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including libs, first pass

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This commit is contained in:
brent s. 2022-06-05 18:38:02 -04:00
parent 2a7d9a478e
commit 8e362c72bf
Signed by: bts
GPG Key ID: 8C004C2F93481F6B
24 changed files with 8902 additions and 0 deletions
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98
chacha20poly1305/chacha20poly1305.go Normal file
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// Copyright 2016 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 chacha20poly1305 implements the ChaCha20-Poly1305 AEAD and its
// extended nonce variant XChaCha20-Poly1305, as specified in RFC 8439 and
// draft-irtf-cfrg-xchacha-01.
package chacha20poly1305 // import "golang.org/x/crypto/chacha20poly1305"

import (
"crypto/cipher"
"errors"
)

const (
// KeySize is the size of the key used by this AEAD, in bytes.
KeySize = 32

// NonceSize is the size of the nonce used with the standard variant of this
// AEAD, in bytes.
//
// Note that this is too short to be safely generated at random if the same
// key is reused more than 2³² times.
NonceSize = 12

// NonceSizeX is the size of the nonce used with the XChaCha20-Poly1305
// variant of this AEAD, in bytes.
NonceSizeX = 24

// Overhead is the size of the Poly1305 authentication tag, and the
// difference between a ciphertext length and its plaintext.
Overhead = 16
)

type chacha20poly1305 struct {
key [KeySize]byte
}

// New returns a ChaCha20-Poly1305 AEAD that uses the given 256-bit key.
func New(key []byte) (cipher.AEAD, error) {
if len(key) != KeySize {
return nil, errors.New("chacha20poly1305: bad key length")
}
ret := new(chacha20poly1305)
copy(ret.key[:], key)
return ret, nil
}

func (c *chacha20poly1305) NonceSize() int {
return NonceSize
}

func (c *chacha20poly1305) Overhead() int {
return Overhead
}

func (c *chacha20poly1305) Seal(dst, nonce, plaintext, additionalData []byte) []byte {
if len(nonce) != NonceSize {
panic("chacha20poly1305: bad nonce length passed to Seal")
}

if uint64(len(plaintext)) > (1<<38)-64 {
panic("chacha20poly1305: plaintext too large")
}

return c.seal(dst, nonce, plaintext, additionalData)
}

var errOpen = errors.New("chacha20poly1305: message authentication failed")

func (c *chacha20poly1305) Open(dst, nonce, ciphertext, additionalData []byte) ([]byte, error) {
if len(nonce) != NonceSize {
panic("chacha20poly1305: bad nonce length passed to Open")
}
if len(ciphertext) < 16 {
return nil, errOpen
}
if uint64(len(ciphertext)) > (1<<38)-48 {
panic("chacha20poly1305: ciphertext too large")
}

return c.open(dst, nonce, ciphertext, additionalData)
}

// sliceForAppend takes a slice and a requested number of bytes. It returns a
// slice with the contents of the given slice followed by that many bytes and a
// second slice that aliases into it and contains only the extra bytes. If the
// original slice has sufficient capacity then no allocation is performed.
func sliceForAppend(in []byte, n int) (head, tail []byte) {
if total := len(in) + n; cap(in) >= total {
head = in[:total]
} else {
head = make([]byte, total)
copy(head, in)
}
tail = head[len(in):]
return
}

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chacha20poly1305/chacha20poly1305_amd64.go Normal file
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// Copyright 2016 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.

//go:build gc && !purego
// +build gc,!purego

package chacha20poly1305

import (
"encoding/binary"

"golang.org/x/crypto/internal/subtle"
"golang.org/x/sys/cpu"
)

//go:noescape
func chacha20Poly1305Open(dst []byte, key []uint32, src, ad []byte) bool

//go:noescape
func chacha20Poly1305Seal(dst []byte, key []uint32, src, ad []byte)

var (
useAVX2 = cpu.X86.HasAVX2 && cpu.X86.HasBMI2
)

