPass(username, password, ip string) (Admin, error)
	checkAvailability() error
	close() error
	reloadConfig() error
	initializeDatabase() error
	migrateDatabase() error
	revertDatabase(targetVersion int) error
}

type fsValidatorHelper interface {
	GetGCSCredentialsFilePath() string
	GetEncrytionAdditionalData() string
}

// Initialize the data provider.
// An error is returned if the configured driver is invalid or if the data provider cannot be initialized
func Initialize(cnf Config, basePath string, checkAdmins bool) error {
	var err error
	config = cnf

	if filepath.IsAbs(config.CredentialsPath) {
		credentialsDirPath = config.CredentialsPath
	} else {
		credentialsDirPath = filepath.Join(basePath, config.CredentialsPath)
	}
	vfs.SetCredentialsDirPath(credentialsDirPath)
	argon2Params = &argon2id.Params{
		Memory:      cnf.PasswordHashing.Argon2Options.Memory,
		Iterations:  cnf.PasswordHashing.Argon2Options.Iterations,
		Parallelism: cnf.PasswordHashing.Argon2Options.Parallelism,
		SaltLength:  16,
		KeyLength:   32,
	}

	if err = validateHooks(); err != nil {
		return err
	}
	err = createProvider(basePath)
	if err != nil {
		return err
	}
	if cnf.UpdateMode == 0 {
		err = provider.initializeDatabase()
		if err != nil && err != ErrNoInitRequired {
			logger.WarnToConsole("Unable to initialize data provider: %v", err)
			providerLog(logger.LevelWarn, "Unable to initialize data provider: %v", err)
			return err
		}
		if err == nil {
			logger.DebugToConsole("Data provider successfully initialized")
		}
		err = provider.migrateDatabase()
		if err != nil && err != ErrNoInitRequired {
			providerLog(logger.LevelWarn, "database migration error: %v", err)
			return err
		}
		if checkAdmins {
			err = checkDefaultAdmin()
			if err != nil {
				providerLog(logger.LevelWarn, "check default admin error: %v", err)
				return err
			}
		}
	} else {
		providerLog(logger.LevelInfo, "database initialization/migration skipped, manual mode is configured")
	}
	startAvailabilityTimer()
	return nil
}

func validateHooks() error {
	var hooks []string
	if config.PreLoginHook != "" && !strings.HasPrefix(config.PreLoginHook, "http") {
		hooks = append(hooks, config.PreLoginHook)
	}
	if config.ExternalAuthHook != "" && !strings.HasPrefix(config.ExternalAuthHook, "http") {
		hooks = append(hooks, config.ExternalAuthHook)
	}
	if config.PostLoginHook != "" && !strings.HasPrefix(config.PostLoginHook, "http") {
		hooks = append(hooks, config.PostLoginHook)
	}
	if config.CheckPasswordHook != "" && !strings.HasPrefix(config.CheckPasswordHook, "http") {
		hooks = append(hooks, config.CheckPasswordHook)
	}

	for _, hook := range hooks {
		if !filepath.IsAbs(hook) {
			return fmt.Errorf("invalid hook: %#v must be an absolute path", hook)
		}
		_, err := os.Stat(hook)
		if err != nil {
			providerLog(logger.LevelWarn, "invalid hook: %v", err)
			return err
		}
	}

	return nil
}

func validateSQLTablesPrefix() error {
	if len(config.SQLTablesPrefix) > 0 {
		for _, char := range config.SQLTablesPrefix {
			if !strings.Contains(sqlPrefixValidChars, strings.ToLower(string(char))) {
				return errors.New("invalid sql_tables_prefix only chars in range 'a..z', 'A..Z' and '_' are allowed")
			}
		}
		sqlTableUsers = config.SQLTablesPrefix + sqlTableUsers
		sqlTableFolders = config.SQLTablesPrefix + sqlTableFolders
		sqlTableFoldersMapping = config.SQLTablesPrefix + sqlTableFoldersMapping
		sqlTableAdmins = config.SQLTablesPrefix + sqlTableAdmins
		sqlTableSchemaVersion = config.SQLTablesPrefix + sqlTableSchemaVersion
		providerLog(logger.LevelDebug, "sql table for users %#v, folders %#v folders mapping %#v admins %#v schema version %#v",
			sqlTableUsers, sqlTableFolders, sqlTableFoldersMapping, sqlTableAdmins, sqlTableSchemaVersion)
	}
	return nil
}

func checkDefaultAdmin() error {
	admins, err := provider.getAdmins(1, 0, OrderASC)
	if err != nil {
		return err
	}
	if len(admins) > 0 {
		return nil
	}
	logger.Debug(logSender, "", "no admins found, try to create the default one")
	// we need to create the default admin
	admin := &Admin{}
	admin.setDefaults()
	return provider.addAdmin(admin)
}

// InitializeDatabase creates the initial database structure
func InitializeDatabase(cnf Config, basePath string) error {
	config = cnf

	if filepath.IsAbs(config.CredentialsPath) {
		credentialsDirPath = config.CredentialsPath
	} else {
		credentialsDirPath = filepath.Join(basePath, config.CredentialsPath)
	}

	err := createProvider(basePath)
	if err != nil {
		return err
	}
	err = provider.initializeDatabase()
	if err != nil && err != ErrNoInitRequired {
		return err
	}
	return provider.migrateDatabase()
}

// RevertDatabase restores schema and/or data to a previous version
func RevertDatabase(cnf Config, basePath string, targetVersion int) error {
	config = cnf

	if filepath.IsAbs(config.CredentialsPath) {
		credentialsDirPath = config.CredentialsPath
	} else {
		credentialsDirPath = filepath.Join(basePath, config.CredentialsPath)
	}

	err := createProvider(basePath)
	if err != nil {
		return err
	}
	err = provider.initializeDatabase()
	if err != nil && err != ErrNoInitRequired {
		return err
	}
	return provider.revertDatabase(targetVersion)
}

// CheckAdminAndPass validates the given admin and password connecting from ip
func CheckAdminAndPass(username, password, ip string) (Admin, error) {
	return provider.validateAdminAndPass(username, password, ip)
}

// CheckCachedUserCredentials checks the credentials for a cached user
func CheckCachedUserCredentials(user *CachedUser, password, loginMethod, protocol string, tlsCert *x509.Certificate) error {
	if loginMethod != LoginMethodPassword {
		_, err := checkUserAndTLSCertificate(&user.User, protocol, tlsCert)
		if err != nil {
			return err
		}
		if loginMethod == LoginMethodTLSCertificate {
			if !user.User.IsLoginMethodAllowed(LoginMethodTLSCertificate, nil) {
				return fmt.Errorf("certificate login method is not allowed for user %#v", user.User.Username)
			}
			return nil
		}
	}
	if err := checkLoginConditions(&user.User); err != nil {
		return err
	}
	if password == "" {
		return ErrInvalidCredentials
	}
	if user.Password != "" {
		if password == user.Password {
			return nil
		}
	} else {
		if ok, _ := isPasswordOK(&user.User, password); ok {
			return nil
		}
	}
	return ErrInvalidCredentials
}

// CheckCompositeCredentials checks multiple credentials.
// WebDAV users can send both a password and a TLS certificate within the same request
func CheckCompositeCredentials(username, password, ip, loginMethod, protocol string, tlsCert *x509.Certificate) (User, string, error) {
	if loginMethod == LoginMethodPassword {
		user, err := CheckUserAndPass(username, password, ip, protocol)
		return user, loginMethod, err
	}
	user, err := CheckUserBeforeTLSAuth(username, ip, protocol, tlsCert)
	if err != nil {
		return user, loginMethod, err
	}
	if !user.IsTLSUsernameVerificationEnabled() {
		// for backward compatibility with 2.0.x we only check the password and change the login method here
		// in future updates we have to return an error
		user, err := CheckUserAndPass(username, password, ip, protocol)
		return user, LoginMethodPassword, err
	}
	user, err = checkUserAndTLSCertificate(&user, protocol, tlsCert)
	if err != nil {
		return user, loginMethod, err
	}
	if loginMethod == LoginMethodTLSCertificate && !user.IsLoginMethodAllowed(LoginMethodTLSCertificate, nil) {
		return user, loginMethod, fmt.Errorf("certificate login method is not allowed for user %#v", user.Username)
	}
	if loginMethod == LoginMethodTLSCertificateAndPwd {
		if config.ExternalAuthHook != "" && (config.ExternalAuthScope == 0 || config.ExternalAuthScope&1 != 0) {
			user, err = doExternalAuth(username, password, nil, "", ip, protocol, nil)
			if err != nil {
				return user, loginMethod, err
			}
		}
		if config.PreLoginHook != "" {
			user, err = executePreLoginHook(username, LoginMethodPassword, ip, protocol)
			if err != nil {
				return user, loginMethod, err
			}
		}
		user, err = checkUserAndPass(&user, password, ip, protocol)
	}
	return user, loginMethod, err
}

// CheckUserBeforeTLSAuth checks if a user exits before trying mutual TLS
func CheckUserBeforeTLSAuth(username, ip, protocol string, tlsCert *x509.Certificate) (User, error) {
	if config.ExternalAuthHook != "" && (config.ExternalAuthScope == 0 || config.ExternalAuthScope&8 != 0) {
		return doExternalAuth(username, "", nil, "", ip, protocol, tlsCert)
	}
	if config.PreLoginHook != "" {
		return executePreLoginHook(username, LoginMethodTLSCertificate, ip, protocol)
	}
	return UserExists(username)
}

