package main

import (
	"encoding/base64"
	"encoding/json"
	"errors"
	"fmt"
	"log"
	"os"
	"regexp"
	"strconv"
	"strings"
	"time"

	hibp "github.com/mattevans/pwned-passwords"
)

type vpnSession struct {
	Time          time.Time `json:"time"`
	Login         string    `json:"username"`
	Operation     string    `json:"operation"`
	Status        string    `json:"status"`
	Profile       string    `json:"profile"`
	TwoFA         bool      `json:"2fa_auth"`
	IP            string    `json:"client_ip"`
	PrivIP        string    `json:"private_ip"`
	AsNumber      string    `json:"as_number"`
	AsName        string    `json:"as_name"`
	NewAS         bool      `json:"as_new"`
	PwnedPasswd   bool      `json:"pwned_passwd"`
	Hostname      string    `json:"hostname"`
	TooMuchPwn    bool      `json:"too_much_pwn"`
	Mail          string    `json:"-"`
	cID           int       `json:"-"`
	kID           int       `json:"-"`
	port          int       `json:"-"`
	dev           string    `json:"-"`
	password      string    `json:"-"`
	otpCode       string    `json:"-"`
	localIP       string    `json:"-"`
	vpnserver     string    `json:"-"`
	pwnMail       string    `json:"-"`
	newAsMail     string    `json:"-"`
	MailFrom      string    `json:"-"`
	CcPwnPassword string    `json:"-"`
}

func NewVPNSession(operation string) *vpnSession {
	v := vpnSession{
		Time:      time.Now().Round(time.Second),
		Status:    "system failure",
		Operation: operation,
	}
	v.Hostname, _ = os.Hostname()

	return &v
}

func (c *vpnSession) String() string {
	if res, err := json.MarshalIndent(c, " ", "  "); err == nil {
		return string(res)
	}
	return ""
}

func (c *vpnSession) b64Login() string {
	return base64.StdEncoding.EncodeToString([]byte(c.Login))
}

func (c *vpnSession) baseHash(salt string, i int64) string {
	return fmt.Sprintf("%s%s%s%s", salt, c.Login, c.IP, i)
}

func (c *vpnSession) ParseSessionId(line string) error {
	var err error
	client_id := strings.Split(strings.Replace(line, ">CLIENT:CONNECT,", "", 1), ",")
	if c.cID, err = strconv.Atoi(client_id[0]); err != nil {
		return err
	}
	if c.kID, err = strconv.Atoi(client_id[1]); err != nil {
		return err
	}
	return nil
}

func (c *vpnSession) CheckPwn(password string) error {
	client := hibp.NewClient()
	pwned, err := client.Pwned.Compromised(password)
	if err != nil {
		return err
	}
	c.PwnedPasswd = pwned
	return nil
}

func (c *vpnSession) ParseEnv(infos *[]string) error {
	var err error
	r := regexp.MustCompile("[^a-zA-Z0-9./_@-]")

	for _, line := range *infos {
		p := strings.Split(strings.Replace(line, ">CLIENT:ENV,", "", 1), "=")
		switch p[0] {
		case "trusted_port":
			if c.port, err = strconv.Atoi(r.ReplaceAllString(p[1], "")); err != nil {
				return err
			}
		case "untrusted_port":
			if c.port, err = strconv.Atoi(r.ReplaceAllString(p[1], "")); err != nil {
				return err
			}
		case "trusted_ip":
			c.IP = r.ReplaceAllString(p[1], "")
		case "untrusted_ip":
			c.IP = r.ReplaceAllString(p[1], "")
		case "ifconfig_pool_remote_ip":
			c.PrivIP = r.ReplaceAllString(p[1], "")
		case "ifconfig_local":
			c.localIP = r.ReplaceAllString(p[1], "")
		case "password":
			switch {
			case strings.HasPrefix(p[1], "CRV1"):
				split := strings.Split(p[1], ":")
				if len(split) != 5 {
					break
				}
				c.password = split[2]
				c.otpCode = split[4]
				if c.otpCode == "" {
					c.otpCode = "***"
				}
				go c.CheckPwn(c.password)

			case strings.HasPrefix(p[1], "SCRV1"):
				split := strings.Split(p[1], ":")
				if len(split) != 3 {
					break
				}
				data, err := base64.StdEncoding.DecodeString(split[1])
				if err != nil {
					break
				}
				c.password = string(data)

				data, err = base64.StdEncoding.DecodeString(split[2])
				if err != nil {
					c.password = p[1]
					break
				}
				c.otpCode = string(data)

