/
applet.go
134 lines (107 loc) · 3.01 KB
/
applet.go
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// Package applecrypto provides necseessray tools for working with ApplePay tokens
package applecrypto
import (
"crypto/aes"
"crypto/cipher"
"crypto/ecdsa"
"crypto/elliptic"
"crypto/sha256"
"crypto/x509"
"encoding/base64"
"encoding/hex"
"encoding/pem"
"errors"
"io/ioutil"
"golang.org/x/crypto/pkcs12"
)
// extractPrivateKey assumes file containts both PrivateKey and Certificate
func extractPrivateKey(filename, password string) (*ecdsa.PrivateKey, *x509.Certificate, error) {
data, err := ioutil.ReadFile(filename)
if err != nil {
return nil, nil, err
}
privateKey, cerf, err := pkcs12.Decode(data, password)
if err != nil {
return nil, nil, err
}
pkbyte := privateKey.(*ecdsa.PrivateKey)
return pkbyte, cerf, nil
}
// getMerchID extracts MerchantId field from certificate
func getMerchID(cert *x509.Certificate) ([]byte, error) {
var merchID []byte
var merch []byte
for _, e := range cert.Extensions {
id := e.Id.String()
if id == oIDMerchantID {
merch = e.Value
}
}
if len(merch) != 66 {
return merchID, errors.New("merchantId is not 66 bytes long")
}
merch = merch[2:]
merchID, err := hex.DecodeString(string(merch))
if err != nil {
return merchID, err
}
return merchID, nil
}
func generatePublicKey(base string) (*ecdsa.PublicKey, error) {
var pbkey *ecdsa.PublicKey
block, _ := pem.Decode([]byte("-----BEGIN PUBLIC KEY-----\n" + base + "\n-----END PUBLIC KEY-----"))
pubKey, err := x509.ParsePKIXPublicKey(block.Bytes)
if err != nil {
return pbkey, err
}
pbkey = pubKey.(*ecdsa.PublicKey)
return pbkey, nil
}
func computeSecret(pbk *ecdsa.PublicKey, prk []byte) ([]byte, error) {
var secret []byte
curve := elliptic.P256()
if !curve.IsOnCurve(pbk.X, pbk.Y) {
return secret, errors.New("point is not on curve")
}
x, _ := curve.ScalarMult(pbk.X, pbk.Y, prk)
secret = x.Bytes()
return secret, nil
}
// resotoreSymmetricKey using apple guidlines
func restoreSymmetricKey(merchID, secret []byte) []byte {
hasher := sha256.New()
hasher.Write([]byte{0, 0, 0, 1})
hasher.Write(secret)
hasher.Write([]byte{13})
hasher.Write([]byte("id-aes256-GCM"))
hasher.Write([]byte("Apple"))
hasher.Write([]byte(merchID))
key := hasher.Sum(nil)
return key
}
// decryptData AES decrypts data string using apple guidlines
func decryptData(aesKey []byte, data string) ([]byte, error) {
var decrypted []byte
iv := make([]byte, 16)
dataDec, err := base64.StdEncoding.DecodeString(data)
if err != nil {
return decrypted, err
}
block, err := aes.NewCipher(aesKey)
if err != nil {
return decrypted, err
}
d, _ := cipher.NewGCMWithNonceSize(block, len(iv))
decrypted, err = d.Open(nil, iv, dataDec, nil)
return decrypted, err
}
// encryptData AES encrypts data string using apple guidlines
func encryptData(aesKey []byte, data string) ([]byte, error) {
var encrypted []byte
iv := make([]byte, 16)
dataEnc := []byte(data)
block, err := aes.NewCipher(aesKey)
e, _ := cipher.NewGCMWithNonceSize(block, len(iv))
encrypted = e.Seal(nil, iv, []byte(dataEnc), nil)
return encrypted, err
}