// CheckUserAndTLSCert returns the SFTPGo user with the given username and check if the
// given TLS certificate allow authentication without password
func CheckUserAndTLSCert(username, ip, protocol string, tlsCert *x509.Certificate) (User, error) {
	if config.ExternalAuthHook != "" && (config.ExternalAuthScope == 0 || config.ExternalAuthScope&8 != 0) {
		user, err := doExternalAuth(username, "", nil, "", ip, protocol, tlsCert)
		if err != nil {
			return user, err
		}
		return checkUserAndTLSCertificate(&user, protocol, tlsCert)
	}
	if config.PreLoginHook != "" {
		user, err := executePreLoginHook(username, LoginMethodTLSCertificate, ip, protocol)
		if err != nil {
			return user, err
		}
		return checkUserAndTLSCertificate(&user, protocol, tlsCert)
	}
	return provider.validateUserAndTLSCert(username, protocol, tlsCert)
}

// CheckUserAndPass retrieves the SFTPGo user with the given username and password if a match is found or an error
func CheckUserAndPass(username, password, ip, protocol string) (User, error) {
	if config.ExternalAuthHook != "" && (config.ExternalAuthScope == 0 || config.ExternalAuthScope&1 != 0) {
		user, err := doExternalAuth(username, password, nil, "", ip, protocol, nil)
		if err != nil {
			return user, err
		}
		return checkUserAndPass(&user, password, ip, protocol)
	}
	if config.PreLoginHook != "" {
		user, err := executePreLoginHook(username, LoginMethodPassword, ip, protocol)
		if err != nil {
			return user, err
		}
		return checkUserAndPass(&user, password, ip, protocol)
	}
	return provider.validateUserAndPass(username, password, ip, protocol)
}

// CheckUserAndPubKey retrieves the SFTP user with the given username and public key if a match is found or an error
func CheckUserAndPubKey(username string, pubKey []byte, ip, protocol string) (User, string, error) {
	if config.ExternalAuthHook != "" && (config.ExternalAuthScope == 0 || config.ExternalAuthScope&2 != 0) {
		user, err := doExternalAuth(username, "", pubKey, "", ip, protocol, nil)
		if err != nil {
			return user, "", err
		}
		return checkUserAndPubKey(&user, pubKey)
	}
	if config.PreLoginHook != "" {
		user, err := executePreLoginHook(username, SSHLoginMethodPublicKey, ip, protocol)
		if err != nil {
			return user, "", err
		}
		return checkUserAndPubKey(&user, pubKey)
	}
	return provider.validateUserAndPubKey(username, pubKey)
}

// CheckKeyboardInteractiveAuth checks the keyboard interactive authentication and returns
// the authenticated user or an error
func CheckKeyboardInteractiveAuth(username, authHook string, client ssh.KeyboardInteractiveChallenge, ip, protocol string) (User, error) {
	var user User
	var err error
	if config.ExternalAuthHook != "" && (config.ExternalAuthScope == 0 || config.ExternalAuthScope&4 != 0) {
		user, err = doExternalAuth(username, "", nil, "1", ip, protocol, nil)
	} else if config.PreLoginHook != "" {
		user, err = executePreLoginHook(username, SSHLoginMethodKeyboardInteractive, ip, protocol)
	} else {
		user, err = provider.userExists(username)
	}
	if err != nil {
		return user, err
	}
	return doKeyboardInteractiveAuth(&user, authHook, client, ip, protocol)
}

// UpdateLastLogin updates the last login fields for the given SFTP user
func UpdateLastLogin(user *User) error {
	lastLogin := utils.GetTimeFromMsecSinceEpoch(user.LastLogin)
	diff := -time.Until(lastLogin)
	if diff < 0 || diff > lastLoginMinDelay {
		err := provider.updateLastLogin(user.Username)
		if err == nil {
			updateWebDavCachedUserLastLogin(user.Username)
		}
		return err
	}
	return nil
}

// UpdateUserQuota updates the quota for the given SFTP user adding filesAdd and sizeAdd.
// If reset is true filesAdd and sizeAdd indicates the total files and the total size instead of the difference.
func UpdateUserQuota(user *User, filesAdd int, sizeAdd int64, reset bool) error {
	if config.TrackQuota == 0 {
		return &MethodDisabledError{err: trackQuotaDisabledError}
	} else if config.TrackQuota == 2 && !reset && !user.HasQuotaRestrictions() {
		return nil
	}
	if filesAdd == 0 && sizeAdd == 0 && !reset {
		return nil
	}
	return provider.updateQuota(user.Username, filesAdd, sizeAdd, reset)
}

// UpdateVirtualFolderQuota updates the quota for the given virtual folder adding filesAdd and sizeAdd.
// If reset is true filesAdd and sizeAdd indicates the total files and the total size instead of the difference.
func UpdateVirtualFolderQuota(vfolder *vfs.BaseVirtualFolder, filesAdd int, sizeAdd int64, reset bool) error {
	if config.TrackQuota == 0 {
		return &MethodDisabledError{err: trackQuotaDisabledError}
	}
	if filesAdd == 0 && sizeAdd == 0 && !reset {
		return nil
	}
	return provider.updateFolderQuota(vfolder.Name, filesAdd, sizeAdd, reset)
}

// GetUsedQuota returns the used quota for the given SFTP user.
func GetUsedQuota(username string) (int, int64, error) {
	if config.TrackQuota == 0 {
		return 0, 0, &MethodDisabledError{err: trackQuotaDisabledError}
	}
	return provider.getUsedQuota(username)
}

// GetUsedVirtualFolderQuota returns the used quota for the given virtual folder.
func GetUsedVirtualFolderQuota(name string) (int, int64, error) {
	if config.TrackQuota == 0 {
		return 0, 0, &MethodDisabledError{err: trackQuotaDisabledError}
	}
	return provider.getUsedFolderQuota(name)
}

// AddAdmin adds a new SFTPGo admin
func AddAdmin(admin *Admin) error {
	return provider.addAdmin(admin)
}

// UpdateAdmin updates an existing SFTPGo admin
func UpdateAdmin(admin *Admin) error {
	return provider.updateAdmin(admin)
}

// DeleteAdmin deletes an existing SFTPGo admin
func DeleteAdmin(username string) error {
	admin, err := provider.adminExists(username)
	if err != nil {
		return err
	}
	return provider.deleteAdmin(&admin)
}

// AdminExists returns the given admins if it exists
func AdminExists(username string) (Admin, error) {
	return provider.adminExists(username)
}

// UserExists checks if the given SFTPGo username exists, returns an error if no match is found
func UserExists(username string) (User, error) {
	return provider.userExists(username)
}

// AddUser adds a new SFTPGo user.
func AddUser(user *User) error {
	err := provider.addUser(user)
	if err == nil {
		executeAction(operationAdd, user)
	}
	return err
}

// UpdateUser updates an existing SFTPGo user.
func UpdateUser(user *User) error {
	err := provider.updateUser(user)
	if err == nil {
		RemoveCachedWebDAVUser(user.Username)
		executeAction(operationUpdate, user)
	}
	return err
}

// DeleteUser deletes an existing SFTPGo user.
func DeleteUser(username string) error {
	user, err := provider.userExists(username)
	if err != nil {
		return err
	}
	err = provider.deleteUser(&user)
	if err == nil {
		RemoveCachedWebDAVUser(user.Username)
		executeAction(operationDelete, &user)
	}
	return err
}

// ReloadConfig reloads provider configuration.
// Currently only implemented for memory provider, allows to reload the users
// from the configured file, if defined
func ReloadConfig() error {
	return provider.reloadConfig()
}

// GetAdmins returns an array of admins respecting limit and offset
func GetAdmins(limit, offset int, order string) ([]Admin, error) {
	return provider.getAdmins(limit, offset, order)
}

// GetUsers returns an array of users respecting limit and offset and filtered by username exact match if not empty
func GetUsers(limit, offset int, order string) ([]User, error) {
	return provider.getUsers(limit, offset, order)
}

// AddFolder adds a new virtual folder.
func AddFolder(folder *vfs.BaseVirtualFolder) error {
	return provider.addFolder(folder)
}

// UpdateFolder updates the specified virtual folder
func UpdateFolder(folder *vfs.BaseVirtualFolder, users []string) error {
	err := provider.updateFolder(folder)
	if err == nil {
		for _, user := range users {
			RemoveCachedWebDAVUser(user)
		}
	}
	return err
}

// DeleteFolder deletes an existing folder.
func DeleteFolder(folderName string) error {
	folder, err := provider.getFolderByName(folderName)
	if err != nil {
		return err
	}
	err = provider.deleteFolder(&folder)
	if err == nil {
		for _, user := range folder.Users {
			RemoveCachedWebDAVUser(user)
		}
	}
	return err
}

// GetFolderByName returns the folder with the specified name if any
func GetFolderByName(name string) (vfs.BaseVirtualFolder, error) {
	return provider.getFolderByName(name)
}

// GetFolders returns an array of folders respecting limit and offset
func GetFolders(limit, offset int, order string) ([]vfs.BaseVirtualFolder, error) {
	return provider.getFolders(limit, offset, order)
}

// DumpData returns all users and folders
func DumpData() (BackupData, error) {
	var data BackupData
	users, err := provider.dumpUsers()
	if err != nil {
		return data, err
	}
	folders, err := provider.dumpFolders()
	if err != nil {
		return data, err
	}
	admins, err := provider.dumpAdmins()
	if err != nil {
		return data, err
	}
	data.Users = users
	data.Folders = folders
	data.Admins = admins
	data.Version = DumpVersion
	return data, err
}

// ParseDumpData tries to parse data as BackupData
func ParseDumpData(data []byte) (BackupData, error) {
	var dump BackupData
	err := json.Unmarshal(data, &dump)
	return dump, err
}

// GetProviderStatus returns an error if the provider is not available
func GetProviderStatus() ProviderStatus {
	err := provider.checkAvailability()
	status := ProviderStatus{
		Driver: config.Driver,
	}
	if err == nil {
		status.IsActive = true
	} else {
		status.IsActive = false
		status.Error = err.Error()
	}
	return status
}

