147 lines
3.2 KiB
Go
147 lines
3.2 KiB
Go
package crypto
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import (
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"bytes"
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"crypto/aes"
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"crypto/cipher"
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"crypto/ecdsa"
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"crypto/rand"
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"crypto/sha256"
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"crypto/sha512"
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"errors"
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"github.com/ethereum/go-ethereum/crypto"
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"golang.org/x/crypto/pbkdf2"
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"golang.org/x/text/unicode/norm"
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)
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const PairingTokenSalt = "Keycard Pairing Password Salt"
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var ErrInvalidCardCryptogram = errors.New("invalid card cryptogram")
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func GenerateECDHSharedSecret(priv *ecdsa.PrivateKey, pub *ecdsa.PublicKey) []byte {
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x, _ := crypto.S256().ScalarMult(pub.X, pub.Y, priv.D.Bytes())
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return x.Bytes()
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}
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func VerifyCryptogram(challenge []byte, pairingPass string, cardCryptogram []byte) ([]byte, error) {
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secretHash := pbkdf2.Key(norm.NFKD.Bytes([]byte(pairingPass)), norm.NFKD.Bytes([]byte(PairingTokenSalt)), 50000, 32, sha256.New)
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h := sha256.New()
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h.Write(secretHash[:])
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h.Write(challenge)
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expectedCryptogram := h.Sum(nil)
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if !bytes.Equal(expectedCryptogram, cardCryptogram) {
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return nil, ErrInvalidCardCryptogram
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}
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return secretHash, nil
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}
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func OneShotEncrypt(pubKeyData, secret, data []byte) ([]byte, error) {
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data = appendPadding(16, data)
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iv := make([]byte, 16)
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_, err := rand.Read(iv)
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if err != nil {
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return nil, err
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}
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block, err := aes.NewCipher(secret)
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if err != nil {
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return nil, err
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}
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ciphertext := make([]byte, len(data))
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mode := cipher.NewCBCEncrypter(block, iv)
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mode.CryptBlocks(ciphertext, data)
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encrypted := append([]byte{byte(len(pubKeyData))}, pubKeyData...)
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encrypted = append(encrypted, iv...)
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encrypted = append(encrypted, ciphertext...)
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return encrypted, nil
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}
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func DeriveSessionKeys(secret, pairingKey, cardData []byte) ([]byte, []byte, []byte) {
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salt := cardData[:32]
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iv := cardData[32:]
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h := sha512.New()
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h.Write(secret)
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h.Write(pairingKey)
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h.Write(salt)
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data := h.Sum(nil)
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encKey := data[:32]
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macKey := data[32:]
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return encKey, macKey, iv
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}
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func EncryptData(data []byte, encKey []byte, iv []byte) ([]byte, error) {
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data = appendPadding(16, data)
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block, err := aes.NewCipher(encKey)
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if err != nil {
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return nil, err
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}
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ciphertext := make([]byte, len(data))
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mode := cipher.NewCBCEncrypter(block, iv)
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mode.CryptBlocks(ciphertext, data)
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return ciphertext, nil
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}
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func DecryptData(data []byte, encKey []byte, iv []byte) ([]byte, error) {
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block, err := aes.NewCipher(encKey)
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if err != nil {
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return nil, err
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}
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plaintext := make([]byte, len(data))
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mode := cipher.NewCBCDecrypter(block, iv)
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mode.CryptBlocks(plaintext, data)
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return removePadding(16, plaintext), nil
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}
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func CalculateMac(meta []byte, data []byte, macKey []byte) ([]byte, error) {
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data = appendPadding(16, data)
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block, err := aes.NewCipher(macKey)
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if err != nil {
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return nil, err
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}
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mode := cipher.NewCBCEncrypter(block, make([]byte, 16))
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mode.CryptBlocks(meta, meta)
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mode.CryptBlocks(data, data)
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mac := data[len(data)-32 : len(data)-16]
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return mac, nil
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}
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func appendPadding(blockSize int, data []byte) []byte {
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paddingSize := blockSize - (len(data) % blockSize)
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newData := make([]byte, len(data)+paddingSize)
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copy(newData, data)
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newData[len(data)] = 0x80
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return newData
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}
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func removePadding(blockSize int, data []byte) []byte {
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i := len(data) - 1
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for ; i > len(data)-blockSize; i-- {
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if data[i] == 0x80 {
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break
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}
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}
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return data[:i]
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}
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