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|
package scrypt
import (
"crypto/hmac"
"crypto/rand"
"crypto/sha256"
"encoding/binary"
"encoding/hex"
"errors"
"fmt"
"hash"
"io"
"math/bits"
"os"
"slices"
)
const (
saltMinLength = 32
desiredLength = 32
maxInt = int((^uint(0)) >> 1)
MinimumPasswordLength = 16
_N = 1 << 15
r = 8
p = 1
)
var (
ErrBadN = errors.New("scrypt: N must be > 1 and a power of 2")
ErrParamsTooLarge = errors.New("scrypt: parameters are too large")
ErrSaltTooSmall = errors.New("scrypt: salt is too small")
)
// Package pbkdf2 implements the key derivation function PBKDF2 as defined in
// RFC 2898 / PKCS #5 v2.0.
//
// A key derivation function is useful when encrypting data based on a password
// or any other not-fully-random data. It uses a pseudorandom function to derive
// a secure encryption key based on the password.
//
// While v2.0 of the standard defines only one pseudorandom function to use,
// HMAC-SHA1, the drafted v2.1 specification allows use of all five FIPS
// Approved Hash Functions SHA-1, SHA-224, SHA-256, SHA-384 and SHA-512 for
// HMAC. To choose, you can pass the `New` functions from the different SHA
// packages to pbkdf2.Key.
//
//
// Key derives a key from the password, salt and iteration count, returning a
// []byte of length keylen that can be used as cryptographic key. The key is
// derived based on the method described as PBKDF2 with the HMAC variant using
// the supplied hash function.
//
// For example, to use a HMAC-SHA-1 based PBKDF2 key derivation function, you
// can get a derived key for e.g. AES-256 (which needs a 32-byte key) by
// doing:
//
// dk := pbkdf2.Key([]byte("some password"), salt, 4096, 32, sha1.New)
//
// Remember to get a good random salt. At least 8 bytes is recommended by the
// RFC.
//
// Using a higher iteration count will increase the cost of an exhaustive
// search but will also make derivation proportionally slower.
func _PBKDF2Key(
password []byte,
salt []byte,
iter int,
keyLen int,
h func() hash.Hash,
) []byte {
prf := hmac.New(h, password)
hashLen := prf.Size()
numBlocks := (keyLen + hashLen - 1) / hashLen
var buffer [4]byte
dk := make([]byte, 0, numBlocks*hashLen)
U := make([]byte, hashLen)
for block := 1; block <= numBlocks; block++ {
// N.B.: || means concatenation, ^ means XOR
// for each block T_i = U_1 ^ U_2 ^ ... ^ U_iter
// U_1 = PRF(password, salt || uint(i))
prf.Reset()
prf.Write(salt)
buffer[0] = byte(block >> 24)
buffer[1] = byte(block >> 16)
buffer[2] = byte(block >> 8)
buffer[3] = byte(block >> 0)
prf.Write(buffer[:4])
dk = prf.Sum(dk)
T := dk[len(dk) - hashLen:]
copy(U, T)
// U_n = PRF(password, U_(n - 1))
for n := 2; n <= iter; n++ {
prf.Reset()
prf.Write(U)
U = U[:0]
U = prf.Sum(U)
for x := range U {
T[x] ^= U[x]
}
}
}
return dk[:keyLen]
}
// blockCopy copies n numbers from src into dst.
func blockCopy(dst []uint32, src []uint32, n int) {
copy(dst, src[:n])
}
// blockXOR XORs numbers from dst with n numbers from src.
func blockXOR(dst []uint32, src []uint32, n int) {
for i, v := range src[:n] {
dst[i] ^= v
}
}
// salsaXOR applies Salsa20/8 to the XOR of 16 numbers from tmp and in,
// and puts the result into both tmp and out.