// Close releases all provider resources.
// This method is used in test cases.
// Closing an uninitialized provider is not supported
func Close() error {
	if availabilityTicker != nil {
		availabilityTicker.Stop()
		availabilityTickerDone <- true
		availabilityTicker = nil
	}
	return provider.close()
}

func createProvider(basePath string) error {
	var err error
	sqlPlaceholders = getSQLPlaceholders()
	if err = validateSQLTablesPrefix(); err != nil {
		return err
	}
	logSender = fmt.Sprintf("dataprovider_%v", config.Driver)

	switch config.Driver {
	case SQLiteDataProviderName:
		return initializeSQLiteProvider(basePath)
	case PGSQLDataProviderName, CockroachDataProviderName:
		return initializePGSQLProvider()
	case MySQLDataProviderName:
		return initializeMySQLProvider()
	case BoltDataProviderName:
		return initializeBoltProvider(basePath)
	case MemoryDataProviderName:
		initializeMemoryProvider(basePath)
		return nil
	default:
		return fmt.Errorf("unsupported data provider: %v", config.Driver)
	}
}

func buildUserHomeDir(user *User) {
	if user.HomeDir == "" {
		if config.UsersBaseDir != "" {
			user.HomeDir = filepath.Join(config.UsersBaseDir, user.Username)
		} else if user.FsConfig.Provider == vfs.SFTPFilesystemProvider {
			user.HomeDir = filepath.Join(os.TempDir(), user.Username)
		}
	}
}

func isVirtualDirOverlapped(dir1, dir2 string, fullCheck bool) bool {
	if dir1 == dir2 {
		return true
	}
	if fullCheck {
		if len(dir1) > len(dir2) {
			if strings.HasPrefix(dir1, dir2+"/") {
				return true
			}
		}
		if len(dir2) > len(dir1) {
			if strings.HasPrefix(dir2, dir1+"/") {
				return true
			}
		}
	}
	return false
}

func isMappedDirOverlapped(dir1, dir2 string, fullCheck bool) bool {
	if dir1 == dir2 {
		return true
	}
	if fullCheck {
		if len(dir1) > len(dir2) {
			if strings.HasPrefix(dir1, dir2+string(os.PathSeparator)) {
				return true
			}
		}
		if len(dir2) > len(dir1) {
			if strings.HasPrefix(dir2, dir1+string(os.PathSeparator)) {
				return true
			}
		}
	}
	return false
}

func validateFolderQuotaLimits(folder vfs.VirtualFolder) error {
	if folder.QuotaSize < -1 {
		return &ValidationError{err: fmt.Sprintf("invalid quota_size: %v folder path %#v", folder.QuotaSize, folder.MappedPath)}
	}
	if folder.QuotaFiles < -1 {
		return &ValidationError{err: fmt.Sprintf("invalid quota_file: %v folder path %#v", folder.QuotaFiles, folder.MappedPath)}
	}
	if (folder.QuotaSize == -1 && folder.QuotaFiles != -1) || (folder.QuotaFiles == -1 && folder.QuotaSize != -1) {
		return &ValidationError{err: fmt.Sprintf("virtual folder quota_size and quota_files must be both -1 or >= 0, quota_size: %v quota_files: %v",
			folder.QuotaFiles, folder.QuotaSize)}
	}
	return nil
}

func getVirtualFolderIfInvalid(folder *vfs.BaseVirtualFolder) *vfs.BaseVirtualFolder {
	if err := ValidateFolder(folder); err == nil {
		return folder
	}
	// we try to get the folder from the data provider if only the Name is populated
	if folder.MappedPath != "" {
		return folder
	}
	if folder.Name == "" {
		return folder
	}
	if folder.FsConfig.Provider != vfs.LocalFilesystemProvider {
		return folder
	}
	if f, err := GetFolderByName(folder.Name); err == nil {
		return &f
	}
	return folder
}

func hasSFTPLoopForFolder(user *User, folder *vfs.BaseVirtualFolder) bool {
	if folder.FsConfig.Provider == vfs.SFTPFilesystemProvider {
		// FIXME: this could be inaccurate, it is not easy to check the endpoint too
		if folder.FsConfig.SFTPConfig.Username == user.Username {
			return true
		}
	}
	return false
}

func validateUserVirtualFolders(user *User) error {
	if len(user.VirtualFolders) == 0 {
		user.VirtualFolders = []vfs.VirtualFolder{}
		return nil
	}
	var virtualFolders []vfs.VirtualFolder
	mappedPaths := make(map[string]bool)
	virtualPaths := make(map[string]bool)
	for _, v := range user.VirtualFolders {
		cleanedVPath := filepath.ToSlash(path.Clean(v.VirtualPath))
		if !path.IsAbs(cleanedVPath) || cleanedVPath == "/" {
			return &ValidationError{err: fmt.Sprintf("invalid virtual folder %#v", v.VirtualPath)}
		}
		if err := validateFolderQuotaLimits(v); err != nil {
			return err
		}
		folder := getVirtualFolderIfInvalid(&v.BaseVirtualFolder)
		if err := ValidateFolder(folder); err != nil {
			return err
		}
		if hasSFTPLoopForFolder(user, folder) {
			return &ValidationError{err: fmt.Sprintf("SFTP folder %#v could point to the same SFTPGo account, this is not allowed",
				folder.Name)}
		}
		cleanedMPath := folder.MappedPath
		if folder.IsLocalOrLocalCrypted() {
			if isMappedDirOverlapped(cleanedMPath, user.GetHomeDir(), true) {
				return &ValidationError{err: fmt.Sprintf("invalid mapped folder %#v cannot be inside or contain the user home dir %#v",
					folder.MappedPath, user.GetHomeDir())}
			}
			for mPath := range mappedPaths {
				if folder.IsLocalOrLocalCrypted() && isMappedDirOverlapped(mPath, cleanedMPath, false) {
					return &ValidationError{err: fmt.Sprintf("invalid mapped folder %#v overlaps with mapped folder %#v",
						v.MappedPath, mPath)}
				}
			}
			mappedPaths[cleanedMPath] = true
		}
		for vPath := range virtualPaths {
			if isVirtualDirOverlapped(vPath, cleanedVPath, false) {
				return &ValidationError{err: fmt.Sprintf("invalid virtual folder %#v overlaps with virtual folder %#v",
					v.VirtualPath, vPath)}
			}
		}
		virtualPaths[cleanedVPath] = true
		virtualFolders = append(virtualFolders, vfs.VirtualFolder{
			BaseVirtualFolder: *folder,
			VirtualPath:       cleanedVPath,
			QuotaSize:         v.QuotaSize,
			QuotaFiles:        v.QuotaFiles,
		})
	}
	user.VirtualFolders = virtualFolders
	return nil
}

func validatePermissions(user *User) error {
	if len(user.Permissions) == 0 {
		return &ValidationError{err: "please grant some permissions to this user"}
	}
	permissions := make(map[string][]string)
	if _, ok := user.Permissions["/"]; !ok {
		return &ValidationError{err: "permissions for the root dir \"/\" must be set"}
	}
	for dir, perms := range user.Permissions {
		if len(perms) == 0 && dir == "/" {
			return &ValidationError{err: fmt.Sprintf("no permissions granted for the directory: %#v", dir)}
		}
		if len(perms) > len(ValidPerms) {
			return &ValidationError{err: "invalid permissions"}
		}
		for _, p := range perms {
			if !utils.IsStringInSlice(p, ValidPerms) {
				return &ValidationError{err: fmt.Sprintf("invalid permission: %#v", p)}
			}
		}
		cleanedDir := filepath.ToSlash(path.Clean(dir))
		if cleanedDir != "/" {
			cleanedDir = strings.TrimSuffix(cleanedDir, "/")
		}
		if !path.IsAbs(cleanedDir) {
			return &ValidationError{err: fmt.Sprintf("cannot set permissions for non absolute path: %#v", dir)}
		}
		if dir != cleanedDir && cleanedDir == "/" {
			return &ValidationError{err: fmt.Sprintf("cannot set permissions for invalid subdirectory: %#v is an alias for \"/\"", dir)}
		}
		if utils.IsStringInSlice(PermAny, perms) {
			permissions[cleanedDir] = []string{PermAny}
		} else {
			permissions[cleanedDir] = utils.RemoveDuplicates(perms)
		}
	}
	user.Permissions = permissions
	return nil
}

func validatePublicKeys(user *User) error {
	if len(user.PublicKeys) == 0 {
		user.PublicKeys = []string{}
	}
	for i, k := range user.PublicKeys {
		_, _, _, _, err := ssh.ParseAuthorizedKey([]byte(k))
		if err != nil {
			return &ValidationError{err: fmt.Sprintf("could not parse key nr. %d: %s", i, err)}
		}
	}
	return nil
}

func validateFiltersPatternExtensions(user *User) error {
	if len(user.Filters.FilePatterns) == 0 {
		user.Filters.FilePatterns = []PatternsFilter{}
		return nil
	}
	filteredPaths := []string{}
	var filters []PatternsFilter
	for _, f := range user.Filters.FilePatterns {
		cleanedPath := filepath.ToSlash(path.Clean(f.Path))
		if !path.IsAbs(cleanedPath) {
			return &ValidationError{err: fmt.Sprintf("invalid path %#v for file patterns filter", f.Path)}
		}
		if utils.IsStringInSlice(cleanedPath, filteredPaths) {
			return &ValidationError{err: fmt.Sprintf("duplicate file patterns filter for path %#v", f.Path)}
		}
		if len(f.AllowedPatterns) == 0 && len(f.DeniedPatterns) == 0 {
			return &ValidationError{err: fmt.Sprintf("empty file patterns filter for path %#v", f.Path)}
		}
		f.Path = cleanedPath
		allowed := make([]string, 0, len(f.AllowedPatterns))
		denied := make([]string, 0, len(f.DeniedPatterns))
		for _, pattern := range f.AllowedPatterns {
			_, err := path.Match(pattern, "abc")
			if err != nil {
				return &ValidationError{err: fmt.Sprintf("invalid file pattern filter %#v", pattern)}
			}
			allowed = append(allowed, strings.ToLower(pattern))
		}
		for _, pattern := range f.DeniedPatterns {
			_, err := path.Match(pattern, "abc")
			if err != nil {
				return &ValidationError{err: fmt.Sprintf("invalid file pattern filter %#v", pattern)}
			}
			denied = append(denied, strings.ToLower(pattern))
		}
		f.AllowedPatterns = allowed
		f.DeniedPatterns = denied
		filters = append(filters, f)
		filteredPaths = append(filteredPaths, cleanedPath)
	}
	user.Filters.FilePatterns = filters
	return nil
}

