// bigIntToNetIPv6 is a helper function that correctly returns a net.IP with the
// correctly padded values.
func bigIntToNetIPv6(bi *big.Int) *net.IP {
x := make(net.IP, IPv6len)
ipv6Bytes := bi.Bytes()
// It's possibe for ipv6Bytes to be less than IPv6len bytes in size. If
// they are different sizes we to pad the size of response.
if len(ipv6Bytes) < IPv6len {
buf := new(bytes.Buffer)
buf.Grow(IPv6len)
for i := len(ipv6Bytes); i < IPv6len; i++ {
if err := binary.Write(buf, binary.BigEndian, byte(0)); err != nil {
panic(fmt.Sprintf("Unable to pad byte %d of input %v: %v", i, bi, err))
}
}
for _, b := range ipv6Bytes {
if err := binary.Write(buf, binary.BigEndian, b); err != nil {
panic(fmt.Sprintf("Unable to preserve endianness of input %v: %v", bi, err))
}
}
ipv6Bytes = buf.Bytes()
}
i := copy(x, ipv6Bytes)
if i != IPv6len {
panic("IPv6 wrong size")
}
return &x
}
// Appends to data the first (len(data) / 32)bits of the result of sha256(data)
// Currently only supports data up to 32 bytes
func addChecksum(data []byte) []byte {
// Get first byte of sha256
hasher := sha256.New()
hasher.Write(data)
hash := hasher.Sum(nil)
firstChecksumByte := hash[0]
// len() is in bytes so we divide by 4
checksumBitLength := uint(len(data) / 4)
// For each bit of check sum we want we shift the data one the left
// and then set the (new) right most bit equal to checksum bit at that index
// staring from the left
dataBigInt := new(big.Int).SetBytes(data)
for i := uint(0); i < checksumBitLength; i++ {
// Bitshift 1 left
dataBigInt.Mul(dataBigInt, BigTwo)
// Set rightmost bit if leftmost checksum bit is set
if uint8(firstChecksumByte&(1<<(7-i))) > 0 {
dataBigInt.Or(dataBigInt, BigOne)
}
}
return dataBigInt.Bytes()
}
// privateEncrypt implements OpenSSL's RSA_private_encrypt function
func privateEncrypt(key *rsa.PrivateKey, data []byte) (enc []byte, err error) {
k := (key.N.BitLen() + 7) / 8
tLen := len(data)
// rfc2313, section 8:
// The length of the data D shall not be more than k-11 octets
if tLen > k-11 {
err = errors.New("Data too long")
return
}
em := make([]byte, k)
em[1] = 1
for i := 2; i < k-tLen-1; i++ {
em[i] = 0xff
}
copy(em[k-tLen:k], data)
c := new(big.Int).SetBytes(em)
if c.Cmp(key.N) > 0 {
err = nil
return
}
var m *big.Int
var ir *big.Int
if key.Precomputed.Dp == nil {
m = new(big.Int).Exp(c, key.D, key.N)
} else {
// We have the precalculated values needed for the CRT.
m = new(big.Int).Exp(c, key.Precomputed.Dp, key.Primes[0])
m2 := new(big.Int).Exp(c, key.Precomputed.Dq, key.Primes[1])
m.Sub(m, m2)
if m.Sign() < 0 {
m.Add(m, key.Primes[0])
}
m.Mul(m, key.Precomputed.Qinv)
m.Mod(m, key.Primes[0])
m.Mul(m, key.Primes[1])
m.Add(m, m2)
for i, values := range key.Precomputed.CRTValues {
prime := key.Primes[2+i]
m2.Exp(c, values.Exp, prime)
m2.Sub(m2, m)
m2.Mul(m2, values.Coeff)
m2.Mod(m2, prime)
if m2.Sign() < 0 {
m2.Add(m2, prime)
}
m2.Mul(m2, values.R)
m.Add(m, m2)
}
}
if ir != nil {
// Unblind.
