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// Copyright 2012 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
// 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).
package scrypt // import "golang.org/x/crypto/scrypt"
import (
"crypto/sha256"
"errors"
"golang.org/x/crypto/pbkdf2"
)
const maxInt = int(^uint(0) >> 1)
// blockCopy copies n numbers from src into dst.
func blockCopy(dst, src []uint32, n int) {
copy(dst, src[:n])
}
// blockXOR XORs numbers from dst with n numbers from src.
func blockXOR(dst, 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, 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, x1, x2, x3, x4, x5, x6, x7, x8 := w0, w1, w2, w3, w4, w5, w6, w7, w8
x9, x10, x11, x12, x13, x14, x15 := w9, w10, w11, w12, w13, w14, w15
for i := 0; i < 8; i += 2 {
u := x0 + x12
x4 ^= u<<7 | u>>(32-7)
u = x4 + x0
x8 ^= u<<9 | u>>(32-9)
u = x8 + x4
x12 ^= u<<13 | u>>(32-13)
u = x12 + x8
x0 ^= u<<18 | u>>(32-18)
u = x5 + x1
x9 ^= u<<7 | u>>(32-7)
u = x9 + x5
x13 ^= u<<9 | u>>(32-9)
u = x13 + x9
x1 ^= u<<13 | u>>(32-13)
u = x1 + x13
x5 ^= u<<18 | u>>(32-18)
u = x10 + x6
x14 ^= u<<7 | u>>(32-7)
u = x14 + x10
x2 ^= u<<9 | u>>(32-9)
u = x2 + x14
x6 ^= u<<13 | u>>(32-13)
u = x6 + x2
x10 ^= u<<18 | u>>(32-18)
u = x15 + x11
x3 ^= u<<7 | u>>(32-7)
u = x3 + x15
x7 ^= u<<9 | u>>(32-9)
u = x7 + x3
x11 ^= u<<13 | u>>(32-13)
u = x11 + x7
x15 ^= u<<18 | u>>(32-18)
u = x0 + x3
x1 ^= u<<7 | u>>(32-7)
u = x1 + x0
x2 ^= u<<9 | u>>(32-9)
u = x2 + x1
x3 ^= u<<13 | u>>(32-13)
u = x3 + x2
x0 ^= u<<18 | u>>(32-18)
u = x5 + x4
x6 ^= u<<7 | u>>(32-7)
u = x6 + x5
x7 ^= u<<9 | u>>(32-9)
u = x7 + x6
x4 ^= u<<13 | u>>(32-13)
u = x4 + x7
x5 ^= u<<18 | u>>(32-18)
u = x10 + x9
x11 ^= u<<7 | u>>(32-7)
u = x11 + x10
x8 ^= u<<9 | u>>(32-9)
u = x8 + x11
x9 ^= u<<13 | u>>(32-13)
u = x9 + x8
x10 ^= u<<18 | u>>(32-18)
u = x15 + x14
x12 ^= u<<7 | u>>(32-7)
u = x12 + x15
x13 ^= u<<9 | u>>(32-9)
u = x13 + x12
x14 ^= u<<13 | u>>(32-13)
u = x14 + x13
x15 ^= u<<18 | u>>(32-18)
}
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, 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, N int, v, xy []uint32) {
var tmp [16]uint32
x := xy
y := xy[32*r:]
j := 0
for i := 0; i < 32*r; i++ {
x[i] = uint32(b[j]) | uint32(b[j+1])<<8 | uint32(b[j+2])<<16 | uint32(b[j+3])<<24
j += 4
}
for i := 0; i < N; i += 2 {
blockCopy(v[i*(32*r):], x, 32*r)
blockMix(&tmp, x, y, r)
blockCopy(v[(i+1)*(32*r):], y, 32*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*(32*r):], 32*r)
blockMix(&tmp, x, y, r)
j = int(integer(y, r) & uint64(N-1))
blockXOR(y, v[j*(32*r):], 32*r)
blockMix(&tmp, y, x, r)
}
j = 0
for _, v := range x[:32*r] {
b[j+0] = byte(v >> 0)
b[j+1] = byte(v >> 8)
b[j+2] = byte(v >> 16)
b[j+3] = byte(v >> 24)
j += 4
}
}
// 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 two 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 Key(password, salt []byte, N, r, p, keyLen int) ([]byte, error) {
if N <= 1 || N&(N-1) != 0 {
return nil, errors.New("scrypt: N must be > 1 and a power of 2")
}
if uint64(r)*uint64(p) >= 1<<30 || r > maxInt/128/p || r > maxInt/256 || N > maxInt/128/r {
return nil, errors.New("scrypt: parameters are too large")
}
xy := make([]uint32, 64*r)
v := make([]uint32, 32*N*r)
b := pbkdf2.Key(password, salt, 1, p*128*r, sha256.New)
for i := 0; i < p; i++ {
smix(b[i*128*r:], r, N, v, xy)
}
return pbkdf2.Key(password, b, 1, keyLen, sha256.New), nil
}