func validateFiltersFileExtensions(user *User) error {
	if len(user.Filters.FileExtensions) == 0 {
		user.Filters.FileExtensions = []ExtensionsFilter{}
		return nil
	}
	filteredPaths := []string{}
	var filters []ExtensionsFilter
	for _, f := range user.Filters.FileExtensions {
		cleanedPath := filepath.ToSlash(path.Clean(f.Path))
		if !path.IsAbs(cleanedPath) {
			return &ValidationError{err: fmt.Sprintf("invalid path %#v for file extensions filter", f.Path)}
		}
		if utils.IsStringInSlice(cleanedPath, filteredPaths) {
			return &ValidationError{err: fmt.Sprintf("duplicate file extensions filter for path %#v", f.Path)}
		}
		if len(f.AllowedExtensions) == 0 && len(f.DeniedExtensions) == 0 {
			return &ValidationError{err: fmt.Sprintf("empty file extensions filter for path %#v", f.Path)}
		}
		f.Path = cleanedPath
		allowed := make([]string, 0, len(f.AllowedExtensions))
		denied := make([]string, 0, len(f.DeniedExtensions))
		for _, ext := range f.AllowedExtensions {
			allowed = append(allowed, strings.ToLower(ext))
		}
		for _, ext := range f.DeniedExtensions {
			denied = append(denied, strings.ToLower(ext))
		}
		f.AllowedExtensions = allowed
		f.DeniedExtensions = denied
		filters = append(filters, f)
		filteredPaths = append(filteredPaths, cleanedPath)
	}
	user.Filters.FileExtensions = filters
	return nil
}

func validateFileFilters(user *User) error {
	if err := validateFiltersFileExtensions(user); err != nil {
		return err
	}
	return validateFiltersPatternExtensions(user)
}

func checkEmptyFiltersStruct(user *User) {
	if len(user.Filters.AllowedIP) == 0 {
		user.Filters.AllowedIP = []string{}
	}
	if len(user.Filters.DeniedIP) == 0 {
		user.Filters.DeniedIP = []string{}
	}
	if len(user.Filters.DeniedLoginMethods) == 0 {
		user.Filters.DeniedLoginMethods = []string{}
	}
	if len(user.Filters.DeniedProtocols) == 0 {
		user.Filters.DeniedProtocols = []string{}
	}
}

func validateFilters(user *User) error {
	checkEmptyFiltersStruct(user)
	for _, IPMask := range user.Filters.DeniedIP {
		_, _, err := net.ParseCIDR(IPMask)
		if err != nil {
			return &ValidationError{err: fmt.Sprintf("could not parse denied IP/Mask %#v : %v", IPMask, err)}
		}
	}
	for _, IPMask := range user.Filters.AllowedIP {
		_, _, err := net.ParseCIDR(IPMask)
		if err != nil {
			return &ValidationError{err: fmt.Sprintf("could not parse allowed IP/Mask %#v : %v", IPMask, err)}
		}
	}
	if len(user.Filters.DeniedLoginMethods) >= len(ValidLoginMethods) {
		return &ValidationError{err: "invalid denied_login_methods"}
	}
	for _, loginMethod := range user.Filters.DeniedLoginMethods {
		if !utils.IsStringInSlice(loginMethod, ValidLoginMethods) {
			return &ValidationError{err: fmt.Sprintf("invalid login method: %#v", loginMethod)}
		}
	}
	if len(user.Filters.DeniedProtocols) >= len(ValidProtocols) {
		return &ValidationError{err: "invalid denied_protocols"}
	}
	for _, p := range user.Filters.DeniedProtocols {
		if !utils.IsStringInSlice(p, ValidProtocols) {
			return &ValidationError{err: fmt.Sprintf("invalid protocol: %#v", p)}
		}
	}
	if user.Filters.TLSUsername != "" {
		if !utils.IsStringInSlice(string(user.Filters.TLSUsername), validTLSUsernames) {
			return &ValidationError{err: fmt.Sprintf("invalid TLS username: %#v", user.Filters.TLSUsername)}
		}
	}
	return validateFileFilters(user)
}

func saveGCSCredentials(fsConfig *vfs.Filesystem, helper fsValidatorHelper) error {
	if fsConfig.Provider != vfs.GCSFilesystemProvider {
		return nil
	}
	if fsConfig.GCSConfig.Credentials.GetPayload() == "" {
		return nil
	}
	if config.PreferDatabaseCredentials {
		if fsConfig.GCSConfig.Credentials.IsPlain() {
			fsConfig.GCSConfig.Credentials.SetAdditionalData(helper.GetEncrytionAdditionalData())
			err := fsConfig.GCSConfig.Credentials.Encrypt()
			if err != nil {
				return err
			}
		}
		return nil
	}
	if fsConfig.GCSConfig.Credentials.IsPlain() {
		fsConfig.GCSConfig.Credentials.SetAdditionalData(helper.GetEncrytionAdditionalData())
		err := fsConfig.GCSConfig.Credentials.Encrypt()
		if err != nil {
			return &ValidationError{err: fmt.Sprintf("could not encrypt GCS credentials: %v", err)}
		}
	}
	creds, err := json.Marshal(fsConfig.GCSConfig.Credentials)
	if err != nil {
		return &ValidationError{err: fmt.Sprintf("could not marshal GCS credentials: %v", err)}
	}
	credentialsFilePath := helper.GetGCSCredentialsFilePath()
	err = os.MkdirAll(filepath.Dir(credentialsFilePath), 0700)
	if err != nil {
		return &ValidationError{err: fmt.Sprintf("could not create GCS credentials dir: %v", err)}
	}
	err = os.WriteFile(credentialsFilePath, creds, 0600)
	if err != nil {
		return &ValidationError{err: fmt.Sprintf("could not save GCS credentials: %v", err)}
	}
	fsConfig.GCSConfig.Credentials = kms.NewEmptySecret()
	return nil
}

func validateFilesystemConfig(fsConfig *vfs.Filesystem, helper fsValidatorHelper) error {
	if fsConfig.Provider == vfs.S3FilesystemProvider {
		if err := fsConfig.S3Config.Validate(); err != nil {
			return &ValidationError{err: fmt.Sprintf("could not validate s3config: %v", err)}
		}
		if err := fsConfig.S3Config.EncryptCredentials(helper.GetEncrytionAdditionalData()); err != nil {
			return &ValidationError{err: fmt.Sprintf("could not encrypt s3 access secret: %v", err)}
		}
		fsConfig.GCSConfig = vfs.GCSFsConfig{}
		fsConfig.AzBlobConfig = vfs.AzBlobFsConfig{}
		fsConfig.CryptConfig = vfs.CryptFsConfig{}
		fsConfig.SFTPConfig = vfs.SFTPFsConfig{}
		return nil
	} else if fsConfig.Provider == vfs.GCSFilesystemProvider {
		if err := fsConfig.GCSConfig.Validate(helper.GetGCSCredentialsFilePath()); err != nil {
			return &ValidationError{err: fmt.Sprintf("could not validate GCS config: %v", err)}
		}
		fsConfig.S3Config = vfs.S3FsConfig{}
		fsConfig.AzBlobConfig = vfs.AzBlobFsConfig{}
		fsConfig.CryptConfig = vfs.CryptFsConfig{}
		fsConfig.SFTPConfig = vfs.SFTPFsConfig{}
		return nil
	} else if fsConfig.Provider == vfs.AzureBlobFilesystemProvider {
		if err := fsConfig.AzBlobConfig.Validate(); err != nil {
			return &ValidationError{err: fmt.Sprintf("could not validate Azure Blob config: %v", err)}
		}
		if err := fsConfig.AzBlobConfig.EncryptCredentials(helper.GetEncrytionAdditionalData()); err != nil {
			return &ValidationError{err: fmt.Sprintf("could not encrypt Azure blob account key: %v", err)}
		}
		fsConfig.S3Config = vfs.S3FsConfig{}
		fsConfig.GCSConfig = vfs.GCSFsConfig{}
		fsConfig.CryptConfig = vfs.CryptFsConfig{}
		fsConfig.SFTPConfig = vfs.SFTPFsConfig{}
		return nil
	} else if fsConfig.Provider == vfs.CryptedFilesystemProvider {
		if err := fsConfig.CryptConfig.Validate(); err != nil {
			return &ValidationError{err: fmt.Sprintf("could not validate Crypt fs config: %v", err)}
		}
		if err := fsConfig.CryptConfig.EncryptCredentials(helper.GetEncrytionAdditionalData()); err != nil {
			return &ValidationError{err: fmt.Sprintf("could not encrypt Crypt fs passphrase: %v", err)}
		}
		fsConfig.S3Config = vfs.S3FsConfig{}
		fsConfig.GCSConfig = vfs.GCSFsConfig{}
		fsConfig.AzBlobConfig = vfs.AzBlobFsConfig{}
		fsConfig.SFTPConfig = vfs.SFTPFsConfig{}
		return nil
	} else if fsConfig.Provider == vfs.SFTPFilesystemProvider {
		if err := fsConfig.SFTPConfig.Validate(); err != nil {
			return &ValidationError{err: fmt.Sprintf("could not validate SFTP fs config: %v", err)}
		}
		if err := fsConfig.SFTPConfig.EncryptCredentials(helper.GetEncrytionAdditionalData()); err != nil {
			return &ValidationError{err: fmt.Sprintf("could not encrypt SFTP fs credentials: %v", err)}
		}
		fsConfig.S3Config = vfs.S3FsConfig{}
		fsConfig.GCSConfig = vfs.GCSFsConfig{}
		fsConfig.AzBlobConfig = vfs.AzBlobFsConfig{}
		fsConfig.CryptConfig = vfs.CryptFsConfig{}
		return nil
	}
	fsConfig.Provider = vfs.LocalFilesystemProvider
	fsConfig.S3Config = vfs.S3FsConfig{}
	fsConfig.GCSConfig = vfs.GCSFsConfig{}
	fsConfig.AzBlobConfig = vfs.AzBlobFsConfig{}
	fsConfig.CryptConfig = vfs.CryptFsConfig{}
	fsConfig.SFTPConfig = vfs.SFTPFsConfig{}
	return nil
}