m.Mul(m, ir)
m.Mod(m, key.N)
}
enc = m.Bytes()
return
}
func (ka *dheKeyAgreement) generateServerKeyExchange(config *Config, cert *Certificate, clientHello *clientHelloMsg, hello *serverHelloMsg) (*serverKeyExchangeMsg, error) {
var q *big.Int
if p := config.Bugs.DHGroupPrime; p != nil {
ka.p = p
ka.g = big.NewInt(2)
q = p
} else {
// 2048-bit MODP Group with 256-bit Prime Order Subgroup (RFC
// 5114, Section 2.3)
ka.p, _ = new(big.Int).SetString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
ka.g, _ = new(big.Int).SetString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
q, _ = new(big.Int).SetString("8CF83642A709A097B447997640129DA299B1A47D1EB3750BA308B0FE64F5FBD3", 16)
}
var err error
ka.xOurs, err = rand.Int(config.rand(), q)
if err != nil {
return nil, err
}
yOurs := new(big.Int).Exp(ka.g, ka.xOurs, ka.p)
// http://tools.ietf.org/html/rfc5246#section-7.4.3
pBytes := ka.p.Bytes()
gBytes := ka.g.Bytes()
yBytes := yOurs.Bytes()
serverDHParams := make([]byte, 0, 2+len(pBytes)+2+len(gBytes)+2+len(yBytes))
serverDHParams = append(serverDHParams, byte(len(pBytes)>>8), byte(len(pBytes)))
serverDHParams = append(serverDHParams, pBytes...)
serverDHParams = append(serverDHParams, byte(len(gBytes)>>8), byte(len(gBytes)))
serverDHParams = append(serverDHParams, gBytes...)
serverDHParams = append(serverDHParams, byte(len(yBytes)>>8), byte(len(yBytes)))
serverDHParams = append(serverDHParams, yBytes...)
return ka.auth.signParameters(config, cert, clientHello, hello, serverDHParams)
}
// Sign signs an arbitrary length hash (which should be the result of hashing a
// larger message) using the private key, priv. It returns the signature as a
// pair of integers. The security of the private key depends on the entropy of
// rand.
func Sign(rand io.Reader, priv *PrivateKey, hash []byte) (r, s *big.Int, err error) {
// See [NSA] 3.4.1
c := priv.PublicKey.Curve
N := c.Params().N
var k, kInv *big.Int
for {
for {
k, err = randFieldElement(c, rand)
if err != nil {
r = nil
return
}
kInv = new(big.Int).ModInverse(k, N)
r, _ = priv.Curve.ScalarBaseMult(k.Bytes())
r.Mod(r, N)
if r.Sign() != 0 {
break
}
}
e := hashToInt(hash, c)
s = new(big.Int).Mul(priv.D, r)
s.Add(s, e)
s.Mul(s, kInv)
s.Mod(s, N)
if s.Sign() != 0 {
break
}
}
return
}
func makeBigInt(n *big.Int) (encoder, error) {
if n == nil {
return nil, StructuralError{"empty integer"}
}
if n.Sign() < 0 {
// A negative number has to be converted to two's-complement
// form. So we'll invert and subtract 1. If the
// most-significant-bit isn't set then we'll need to pad the
// beginning with 0xff in order to keep the number negative.
nMinus1 := new(big.Int).Neg(n)
nMinus1.Sub(nMinus1, bigOne)
bytes := nMinus1.Bytes()
for i := range bytes {
bytes[i] ^= 0xff
}
if len(bytes) == 0 || bytes[0]&0x80 == 0 {
return multiEncoder([]encoder{byteFFEncoder, bytesEncoder(bytes)}), nil
}
return bytesEncoder(bytes), nil
} else if n.Sign() == 0 {
// Zero is written as a single 0 zero rather than no bytes.
return byte00Encoder, nil
} else {
bytes := n.Bytes()
if len(bytes) > 0 && bytes[0]&0x80 != 0 {
// We'll have to pad this with 0x00 in order to stop it
// looking like a negative number.
