path: root/crypto/crypto.go

package crypto

import (
    "crypto/aes"
    "crypto/cipher"
    "crypto/ecdsa"
    "crypto/elliptic"
    "crypto/rand"
    "crypto/sha256"
    "fmt"
    "io"
    "os"

    "encoding/hex"
    "encoding/json"
    "errors"

    "code.google.com/p/go-uuid/uuid"
    "github.com/ethereum/go-ethereum/common"
    "github.com/ethereum/go-ethereum/crypto/ecies"
    "github.com/ethereum/go-ethereum/crypto/secp256k1"
    "github.com/ethereum/go-ethereum/crypto/sha3"
    "golang.org/x/crypto/pbkdf2"
    "golang.org/x/crypto/ripemd160"
)

func init() {
    // specify the params for the s256 curve
    ecies.AddParamsForCurve(S256(), ecies.ECIES_AES128_SHA256)
}

func Sha3(data ...[]byte) []byte {
    d := sha3.NewKeccak256()
    for _, b := range data {
        d.Write(b)
    }
    return d.Sum(nil)
}

func Sha3Hash(data ...[]byte) (h common.Hash) {
    d := sha3.NewKeccak256()
    for _, b := range data {
        d.Write(b)
    }
    d.Sum(h[:0])
    return h
}

// Creates an ethereum address given the bytes and the nonce
func CreateAddress(b []byte, nonce uint64) []byte {
    return Sha3(common.NewValue([]interface{}{b, nonce}).Encode())[12:]
}

func Sha256(data []byte) []byte {
    hash := sha256.Sum256(data)

    return hash[:]
}

func Ripemd160(data []byte) []byte {
    ripemd := ripemd160.New()
    ripemd.Write(data)

    return ripemd.Sum(nil)
}

func Ecrecover(data []byte) []byte {
    var in = struct {
        hash []byte
        sig  []byte
    }{data[:32], data[32:]}

    r, _ := secp256k1.RecoverPubkey(in.hash, in.sig)

    return r
}

// New methods using proper ecdsa keys from the stdlib
func ToECDSA(prv []byte) *ecdsa.PrivateKey {
    if len(prv) == 0 {
        return nil
    }

    priv := new(ecdsa.PrivateKey)
    priv.PublicKey.Curve = S256()
    priv.D = common.BigD(prv)
    priv.PublicKey.X, priv.PublicKey.Y = S256().ScalarBaseMult(prv)
    return priv
}

func FromECDSA(prv *ecdsa.PrivateKey) []byte {
    if prv == nil {
        return nil
    }
    return prv.D.Bytes()
}

func ToECDSAPub(pub []byte) *ecdsa.PublicKey {
    if len(pub) == 0 {
        return nil
    }
    x, y := elliptic.Unmarshal(S256(), pub)
    return &ecdsa.PublicKey{S256(), x, y}
}

func FromECDSAPub(pub *ecdsa.PublicKey) []byte {
    if pub == nil || pub.X == nil || pub.Y == nil {
        return nil
    }
    return elliptic.Marshal(S256(), pub.X, pub.Y)
}

// HexToECDSA parses a secp256k1 private key.
func HexToECDSA(hexkey string) (*ecdsa.PrivateKey, error) {
    b, err := hex.DecodeString(hexkey)
    if err != nil {
        return nil, errors.New("invalid hex string")
    }
    if len(b) != 32 {
        return nil, errors.New("invalid length, need 256 bits")
    }
    return ToECDSA(b), nil
}

// LoadECDSA loads a secp256k1 private key from the given file.
func LoadECDSA(file string) (*ecdsa.PrivateKey, error) {
    buf := make([]byte, 32)
    fd, err := os.Open(file)
    if err != nil {
        return nil, err
    }
    defer fd.Close()
    if _, err := io.ReadFull(fd, buf); err != nil {
        return nil, err
    }
    return ToECDSA(buf), nil
}

func GenerateKey() (*ecdsa.PrivateKey, error) {
    return ecdsa.GenerateKey(S256(), rand.Reader)
}

func SigToPub(hash, sig []byte) *ecdsa.PublicKey {
    s := Ecrecover(append(hash, sig...))
    x, y := elliptic.Unmarshal(S256(), s)