func validateBaseParams(user *User) error {
	if user.Username == "" {
		return &ValidationError{err: "username is mandatory"}
	}
	if !config.SkipNaturalKeysValidation && !usernameRegex.MatchString(user.Username) {
		return &ValidationError{err: fmt.Sprintf("username %#v is not valid, the following characters are allowed: a-zA-Z0-9-_.~",
			user.Username)}
	}
	if user.HomeDir == "" {
		return &ValidationError{err: "home_dir is mandatory"}
	}
	if user.Password == "" && len(user.PublicKeys) == 0 {
		return &ValidationError{err: "please set a password or at least a public_key"}
	}
	if !filepath.IsAbs(user.HomeDir) {
		return &ValidationError{err: fmt.Sprintf("home_dir must be an absolute path, actual value: %v", user.HomeDir)}
	}
	return nil
}

func createUserPasswordHash(user *User) error {
	if user.Password != "" && !user.IsPasswordHashed() {
		pwd, err := argon2id.CreateHash(user.Password, argon2Params)
		if err != nil {
			return err
		}
		user.Password = pwd
	}
	return nil
}

// ValidateFolder returns an error if the folder is not valid
// FIXME: this should be defined as Folder struct method
func ValidateFolder(folder *vfs.BaseVirtualFolder) error {
	if folder.Name == "" {
		return &ValidationError{err: "folder name is mandatory"}
	}
	if !config.SkipNaturalKeysValidation && !usernameRegex.MatchString(folder.Name) {
		return &ValidationError{err: fmt.Sprintf("folder name %#v is not valid, the following characters are allowed: a-zA-Z0-9-_.~",
			folder.Name)}
	}
	if folder.FsConfig.Provider == vfs.LocalFilesystemProvider || folder.FsConfig.Provider == vfs.CryptedFilesystemProvider ||
		folder.MappedPath != "" {
		cleanedMPath := filepath.Clean(folder.MappedPath)
		if !filepath.IsAbs(cleanedMPath) {
			return &ValidationError{err: fmt.Sprintf("invalid folder mapped path %#v", folder.MappedPath)}
		}
		folder.MappedPath = cleanedMPath
	}
	if folder.HasRedactedSecret() {
		return errors.New("cannot save a folder with a redacted secret")
	}
	if err := validateFilesystemConfig(&folder.FsConfig, folder); err != nil {
		return err
	}
	if err := saveGCSCredentials(&folder.FsConfig, folder); err != nil {
		return err
	}
	return nil
}

// ValidateUser returns an error if the user is not valid
// FIXME: this should be defined as User struct method
func ValidateUser(user *User) error {
	user.SetEmptySecretsIfNil()
	buildUserHomeDir(user)
	if err := validateBaseParams(user); err != nil {
		return err
	}
	if err := validatePermissions(user); err != nil {
		return err
	}
	if user.hasRedactedSecret() {
		return errors.New("cannot save a user with a redacted secret")
	}
	if err := validateFilesystemConfig(&user.FsConfig, user); err != nil {
		return err
	}
	if err := validateUserVirtualFolders(user); err != nil {
		return err
	}
	if user.Status < 0 || user.Status > 1 {
		return &ValidationError{err: fmt.Sprintf("invalid user status: %v", user.Status)}
	}
	if err := createUserPasswordHash(user); err != nil {
		return err
	}
	if err := validatePublicKeys(user); err != nil {
		return err
	}
	if err := validateFilters(user); err != nil {
		return err
	}
	if err := saveGCSCredentials(&user.FsConfig, user); err != nil {
		return err
	}
	return nil
}

func checkLoginConditions(user *User) error {
	if user.Status < 1 {
		return fmt.Errorf("user %#v is disabled", user.Username)
	}
	if user.ExpirationDate > 0 && user.ExpirationDate < utils.GetTimeAsMsSinceEpoch(time.Now()) {
		return fmt.Errorf("user %#v is expired, expiration timestamp: %v current timestamp: %v", user.Username,
			user.ExpirationDate, utils.GetTimeAsMsSinceEpoch(time.Now()))
	}
	return nil
}

func isPasswordOK(user *User, password string) (bool, error) {
	match := false
	var err error
	if strings.HasPrefix(user.Password, argonPwdPrefix) {
		match, err = argon2id.ComparePasswordAndHash(password, user.Password)
		if err != nil {
			providerLog(logger.LevelWarn, "error comparing password with argon hash: %v", err)
			return match, err
		}
	} else if strings.HasPrefix(user.Password, bcryptPwdPrefix) {
		if err = bcrypt.CompareHashAndPassword([]byte(user.Password), []byte(password)); err != nil {
			providerLog(logger.LevelWarn, "error comparing password with bcrypt hash: %v", err)
			return match, err
		}
		match = true
	} else if utils.IsStringPrefixInSlice(user.Password, pbkdfPwdPrefixes) {
		match, err = comparePbkdf2PasswordAndHash(password, user.Password)
		if err != nil {
			return match, err
		}
	} else if utils.IsStringPrefixInSlice(user.Password, unixPwdPrefixes) {
		match, err = compareUnixPasswordAndHash(user, password)
		if err != nil {
			return match, err
		}
	}
	return match, err
}

func checkUserAndTLSCertificate(user *User, protocol string, tlsCert *x509.Certificate) (User, error) {
	err := checkLoginConditions(user)
	if err != nil {
		return *user, err
	}
	switch protocol {
	case "FTP", "DAV":
		if user.Filters.TLSUsername == TLSUsernameCN {
			if user.Username == tlsCert.Subject.CommonName {
				return *user, nil
			}
			return *user, fmt.Errorf("CN %#v does not match username %#v", tlsCert.Subject.CommonName, user.Username)
		}
		return *user, errors.New("TLS certificate is not valid")
	default:
		return *user, fmt.Errorf("certificate authentication is not supported for protocol %v", protocol)
	}
}

func checkUserAndPass(user *User, password, ip, protocol string) (User, error) {
	err := checkLoginConditions(user)
	if err != nil {
		return *user, err
	}
	if user.Password == "" {
		return *user, errors.New("credentials cannot be null or empty")
	}
	hookResponse, err := executeCheckPasswordHook(user.Username, password, ip, protocol)
	if err != nil {
		providerLog(logger.LevelDebug, "error executing check password hook: %v", err)
		return *user, errors.New("unable to check credentials")
	}
	switch hookResponse.Status {
	case -1:
		// no hook configured
	case 1:
		providerLog(logger.LevelDebug, "password accepted by check password hook")
		return *user, nil
	case 2:
		providerLog(logger.LevelDebug, "partial success from check password hook")
		password = hookResponse.ToVerify
	default:
		providerLog(logger.LevelDebug, "password rejected by check password hook, status: %v", hookResponse.Status)
		return *user, ErrInvalidCredentials
	}

	match, err := isPasswordOK(user, password)
	if !match {
		err = ErrInvalidCredentials
	}
	return *user, err
}

func checkUserAndPubKey(user *User, pubKey []byte) (User, string, error) {
	err := checkLoginConditions(user)
	if err != nil {
		return *user, "", err
	}
	if len(user.PublicKeys) == 0 {
		return *user, "", ErrInvalidCredentials
	}
	for i, k := range user.PublicKeys {
		storedPubKey, comment, _, _, err := ssh.ParseAuthorizedKey([]byte(k))
		if err != nil {
			providerLog(logger.LevelWarn, "error parsing stored public key %d for user %v: %v", i, user.Username, err)
			return *user, "", err
		}
		if bytes.Equal(storedPubKey.Marshal(), pubKey) {
			certInfo := ""
			cert, ok := storedPubKey.(*ssh.Certificate)
			if ok {
				certInfo = fmt.Sprintf(" %v ID: %v Serial: %v CA: %v", cert.Type(), cert.KeyId, cert.Serial,
					ssh.FingerprintSHA256(cert.SignatureKey))
			}
			return *user, fmt.Sprintf("%v:%v%v", ssh.FingerprintSHA256(storedPubKey), comment, certInfo), nil
		}
	}
	return *user, "", ErrInvalidCredentials
}

func compareUnixPasswordAndHash(user *User, password string) (bool, error) {
	var crypter crypt.Crypter
	if strings.HasPrefix(user.Password, sha512cryptPwdPrefix) {
		crypter = sha512_crypt.New()
	} else if strings.HasPrefix(user.Password, md5cryptPwdPrefix) {
		crypter = md5_crypt.New()
	} else if strings.HasPrefix(user.Password, md5cryptApr1PwdPrefix) {
		crypter = apr1_crypt.New()
	} else {
		return false, errors.New("unix crypt: invalid or unsupported hash format")
	}
	if err := crypter.Verify(user.Password, []byte(password)); err != nil {
		return false, err
	}
	return true, nil
}

func comparePbkdf2PasswordAndHash(password, hashedPassword string) (bool, error) {
	vals := strings.Split(hashedPassword, "$")
	if len(vals) != 5 {
		return false, fmt.Errorf("pbkdf2: hash is not in the correct format")
	}
	iterations, err := strconv.Atoi(vals[2])
	if err != nil {
		return false, err
	}
	expected, err := base64.StdEncoding.DecodeString(vals[4])
	if err != nil {
		return false, err
	}
	var salt []byte
	if utils.IsStringPrefixInSlice(hashedPassword, pbkdfPwdB64SaltPrefixes) {
		salt, err = base64.StdEncoding.DecodeString(vals[3])
		if err != nil {
			return false, err
		}
	} else {
		salt = []byte(vals[3])
	}
	var hashFunc func() hash.Hash
	if strings.HasPrefix(hashedPassword, pbkdf2SHA256Prefix) || strings.HasPrefix(hashedPassword, pbkdf2SHA256B64SaltPrefix) {
		hashFunc = sha256.New
	} else if strings.HasPrefix(hashedPassword, pbkdf2SHA512Prefix) {
		hashFunc = sha512.New
	} else if strings.HasPrefix(hashedPassword, pbkdf2SHA1Prefix) {
		hashFunc = sha1.New
	} else {
		return false, fmt.Errorf("pbkdf2: invalid or unsupported hash format %v", vals[1])
	}
	df := pbkdf2.Key([]byte(password), salt, iterations, len(expected), hashFunc)
	return subtle.ConstantTimeCompare(df, expected) == 1, nil
}

func addCredentialsToUser(user *User) error {
	if err := addFolderCredentialsToUser(user); err != nil {
		return err
	}
	if user.FsConfig.Provider != vfs.GCSFilesystemProvider {
		return nil
	}
	if user.FsConfig.GCSConfig.AutomaticCredentials > 0 {
		return nil
	}

