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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.
//
// For a detailed specification of Argon2 see [1].
//
// If you aren't sure which function you need, use Argon2id (IDKey) and
// the parameter recommendations for your scenario.
//
//
// Argon2i
//
// Argon2i (implemented by Key) is the side-channel resistant version of Argon2.
// It uses data-independent memory access, which is preferred for password
// hashing and password-based key derivation. Argon2i requires more passes over
// memory than Argon2id to protect from trade-off attacks. The recommended
// parameters (taken from [2]) for non-interactive operations are time=3 and to
// use the maximum available memory.
//
//
// Argon2id
//
// Argon2id (implemented by IDKey) is a hybrid version of Argon2 combining
// Argon2i and Argon2d. It uses data-independent memory access for the first
// half of the first iteration over the memory and data-dependent memory access
// for the rest. Argon2id is side-channel resistant and provides better brute-
// force cost savings due to time-memory tradeoffs than Argon2i. The recommended
// parameters for non-interactive operations (taken from [2]) are time=1 and to
// use the maximum available memory.
//
// [1] https://github.com/P-H-C/phc-winner-argon2/blob/master/argon2-specs.pdf
// [2] https://tools.ietf.org/html/draft-irtf-cfrg-argon2-03#section-9.3
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 parallelism 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, 3, 32*1024, 4, 32)
//
// The draft RFC recommends[2] time=3, and memory=32*1024 is a sensible number.
// If using that amount of memory (32 MB) is not possible in some contexts then
// the time parameter can be increased to compensate.
//
// 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 number of threads can be
// adjusted to the number of available CPUs. 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)
}
// IDKey derives a key from the password, salt, and cost parameters using
// Argon2id returning a byte slice of length keyLen that can be used as
// cryptographic key. The CPU cost and parallelism 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.IDKey([]byte("some password"), salt, 1, 64*1024, 4, 32)
//
// The draft RFC recommends[2] time=1, and memory=64*1024 is a sensible number.
// If using that amount of memory (64 MB) is not possible in some contexts then
// the time parameter can be increased to compensate.
//
// 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=64*1024 sets the memory cost to ~64 MB. The number of threads can be
// adjusted to the numbers of available CPUs. The cost parameters should be
// increased as memory latency and CPU parallelism increases. Remember to get a
// good random salt.
func IDKey(password, salt []byte, time, memory uint32, threads uint8, keyLen uint32) []byte {
return deriveKey(argon2id, 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: parallelism degree too low")
}
h0 := initHash(password, salt, secret, data, time, memory, uint32(threads), keyLen, mode)
memory = memory / (syncPoints * uint32(threads)) * (syncPoints * uint32(threads))
if memory < 2*syncPoints*uint32(threads) {
memory = 2 * syncPoints * uint32(threads)
}
B := initBlocks(&h0, memory, uint32(threads))
processBlocks(B, time, memory, uint32(threads), mode)
return extractKey(B, memory, uint32(threads), keyLen)
}
const (
blockLength = 128
syncPoints = 4
)
type block [blockLength]uint64
func initHash(password, salt, key, data []byte, time, memory, threads, keyLen uint32, mode int) [blake2b.Size + 8]byte {
var (
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])
return h0
}
func initBlocks(h0 *[blake2b.Size + 8]byte, memory, threads uint32) []block {
var block0 [1024]byte
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[j+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[j+1] {
B[j+1][i] = binary.LittleEndian.Uint64(block0[i*8:])
}
}
return B
}
func processBlocks(B []block, time, memory, threads uint32, mode int) {
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 {
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 += lanes // 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
if n == 0 && slice == 0 {
refLane = lane
}
m, s := 3*segments, ((slice+1)%syncPoints)*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))
}
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