    return &ecdsa.PublicKey{S256(), x, y}
}

func Sign(hash []byte, prv *ecdsa.PrivateKey) (sig []byte, err error) {
    if len(hash) != 32 {
        return nil, fmt.Errorf("hash is required to be exactly 32 bytes (%d)", len(hash))
    }

    sig, err = secp256k1.Sign(hash, common.LeftPadBytes(prv.D.Bytes(), prv.Params().BitSize/8))
    return
}

func Encrypt(pub *ecdsa.PublicKey, message []byte) ([]byte, error) {
    return ecies.Encrypt(rand.Reader, ecies.ImportECDSAPublic(pub), message, nil, nil)
}

func Decrypt(prv *ecdsa.PrivateKey, ct []byte) ([]byte, error) {
    key := ecies.ImportECDSA(prv)
    return key.Decrypt(rand.Reader, ct, nil, nil)
}

// creates a Key and stores that in the given KeyStore by decrypting a presale key JSON
func ImportPreSaleKey(keyStore KeyStore2, keyJSON []byte, password string) (*Key, error) {
    key, err := decryptPreSaleKey(keyJSON, password)
    if err != nil {
        return nil, err
    }
    key.Id = uuid.NewRandom()
    err = keyStore.StoreKey(key, password)
    return key, err
}

func decryptPreSaleKey(fileContent []byte, password string) (key *Key, err error) {
    preSaleKeyStruct := struct {
        EncSeed string
        EthAddr string
        Email   string
        BtcAddr string
    }{}
    err = json.Unmarshal(fileContent, &preSaleKeyStruct)
    if err != nil {
        return nil, err
    }
    encSeedBytes, err := hex.DecodeString(preSaleKeyStruct.EncSeed)
    iv := encSeedBytes[:16]
    cipherText := encSeedBytes[16:]
    /*
        See https://github.com/ethereum/pyethsaletool

        pyethsaletool generates the encryption key from password by
        2000 rounds of PBKDF2 with HMAC-SHA-256 using password as salt (:().
        16 byte key length within PBKDF2 and resulting key is used as AES key
    */
    passBytes := []byte(password)
    derivedKey := pbkdf2.Key(passBytes, passBytes, 2000, 16, sha256.New)
    plainText, err := aesCBCDecrypt(derivedKey, cipherText, iv)
    ethPriv := Sha3(plainText)
    ecKey := ToECDSA(ethPriv)
    key = &Key{
        Id:         nil,
        Address:    PubkeyToAddress(ecKey.PublicKey),
        PrivateKey: ecKey,
    }
    derivedAddr := common.Bytes2Hex(key.Address)
    expectedAddr := preSaleKeyStruct.EthAddr
    if derivedAddr != expectedAddr {
        err = errors.New("decrypted addr not equal to expected addr")
    }
    return key, err
}

func aesCBCDecrypt(key []byte, cipherText []byte, iv []byte) (plainText []byte, err error) {
    aesBlock, err := aes.NewCipher(key)
    if err != nil {
        return plainText, err
    }
    decrypter := cipher.NewCBCDecrypter(aesBlock, iv)
    paddedPlainText := make([]byte, len(cipherText))
    decrypter.CryptBlocks(paddedPlainText, cipherText)
    plainText = PKCS7Unpad(paddedPlainText)
    if plainText == nil {
        err = errors.New("Decryption failed: PKCS7Unpad failed after decryption")
    }
    return plainText, err
}

// From https://leanpub.com/gocrypto/read#leanpub-auto-block-cipher-modes
func PKCS7Pad(in []byte) []byte {
    padding := 16 - (len(in) % 16)
    if padding == 0 {
        padding = 16
    }
    for i := 0; i < padding; i++ {
        in = append(in, byte(padding))
    }
    return in
}

func PKCS7Unpad(in []byte) []byte {
    if len(in) == 0 {
        return nil
    }

    padding := in[len(in)-1]
    if int(padding) > len(in) || padding > aes.BlockSize {
        return nil
    } else if padding == 0 {
        return nil
    }

    for i := len(in) - 1; i > len(in)-int(padding)-1; i-- {
        if in[i] != padding {
            return nil
        }
    }
    return in[:len(in)-int(padding)]
}

func PubkeyToAddress(p ecdsa.PublicKey) []byte {
    pubBytes := FromECDSAPub(&p)
    return Sha3(pubBytes[1:])[12:]
}