	// Don't read from file if credentials have already been set
	if user.FsConfig.GCSConfig.Credentials.IsValid() {
		return nil
	}

	cred, err := os.ReadFile(user.GetGCSCredentialsFilePath())
	if err != nil {
		return err
	}
	return json.Unmarshal(cred, &user.FsConfig.GCSConfig.Credentials)
}

func addFolderCredentialsToUser(user *User) error {
	for idx := range user.VirtualFolders {
		f := &user.VirtualFolders[idx]
		if f.FsConfig.Provider != vfs.GCSFilesystemProvider {
			continue
		}
		if f.FsConfig.GCSConfig.AutomaticCredentials > 0 {
			continue
		}
		// Don't read from file if credentials have already been set
		if f.FsConfig.GCSConfig.Credentials.IsValid() {
			continue
		}
		cred, err := os.ReadFile(f.GetGCSCredentialsFilePath())
		if err != nil {
			return err
		}
		err = json.Unmarshal(cred, f.FsConfig.GCSConfig.Credentials)
		if err != nil {
			return err
		}
	}
	return nil
}

func getSSLMode() string {
	if config.Driver == PGSQLDataProviderName || config.Driver == CockroachDataProviderName {
		if config.SSLMode == 0 {
			return "disable"
		} else if config.SSLMode == 1 {
			return "require"
		} else if config.SSLMode == 2 {
			return "verify-ca"
		} else if config.SSLMode == 3 {
			return "verify-full"
		}
	} else if config.Driver == MySQLDataProviderName {
		if config.SSLMode == 0 {
			return "false"
		} else if config.SSLMode == 1 {
			return "true"
		} else if config.SSLMode == 2 {
			return "skip-verify"
		} else if config.SSLMode == 3 {
			return "preferred"
		}
	}
	return ""
}

func startAvailabilityTimer() {
	availabilityTicker = time.NewTicker(30 * time.Second)
	availabilityTickerDone = make(chan bool)
	checkDataprovider()
	go func() {
		for {
			select {
			case <-availabilityTickerDone:
				return
			case <-availabilityTicker.C:
				checkDataprovider()
			}
		}
	}()
}

func checkDataprovider() {
	err := provider.checkAvailability()
	if err != nil {
		providerLog(logger.LevelWarn, "check availability error: %v", err)
	}
	metrics.UpdateDataProviderAvailability(err)
}

func terminateInteractiveAuthProgram(cmd *exec.Cmd, isFinished bool) {
	if isFinished {
		return
	}
	providerLog(logger.LevelInfo, "kill interactive auth program after an unexpected error")
	err := cmd.Process.Kill()
	if err != nil {
		providerLog(logger.LevelDebug, "error killing interactive auth program: %v", err)
	}
}

func validateKeyboardAuthResponse(response keyboardAuthHookResponse) error {
	if len(response.Questions) == 0 {
		err := errors.New("interactive auth error: hook response does not contain questions")
		providerLog(logger.LevelInfo, "%v", err)
		return err
	}
	if len(response.Questions) != len(response.Echos) {
		err := fmt.Errorf("interactive auth error, http hook response questions don't match echos: %v %v",
			len(response.Questions), len(response.Echos))
		providerLog(logger.LevelInfo, "%v", err)
		return err
	}
	return nil
}

func sendKeyboardAuthHTTPReq(url *url.URL, request keyboardAuthHookRequest) (keyboardAuthHookResponse, error) {
	var response keyboardAuthHookResponse
	httpClient := httpclient.GetHTTPClient()
	reqAsJSON, err := json.Marshal(request)
	if err != nil {
		providerLog(logger.LevelWarn, "error serializing keyboard interactive auth request: %v", err)
		return response, err
	}
	resp, err := httpClient.Post(url.String(), "application/json", bytes.NewBuffer(reqAsJSON))
	if err != nil {
		providerLog(logger.LevelWarn, "error getting keyboard interactive auth hook HTTP response: %v", err)
		return response, err
	}
	defer resp.Body.Close()
	if resp.StatusCode != http.StatusOK {
		return response, fmt.Errorf("wrong keyboard interactive auth http status code: %v, expected 200", resp.StatusCode)
	}
	err = render.DecodeJSON(resp.Body, &response)
	return response, err
}

func executeKeyboardInteractiveHTTPHook(user *User, authHook string, client ssh.KeyboardInteractiveChallenge, ip, protocol string) (int, error) {
	authResult := 0
	var url *url.URL
	url, err := url.Parse(authHook)
	if err != nil {
		providerLog(logger.LevelWarn, "invalid url for keyboard interactive hook %#v, error: %v", authHook, err)
		return authResult, err
	}
	requestID := xid.New().String()
	req := keyboardAuthHookRequest{
		Username:  user.Username,
		IP:        ip,
		Password:  user.Password,
		RequestID: requestID,
	}
	var response keyboardAuthHookResponse
	for {
		response, err = sendKeyboardAuthHTTPReq(url, req)
		if err != nil {
			return authResult, err
		}
		if response.AuthResult != 0 {
			return response.AuthResult, err
		}
		if err = validateKeyboardAuthResponse(response); err != nil {
			return authResult, err
		}
		answers, err := getKeyboardInteractiveAnswers(client, response, user, ip, protocol)
		if err != nil {
			return authResult, err
		}
		req = keyboardAuthHookRequest{
			RequestID: requestID,
			Username:  user.Username,
			Password:  user.Password,
			Answers:   answers,
			Questions: response.Questions,
		}
	}
}

func getKeyboardInteractiveAnswers(client ssh.KeyboardInteractiveChallenge, response keyboardAuthHookResponse,
	user *User, ip, protocol string) ([]string, error) {
	questions := response.Questions
	answers, err := client(user.Username, response.Instruction, questions, response.Echos)
	if err != nil {
		providerLog(logger.LevelInfo, "error getting interactive auth client response: %v", err)
		return answers, err
	}
	if len(answers) != len(questions) {
		err = fmt.Errorf("client answers does not match questions, expected: %v actual: %v", questions, answers)
		providerLog(logger.LevelInfo, "keyboard interactive auth error: %v", err)
		return answers, err
	}
	if len(answers) == 1 && response.CheckPwd > 0 {
		_, err = checkUserAndPass(user, answers[0], ip, protocol)
		providerLog(logger.LevelInfo, "interactive auth hook requested password validation for user %#v, validation error: %v",
			user.Username, err)
		if err != nil {
			return answers, err
		}
		answers[0] = "OK"
	}
	return answers, err
}

func handleProgramInteractiveQuestions(client ssh.KeyboardInteractiveChallenge, response keyboardAuthHookResponse,
	user *User, stdin io.WriteCloser, ip, protocol string) error {
	answers, err := getKeyboardInteractiveAnswers(client, response, user, ip, protocol)
	if err != nil {
		return err
	}
	for _, answer := range answers {
		if runtime.GOOS == "windows" {
			answer += "\r"
		}
		answer += "\n"
		_, err = stdin.Write([]byte(answer))
		if err != nil {
			providerLog(logger.LevelError, "unable to write client answer to keyboard interactive program: %v", err)
			return err
		}
	}
	return nil
}

func executeKeyboardInteractiveProgram(user *User, authHook string, client ssh.KeyboardInteractiveChallenge, ip, protocol string) (int, error) {
	authResult := 0
	ctx, cancel := context.WithTimeout(context.Background(), 60*time.Second)
	defer cancel()
	cmd := exec.CommandContext(ctx, authHook)
	cmd.Env = append(os.Environ(),
		fmt.Sprintf("SFTPGO_AUTHD_USERNAME=%v", user.Username),
		fmt.Sprintf("SFTPGO_AUTHD_IP=%v", ip),
		fmt.Sprintf("SFTPGO_AUTHD_PASSWORD=%v", user.Password))
	stdout, err := cmd.StdoutPipe()
	if err != nil {
		return authResult, err
	}
	stdin, err := cmd.StdinPipe()
	if err != nil {
		return authResult, err
	}
	err = cmd.Start()
	if err != nil {
		return authResult, err
	}
	var once sync.Once
	scanner := bufio.NewScanner(stdout)
	for scanner.Scan() {
		var response keyboardAuthHookResponse
		err = json.Unmarshal(scanner.Bytes(), &response)
		if err != nil {
			providerLog(logger.LevelInfo, "interactive auth error parsing response: %v", err)
			once.Do(func() { terminateInteractiveAuthProgram(cmd, false) })
			break
		}
		if response.AuthResult != 0 {
			authResult = response.AuthResult
			break
		}
		if err = validateKeyboardAuthResponse(response); err != nil {
			once.Do(func() { terminateInteractiveAuthProgram(cmd, false) })
			break
		}
		go func() {
			err := handleProgramInteractiveQuestions(client, response, user, stdin, ip, protocol)
			if err != nil {
				once.Do(func() { terminateInteractiveAuthProgram(cmd, false) })
			}
		}()
	}
	stdin.Close()
	once.Do(func() { terminateInteractiveAuthProgram(cmd, true) })
	go func() {
		_, err := cmd.Process.Wait()
		if err != nil {
			providerLog(logger.LevelWarn, "error waiting for #%v process to exit: %v", authHook, err)
		}
	}()

