// Copyright 2014 The Gogs Authors. All rights reserved.
// Copyright 2019 The Gitea Authors. All rights reserved.
// Use of this source code is governed by a MIT-style
// license that can be found in the LICENSE file.

package models

import (
	"crypto/tls"
	"errors"
	"fmt"
	"net/smtp"
	"net/textproto"
	"strconv"
	"strings"

	"code.gitea.io/gitea/modules/auth/ldap"
	"code.gitea.io/gitea/modules/auth/oauth2"
	"code.gitea.io/gitea/modules/auth/pam"
	"code.gitea.io/gitea/modules/log"
	"code.gitea.io/gitea/modules/setting"
	"code.gitea.io/gitea/modules/timeutil"
	"code.gitea.io/gitea/modules/util"
	gouuid "github.com/google/uuid"
	jsoniter "github.com/json-iterator/go"

	"xorm.io/xorm"
	"xorm.io/xorm/convert"
)

// LoginType represents an login type.
type LoginType int

// Note: new type must append to the end of list to maintain compatibility.
const (
	LoginNoType LoginType = iota
	LoginPlain            // 1
	LoginLDAP             // 2
	LoginSMTP             // 3
	LoginPAM              // 4
	LoginDLDAP            // 5
	LoginOAuth2           // 6
	LoginSSPI             // 7
)

// LoginNames contains the name of LoginType values.
var LoginNames = map[LoginType]string{
	LoginLDAP:   "LDAP (via BindDN)",
	LoginDLDAP:  "LDAP (simple auth)", // Via direct bind
	LoginSMTP:   "SMTP",
	LoginPAM:    "PAM",
	LoginOAuth2: "OAuth2",
	LoginSSPI:   "SPNEGO with SSPI",
}

// SecurityProtocolNames contains the name of SecurityProtocol values.
var SecurityProtocolNames = map[ldap.SecurityProtocol]string{
	ldap.SecurityProtocolUnencrypted: "Unencrypted",
	ldap.SecurityProtocolLDAPS:       "LDAPS",
	ldap.SecurityProtocolStartTLS:    "StartTLS",
}

// Ensure structs implemented interface.
var (
	_ convert.Conversion = &LDAPConfig{}
	_ convert.Conversion = &SMTPConfig{}
	_ convert.Conversion = &PAMConfig{}
	_ convert.Conversion = &OAuth2Config{}
	_ convert.Conversion = &SSPIConfig{}
)

// jsonUnmarshalIgnoreErroneousBOM - due to a bug in xorm (see https://gitea.com/xorm/xorm/pulls/1957) - it's
// possible that a Blob may gain an unwanted prefix of 0xff 0xfe.
func jsonUnmarshalIgnoreErroneousBOM(bs []byte, v interface{}) error {
	json := jsoniter.ConfigCompatibleWithStandardLibrary
	err := json.Unmarshal(bs, v)
	if err != nil && len(bs) > 2 && bs[0] == 0xff && bs[1] == 0xfe {
		err = json.Unmarshal(bs[2:], v)
	}
	return err
}

// LDAPConfig holds configuration for LDAP login source.
type LDAPConfig struct {
	*ldap.Source
}

// FromDB fills up a LDAPConfig from serialized format.
func (cfg *LDAPConfig) FromDB(bs []byte) error {
	return jsonUnmarshalIgnoreErroneousBOM(bs, &cfg)
}

// ToDB exports a LDAPConfig to a serialized format.
func (cfg *LDAPConfig) ToDB() ([]byte, error) {
	json := jsoniter.ConfigCompatibleWithStandardLibrary
	return json.Marshal(cfg)
}

// SecurityProtocolName returns the name of configured security
// protocol.
func (cfg *LDAPConfig) SecurityProtocolName() string {
	return SecurityProtocolNames[cfg.SecurityProtocol]
}

// SMTPConfig holds configuration for the SMTP login source.
type SMTPConfig struct {
	Auth           string
	Host           string
	Port           int
	AllowedDomains string `xorm:"TEXT"`
	TLS            bool
	SkipVerify     bool
}

