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// Copyright 2017 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 argon2 implements the key derivation function Argon2.
// Argon2 was selected as the winner of the Password Hashing Competition and can
// be used to derive cryptographic keys from passwords.
// Argon2 is specfifed at https://github.com/P-H-C/phc-winner-argon2/blob/master/argon2-specs.pdf
package argon2
import (
"encoding/binary"
"sync"
"golang.org/x/crypto/blake2b"
)
// The Argon2 version implemented by this package.
const Version = 0x13
const (
argon2d = iota
argon2i
argon2id
)
// Key derives a key from the password, salt, and cost parameters using Argon2i
// returning a byte slice of length keyLen that can be used as cryptographic key.
// The CPU cost and parallism degree must be greater than zero.
//
// For example, you can get a derived key for e.g. AES-256 (which needs a 32-byte key) by doing:
// `key := argon2.Key([]byte("some password"), salt, 4, 32*1024, 4, 32)`
//
// The recommended parameters for interactive logins as of 2017 are time=4, memory=32*1024.
// The number of threads can be adjusted to the numbers of available CPUs.
// The time parameter specifies the number of passes over the memory and the memory
// parameter specifies the size of the memory in KiB. For example memory=32*1024 sets the
// memory cost to ~32 MB.
// The cost parameters should be increased as memory latency and CPU parallelism increases.
// Remember to get a good random salt.
func Key(password, salt []byte, time, memory uint32, threads uint8, keyLen uint32) []byte {
return deriveKey(argon2i, password, salt, nil, nil, time, memory, threads, keyLen)
}
func deriveKey(mode int, password, salt, secret, data []byte, time, memory uint32, threads uint8, keyLen uint32) []byte {
if time < 1 {
panic("argon2: number of rounds too small")
}
if threads < 1 {
panic("argon2: paralisim degree too low")
}
mem := memory / (4 * uint32(threads)) * (4 * uint32(threads))
if mem < 8*uint32(threads) {
mem = 8 * uint32(threads)
}
B := initBlocks(password, salt, secret, data, time, mem, uint32(threads), keyLen, mode)
processBlocks(B, time, mem, uint32(threads), mode)
return extractKey(B, mem, uint32(threads), keyLen)
}
const blockLength = 128
type block [blockLength]uint64
func initBlocks(password, salt, key, data []byte, time, memory, threads, keyLen uint32, mode int) []block {
var (
block0 [1024]byte
h0 [blake2b.Size + 8]byte
params [24]byte
tmp [4]byte
)
b2, _ := blake2b.New512(nil)
binary.LittleEndian.PutUint32(params[0:4], threads)
binary.LittleEndian.PutUint32(params[4:8], keyLen)
binary.LittleEndian.PutUint32(params[8:12], memory)
binary.LittleEndian.PutUint32(params[12:16], time)
binary.LittleEndian.PutUint32(params[16:20], uint32(Version))
binary.LittleEndian.PutUint32(params[20:24], uint32(mode))
b2.Write(params[:])
binary.LittleEndian.PutUint32(tmp[:], uint32(len(password)))
b2.Write(tmp[:])
b2.Write(password)
binary.LittleEndian.PutUint32(tmp[:], uint32(len(salt)))
b2.Write(tmp[:])
b2.Write(salt)
binary.LittleEndian.PutUint32(tmp[:], uint32(len(key)))
b2.Write(tmp[:])
b2.Write(key)
binary.LittleEndian.PutUint32(tmp[:], uint32(len(data)))
b2.Write(tmp[:])
b2.Write(data)
b2.Sum(h0[:0])
B := make([]block, memory)
for lane := uint32(0); lane < threads; lane++ {
j := lane * (memory / threads)
binary.LittleEndian.PutUint32(h0[blake2b.Size+4:], lane)
binary.LittleEndian.PutUint32(h0[blake2b.Size:], 0)
blake2bHash(block0[:], h0[:])
for i := range B[0] {
B[j+0][i] = binary.LittleEndian.Uint64(block0[i*8:])
}
binary.LittleEndian.PutUint32(h0[blake2b.Size:], 1)
blake2bHash(block0[:], h0[:])
for i := range B[0] {
B[j+1][i] = binary.LittleEndian.Uint64(block0[i*8:])
}
}
return B
}
func processBlocks(B []block, time, memory, threads uint32, mode int) {
const syncPoints = 4
lanes := memory / threads
segments := lanes / syncPoints
processSegment := func(n, slice, lane uint32, wg *sync.WaitGroup) {
var addresses, in, zero block
if mode == argon2i || (mode == argon2id && n == 0 && slice < syncPoints/2) {
in[0] = uint64(n)
in[1] = uint64(lane)
in[2] = uint64(slice)
in[3] = uint64(memory)
in[4] = uint64(time)
in[5] = uint64(mode)
}
index := uint32(0)
if n == 0 && slice == 0 {
index = 2 // we have already generated the first two blocks
if mode == argon2i || (mode == argon2id && n == 0 && slice < syncPoints/2) {
in[6]++
processBlock(&addresses, &in, &zero)
processBlock(&addresses, &addresses, &zero)
}
}
offset := lane*lanes + slice*segments + index
var random uint64
for index < segments {
prev := offset - 1
if index == 0 && slice == 0 {
prev = lane*lanes + lanes - 1 // last block in lane
}
if mode == argon2i || (mode == argon2id && n == 0 && slice < syncPoints/2) {
if index%blockLength == 0 {
in[6]++
processBlock(&addresses, &in, &zero)
processBlock(&addresses, &addresses, &zero)
}
random = addresses[index%blockLength]
} else {
random = B[prev][0]
}
newOffset := indexAlpha(random, lanes, segments, threads, n, slice, lane, index)
processBlockXOR(&B[offset], &B[prev], &B[newOffset])
index, offset = index+1, offset+1
}
wg.Done()
}
for n := uint32(0); n < time; n++ {
for slice := uint32(0); slice < syncPoints; slice++ {
var wg sync.WaitGroup
for lane := uint32(0); lane < threads; lane++ {
wg.Add(1)
go processSegment(n, slice, lane, &wg)
}
wg.Wait()
}
}
}
func extractKey(B []block, memory, threads, keyLen uint32) []byte {
lanes := memory / threads
for lane := uint32(0); lane < threads-1; lane++ {
for i, v := range B[(lane*lanes)+lanes-1] {
B[memory-1][i] ^= v
}
}
var block [1024]byte
for i, v := range B[memory-1] {
binary.LittleEndian.PutUint64(block[i*8:], v)
}
key := make([]byte, keyLen)
blake2bHash(key, block[:])
return key
}
func indexAlpha(rand uint64, lanes, segments, threads, n, slice, lane, index uint32) uint32 {
refLane := uint32(rand>>32) % threads
m, s := 3*segments, (slice+1)%4*segments
if lane == refLane {
m += index
}
if n == 0 {
m, s = slice*segments, 0
if slice == 0 || lane == refLane {
m += index
}
}
if index == 0 || lane == refLane {
m--
}
return phi(rand, uint64(m), uint64(s), refLane, lanes)
}
func phi(rand, m, s uint64, lane, lanes uint32) uint32 {
p := rand & 0xFFFFFFFF
p = (p * p) >> 32
p = (p * m) >> 32
return lane*lanes + uint32((s+m-(p+1))%uint64(lanes))
}