return multiEncoder([]encoder{byte00Encoder, bytesEncoder(bytes)}), nil
}
return bytesEncoder(bytes), nil
}
}
/*公钥解密*/
func pubKeyDecrypt(pub *rsa.PublicKey, data []byte) ([]byte, error) {
k := (pub.N.BitLen() + 7) / 8
if k != len(data) {
return nil, ErrDataLen
}
m := new(big.Int).SetBytes(data)
if m.Cmp(pub.N) > 0 {
return nil, ErrDataToLarge
}
m.Exp(m, big.NewInt(int64(pub.E)), pub.N)
d := leftPad(m.Bytes(), k)
if d[0] != 0 {
return nil, ErrDataBroken
}
if d[1] != 0 && d[1] != 1 {
return nil, ErrKeyPairDismatch
}
var i = 2
for ; i < len(d); i++ {
if d[i] == 0 {
break
}
}
i++
if i == len(d) {
return nil, nil
}
return d[i:], nil
}
func TestP256BaseMult(t *testing.T) {
p256 := P256()
p256Generic := p256.Params()
scalars := make([]*big.Int, 0, len(p224BaseMultTests)+1)
for _, e := range p224BaseMultTests {
k, _ := new(big.Int).SetString(e.k, 10)
scalars = append(scalars, k)
}
k := new(big.Int).SetInt64(1)
k.Lsh(k, 500)
scalars = append(scalars, k)
for i, k := range scalars {
x, y := p256.ScalarBaseMult(k.Bytes())
x2, y2 := p256Generic.ScalarBaseMult(k.Bytes())
if x.Cmp(x2) != 0 || y.Cmp(y2) != 0 {
t.Errorf("#%d: got (%x, %x), want (%x, %x)", i, x, y, x2, y2)
}
if testing.Short() && i > 5 {
break
}
}
}
// Compile instruction
//
// Attempts to compile and parse the given instruction in "s"
// and returns the byte sequence
func CompileInstr(s interface{}) ([]byte, error) {
switch s.(type) {
case string:
str := s.(string)
isOp := IsOpCode(str)
if isOp {
return []byte{OpCodes[str]}, nil
}
// Check for pre formatted byte array
// Jumps are preformatted
if []byte(str)[0] == 0 {
return []byte(str), nil
}
num := new(big.Int)
_, success := num.SetString(str, 0)
// Assume regular bytes during compilation
if !success {
num.SetBytes([]byte(str))
}
return num.Bytes(), nil
case int:
//num := bigToBytes(big.NewInt(int64(s.(int))), 256)
return big.NewInt(int64(s.(int))).Bytes(), nil
case []byte:
return new(big.Int).SetBytes(s.([]byte)).Bytes(), nil
}
return nil, nil
}
func EncodePublicKey(x, y *big.Int, compressed bool) ([]byte, error) {
var pubkey []byte
if compressed {
pubkey = make([]byte, 33)
pubkey[0] = 2 + byte(y.Bit(0))
} else {
pubkey = make([]byte, 65)
pubkey[0] = 4
}
// Right-align x coordinate
bytes := x.Bytes()
if len(bytes) > 32 {
return nil, fmt.Errorf("Value of x has > 32 bytes")
}
copy(pubkey[1+(32-len(bytes)):33], bytes)
if !compressed {
// Right-align y coordinate
bytes = y.Bytes()
if len(bytes) > 32 {
return nil, fmt.Errorf("Value of y has > 32 bytes")
}
copy(pubkey[33+(32-len(bytes)):65], bytes)
}
return pubkey, nil
}
// Converts a number to a binary byte slice
// i.e. 4 => [0,0,0,4]
// 256 => [0,0,1,0]
// or in the case of 64
// 4 = > [0,0,0,0,0,0,0,4]
func makeBinary(value interface{}) []byte {
var z []byte
var val uint64
amount := 4
if v, ok := value.(uint64); ok {
amount = 8
val = v
} else if v, ok := value.(uint32); ok {
val = uint64(v)
} else {
log.Panic("makeBinary requires a value that's either a uint32 or an uint64, got:", value)
}
str := strconv.FormatUint(val, 10)
number := new(big.Int)
number.SetString(str, 10)
template := make([]byte, amount)
x := number.Bytes()
z = append(template[:(amount-len(x))], x...)