// setupState writes a ChaCha20 input matrix to state. See
// https://tools.ietf.org/html/rfc7539#section-2.3.
func setupState(state *[16]uint32, key *[32]byte, nonce []byte) {
state[0] = 0x61707865
state[1] = 0x3320646e
state[2] = 0x79622d32
state[3] = 0x6b206574

state[4] = binary.LittleEndian.Uint32(key[0:4])
state[5] = binary.LittleEndian.Uint32(key[4:8])
state[6] = binary.LittleEndian.Uint32(key[8:12])
state[7] = binary.LittleEndian.Uint32(key[12:16])
state[8] = binary.LittleEndian.Uint32(key[16:20])
state[9] = binary.LittleEndian.Uint32(key[20:24])
state[10] = binary.LittleEndian.Uint32(key[24:28])
state[11] = binary.LittleEndian.Uint32(key[28:32])

state[12] = 0
state[13] = binary.LittleEndian.Uint32(nonce[0:4])
state[14] = binary.LittleEndian.Uint32(nonce[4:8])
state[15] = binary.LittleEndian.Uint32(nonce[8:12])
}

func (c *chacha20poly1305) seal(dst, nonce, plaintext, additionalData []byte) []byte {
if !cpu.X86.HasSSSE3 {
return c.sealGeneric(dst, nonce, plaintext, additionalData)
}

var state [16]uint32
setupState(&state, &c.key, nonce)

ret, out := sliceForAppend(dst, len(plaintext)+16)
if subtle.InexactOverlap(out, plaintext) {
panic("chacha20poly1305: invalid buffer overlap")
}
chacha20Poly1305Seal(out[:], state[:], plaintext, additionalData)
return ret
}

func (c *chacha20poly1305) open(dst, nonce, ciphertext, additionalData []byte) ([]byte, error) {
if !cpu.X86.HasSSSE3 {
return c.openGeneric(dst, nonce, ciphertext, additionalData)
}

var state [16]uint32
setupState(&state, &c.key, nonce)

ciphertext = ciphertext[:len(ciphertext)-16]
ret, out := sliceForAppend(dst, len(ciphertext))
if subtle.InexactOverlap(out, ciphertext) {
panic("chacha20poly1305: invalid buffer overlap")
}
if !chacha20Poly1305Open(out, state[:], ciphertext, additionalData) {
for i := range out {
out[i] = 0
}
return nil, errOpen
}

return ret, nil
}

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chacha20poly1305/chacha20poly1305_amd64.s Normal file
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chacha20poly1305/chacha20poly1305_generic.go Normal file
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// Copyright 2016 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 chacha20poly1305

import (
"encoding/binary"

"golang.org/x/crypto/chacha20"
"golang.org/x/crypto/internal/poly1305"
"golang.org/x/crypto/internal/subtle"
)

func writeWithPadding(p *poly1305.MAC, b []byte) {
p.Write(b)
if rem := len(b) % 16; rem != 0 {
var buf [16]byte
padLen := 16 - rem
p.Write(buf[:padLen])
}
}

func writeUint64(p *poly1305.MAC, n int) {
var buf [8]byte
binary.LittleEndian.PutUint64(buf[:], uint64(n))
p.Write(buf[:])
}

func (c *chacha20poly1305) sealGeneric(dst, nonce, plaintext, additionalData []byte) []byte {
ret, out := sliceForAppend(dst, len(plaintext)+poly1305.TagSize)
ciphertext, tag := out[:len(plaintext)], out[len(plaintext):]
if subtle.InexactOverlap(out, plaintext) {
panic("chacha20poly1305: invalid buffer overlap")
}

var polyKey [32]byte
s, _ := chacha20.NewUnauthenticatedCipher(c.key[:], nonce)
s.XORKeyStream(polyKey[:], polyKey[:])
s.SetCounter(1) // set the counter to 1, skipping 32 bytes
s.XORKeyStream(ciphertext, plaintext)

p := poly1305.New(&polyKey)
writeWithPadding(p, additionalData)
writeWithPadding(p, ciphertext)
writeUint64(p, len(additionalData))
writeUint64(p, len(plaintext))
p.Sum(tag[:0])

return ret
}

func (c *chacha20poly1305) openGeneric(dst, nonce, ciphertext, additionalData []byte) ([]byte, error) {
tag := ciphertext[len(ciphertext)-16:]
ciphertext = ciphertext[:len(ciphertext)-16]

var polyKey [32]byte
s, _ := chacha20.NewUnauthenticatedCipher(c.key[:], nonce)
s.XORKeyStream(polyKey[:], polyKey[:])
s.SetCounter(1) // set the counter to 1, skipping 32 bytes

p := poly1305.New(&polyKey)
writeWithPadding(p, additionalData)
writeWithPadding(p, ciphertext)
writeUint64(p, len(additionalData))
writeUint64(p, len(ciphertext))

ret, out := sliceForAppend(dst, len(ciphertext))
if subtle.InexactOverlap(out, ciphertext) {
panic("chacha20poly1305: invalid buffer overlap")
}
if !p.Verify(tag) {
for i := range out {
out[i] = 0
}
return nil, errOpen
}

s.XORKeyStream(out, ciphertext)
return ret, nil
}

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// Copyright 2016 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.