func salsaXOR(tmp *[16]uint32, in []uint32, out []uint32) {
w0 := tmp[0] ^ in[0]
w1 := tmp[1] ^ in[1]
w2 := tmp[2] ^ in[2]
w3 := tmp[3] ^ in[3]
w4 := tmp[4] ^ in[4]
w5 := tmp[5] ^ in[5]
w6 := tmp[6] ^ in[6]
w7 := tmp[7] ^ in[7]
w8 := tmp[8] ^ in[8]
w9 := tmp[9] ^ in[9]
w10 := tmp[10] ^ in[10]
w11 := tmp[11] ^ in[11]
w12 := tmp[12] ^ in[12]
w13 := tmp[13] ^ in[13]
w14 := tmp[14] ^ in[14]
w15 := tmp[15] ^ in[15]
x0 := w0
x1 := w1
x2 := w2
x3 := w3
x4 := w4
x5 := w5
x6 := w6
x7 := w7
x8 := w8
x9 := w9
x10 := w10
x11 := w11
x12 := w12
x13 := w13
x14 := w14
x15 := w15
for i := 0; i < 8; i += 2 {
x4 ^= bits.RotateLeft32(x0 + x12, 7)
x8 ^= bits.RotateLeft32(x4 + x0, 9)
x12 ^= bits.RotateLeft32(x8 + x4, 13)
x0 ^= bits.RotateLeft32(x12 + x8, 18)
x9 ^= bits.RotateLeft32(x5 + x1, 7)
x13 ^= bits.RotateLeft32(x9 + x5, 9)
x1 ^= bits.RotateLeft32(x13 + x9, 13)
x5 ^= bits.RotateLeft32(x1 + x13, 18)
x14 ^= bits.RotateLeft32(x10 + x6, 7)
x2 ^= bits.RotateLeft32(x14 + x10, 9)
x6 ^= bits.RotateLeft32(x2 + x14, 13)
x10 ^= bits.RotateLeft32(x6 + x2, 18)
x3 ^= bits.RotateLeft32(x15 + x11, 7)
x7 ^= bits.RotateLeft32(x3 + x15, 9)
x11 ^= bits.RotateLeft32(x7 + x3, 13)
x15 ^= bits.RotateLeft32(x11 + x7, 18)
x1 ^= bits.RotateLeft32(x0 + x3, 7)
x2 ^= bits.RotateLeft32(x1 + x0, 9)
x3 ^= bits.RotateLeft32(x2 + x1, 13)
x0 ^= bits.RotateLeft32(x3 + x2, 18)
x6 ^= bits.RotateLeft32(x5 + x4, 7)
x7 ^= bits.RotateLeft32(x6 + x5, 9)
x4 ^= bits.RotateLeft32(x7 + x6, 13)
x5 ^= bits.RotateLeft32(x4 + x7, 18)
x11 ^= bits.RotateLeft32(x10 + x9, 7)
x8 ^= bits.RotateLeft32(x11 + x10, 9)
x9 ^= bits.RotateLeft32(x8 + x11, 13)
x10 ^= bits.RotateLeft32(x9 + x8, 18)
x12 ^= bits.RotateLeft32(x15 + x14, 7)
x13 ^= bits.RotateLeft32(x12 + x15, 9)
x14 ^= bits.RotateLeft32(x13 + x12, 13)
x15 ^= bits.RotateLeft32(x14 + x13, 18)
}
x0 += w0
x1 += w1
x2 += w2
x3 += w3
x4 += w4
x5 += w5
x6 += w6
x7 += w7
x8 += w8
x9 += w9
x10 += w10
x11 += w11
x12 += w12
x13 += w13
x14 += w14
x15 += w15
out[0], tmp[0] = x0, x0
out[1], tmp[1] = x1, x1
out[2], tmp[2] = x2, x2
out[3], tmp[3] = x3, x3
out[4], tmp[4] = x4, x4
out[5], tmp[5] = x5, x5
out[6], tmp[6] = x6, x6
out[7], tmp[7] = x7, x7
out[8], tmp[8] = x8, x8
out[9], tmp[9] = x9, x9
out[10], tmp[10] = x10, x10
out[11], tmp[11] = x11, x11
out[12], tmp[12] = x12, x12
out[13], tmp[13] = x13, x13
out[14], tmp[14] = x14, x14
out[15], tmp[15] = x15, x15
}
func blockMix(tmp *[16]uint32, in []uint32, out []uint32, r int) {
blockCopy(tmp[:], in[(2 * r - 1) * 16:], 16)
for i := 0; i < 2 * r; i += 2 {
salsaXOR(tmp, in[i * 16:], out[i * 8:])
salsaXOR(tmp, in[i * 16 + 16:], out[i * 8 + r * 16:])
}
}
func integer(b []uint32, r int) uint64 {
j := (2 * r - 1) * 16
return uint64(b[j]) | (uint64(b[j + 1]) << 32)
}
func smix(b []byte, r int, N int, v []uint32, xy []uint32) {
var tmp [16]uint32
R := 32 * r
x := xy
y := xy[R:]
j := 0
for i := 0; i < R; i++ {
x[i] = binary.LittleEndian.Uint32(b[j:])
j += 4
}
for i := 0; i < N; i += 2 {
blockCopy(v[i * R:], x, R)
blockMix(&tmp, x, y, r)
blockCopy(v[(i + 1) * R:], y, R)