return z
}
func wipeBigInt(k *big.Int) {
if k == nil {
return
}
k.SetBytes(zeroes(len(k.Bytes())))
}
// powerOffset computes the offset by (n + 2^exp) % (2^mod)
func powerOffset(id []byte, exp int, mod int) []byte {
// Copy the existing slice
off := make([]byte, len(id))
copy(off, id)
// Convert the ID to a bigint
idInt := big.Int{}
idInt.SetBytes(id)
// Get the offset
two := big.NewInt(2)
offset := big.Int{}
offset.Exp(two, big.NewInt(int64(exp)), nil)
// Sum
sum := big.Int{}
sum.Add(&idInt, &offset)
// Get the ceiling
ceil := big.Int{}
ceil.Exp(two, big.NewInt(int64(mod)), nil)
// Apply the mod
idInt.Mod(&sum, &ceil)
// Add together
return idInt.Bytes()
}
func Unblind(key *rsa.PublicKey, blindedSig, unblinder []byte) []byte {
m := new(big.Int).SetBytes(blindedSig)
unblinderBig := new(big.Int).SetBytes(unblinder)
m.Mul(m, unblinderBig)
m.Mod(m, key.N)
return m.Bytes()
}
func SendToConn(data []byte, conn *net.TCPConn, path *big.Int) {
// making variable for combining send data
var (
err tree_lib.TreeError
path_len_data = make([]byte, 4)
msg_len_data = make([]byte, 4)
path_data = path.Bytes()
path_len = uint32(len(path_data))
buf = bytes.Buffer{}
)
err.From = tree_lib.FROM_SEND_TO_CONN
binary.LittleEndian.PutUint32(path_len_data, path_len)
binary.LittleEndian.PutUint32(msg_len_data, path_len+uint32(len(data))+uint32(4))
buf.Write(msg_len_data)
buf.Write(path_len_data)
buf.Write(path_data)
buf.Write(data)
if conn != nil {
_, err.Err = conn.Write(buf.Bytes())
if !err.IsNull() {
tree_log.Error(err.From, fmt.Sprintf("Error sending data to path [%s]", path.String()), err.Error())
}
}
buf.Reset()
}
// countBits returns the number of set bits in n
func countBits(n *big.Int) int {
var count int = 0
for _, b := range n.Bytes() {
count += int(bitCounts[b])
}
return count
}
func (dag *Dagger) Eval(N *big.Int) *big.Int {
pow := common.BigPow(2, 26)
dag.xn = pow.Div(N, pow)
sha := sha3.NewKeccak256()
sha.Reset()
ret := new(big.Int)
for k := 0; k < 4; k++ {
d := sha3.NewKeccak256()
b := new(big.Int)
d.Reset()
d.Write(dag.hash.Bytes())
d.Write(dag.xn.Bytes())
d.Write(N.Bytes())
d.Write(big.NewInt(int64(k)).Bytes())
b.SetBytes(Sum(d))
pk := (b.Uint64() & 0x1ffffff)
sha.Write(dag.Node(9, pk).Bytes())
}
return ret.SetBytes(Sum(sha))
}
// Put implements storage.Contacts.
func (c *contacts) Put(name string, key *sf.PublicKey) error {
if len(name) == 0 {
return errgo.New("empty key name")
}
return c.db.Update(func(tx *bolt.Tx) error {
contactsBucket, err := tx.CreateBucketIfNotExists([]byte("contacts"))
if err != nil {
return errgo.Mask(err)
}
err = contactsBucket.Put(key[:], []byte(name))
if err != nil {
return errgo.Mask(err)
}
keysBucket, err := contactsBucket.CreateBucketIfNotExists([]byte(name))
if err != nil {
return errgo.Mask(err)
}
lastSeqBytes, _ := keysBucket.Cursor().Last()
var seq big.Int
seq.SetBytes(lastSeqBytes)
seq.Add(&seq, bigOne)
err = keysBucket.Put(seq.Bytes(), key[:])
if err != nil {
return errgo.Mask(err)
}
return nil
})
}
// BigAffineToField takes an affine point (x, y) as big integers and converts
// it to an affine point as field values.
func (curve *KoblitzCurve) BigAffineToField(x, y *big.Int) (*FieldVal, *FieldVal) {
x3, y3 := new(FieldVal), new(FieldVal)
x3.SetByteSlice(x.Bytes())
y3.SetByteSlice(y.Bytes())
return x3, y3
}
// Sign creates a signature on the hash under the given secret key.