//go:build !amd64 || !gc || purego
// +build !amd64 !gc purego

package chacha20poly1305

func (c *chacha20poly1305) seal(dst, nonce, plaintext, additionalData []byte) []byte {
return c.sealGeneric(dst, nonce, plaintext, additionalData)
}

func (c *chacha20poly1305) open(dst, nonce, ciphertext, additionalData []byte) ([]byte, error) {
return c.openGeneric(dst, nonce, ciphertext, additionalData)
}

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chacha20poly1305/chacha20poly1305_test.go Normal file
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// Copyright 2016 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 chacha20poly1305

import (
"bytes"
"crypto/cipher"
cryptorand "crypto/rand"
"encoding/hex"
"fmt"
mathrand "math/rand"
"strconv"
"testing"
)

func TestVectors(t *testing.T) {
for i, test := range chacha20Poly1305Tests {
key, _ := hex.DecodeString(test.key)
nonce, _ := hex.DecodeString(test.nonce)
ad, _ := hex.DecodeString(test.aad)
plaintext, _ := hex.DecodeString(test.plaintext)

var (
aead cipher.AEAD
err error
)
switch len(nonce) {
case NonceSize:
aead, err = New(key)
case NonceSizeX:
aead, err = NewX(key)
default:
t.Fatalf("#%d: wrong nonce length: %d", i, len(nonce))
}
if err != nil {
t.Fatal(err)
}

ct := aead.Seal(nil, nonce, plaintext, ad)
if ctHex := hex.EncodeToString(ct); ctHex != test.out {
t.Errorf("#%d: got %s, want %s", i, ctHex, test.out)
continue
}

plaintext2, err := aead.Open(nil, nonce, ct, ad)
if err != nil {
t.Errorf("#%d: Open failed", i)
continue
}

if !bytes.Equal(plaintext, plaintext2) {
t.Errorf("#%d: plaintext's don't match: got %x vs %x", i, plaintext2, plaintext)
continue
}

if len(ad) > 0 {
alterAdIdx := mathrand.Intn(len(ad))
ad[alterAdIdx] ^= 0x80
if _, err := aead.Open(nil, nonce, ct, ad); err == nil {
t.Errorf("#%d: Open was successful after altering additional data", i)
}
ad[alterAdIdx] ^= 0x80
}

alterNonceIdx := mathrand.Intn(aead.NonceSize())
nonce[alterNonceIdx] ^= 0x80
if _, err := aead.Open(nil, nonce, ct, ad); err == nil {
t.Errorf("#%d: Open was successful after altering nonce", i)
}
nonce[alterNonceIdx] ^= 0x80

alterCtIdx := mathrand.Intn(len(ct))
ct[alterCtIdx] ^= 0x80
if _, err := aead.Open(nil, nonce, ct, ad); err == nil {
t.Errorf("#%d: Open was successful after altering ciphertext", i)
}
ct[alterCtIdx] ^= 0x80
}
}

func TestRandom(t *testing.T) {
// Some random tests to verify Open(Seal) == Plaintext
f := func(t *testing.T, nonceSize int) {
for i := 0; i < 256; i++ {
var nonce = make([]byte, nonceSize)
var key [32]byte

al := mathrand.Intn(128)
pl := mathrand.Intn(16384)
ad := make([]byte, al)
plaintext := make([]byte, pl)
cryptorand.Read(key[:])
cryptorand.Read(nonce[:])
cryptorand.Read(ad)
cryptorand.Read(plaintext)

var (
aead cipher.AEAD
err error
)
switch len(nonce) {
case NonceSize:
aead, err = New(key[:])
case NonceSizeX:
aead, err = NewX(key[:])
default:
t.Fatalf("#%d: wrong nonce length: %d", i, len(nonce))
}
if err != nil {
t.Fatal(err)
}

ct := aead.Seal(nil, nonce[:], plaintext, ad)

plaintext2, err := aead.Open(nil, nonce[:], ct, ad)
if err != nil {
t.Errorf("Random #%d: Open failed", i)
continue
}

if !bytes.Equal(plaintext, plaintext2) {
t.Errorf("Random #%d: plaintext's don't match: got %x vs %x", i, plaintext2, plaintext)
continue
}

if len(ad) > 0 {
alterAdIdx := mathrand.Intn(len(ad))
ad[alterAdIdx] ^= 0x80
if _, err := aead.Open(nil, nonce[:], ct, ad); err == nil {
t.Errorf("Random #%d: Open was successful after altering additional data", i)
}
ad[alterAdIdx] ^= 0x80
}