// FromDB fills up an SMTPConfig from serialized format.
func (cfg *SMTPConfig) FromDB(bs []byte) error {
	return jsonUnmarshalIgnoreErroneousBOM(bs, cfg)
}

// ToDB exports an SMTPConfig to a serialized format.
func (cfg *SMTPConfig) ToDB() ([]byte, error) {
	json := jsoniter.ConfigCompatibleWithStandardLibrary
	return json.Marshal(cfg)
}

// PAMConfig holds configuration for the PAM login source.
type PAMConfig struct {
	ServiceName string // pam service (e.g. system-auth)
	EmailDomain string
}

// FromDB fills up a PAMConfig from serialized format.
func (cfg *PAMConfig) FromDB(bs []byte) error {
	return jsonUnmarshalIgnoreErroneousBOM(bs, cfg)
}

// ToDB exports a PAMConfig to a serialized format.
func (cfg *PAMConfig) ToDB() ([]byte, error) {
	json := jsoniter.ConfigCompatibleWithStandardLibrary
	return json.Marshal(cfg)
}

// OAuth2Config holds configuration for the OAuth2 login source.
type OAuth2Config struct {
	Provider                      string
	ClientID                      string
	ClientSecret                  string
	OpenIDConnectAutoDiscoveryURL string
	CustomURLMapping              *oauth2.CustomURLMapping
	IconURL                       string
}

// FromDB fills up an OAuth2Config from serialized format.
func (cfg *OAuth2Config) FromDB(bs []byte) error {
	return jsonUnmarshalIgnoreErroneousBOM(bs, cfg)
}

// ToDB exports an SMTPConfig to a serialized format.
func (cfg *OAuth2Config) ToDB() ([]byte, error) {
	json := jsoniter.ConfigCompatibleWithStandardLibrary
	return json.Marshal(cfg)
}

// SSPIConfig holds configuration for SSPI single sign-on.
type SSPIConfig struct {
	AutoCreateUsers      bool
	AutoActivateUsers    bool
	StripDomainNames     bool
	SeparatorReplacement string
	DefaultLanguage      string
}

// FromDB fills up an SSPIConfig from serialized format.
func (cfg *SSPIConfig) FromDB(bs []byte) error {
	return jsonUnmarshalIgnoreErroneousBOM(bs, cfg)
}

// ToDB exports an SSPIConfig to a serialized format.
func (cfg *SSPIConfig) ToDB() ([]byte, error) {
	json := jsoniter.ConfigCompatibleWithStandardLibrary
	return json.Marshal(cfg)
}

// LoginSource represents an external way for authorizing users.
type LoginSource struct {
	ID            int64 `xorm:"pk autoincr"`
	Type          LoginType
	Name          string             `xorm:"UNIQUE"`
	IsActived     bool               `xorm:"INDEX NOT NULL DEFAULT false"`
	IsSyncEnabled bool               `xorm:"INDEX NOT NULL DEFAULT false"`
	Cfg           convert.Conversion `xorm:"TEXT"`

	CreatedUnix timeutil.TimeStamp `xorm:"INDEX created"`
	UpdatedUnix timeutil.TimeStamp `xorm:"INDEX updated"`
}

// Cell2Int64 converts a xorm.Cell type to int64,
// and handles possible irregular cases.
func Cell2Int64(val xorm.Cell) int64 {
	switch (*val).(type) {
	case []uint8:
		log.Trace("Cell2Int64 ([]uint8): %v", *val)

		v, _ := strconv.ParseInt(string((*val).([]uint8)), 10, 64)
		return v
	}
	return (*val).(int64)
}

// BeforeSet is invoked from XORM before setting the value of a field of this object.
func (source *LoginSource) BeforeSet(colName string, val xorm.Cell) {
	if colName == "type" {
		switch LoginType(Cell2Int64(val)) {
		case LoginLDAP, LoginDLDAP:
			source.Cfg = new(LDAPConfig)
		case LoginSMTP:
			source.Cfg = new(SMTPConfig)
		case LoginPAM:
			source.Cfg = new(PAMConfig)
		case LoginOAuth2:
			source.Cfg = new(OAuth2Config)
		case LoginSSPI:
			source.Cfg = new(SSPIConfig)
		default:
			panic(fmt.Sprintf("unrecognized login source type: %v", *val))
		}
	}
}

