package main

import (
	"crypto/rand"
	"crypto/sha512"
	"encoding/base64"
	"fmt"
	"log"
	randm "math/rand"
	"os"
	"strings"

	"github.com/go-ldap/ldap/v3"
	"github.com/go-yaml/yaml"
)

type conf struct {
	LdapUrl string `yaml:"ldapurl"`
	BaseDN  string `yaml:"basedn"`
	BindDN  string `yaml:"binddn"`
	BindPW  string `yaml:"bindpw"`
}

func (c *conf) get_config() *conf {
	f, err := os.ReadFile("config.yaml")
	if err != nil {
		log.Fatal(err)
	}

	err = yaml.Unmarshal(f, c)
	if err != nil {
		log.Fatal(err)
	}

	return c
}

// Gettings uids of people that needs a password change
func get_uids(ldap_conn *ldap.Conn, basedn string) []string {
	uids := []string{}

	search_req := ldap.NewSearchRequest(basedn, ldap.ScopeWholeSubtree, 0, 0, 0, false, "(uid=*)", []string{"uid", "userPassword"}, nil)
	res, err := ldap_conn.Search(search_req)

	if err != nil {
		log.Fatal(err)
	}

	for _, entry := range res.Entries {
		uid := entry.GetAttributeValue("uid")
		password := entry.GetAttributeValue("userPassword")
		if strings.HasPrefix(password, "{SSHA}") {
			uids = append(uids, uid)
		}
	}

	return uids
}

func get_random_password(length int) string {
	characters := []rune("ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789")
	var sb strings.Builder

	for i := 0; i < length; i++ {
		sb.WriteRune(characters[randm.Intn(len(characters))])
	}

	return sb.String()
}

func get_salt() ([]byte, error) {
	salt := make([]byte, 4)
	_, err := rand.Read(salt)
	if err != nil {
		return nil, err
	}

	return salt, nil
}

func get_hash(password string, salt []byte) []byte {
	password_bytes := []byte(password)
	password_salt := append(password_bytes, salt...)
	sum := sha512.Sum512(password_salt)
	res := append(sum[:], salt...)

	return res
}

func change_password(ldap_conn *ldap.Conn, basedn string, uid string) {
	password := get_random_password(20)

	salt, err := get_salt()
	if err != nil {
		log.Fatal(err)
	}

	new_pass := "{SSHA512}" + base64.StdEncoding.EncodeToString(get_hash(password, salt))

	modify_req := ldap.NewModifyRequest("uid="+uid+","+basedn, nil)
	modify_req.Replace("userPassword", []string{new_pass})
	err = ldap_conn.Modify(modify_req)

	if err != nil {
		log.Fatal(err)
	}

	fmt.Printf("%s : %s \n", uid, password)
}

func main() {
	var c conf
	c.get_config()

	l, err := ldap.DialURL(c.LdapUrl)
	if err != nil {
		log.Fatal(err)
	}
	defer l.Close()

	err = l.Bind(c.BindDN, c.BindPW)

	if err != nil {
		log.Fatal(err)
	}

	uids := get_uids(l, c.BaseDN)

	for _, uid := range uids {
		change_password(l, c.BaseDN, uid)
	}
}