alterNonceIdx := mathrand.Intn(aead.NonceSize())
nonce[alterNonceIdx] ^= 0x80
if _, err := aead.Open(nil, nonce[:], ct, ad); err == nil {
t.Errorf("Random #%d: Open was successful after altering nonce", i)
}
nonce[alterNonceIdx] ^= 0x80

alterCtIdx := mathrand.Intn(len(ct))
ct[alterCtIdx] ^= 0x80
if _, err := aead.Open(nil, nonce[:], ct, ad); err == nil {
t.Errorf("Random #%d: Open was successful after altering ciphertext", i)
}
ct[alterCtIdx] ^= 0x80
}
}
t.Run("Standard", func(t *testing.T) { f(t, NonceSize) })
t.Run("X", func(t *testing.T) { f(t, NonceSizeX) })
}

func benchamarkChaCha20Poly1305Seal(b *testing.B, buf []byte, nonceSize int) {
b.ReportAllocs()
b.SetBytes(int64(len(buf)))

var key [32]byte
var nonce = make([]byte, nonceSize)
var ad [13]byte
var out []byte

var aead cipher.AEAD
switch len(nonce) {
case NonceSize:
aead, _ = New(key[:])
case NonceSizeX:
aead, _ = NewX(key[:])
}

b.ResetTimer()
for i := 0; i < b.N; i++ {
out = aead.Seal(out[:0], nonce[:], buf[:], ad[:])
}
}

func benchamarkChaCha20Poly1305Open(b *testing.B, buf []byte, nonceSize int) {
b.ReportAllocs()
b.SetBytes(int64(len(buf)))

var key [32]byte
var nonce = make([]byte, nonceSize)
var ad [13]byte
var ct []byte
var out []byte

var aead cipher.AEAD
switch len(nonce) {
case NonceSize:
aead, _ = New(key[:])
case NonceSizeX:
aead, _ = NewX(key[:])
}
ct = aead.Seal(ct[:0], nonce[:], buf[:], ad[:])

b.ResetTimer()
for i := 0; i < b.N; i++ {
out, _ = aead.Open(out[:0], nonce[:], ct[:], ad[:])
}
}

func BenchmarkChacha20Poly1305(b *testing.B) {
for _, length := range []int{64, 1350, 8 * 1024} {
b.Run("Open-"+strconv.Itoa(length), func(b *testing.B) {
benchamarkChaCha20Poly1305Open(b, make([]byte, length), NonceSize)
})
b.Run("Seal-"+strconv.Itoa(length), func(b *testing.B) {
benchamarkChaCha20Poly1305Seal(b, make([]byte, length), NonceSize)
})

b.Run("Open-"+strconv.Itoa(length)+"-X", func(b *testing.B) {
benchamarkChaCha20Poly1305Open(b, make([]byte, length), NonceSizeX)
})
b.Run("Seal-"+strconv.Itoa(length)+"-X", func(b *testing.B) {
benchamarkChaCha20Poly1305Seal(b, make([]byte, length), NonceSizeX)
})
}
}

func ExampleNewX() {
// key should be randomly generated or derived from a function like Argon2.
key := make([]byte, KeySize)
if _, err := cryptorand.Read(key); err != nil {
panic(err)
}

aead, err := NewX(key)
if err != nil {
panic(err)
}

// Encryption.
var encryptedMsg []byte
{
msg := []byte("Gophers, gophers, gophers everywhere!")

// Select a random nonce, and leave capacity for the ciphertext.
nonce := make([]byte, aead.NonceSize(), aead.NonceSize()+len(msg)+aead.Overhead())
if _, err := cryptorand.Read(nonce); err != nil {
panic(err)
}

// Encrypt the message and append the ciphertext to the nonce.
encryptedMsg = aead.Seal(nonce, nonce, msg, nil)
}

// Decryption.
{
if len(encryptedMsg) < aead.NonceSize() {
panic("ciphertext too short")
}

// Split nonce and ciphertext.
nonce, ciphertext := encryptedMsg[:aead.NonceSize()], encryptedMsg[aead.NonceSize():]

// Decrypt the message and check it wasn't tampered with.
plaintext, err := aead.Open(nil, nonce, ciphertext, nil)
if err != nil {
panic(err)
}

fmt.Printf("%s\n", plaintext)
}

// Output: Gophers, gophers, gophers everywhere!
}

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chacha20poly1305/chacha20poly1305_vectors_test.go Normal file
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chacha20poly1305/xchacha20poly1305.go Normal file
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// Copyright 2018 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 chacha20poly1305

import (
"crypto/cipher"
"errors"