blockMix(&tmp, y, x, r)
}
for i := 0; i < N; i += 2 {
j := int(integer(x, r) & uint64(N - 1))
blockXOR(x, v[j * R:], R)
blockMix(&tmp, x, y, r)
j = int(integer(y, r) & uint64(N - 1))
blockXOR(y, v[j * R:], R)
blockMix(&tmp, y, x, r)
}
j = 0
for _, v := range x[:R] {
binary.LittleEndian.PutUint32(b[j:], v)
j += 4
}
}
func validateParams(N int, r int, p int) error {
if N <= 1 || N & (N - 1) != 0 {
return ErrBadN
}
if ((uint64(r) * uint64(p)) >= (1 << 30)) ||
r > maxInt / 128 / p ||
r > maxInt / 256 ||
N > maxInt / 128 / r {
return ErrParamsTooLarge
}
return nil
}
// Package scrypt implements the scrypt key derivation function as defined in
// Colin Percival's paper "Stronger Key Derivation via Sequential Memory-Hard
// Functions" (https://www.tarsnap.com/scrypt/scrypt.pdf).
//
//
// Key derives a key from the password, salt, and cost parameters, returning
// a byte slice of length keyLen that can be used as cryptographic key.
//
// N is a CPU/memory cost parameter, which must be a power of 2 greater than 1.
// r and p must satisfy r * p < 2³⁰. If the parameters do not satisfy the
// limits, the function returns a nil byte slice and an error.
//
// For example, you can get a derived key for e.g. AES-256 (which needs a
// 32-byte key) by doing:
//
// dk, err := scrypt.Key([]byte("some password"), salt, 32768, 8, 1, 32)
//
// The recommended parameters for interactive logins as of 2017 are N=32768, r=8
// and p=1. The parameters N, r, and p should be increased as memory latency and
// CPU parallelism increases; consider setting N to the highest power of 2 you
// can derive within 100 milliseconds. Remember to get a good random salt.
func scrypt(
password []byte,
salt []byte,
N int,
r int,
p int,
keyLen int,
) ([]byte, error) {
err := validateParams(N, r, p)
if err != nil {
return nil, err
}
xy := make([]uint32, 64 * r)
v := make([]uint32, 32 * r * N)
b := _PBKDF2Key(password, salt, 1, p * 128 * r, sha256.New)
for i := 0; i < p; i++ {
smix(b[i * 128 * r:], r, N, v, xy)
}
return _PBKDF2Key(password, b, 1, keyLen, sha256.New), nil
}
func SaltFrom(r io.Reader) ([]byte, error) {
buffer := make([]byte, saltMinLength)
_, err := io.ReadFull(r, buffer)
if err != nil {
return nil, err
}
return buffer, nil
}
func Salt() ([]byte, error) {
return SaltFrom(rand.Reader)
}
func Hash(password []byte, salt []byte) ([]byte, error) {
if len(salt) < saltMinLength {
return nil, ErrSaltTooSmall
}
hash, err := scrypt(
password,
salt,
_N,
r,
p,
desiredLength,
)
if err != nil {
return nil, err
}
return hash, nil
}
func Check(password []byte, salt []byte, hash []byte) (bool, error) {
candidate, err := Hash(password, salt)
if err != nil {
return false, err
}
return slices.Equal(candidate, hash), nil
}
func Main() {
if len(os.Args) != 3 {
fmt.Fprintf(os.Stderr, "Usage: scrypt PASSWORD SALT\n")
os.Exit(2)
}
payload, err := Hash([]byte(os.Args[1]), []byte(os.Args[2]))
if err != nil {
if err == ErrSaltTooSmall {
fmt.Fprintln(os.Stderr, err)
os.Exit(2)
}
panic(err)
}
fmt.Println(hex.EncodeToString(payload))
}
|