// TypeName return name of this login source type.
func (source *LoginSource) TypeName() string {
	return LoginNames[source.Type]
}

// IsLDAP returns true of this source is of the LDAP type.
func (source *LoginSource) IsLDAP() bool {
	return source.Type == LoginLDAP
}

// IsDLDAP returns true of this source is of the DLDAP type.
func (source *LoginSource) IsDLDAP() bool {
	return source.Type == LoginDLDAP
}

// IsSMTP returns true of this source is of the SMTP type.
func (source *LoginSource) IsSMTP() bool {
	return source.Type == LoginSMTP
}

// IsPAM returns true of this source is of the PAM type.
func (source *LoginSource) IsPAM() bool {
	return source.Type == LoginPAM
}

// IsOAuth2 returns true of this source is of the OAuth2 type.
func (source *LoginSource) IsOAuth2() bool {
	return source.Type == LoginOAuth2
}

// IsSSPI returns true of this source is of the SSPI type.
func (source *LoginSource) IsSSPI() bool {
	return source.Type == LoginSSPI
}

// HasTLS returns true of this source supports TLS.
func (source *LoginSource) HasTLS() bool {
	return ((source.IsLDAP() || source.IsDLDAP()) &&
		source.LDAP().SecurityProtocol > ldap.SecurityProtocolUnencrypted) ||
		source.IsSMTP()
}

// UseTLS returns true of this source is configured to use TLS.
func (source *LoginSource) UseTLS() bool {
	switch source.Type {
	case LoginLDAP, LoginDLDAP:
		return source.LDAP().SecurityProtocol != ldap.SecurityProtocolUnencrypted
	case LoginSMTP:
		return source.SMTP().TLS
	}

	return false
}

// SkipVerify returns true if this source is configured to skip SSL
// verification.
func (source *LoginSource) SkipVerify() bool {
	switch source.Type {
	case LoginLDAP, LoginDLDAP:
		return source.LDAP().SkipVerify
	case LoginSMTP:
		return source.SMTP().SkipVerify
	}

	return false
}

// LDAP returns LDAPConfig for this source, if of LDAP type.
func (source *LoginSource) LDAP() *LDAPConfig {
	return source.Cfg.(*LDAPConfig)
}

// SMTP returns SMTPConfig for this source, if of SMTP type.
func (source *LoginSource) SMTP() *SMTPConfig {
	return source.Cfg.(*SMTPConfig)
}

// PAM returns PAMConfig for this source, if of PAM type.
func (source *LoginSource) PAM() *PAMConfig {
	return source.Cfg.(*PAMConfig)
}

// OAuth2 returns OAuth2Config for this source, if of OAuth2 type.
func (source *LoginSource) OAuth2() *OAuth2Config {
	return source.Cfg.(*OAuth2Config)
}

// SSPI returns SSPIConfig for this source, if of SSPI type.
func (source *LoginSource) SSPI() *SSPIConfig {
	return source.Cfg.(*SSPIConfig)
}

// CreateLoginSource inserts a LoginSource in the DB if not already
// existing with the given name.
func CreateLoginSource(source *LoginSource) error {
	has, err := x.Where("name=?", source.Name).Exist(new(LoginSource))
	if err != nil {
		return err
	} else if has {
		return ErrLoginSourceAlreadyExist{source.Name}
	}
	// Synchronization is only aviable with LDAP for now
	if !source.IsLDAP() {
		source.IsSyncEnabled = false
	}

	_, err = x.Insert(source)
	if err == nil && source.IsOAuth2() && source.IsActived {
		oAuth2Config := source.OAuth2()
		err = oauth2.RegisterProvider(source.Name, oAuth2Config.Provider, oAuth2Config.ClientID, oAuth2Config.ClientSecret, oAuth2Config.OpenIDConnectAutoDiscoveryURL, oAuth2Config.CustomURLMapping)
		err = wrapOpenIDConnectInitializeError(err, source.Name, oAuth2Config)
		if err != nil {
			// remove the LoginSource in case of errors while registering OAuth2 providers
			if _, err := x.Delete(source); err != nil {
				log.Error("CreateLoginSource: Error while wrapOpenIDConnectInitializeError: %v", err)
			}
			return err
		}
	}
	return err
}