func Sign(sk *eckey.SecretKey, hash []byte) (*Signature, error) {
// Generate random nonce
nonce:
k, kG, err := eckey.GenerateKeyPair()
if err != nil {
return nil, err
}
// Try again if kG is nil (point at infinity)
if kG == nil {
goto nonce
}
// Clear nonce after completion
defer k.Zero()
// Compute non-interactive challenge
e := util.Hash256d(append([]byte(hash), kG[:]...))
kInt := new(big.Int).SetBytes(k[:])
eInt := new(big.Int).SetBytes(e[:])
rInt := new(big.Int).SetBytes(sk[:])
// Compute s = k - er
s := new(big.Int)
s.Mul(eInt, rInt)
s.Sub(kInt, s)
s.Mod(s, eckey.S256.N)
// Serialize signature
sig := new(Signature)
copy(sig[:SignatureSize/2], e[:])
util.PaddedCopy(sig[SignatureSize/2:], s.Bytes(), SignatureSize/2)
return sig, nil
}
// Generates and opens a temporary file with a defined prefix and suffix
// This is the same api as ioutil.TempFile accept it accepts a suffix
// TODO: see if this is too slow
func TempFile(dir, prefix string, suffix string) (f *os.File, err error) {
if dir == "" {
dir = os.TempDir()
}
// The maximum size of random file count
// TODO: see if we can do this at package scope somehow
var maxRand *big.Int = big.NewInt(0)
maxRand.SetString("FFFFFFFFFFFFFFFF", 16)
var randNum *big.Int
for i := 0; i < 10000; i++ {
// Generate random part of the path name
randNum, err = rand.Int(rand.Reader, maxRand)
if err != nil {
return
}
// Transform to an int
randString := hex.EncodeToString(randNum.Bytes())
// Attempt to open file and fail if it already exists
name := filepath.Join(dir, prefix+randString+suffix)
f, err = os.OpenFile(name, os.O_RDWR|os.O_CREATE|os.O_EXCL, 0600)
if os.IsExist(err) {
continue
}
break
}
return
}
// Decrypt takes two integers, resulting from an ElGamal encryption, and
// returns the plaintext of the message. An error can result only if the
// ciphertext is invalid. Users should keep in mind that this is a padding
// oracle and thus, if exposed to an adaptive chosen ciphertext attack, can
// be used to break the cryptosystem. See ``Chosen Ciphertext Attacks
// Against Protocols Based on the RSA Encryption Standard PKCS #1'', Daniel
// Bleichenbacher, Advances in Cryptology (Crypto '98),
func Decrypt(priv *PrivateKey, c1, c2 *big.Int) (msg []byte, err error) {
s := new(big.Int).Exp(c1, priv.X, priv.P)
s.ModInverse(s, priv.P)
s.Mul(s, c2)
s.Mod(s, priv.P)
em := s.Bytes()
firstByteIsTwo := subtle.ConstantTimeByteEq(em[0], 2)
// The remainder of the plaintext must be a string of non-zero random
// octets, followed by a 0, followed by the message.
// lookingForIndex: 1 iff we are still looking for the zero.
// index: the offset of the first zero byte.
var lookingForIndex, index int
lookingForIndex = 1
for i := 1; i < len(em); i++ {
equals0 := subtle.ConstantTimeByteEq(em[i], 0)
index = subtle.ConstantTimeSelect(lookingForIndex&equals0, i, index)
lookingForIndex = subtle.ConstantTimeSelect(equals0, 0, lookingForIndex)
}
if firstByteIsTwo != 1 || lookingForIndex != 0 || index < 9 {
return nil, errors.New("elgamal: decryption error")
}
return em[index+1:], nil
}
func getWorkPackage(difficulty *big.Int) string {
if currWork == nil {
return getErrorResponse("Current work unavailable")
}
// Our response object
response := &ResponseArray{
Id: currWork.Id,
Jsonrpc: currWork.Jsonrpc,
Result: currWork.Result[:],
}
// Calculte requested difficulty
diff := new(big.Int).Div(pow256, difficulty)
diffBytes := string(common.ToHex(diff.Bytes()))
// Adjust the difficulty for the miner
response.Result[2] = diffBytes
// Convert respone object to JSON
b, _ := json.Marshal(response)
return string(b)
}
// writeIntPadded writes x into b, padded up with leading zeros as
// needed.