	return authResult, err
}

func doKeyboardInteractiveAuth(user *User, authHook string, client ssh.KeyboardInteractiveChallenge, ip, protocol string) (User, error) {
	var authResult int
	var err error
	if strings.HasPrefix(authHook, "http") {
		authResult, err = executeKeyboardInteractiveHTTPHook(user, authHook, client, ip, protocol)
	} else {
		authResult, err = executeKeyboardInteractiveProgram(user, authHook, client, ip, protocol)
	}
	if err != nil {
		return *user, err
	}
	if authResult != 1 {
		return *user, fmt.Errorf("keyboard interactive auth failed, result: %v", authResult)
	}
	err = checkLoginConditions(user)
	if err != nil {
		return *user, err
	}
	return *user, nil
}

func isCheckPasswordHookDefined(protocol string) bool {
	if config.CheckPasswordHook == "" {
		return false
	}
	if config.CheckPasswordScope == 0 {
		return true
	}
	switch protocol {
	case "SSH":
		return config.CheckPasswordScope&1 != 0
	case "FTP":
		return config.CheckPasswordScope&2 != 0
	case "DAV":
		return config.CheckPasswordScope&4 != 0
	default:
		return false
	}
}

func getPasswordHookResponse(username, password, ip, protocol string) ([]byte, error) {
	if strings.HasPrefix(config.CheckPasswordHook, "http") {
		var result []byte
		var url *url.URL
		url, err := url.Parse(config.CheckPasswordHook)
		if err != nil {
			providerLog(logger.LevelWarn, "invalid url for check password hook %#v, error: %v", config.CheckPasswordHook, err)
			return result, err
		}
		req := checkPasswordRequest{
			Username: username,
			Password: password,
			IP:       ip,
			Protocol: protocol,
		}
		reqAsJSON, err := json.Marshal(req)
		if err != nil {
			return result, err
		}
		httpClient := httpclient.GetHTTPClient()
		resp, err := httpClient.Post(url.String(), "application/json", bytes.NewBuffer(reqAsJSON))
		if err != nil {
			providerLog(logger.LevelWarn, "error getting check password hook response: %v", err)
			return result, err
		}
		defer resp.Body.Close()
		if resp.StatusCode != http.StatusOK {
			return result, fmt.Errorf("wrong http status code from chek password hook: %v, expected 200", resp.StatusCode)
		}
		return io.ReadAll(resp.Body)
	}
	ctx, cancel := context.WithTimeout(context.Background(), 30*time.Second)
	defer cancel()
	cmd := exec.CommandContext(ctx, config.CheckPasswordHook)
	cmd.Env = append(os.Environ(),
		fmt.Sprintf("SFTPGO_AUTHD_USERNAME=%v", username),
		fmt.Sprintf("SFTPGO_AUTHD_PASSWORD=%v", password),
		fmt.Sprintf("SFTPGO_AUTHD_IP=%v", ip),
		fmt.Sprintf("SFTPGO_AUTHD_PROTOCOL=%v", protocol),
	)
	return cmd.Output()
}

func executeCheckPasswordHook(username, password, ip, protocol string) (checkPasswordResponse, error) {
	var response checkPasswordResponse

	if !isCheckPasswordHookDefined(protocol) {
		response.Status = -1
		return response, nil
	}

	startTime := time.Now()
	out, err := getPasswordHookResponse(username, password, ip, protocol)
	providerLog(logger.LevelDebug, "check password hook executed, error: %v, elapsed: %v", err, time.Since(startTime))
	if err != nil {
		return response, err
	}
	err = json.Unmarshal(out, &response)
	return response, err
}

func getPreLoginHookResponse(loginMethod, ip, protocol string, userAsJSON []byte) ([]byte, error) {
	if strings.HasPrefix(config.PreLoginHook, "http") {
		var url *url.URL
		var result []byte
		url, err := url.Parse(config.PreLoginHook)
		if err != nil {
			providerLog(logger.LevelWarn, "invalid url for pre-login hook %#v, error: %v", config.PreLoginHook, err)
			return result, err
		}
		q := url.Query()
		q.Add("login_method", loginMethod)
		q.Add("ip", ip)
		q.Add("protocol", protocol)
		url.RawQuery = q.Encode()
		httpClient := httpclient.GetHTTPClient()
		resp, err := httpClient.Post(url.String(), "application/json", bytes.NewBuffer(userAsJSON))
		if err != nil {
			providerLog(logger.LevelWarn, "error getting pre-login hook response: %v", err)
			return result, err
		}
		defer resp.Body.Close()
		if resp.StatusCode == http.StatusNoContent {
			return result, nil
		}
		if resp.StatusCode != http.StatusOK {
			return result, fmt.Errorf("wrong pre-login hook http status code: %v, expected 200", resp.StatusCode)
		}
		return io.ReadAll(resp.Body)
	}
	ctx, cancel := context.WithTimeout(context.Background(), 30*time.Second)
	defer cancel()
	cmd := exec.CommandContext(ctx, config.PreLoginHook)
	cmd.Env = append(os.Environ(),
		fmt.Sprintf("SFTPGO_LOGIND_USER=%v", string(userAsJSON)),
		fmt.Sprintf("SFTPGO_LOGIND_METHOD=%v", loginMethod),
		fmt.Sprintf("SFTPGO_LOGIND_IP=%v", ip),
		fmt.Sprintf("SFTPGO_LOGIND_PROTOCOL=%v", protocol),
	)
	return cmd.Output()
}

func executePreLoginHook(username, loginMethod, ip, protocol string) (User, error) {
	u, err := provider.userExists(username)
	if err != nil {
		if _, ok := err.(*RecordNotFoundError); !ok {
			return u, err
		}
		u = User{
			ID:       0,
			Username: username,
		}
	}
	userAsJSON, err := json.Marshal(u)
	if err != nil {
		return u, err
	}
	startTime := time.Now()
	out, err := getPreLoginHookResponse(loginMethod, ip, protocol, userAsJSON)
	if err != nil {
		return u, fmt.Errorf("pre-login hook error: %v, elapsed %v", err, time.Since(startTime))
	}
	providerLog(logger.LevelDebug, "pre-login hook completed, elapsed: %v", time.Since(startTime))
	if strings.TrimSpace(string(out)) == "" {
		providerLog(logger.LevelDebug, "empty response from pre-login hook, no modification requested for user %#v id: %v",
			username, u.ID)
		if u.ID == 0 {
			return u, &RecordNotFoundError{err: fmt.Sprintf("username %v does not exist", username)}
		}
		return u, nil
	}

	userID := u.ID
	userUsedQuotaSize := u.UsedQuotaSize
	userUsedQuotaFiles := u.UsedQuotaFiles
	userLastQuotaUpdate := u.LastQuotaUpdate
	userLastLogin := u.LastLogin
	err = json.Unmarshal(out, &u)
	if err != nil {
		return u, fmt.Errorf("invalid pre-login hook response %#v, error: %v", string(out), err)
	}
	u.ID = userID
	u.UsedQuotaSize = userUsedQuotaSize
	u.UsedQuotaFiles = userUsedQuotaFiles
	u.LastQuotaUpdate = userLastQuotaUpdate
	u.LastLogin = userLastLogin
	if userID == 0 {
		err = provider.addUser(&u)
	} else {
		err = provider.updateUser(&u)
	}
	if err != nil {
		return u, err
	}
	providerLog(logger.LevelDebug, "user %#v added/updated from pre-login hook response, id: %v", username, userID)
	if userID == 0 {
		return provider.userExists(username)
	}
	return u, nil
}

// ExecutePostLoginHook executes the post login hook if defined
func ExecutePostLoginHook(user *User, loginMethod, ip, protocol string, err error) {
	if config.PostLoginHook == "" {
		return
	}
	if config.PostLoginScope == 1 && err == nil {
		return
	}
	if config.PostLoginScope == 2 && err != nil {
		return
	}

	go func() {
		status := "0"
		if err == nil {
			status = "1"
		}

		user.PrepareForRendering()
		userAsJSON, err := json.Marshal(user)
		if err != nil {
			providerLog(logger.LevelWarn, "error serializing user in post login hook: %v", err)
			return
		}
		if strings.HasPrefix(config.PostLoginHook, "http") {
			var url *url.URL
			url, err := url.Parse(config.PostLoginHook)
			if err != nil {
				providerLog(logger.LevelDebug, "Invalid post-login hook %#v", config.PostLoginHook)
				return
			}
			q := url.Query()
			q.Add("login_method", loginMethod)
			q.Add("ip", ip)
			q.Add("protocol", protocol)
			q.Add("status", status)
			url.RawQuery = q.Encode()

