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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" "math/bits" "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 { 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, 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 }