// LoginSources returns a slice of all login sources found in DB.
func LoginSources() ([]*LoginSource, error) {
	auths := make([]*LoginSource, 0, 6)
	return auths, x.Find(&auths)
}

// LoginSourcesByType returns all sources of the specified type
func LoginSourcesByType(loginType LoginType) ([]*LoginSource, error) {
	sources := make([]*LoginSource, 0, 1)
	if err := x.Where("type = ?", loginType).Find(&sources); err != nil {
		return nil, err
	}
	return sources, nil
}

// ActiveLoginSources returns all active sources of the specified type
func ActiveLoginSources(loginType LoginType) ([]*LoginSource, error) {
	sources := make([]*LoginSource, 0, 1)
	if err := x.Where("is_actived = ? and type = ?", true, loginType).Find(&sources); err != nil {
		return nil, err
	}
	return sources, nil
}

// IsSSPIEnabled returns true if there is at least one activated login
// source of type LoginSSPI
func IsSSPIEnabled() bool {
	if !HasEngine {
		return false
	}
	sources, err := ActiveLoginSources(LoginSSPI)
	if err != nil {
		log.Error("ActiveLoginSources: %v", err)
		return false
	}
	return len(sources) > 0
}

// GetLoginSourceByID returns login source by given ID.
func GetLoginSourceByID(id int64) (*LoginSource, error) {
	source := new(LoginSource)
	has, err := x.ID(id).Get(source)
	if err != nil {
		return nil, err
	} else if !has {
		return nil, ErrLoginSourceNotExist{id}
	}
	return source, nil
}

// UpdateSource updates a LoginSource record in DB.
func UpdateSource(source *LoginSource) error {
	var originalLoginSource *LoginSource
	if source.IsOAuth2() {
		// keep track of the original values so we can restore in case of errors while registering OAuth2 providers
		var err error
		if originalLoginSource, err = GetLoginSourceByID(source.ID); err != nil {
			return err
		}
	}

	_, err := x.ID(source.ID).AllCols().Update(source)
	if err == nil && source.IsOAuth2() && source.IsActived {
		oAuth2Config := source.OAuth2()
		err = oauth2.RegisterProvider(source.Name, oAuth2Config.Provider, oAuth2Config.ClientID, oAuth2Config.ClientSecret, oAuth2Config.OpenIDConnectAutoDiscoveryURL, oAuth2Config.CustomURLMapping)
		err = wrapOpenIDConnectInitializeError(err, source.Name, oAuth2Config)
		if err != nil {
			// restore original values since we cannot update the provider it self
			if _, err := x.ID(source.ID).AllCols().Update(originalLoginSource); err != nil {
				log.Error("UpdateSource: Error while wrapOpenIDConnectInitializeError: %v", err)
			}
			return err
		}
	}
	return err
}

// DeleteSource deletes a LoginSource record in DB.
func DeleteSource(source *LoginSource) error {
	count, err := x.Count(&User{LoginSource: source.ID})
	if err != nil {
		return err
	} else if count > 0 {
		return ErrLoginSourceInUse{source.ID}
	}

	count, err = x.Count(&ExternalLoginUser{LoginSourceID: source.ID})
	if err != nil {
		return err
	} else if count > 0 {
		return ErrLoginSourceInUse{source.ID}
	}

	if source.IsOAuth2() {
		oauth2.RemoveProvider(source.Name)
	}

	_, err = x.ID(source.ID).Delete(new(LoginSource))
	return err
}

// CountLoginSources returns number of login sources.
func CountLoginSources() int64 {
	count, _ := x.Count(new(LoginSource))
	return count
}

