gocommon/xboxlive/xboxlive.go

package xboxlive

import (
	"bytes"
	"compress/flate"
	"crypto/aes"
	"crypto/cipher"
	"crypto/hmac"
	"crypto/rand"
	"crypto/rsa"
	"crypto/sha1"
	"crypto/sha256"
	"crypto/x509"
	"errors"
	"io"
	"net/http"
	"os"
	"strings"
	"sync"

	b64 "encoding/base64"
	"encoding/binary"
	"encoding/json"
	"encoding/pem"

	"github.com/golang-jwt/jwt"
	"golang.org/x/crypto/pkcs12"
	//"software.sslmate.com/src/go-pkcs12"
)

type JWT_Header struct {
	Typ string `json:"typ"`
	Alg string `json:"alg"`
	X5t string `json:"x5t"`
	X5u string `json:"x5u"`
}

type JWT_XDI_data struct {
	Dty string `json:"dty"` // Device Type : ex) XboxOne
}

type JWT_XUI_data struct {
	Ptx string `json:"ptx"` // 파트너 Xbox 사용자 ID (ptx) - PXUID (ptx), publisher별로 고유한 ID : ex) 293812B467D21D3295ADA06B121981F805CC38F0
	Gtg string `json:"gtg"` // 게이머 태그
}

type JWT_XBoxLiveBody struct {
	XDI JWT_XDI_data   `json:"xdi"`
	XUI []JWT_XUI_data `json:"xui"`
	Sbx string         `json:"sbx"` // SandBoxID : ex) BLHLQG.99
}

var cachedCert map[string]map[string]string
var cachedCertLock = new(sync.RWMutex)

func getcachedCert(x5u string, x5t string) string {
	cachedCertLock.Lock()
	defer cachedCertLock.Unlock()

	if cachedCert == nil {
		cachedCert = make(map[string]map[string]string)
	}

	var certKey string
	certKey = ""

	if CachedCertURI, existCachedCertURI := cachedCert[x5u]; existCachedCertURI {
		if CachedCert, existCachedCert := CachedCertURI[x5t]; existCachedCert {
			certKey = CachedCert
		}
	}
	return certKey
}

func setcachedCert(x5u string, x5t string, certKey string) {
	cachedCertLock.Lock()
	defer cachedCertLock.Unlock()
	if cachedCert[x5u] == nil {
		cachedCert[x5u] = make(map[string]string)
	}

	cachedCert[x5u][x5t] = certKey
}

func JWT_DownloadXSTSSigningCert(x5u string, x5t string) string {
	certKey := getcachedCert(x5u, x5t)

	// -- 캐싱된 자료가 없으면 웹에서 받아 온다.
	if certKey == "" {
		resp, err := http.Get(x5u) // GET 호출
		if err != nil {
			panic(err)
		}
		defer func() {
			io.Copy(io.Discard, resp.Body)
			resp.Body.Close()
		}()

		// 결과 출력
		data, err := io.ReadAll(resp.Body)
		if err != nil {
			panic(err)
		}

		var parseddata map[string]string
		err = json.Unmarshal([]byte(data), &parseddata)
		if err != nil {
			panic(err)
		}

		if downloadedkey, exist := parseddata[x5t]; exist {
			// downloadedkey = strings.Replace(downloadedkey, "-----BEGIN CERTIFICATE-----\n", "", -1)
			// downloadedkey = strings.Replace(downloadedkey, "\n-----END CERTIFICATE-----\n", "", -1)
			certKey = downloadedkey
		} else {
			panic("JWT_DownloadXSTSSigningCert : Key not found : " + x5t)
		}
	}

	setcachedCert(x5u, x5t, certKey)
	return certKey
}

func jwt_Decrypt_forXBoxLive(jwt_token string) (JWT_Header, JWT_XBoxLiveBody) {
	parts := strings.Split(jwt_token, ".")
	jwt_header, err := b64.RawURLEncoding.DecodeString(parts[0])
	if err != nil {
		panic(err)
	}

	JWT_Header_obj := JWT_Header{}
	json.Unmarshal([]byte(string(jwt_header)), &JWT_Header_obj)

	if JWT_Header_obj.Typ != "JWT" {
		panic("JWT Decrypt Error : typ is not JWT")
	}

	if JWT_Header_obj.Alg != "RS256" {
		panic("JWT Decrypt Error : alg is not RS256")
	}

	var publicKey string
	if len(JWT_Header_obj.X5u) >= len("https://xsts.auth.xboxlive.com") && JWT_Header_obj.X5u[:len("https://xsts.auth.xboxlive.com")] == "https://xsts.auth.xboxlive.com" {
		publicKey = JWT_DownloadXSTSSigningCert(JWT_Header_obj.X5u, JWT_Header_obj.X5t)
	} else {
		panic("JWT Decrypt Error : Invalid x5u host that is not trusted" + JWT_Header_obj.X5u)
	}

	block, _ := pem.Decode([]byte(publicKey))
	var cert *x509.Certificate
	cert, _ = x509.ParseCertificate(block.Bytes)
	rsaPublicKey := cert.PublicKey.(*rsa.PublicKey)