			startTime := time.Now()
			respCode := 0
			httpClient := httpclient.GetRetraybleHTTPClient()
			resp, err := httpClient.Post(url.String(), "application/json", bytes.NewBuffer(userAsJSON))
			if err == nil {
				respCode = resp.StatusCode
				resp.Body.Close()
			}
			providerLog(logger.LevelDebug, "post login hook executed, response code: %v, elapsed: %v err: %v",
				respCode, time.Since(startTime), err)
			return
		}
		ctx, cancel := context.WithTimeout(context.Background(), 20*time.Second)
		defer cancel()
		cmd := exec.CommandContext(ctx, config.PostLoginHook)
		cmd.Env = append(os.Environ(),
			fmt.Sprintf("SFTPGO_LOGIND_USER=%v", string(userAsJSON)),
			fmt.Sprintf("SFTPGO_LOGIND_IP=%v", ip),
			fmt.Sprintf("SFTPGO_LOGIND_METHOD=%v", loginMethod),
			fmt.Sprintf("SFTPGO_LOGIND_STATUS=%v", status),
			fmt.Sprintf("SFTPGO_LOGIND_PROTOCOL=%v", protocol))
		startTime := time.Now()
		err = cmd.Run()
		providerLog(logger.LevelDebug, "post login hook executed, elapsed %v err: %v", time.Since(startTime), err)
	}()
}

func getExternalAuthResponse(username, password, pkey, keyboardInteractive, ip, protocol, tlsCert string) ([]byte, error) {
	if strings.HasPrefix(config.ExternalAuthHook, "http") {
		var url *url.URL
		var result []byte
		url, err := url.Parse(config.ExternalAuthHook)
		if err != nil {
			providerLog(logger.LevelWarn, "invalid url for external auth hook %#v, error: %v", config.ExternalAuthHook, err)
			return result, err
		}
		httpClient := httpclient.GetHTTPClient()
		authRequest := make(map[string]string)
		authRequest["username"] = username
		authRequest["ip"] = ip
		authRequest["password"] = password
		authRequest["public_key"] = pkey
		authRequest["protocol"] = protocol
		authRequest["keyboard_interactive"] = keyboardInteractive
		authRequest["tls_cert"] = tlsCert
		authRequestAsJSON, err := json.Marshal(authRequest)
		if err != nil {
			providerLog(logger.LevelWarn, "error serializing external auth request: %v", err)
			return result, err
		}
		resp, err := httpClient.Post(url.String(), "application/json", bytes.NewBuffer(authRequestAsJSON))
		if err != nil {
			providerLog(logger.LevelWarn, "error getting external auth hook HTTP response: %v", err)
			return result, err
		}
		defer resp.Body.Close()
		providerLog(logger.LevelDebug, "external auth hook executed, response code: %v", resp.StatusCode)
		if resp.StatusCode != http.StatusOK {
			return result, fmt.Errorf("wrong external auth http status code: %v, expected 200", resp.StatusCode)
		}

		return io.ReadAll(resp.Body)
	}
	ctx, cancel := context.WithTimeout(context.Background(), 30*time.Second)
	defer cancel()
	cmd := exec.CommandContext(ctx, config.ExternalAuthHook)
	cmd.Env = append(os.Environ(),
		fmt.Sprintf("SFTPGO_AUTHD_USERNAME=%v", username),
		fmt.Sprintf("SFTPGO_AUTHD_IP=%v", ip),
		fmt.Sprintf("SFTPGO_AUTHD_PASSWORD=%v", password),
		fmt.Sprintf("SFTPGO_AUTHD_PUBLIC_KEY=%v", pkey),
		fmt.Sprintf("SFTPGO_AUTHD_PROTOCOL=%v", protocol),
		fmt.Sprintf("SFTPGO_AUTHD_TLS_CERT=%v", strings.ReplaceAll(tlsCert, "\n", "\\n")),
		fmt.Sprintf("SFTPGO_AUTHD_KEYBOARD_INTERACTIVE=%v", keyboardInteractive))
	return cmd.Output()
}

func doExternalAuth(username, password string, pubKey []byte, keyboardInteractive, ip, protocol string, tlsCert *x509.Certificate) (User, error) {
	var user User
	var pkey, cert string
	if len(pubKey) > 0 {
		k, err := ssh.ParsePublicKey(pubKey)
		if err != nil {
			return user, err
		}
		pkey = string(ssh.MarshalAuthorizedKey(k))
	}
	if tlsCert != nil {
		var err error
		cert, err = utils.EncodeTLSCertToPem(tlsCert)
		if err != nil {
			return user, err
		}
	}
	startTime := time.Now()
	out, err := getExternalAuthResponse(username, password, pkey, keyboardInteractive, ip, protocol, cert)
	if err != nil {
		return user, fmt.Errorf("external auth error: %v, elapsed: %v", err, time.Since(startTime))
	}
	providerLog(logger.LevelDebug, "external auth completed, elapsed: %v", time.Since(startTime))
	err = json.Unmarshal(out, &user)
	if err != nil {
		return user, fmt.Errorf("invalid external auth response: %v", err)
	}
	if user.Username == "" {
		return user, ErrInvalidCredentials
	}
	if password != "" {
		user.Password = password
	}
	if pkey != "" && !utils.IsStringPrefixInSlice(pkey, user.PublicKeys) {
		user.PublicKeys = append(user.PublicKeys, pkey)
	}
	// some users want to map multiple login usernames with a single SFTPGo account
	// for example an SFTP user logins using "user1" or "user2" and the external auth
	// returns "user" in both cases, so we use the username returned from
	// external auth and not the one used to login
	u, err := provider.userExists(user.Username)
	if err == nil {
		user.ID = u.ID
		user.UsedQuotaSize = u.UsedQuotaSize
		user.UsedQuotaFiles = u.UsedQuotaFiles
		user.LastQuotaUpdate = u.LastQuotaUpdate
		user.LastLogin = u.LastLogin
		err = provider.updateUser(&user)
		return user, err
	}
	err = provider.addUser(&user)
	if err != nil {
		return user, err
	}
	return provider.userExists(user.Username)
}

func providerLog(level logger.LogLevel, format string, v ...interface{}) {
	logger.Log(level, logSender, "", format, v...)
}

func executeNotificationCommand(operation string, commandArgs []string, userAsJSON []byte) error {
	if !filepath.IsAbs(config.Actions.Hook) {
		err := fmt.Errorf("invalid notification command %#v", config.Actions.Hook)
		logger.Warn(logSender, "", "unable to execute notification command: %v", err)
		return err
	}

	ctx, cancel := context.WithTimeout(context.Background(), 15*time.Second)
	defer cancel()

	cmd := exec.CommandContext(ctx, config.Actions.Hook, commandArgs...)
	cmd.Env = append(os.Environ(),
		fmt.Sprintf("SFTPGO_USER_ACTION=%v", operation),
		fmt.Sprintf("SFTPGO_USER=%v", string(userAsJSON)))

	startTime := time.Now()
	err := cmd.Run()
	providerLog(logger.LevelDebug, "executed command %#v with arguments: %+v, elapsed: %v, error: %v",
		config.Actions.Hook, commandArgs, time.Since(startTime), err)
	return err
}

func executeAction(operation string, user *User) {
	if !utils.IsStringInSlice(operation, config.Actions.ExecuteOn) {
		return
	}
	if config.Actions.Hook == "" {
		return
	}

	go func() {
		if operation != operationDelete {
			var err error
			u, err := provider.userExists(user.Username)
			if err != nil {
				providerLog(logger.LevelWarn, "unable to get the user to notify for operation %#v: %v", operation, err)
				return
			}
			user = &u
		}
		user.PrepareForRendering()
		userAsJSON, err := json.Marshal(user)
		if err != nil {
			providerLog(logger.LevelWarn, "unable to serialize user as JSON for operation %#v: %v", operation, err)
			return
		}
		if strings.HasPrefix(config.Actions.Hook, "http") {
			var url *url.URL
			url, err := url.Parse(config.Actions.Hook)
			if err != nil {
				providerLog(logger.LevelWarn, "Invalid http_notification_url %#v for operation %#v: %v", config.Actions.Hook, operation, err)
				return
			}
			q := url.Query()
			q.Add("action", operation)
			url.RawQuery = q.Encode()
			startTime := time.Now()
			httpClient := httpclient.GetRetraybleHTTPClient()
			resp, err := httpClient.Post(url.String(), "application/json", bytes.NewBuffer(userAsJSON))
			respCode := 0
			if err == nil {
				respCode = resp.StatusCode
				resp.Body.Close()
			}
			providerLog(logger.LevelDebug, "notified operation %#v to URL: %v status code: %v, elapsed: %v err: %v",
				operation, url.String(), respCode, time.Since(startTime), err)
		} else {
			executeNotificationCommand(operation, user.getNotificationFieldsAsSlice(operation), userAsJSON) //nolint:errcheck // the error is used in test cases only
		}
	}()
}

func updateWebDavCachedUserLastLogin(username string) {
	result, ok := webDAVUsersCache.Load(username)
	if ok {
		cachedUser := result.(*CachedUser)
		cachedUser.User.LastLogin = utils.GetTimeAsMsSinceEpoch(time.Now())
		webDAVUsersCache.Store(cachedUser.User.Username, cachedUser)
	}
}

// CacheWebDAVUser add a user to the WebDAV cache
func CacheWebDAVUser(cachedUser *CachedUser, maxSize int) {
	if maxSize > 0 {
		var cacheSize int
		var userToRemove string
		var expirationTime time.Time

		webDAVUsersCache.Range(func(k, v interface{}) bool {
			cacheSize++
			if userToRemove == "" {
				userToRemove = k.(string)
				expirationTime = v.(*CachedUser).Expiration
				return true
			}
			expireTime := v.(*CachedUser).Expiration
			if !expireTime.IsZero() && expireTime.Before(expirationTime) {
				userToRemove = k.(string)
				expirationTime = expireTime
			}
			return true
		})

		if cacheSize >= maxSize {
			RemoveCachedWebDAVUser(userToRemove)
		}
	}

	if cachedUser.User.Username != "" {
		webDAVUsersCache.Store(cachedUser.User.Username, cachedUser)
	}
}

// GetCachedWebDAVUser returns a previously cached WebDAV user
func GetCachedWebDAVUser(username string) (interface{}, bool) {
	return webDAVUsersCache.Load(username)
}

// RemoveCachedWebDAVUser removes a cached WebDAV user
func RemoveCachedWebDAVUser(username string) {
	if username != "" {
		webDAVUsersCache.Delete(username)
	}
}