// .____     ________      _____ __________
// |    |    \______ \    /  _  \\______   \
// |    |     |    |  \  /  /_\  \|     ___/
// |    |___  |    `   \/    |    \    |
// |_______ \/_______  /\____|__  /____|
//         \/        \/         \/

func composeFullName(firstname, surname, username string) string {
	switch {
	case len(firstname) == 0 && len(surname) == 0:
		return username
	case len(firstname) == 0:
		return surname
	case len(surname) == 0:
		return firstname
	default:
		return firstname + " " + surname
	}
}

// LoginViaLDAP queries if login/password is valid against the LDAP directory pool,
// and create a local user if success when enabled.
func LoginViaLDAP(user *User, login, password string, source *LoginSource) (*User, error) {
	sr := source.Cfg.(*LDAPConfig).SearchEntry(login, password, source.Type == LoginDLDAP)
	if sr == nil {
		// User not in LDAP, do nothing
		return nil, ErrUserNotExist{0, login, 0}
	}

	isAttributeSSHPublicKeySet := len(strings.TrimSpace(source.LDAP().AttributeSSHPublicKey)) > 0

	// Update User admin flag if exist
	if isExist, err := IsUserExist(0, sr.Username); err != nil {
		return nil, err
	} else if isExist {
		if user == nil {
			user, err = GetUserByName(sr.Username)
			if err != nil {
				return nil, err
			}
		}
		if user != nil && !user.ProhibitLogin {
			cols := make([]string, 0)
			if len(source.LDAP().AdminFilter) > 0 && user.IsAdmin != sr.IsAdmin {
				// Change existing admin flag only if AdminFilter option is set
				user.IsAdmin = sr.IsAdmin
				cols = append(cols, "is_admin")
			}
			if !user.IsAdmin && len(source.LDAP().RestrictedFilter) > 0 && user.IsRestricted != sr.IsRestricted {
				// Change existing restricted flag only if RestrictedFilter option is set
				user.IsRestricted = sr.IsRestricted
				cols = append(cols, "is_restricted")
			}
			if len(cols) > 0 {
				err = UpdateUserCols(user, cols...)
				if err != nil {
					return nil, err
				}
			}
		}
	}

	if user != nil {
		if isAttributeSSHPublicKeySet && synchronizeLdapSSHPublicKeys(user, source, sr.SSHPublicKey) {
			return user, RewriteAllPublicKeys()
		}

		return user, nil
	}

	// Fallback.
	if len(sr.Username) == 0 {
		sr.Username = login
	}

	if len(sr.Mail) == 0 {
		sr.Mail = fmt.Sprintf("%s@localhost", sr.Username)
	}

	user = &User{
		LowerName:    strings.ToLower(sr.Username),
		Name:         sr.Username,
		FullName:     composeFullName(sr.Name, sr.Surname, sr.Username),
		Email:        sr.Mail,
		LoginType:    source.Type,
		LoginSource:  source.ID,
		LoginName:    login,
		IsActive:     true,
		IsAdmin:      sr.IsAdmin,
		IsRestricted: sr.IsRestricted,
	}

	err := CreateUser(user)

	if err == nil && isAttributeSSHPublicKeySet && addLdapSSHPublicKeys(user, source, sr.SSHPublicKey) {
		err = RewriteAllPublicKeys()
	}

	return user, err
}

//   _________   __________________________
//  /   _____/  /     \__    ___/\______   \
//  \_____  \  /  \ /  \|    |    |     ___/
//  /        \/    Y    \    |    |    |
// /_______  /\____|__  /____|    |____|
//         \/         \/

type smtpLoginAuth struct {
	username, password string
}

func (auth *smtpLoginAuth) Start(server *smtp.ServerInfo) (string, []byte, error) {
	return "LOGIN", []byte(auth.username), nil
}

func (auth *smtpLoginAuth) Next(fromServer []byte, more bool) ([]byte, error) {
	if more {
		switch string(fromServer) {
		case "Username:":
			return []byte(auth.username), nil
		case "Password:":
			return []byte(auth.password), nil
		}
	}
	return nil, nil
}

// SMTP authentication type names.
const (
	SMTPPlain = "PLAIN"
	SMTPLogin = "LOGIN"
)