	err = verifyJWT_forXBoxLive(jwt_token, rsaPublicKey)
	if err != nil {
		panic(err)
	}
	jwt_body, err := b64.RawURLEncoding.DecodeString(parts[1])
	if err != nil {
		panic(err)
	}
	JWT_XBoxLiveBody_obj := JWT_XBoxLiveBody{}
	json.Unmarshal([]byte(string(jwt_body)), &JWT_XBoxLiveBody_obj)

	return JWT_Header_obj, JWT_XBoxLiveBody_obj

}

func verifyJWT_forXBoxLive(decompressed string, rsaPublicKey *rsa.PublicKey) error {

	token, err := jwt.Parse(decompressed, func(token *jwt.Token) (interface{}, error) {
		return rsaPublicKey, nil
	})

	if err != nil {
		if err := err.(*jwt.ValidationError); err != nil {
			if err.Errors == jwt.ValidationErrorExpired {
				return nil
			}
		}

		return err
	}

	if claims, ok := token.Claims.(jwt.MapClaims); ok && token.Valid {
		if claims["iss"].(string) != "xsts.auth.xboxlive.com" {
			return errors.New("issuer is not valid")
		}
		if claims["aud"].(string) != "rp://actionsquaredev.com/" {
			return errors.New("audience is not valid")
		}
		return nil
	}

	return errors.New("token is not valid")
}

func splitSecretKey(data []byte) ([]byte, []byte) {
	if len(data) < 2 {
		panic(" SplitSecretKey : secretkey is too small.. ")
	}

	if len(data)%2 != 0 {
		panic(" SplitSecretKey : data error ")
	}

	midpoint := len(data) / 2

	firstHalf := data[0:midpoint]
	secondHalf := data[midpoint : midpoint+midpoint]
	return firstHalf, secondHalf
}

func pkcs7UnPadding(origData []byte) []byte {
	length := len(origData)
	unpadding := int(origData[length-1])
	return origData[:(length - unpadding)]
}

func aesCBCDncrypt(plaintext []byte, key []byte, iv []byte) []byte {
	block, _ := aes.NewCipher(key)
	ciphertext := make([]byte, len(plaintext))
	mode := cipher.NewCBCDecrypter(block, iv)
	mode.CryptBlocks(ciphertext, plaintext)
	ciphertext = pkcs7UnPadding(ciphertext)
	return ciphertext
}

func deflate(inflated []byte) string {

	byteReader := bytes.NewReader(inflated)

	wBuf := new(strings.Builder)

	zr := flate.NewReader(byteReader)
	if _, err := io.Copy(wBuf, zr); err != nil {
		panic(err)
	}

	return wBuf.String()
}

var errHashMismatch = errors.New("authentication tag does not match with the computed hash")

func verifyAuthenticationTag(aad []byte, iv []byte, cipherText []byte, hmacKey []byte, authTag []byte) error {

	aadBitLength := make([]byte, 8)
	binary.BigEndian.PutUint64(aadBitLength, uint64(len(aad)*8))

	dataToSign := append(append(append(aad, iv...), cipherText...), aadBitLength...)

	h := hmac.New(sha256.New, []byte(hmacKey))
	h.Write([]byte(dataToSign))
	hash := h.Sum(nil)

	computedAuthTag, _ := splitSecretKey(hash)

	// Check if the auth tag is equal
	// The authentication tag is the first half of the hmac result
	if !bytes.Equal(authTag, computedAuthTag) {
		return errHashMismatch
	}

	return nil
}

var privateKeydata []byte

func privateKeyFile() string {
	return os.Getenv("XBOXLIVE_PTX_FILE_NAME")
}
func privateKeyFilePass() string {
	return os.Getenv("XBOXLIVE_PTX_FILE_PASSWORD")
}

func Init() {
	if len(privateKeyFile()) == 0 || len(privateKeyFilePass()) == 0 {
		return
	}

	var err error
	privateKeydata, err = os.ReadFile(privateKeyFile())
	if err != nil {
		panic("Error reading private key file")
	}
}

// 실제 체크 함수
func AuthCheck(token string) (ptx string, err error) {
	parts := strings.Split(token, ".")

	encryptedData, _ := b64.RawURLEncoding.DecodeString(parts[1])

	privateKey, _, e := pkcs12.Decode(privateKeydata, privateKeyFilePass())
	if e != nil {
		return "", e
	}

	if e := privateKey.(*rsa.PrivateKey).Validate(); e != nil {
		return "", e
	}

	hash := sha1.New()
	random := rand.Reader
	decryptedData, decryptErr := rsa.DecryptOAEP(hash, random, privateKey.(*rsa.PrivateKey), encryptedData, nil)
	if decryptErr != nil {
		return "", decryptErr
	}

	hmacKey, aesKey := splitSecretKey(decryptedData)

	iv, _ := b64.RawURLEncoding.DecodeString(parts[2])
	encryptedContent, _ := b64.RawURLEncoding.DecodeString(parts[3])

	//  Decrypt the payload using the AES + IV
	decrypted := aesCBCDncrypt(encryptedContent, aesKey, iv)
	decompressed := deflate(decrypted)

	_, body := jwt_Decrypt_forXBoxLive(decompressed)

	authTag, _ := b64.RawURLEncoding.DecodeString(parts[4])
	authData := []byte(parts[0])
	err = verifyAuthenticationTag(authData, iv, encryptedContent, hmacKey, authTag)

	return body.XUI[0].Ptx, err

}