func writeIntPadded(b []byte, x *big.Int) {
for i := range b {
b[i] = 0
}
xb := x.Bytes()
copy(b[len(b)-len(xb):], xb)
}
// returns a formatted MIP mapped key by adding prefix, canonical number and level
//
// ex. fn(98, 1000) = (prefix || 1000 || 0)
func mipmapKey(num, level uint64) []byte {
lkey := make([]byte, 8)
binary.BigEndian.PutUint64(lkey, level)
key := new(big.Int).SetUint64(num / level * level)
return append(mipmapPre, append(lkey, key.Bytes()...)...)
}
func NewOcCredLoadFromFile(filename string) (*OcCred, error) {
if filename == "" {
filename = PRIVATE_KEY_FILENAME
}
file, err := util.GetAppData(filename)
if err != nil {
return nil, fmt.Errorf("error getting app data: %v", err.Error())
}
var d big.Int
fmt.Fscanf(file, "%x\n", &d)
curve := elliptic.P256()
x, y := curve.ScalarBaseMult(d.Bytes())
priv := ecdsa.PrivateKey{
PublicKey: ecdsa.PublicKey{
Curve: curve,
X: x,
Y: y,
},
D: &d,
}
ocCred := OcCred{
Priv: &priv,
}
return &ocCred, nil
}
// BigIntToEncodedBytes converts a big integer into its corresponding
// 32 byte little endian representation.
func BigIntToEncodedBytes(a *big.Int) *[32]byte {
s := new([32]byte)
if a == nil {
return s
}
// Caveat: a can be longer than 32 bytes.
aB := a.Bytes()
// If we have a short byte string, expand
// it so that it's long enough.
aBLen := len(aB)
if aBLen < fieldIntSize {
diff := fieldIntSize - aBLen
for i := 0; i < diff; i++ {
aB = append([]byte{0x00}, aB...)
}
}
for i := 0; i < fieldIntSize; i++ {
s[i] = aB[i]
}
// Reverse the byte string --> little endian after
// encoding.
reverse(s)
return s
}
func DecodeBase58(ba []byte) []byte {
if len(ba) == 0 {
return nil
}
x := new(big.Int)
y := big.NewInt(58)
z := new(big.Int)
for _, b := range ba {
v := strings.IndexRune(base58, rune(b))
z.SetInt64(int64(v))
x.Mul(x, y)
x.Add(x, z)
}
xa := x.Bytes()
// Restore leading zeros
i := 0
for i < len(ba) && ba[i] == '1' {
i++
}
ra := make([]byte, i+len(xa))
copy(ra[i:], xa)
return ra
}
func CompileInstr(s interface{}) ([]byte, error) {
switch s.(type) {
case string:
str := s.(string)
isOp := IsOpCode(str)
if isOp {
return []byte{OpCodes[str]}, nil
}
num := new(big.Int)
_, success := num.SetString(str, 0)
// Assume regular bytes during compilation
if !success {
num.SetBytes([]byte(str))
}
return num.Bytes(), nil
case int:
return big.NewInt(int64(s.(int))).Bytes(), nil
case []byte:
return BigD(s.([]byte)).Bytes(), nil
}
return nil, nil
}
// (n - 2^(k-1)) mod 2^m
func calcLastFinger(n []byte, k int) (string, []byte) {
// convert the n to a bigint
nBigInt := big.Int{}
nBigInt.SetBytes(n)
// get the right addend, i.e. 2^(k-1)
two := big.NewInt(2)
addend := big.Int{}
addend.Exp(two, big.NewInt(int64(k-1)), nil)
addend.Mul(&addend, big.NewInt(-1))
//Soustraction
neg := big.Int{}
neg.Add(&addend, &nBigInt)
// calculate 2^m
m := 160
ceil := big.Int{}
ceil.Exp(two, big.NewInt(int64(m)), nil)
// apply the mod
result := big.Int{}
result.Mod(&neg, &ceil)
resultBytes := result.Bytes()
resultHex := fmt.Sprintf("%x", resultBytes)
return resultHex, resultBytes
}