// SMTPAuths contains available SMTP authentication type names.
var SMTPAuths = []string{SMTPPlain, SMTPLogin}

// SMTPAuth performs an SMTP authentication.
func SMTPAuth(a smtp.Auth, cfg *SMTPConfig) error {
	c, err := smtp.Dial(fmt.Sprintf("%s:%d", cfg.Host, cfg.Port))
	if err != nil {
		return err
	}
	defer c.Close()

	if err = c.Hello("gogs"); err != nil {
		return err
	}

	if cfg.TLS {
		if ok, _ := c.Extension("STARTTLS"); ok {
			if err = c.StartTLS(&tls.Config{
				InsecureSkipVerify: cfg.SkipVerify,
				ServerName:         cfg.Host,
			}); err != nil {
				return err
			}
		} else {
			return errors.New("SMTP server unsupports TLS")
		}
	}

	if ok, _ := c.Extension("AUTH"); ok {
		return c.Auth(a)
	}
	return ErrUnsupportedLoginType
}

// LoginViaSMTP queries if login/password is valid against the SMTP,
// and create a local user if success when enabled.
func LoginViaSMTP(user *User, login, password string, sourceID int64, cfg *SMTPConfig) (*User, error) {
	// Verify allowed domains.
	if len(cfg.AllowedDomains) > 0 {
		idx := strings.Index(login, "@")
		if idx == -1 {
			return nil, ErrUserNotExist{0, login, 0}
		} else if !util.IsStringInSlice(login[idx+1:], strings.Split(cfg.AllowedDomains, ","), true) {
			return nil, ErrUserNotExist{0, login, 0}
		}
	}

	var auth smtp.Auth
	if cfg.Auth == SMTPPlain {
		auth = smtp.PlainAuth("", login, password, cfg.Host)
	} else if cfg.Auth == SMTPLogin {
		auth = &smtpLoginAuth{login, password}
	} else {
		return nil, errors.New("Unsupported SMTP auth type")
	}

	if err := SMTPAuth(auth, cfg); err != nil {
		// Check standard error format first,
		// then fallback to worse case.
		tperr, ok := err.(*textproto.Error)
		if (ok && tperr.Code == 535) ||
			strings.Contains(err.Error(), "Username and Password not accepted") {
			return nil, ErrUserNotExist{0, login, 0}
		}
		return nil, err
	}

	if user != nil {
		return user, nil
	}

	username := login
	idx := strings.Index(login, "@")
	if idx > -1 {
		username = login[:idx]
	}

	user = &User{
		LowerName:   strings.ToLower(username),
		Name:        strings.ToLower(username),
		Email:       login,
		Passwd:      password,
		LoginType:   LoginSMTP,
		LoginSource: sourceID,
		LoginName:   login,
		IsActive:    true,
	}
	return user, CreateUser(user)
}

// __________  _____      _____
// \______   \/  _  \    /     \
//  |     ___/  /_\  \  /  \ /  \
//  |    |  /    |    \/    Y    \
//  |____|  \____|__  /\____|__  /
//                  \/         \/

// LoginViaPAM queries if login/password is valid against the PAM,
// and create a local user if success when enabled.
func LoginViaPAM(user *User, login, password string, sourceID int64, cfg *PAMConfig) (*User, error) {
	pamLogin, err := pam.Auth(cfg.ServiceName, login, password)
	if err != nil {
		if strings.Contains(err.Error(), "Authentication failure") {
			return nil, ErrUserNotExist{0, login, 0}
		}
		return nil, err
	}

	if user != nil {
		return user, nil
	}

	// Allow PAM sources with `@` in their name, like from Active Directory
	username := pamLogin
	email := pamLogin
	idx := strings.Index(pamLogin, "@")
	if idx > -1 {
		username = pamLogin[:idx]
	}
	if ValidateEmail(email) != nil {
		if cfg.EmailDomain != "" {
			email = fmt.Sprintf("%s@%s", username, cfg.EmailDomain)
		} else {
			email = fmt.Sprintf("%s@%s", username, setting.Service.NoReplyAddress)
		}
		if ValidateEmail(email) != nil {
			email = gouuid.New().String() + "@localhost"
		}
	}

	user = &User{
		LowerName:   strings.ToLower(username),
		Name:        username,
		Email:       email,
		Passwd:      password,
		LoginType:   LoginPAM,
		LoginSource: sourceID,
		LoginName:   login, // This is what the user typed in
		IsActive:    true,
	}
	return user, CreateUser(user)
}