				if c.otpCode == "" {
					c.otpCode = "***"
				}

			default:
				c.password = p[1]
				c.otpCode = ""
				go c.CheckPwn(c.password)
			}

		case "username":
			c.Login = r.ReplaceAllString(p[1], "")
		case "dev":
			c.dev = r.ReplaceAllString(p[1], "")
		}
	}
	return nil
}

func (c *vpnSession) Auth(s *OpenVpnMgt) {
	var cmd []string
	var ip string
	var errIP error

	err, ok := c.auth(s)
	// if auth is ok, time to get an IP address
	if ok == 0 {
		ip, errIP = s.getIP(c)
		if errIP != nil {
			ok = -10
			err = errIP
		}
	}

	switch {
	case ok == 0:
		cmd = []string{
			fmt.Sprintf("client-auth %d %d", c.cID, c.kID),
			fmt.Sprintf("ifconfig-push %s %s", ip, c.localIP),
		}
		for _, r := range s.ldap[c.Profile].routes {
			cmd = append(cmd, fmt.Sprintf("push \"route %s vpn_gateway\"", r))
		}
		cmd = append(cmd, "END")

	case ok < 0:
		cmd = []string{fmt.Sprintf("client-deny %d %d \"%s\" \"%s\"",
			c.cID, c.kID, err, err)}

	case ok == 1:
		cmd = []string{fmt.Sprintf(
			"client-deny %d %d \"Need OTP\" \"CRV1:R,E:%s:%s:OTP Code \"",
			c.cID, c.kID, c.password, c.b64Login())}
	}

	if err, _ := s.sendCommand(cmd, c.vpnserver); err != nil {
		c.LogPrintln(err)
	}

	return
}

// main authentication function.
// returns 0 if auth is valid
// returns 1 if an TOTP code is necessary
// returns a negative if auth is not valid
func (c *vpnSession) auth(s *OpenVpnMgt) (error, int) {
	// an empty password is not good
	if c.password == "" {
		c.Status = "Empty Password"
		return errors.New("Empty Password"), -1
	}

	// check if the password is a valid token (see TOTP request)
	tokenPasswordOk, tokenPassword := s.TokenPassword(c)

	// password is a token. We remove it from the session object to
	// avoid checking it against the ldap
	if tokenPasswordOk {
		c.password = ""
	}

	// if the otp is not empty, we check it against the valid codes as soon as
	// possible
	otpvalidated := false
	if c.otpCode != "" {
		codes, err := s.GenerateOTP(c.Login)
		if err != nil {
			return err, -2
		}
		for _, possible := range codes {
			if possible == c.otpCode {
				otpvalidated = true
			}
		}
	}

	c.Profile = ""
	login := []string{c.Login}
	pass := c.password

	for {
		n := c.Profile
		for k, ldap := range s.ldap {
			if ldap.upgradeFrom != c.Profile {
				continue
			}
			err, userOk, passOk, secondary := ldap.Auth(login, pass)

			// if there is an error, try the other configurations
			if err != nil {
				c.LogPrintln(err)
				continue
			}

			// we did find a valid User
			if userOk {
				// the login for the new auth level is given by the current one
				login = secondary

				if c.Mail == "" {
					c.Mail = secondary[0]
				}

				if passOk && c.Profile != "" {
					// it's at least the second auth level, and we have a valid
					// password on 2 different auth system. It's a dupplicate
					// password, let's log it
					log.Printf("User %s has a dupplicate password\n", c.Login)
				}

				// we have either a positive auth ok a previous valid one
				if passOk || c.Profile != "" || tokenPasswordOk {
					c.Profile = k
				}
			}
		}

		// no profile update this turn, no need to continue
		if n == c.Profile {
			break
		}
	}

	// no profile validated, we stop here
	if c.Profile == "" {
		c.Status = "fail (password)"
		return errors.New("Authentication Failed"), -3
	}

	// check the MFA requested by the secured profile
	c.TwoFA = true
	switch s.ldap[c.Profile].mfaType {
	case "internal":
		if otpvalidated {
			return nil, 0
		}
		// log that the failure is due to the OTP
		if c.otpCode == "" {
			c.Status = "Need OTP Code"
		} else {
			c.Status = "fail (OTP) : "
		}
		c.password = tokenPassword
		return errors.New("Need OTP Code"), 1
	case "okta":
		//TODO implement okta MFA
		c.Status = "fail (Okta)"
		return nil, -4
	default:
		c.TwoFA = false
	}

	// no MFA requested, the login is valid
	return nil, 0
}