// ExternalUserLogin attempts a login using external source types.
func ExternalUserLogin(user *User, login, password string, source *LoginSource) (*User, error) {
	if !source.IsActived {
		return nil, ErrLoginSourceNotActived
	}

	var err error
	switch source.Type {
	case LoginLDAP, LoginDLDAP:
		user, err = LoginViaLDAP(user, login, password, source)
	case LoginSMTP:
		user, err = LoginViaSMTP(user, login, password, source.ID, source.Cfg.(*SMTPConfig))
	case LoginPAM:
		user, err = LoginViaPAM(user, login, password, source.ID, source.Cfg.(*PAMConfig))
	default:
		return nil, ErrUnsupportedLoginType
	}

	if err != nil {
		return nil, err
	}

	// WARN: DON'T check user.IsActive, that will be checked on reqSign so that
	// user could be hint to resend confirm email.
	if user.ProhibitLogin {
		return nil, ErrUserProhibitLogin{user.ID, user.Name}
	}

	return user, nil
}

// UserSignIn validates user name and password.
func UserSignIn(username, password string) (*User, error) {
	var user *User
	if strings.Contains(username, "@") {
		user = &User{Email: strings.ToLower(strings.TrimSpace(username))}
		// check same email
		cnt, err := x.Count(user)
		if err != nil {
			return nil, err
		}
		if cnt > 1 {
			return nil, ErrEmailAlreadyUsed{
				Email: user.Email,
			}
		}
	} else {
		trimmedUsername := strings.TrimSpace(username)
		if len(trimmedUsername) == 0 {
			return nil, ErrUserNotExist{0, username, 0}
		}

		user = &User{LowerName: strings.ToLower(trimmedUsername)}
	}

	hasUser, err := x.Get(user)
	if err != nil {
		return nil, err
	}

	if hasUser {
		switch user.LoginType {
		case LoginNoType, LoginPlain, LoginOAuth2:
			if user.IsPasswordSet() && user.ValidatePassword(password) {

				// Update password hash if server password hash algorithm have changed
				if user.PasswdHashAlgo != setting.PasswordHashAlgo {
					if err = user.SetPassword(password); err != nil {
						return nil, err
					}
					if err = UpdateUserCols(user, "passwd", "passwd_hash_algo", "salt"); err != nil {
						return nil, err
					}
				}

				// WARN: DON'T check user.IsActive, that will be checked on reqSign so that
				// user could be hint to resend confirm email.
				if user.ProhibitLogin {
					return nil, ErrUserProhibitLogin{user.ID, user.Name}
				}

				return user, nil
			}

			return nil, ErrUserNotExist{user.ID, user.Name, 0}

		default:
			var source LoginSource
			hasSource, err := x.ID(user.LoginSource).Get(&source)
			if err != nil {
				return nil, err
			} else if !hasSource {
				return nil, ErrLoginSourceNotExist{user.LoginSource}
			}

			return ExternalUserLogin(user, user.LoginName, password, &source)
		}
	}

	sources := make([]*LoginSource, 0, 5)
	if err = x.Where("is_actived = ?", true).Find(&sources); err != nil {
		return nil, err
	}

	for _, source := range sources {
		if source.IsOAuth2() || source.IsSSPI() {
			// don't try to authenticate against OAuth2 and SSPI sources here
			continue
		}
		authUser, err := ExternalUserLogin(nil, username, password, source)
		if err == nil {
			return authUser, nil
		}

		log.Warn("Failed to login '%s' via '%s': %v", username, source.Name, err)
	}

	return nil, ErrUserNotExist{user.ID, user.Name, 0}
}