"golang.org/x/crypto/chacha20"
)

type xchacha20poly1305 struct {
key [KeySize]byte
}

// NewX returns a XChaCha20-Poly1305 AEAD that uses the given 256-bit key.
//
// XChaCha20-Poly1305 is a ChaCha20-Poly1305 variant that takes a longer nonce,
// suitable to be generated randomly without risk of collisions. It should be
// preferred when nonce uniqueness cannot be trivially ensured, or whenever
// nonces are randomly generated.
func NewX(key []byte) (cipher.AEAD, error) {
if len(key) != KeySize {
return nil, errors.New("chacha20poly1305: bad key length")
}
ret := new(xchacha20poly1305)
copy(ret.key[:], key)
return ret, nil
}

func (*xchacha20poly1305) NonceSize() int {
return NonceSizeX
}

func (*xchacha20poly1305) Overhead() int {
return Overhead
}

func (x *xchacha20poly1305) Seal(dst, nonce, plaintext, additionalData []byte) []byte {
if len(nonce) != NonceSizeX {
panic("chacha20poly1305: bad nonce length passed to Seal")
}

// XChaCha20-Poly1305 technically supports a 64-bit counter, so there is no
// size limit. However, since we reuse the ChaCha20-Poly1305 implementation,
// the second half of the counter is not available. This is unlikely to be
// an issue because the cipher.AEAD API requires the entire message to be in
// memory, and the counter overflows at 256 GB.
if uint64(len(plaintext)) > (1<<38)-64 {
panic("chacha20poly1305: plaintext too large")
}

c := new(chacha20poly1305)
hKey, _ := chacha20.HChaCha20(x.key[:], nonce[0:16])
copy(c.key[:], hKey)

// The first 4 bytes of the final nonce are unused counter space.
cNonce := make([]byte, NonceSize)
copy(cNonce[4:12], nonce[16:24])

return c.seal(dst, cNonce[:], plaintext, additionalData)
}

func (x *xchacha20poly1305) Open(dst, nonce, ciphertext, additionalData []byte) ([]byte, error) {
if len(nonce) != NonceSizeX {
panic("chacha20poly1305: bad nonce length passed to Open")
}
if len(ciphertext) < 16 {
return nil, errOpen
}
if uint64(len(ciphertext)) > (1<<38)-48 {
panic("chacha20poly1305: ciphertext too large")
}

c := new(chacha20poly1305)
hKey, _ := chacha20.HChaCha20(x.key[:], nonce[0:16])
copy(c.key[:], hKey)

// The first 4 bytes of the final nonce are unused counter space.
cNonce := make([]byte, NonceSize)
copy(cNonce[4:12], nonce[16:24])

return c.open(dst, cNonce[:], ciphertext, additionalData)
}

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// Copyright 2019 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.

//go:build !go1.13
// +build !go1.13

package poly1305

// Generic fallbacks for the math/bits intrinsics, copied from
// src/math/bits/bits.go. They were added in Go 1.12, but Add64 and Sum64 had
// variable time fallbacks until Go 1.13.

func bitsAdd64(x, y, carry uint64) (sum, carryOut uint64) {
sum = x + y + carry
carryOut = ((x & y) | ((x | y) &^ sum)) >> 63
return
}

func bitsSub64(x, y, borrow uint64) (diff, borrowOut uint64) {
diff = x - y - borrow
borrowOut = ((^x & y) | (^(x ^ y) & diff)) >> 63
return
}

func bitsMul64(x, y uint64) (hi, lo uint64) {
const mask32 = 1<<32 - 1
x0 := x & mask32
x1 := x >> 32
y0 := y & mask32
y1 := y >> 32
w0 := x0 * y0
t := x1*y0 + w0>>32
w1 := t & mask32
w2 := t >> 32
w1 += x0 * y1
hi = x1*y1 + w2 + w1>>32
lo = x * y
return
}

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// Copyright 2019 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.

//go:build go1.13
// +build go1.13

package poly1305

import "math/bits"

func bitsAdd64(x, y, carry uint64) (sum, carryOut uint64) {
return bits.Add64(x, y, carry)
}

func bitsSub64(x, y, borrow uint64) (diff, borrowOut uint64) {
return bits.Sub64(x, y, borrow)
}

func bitsMul64(x, y uint64) (hi, lo uint64) {
return bits.Mul64(x, y)
}

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poly1305/mac_noasm.go Normal file
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// Copyright 2018 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.

//go:build (!amd64 && !ppc64le && !s390x) || !gc || purego
// +build !amd64,!ppc64le,!s390x !gc purego

package poly1305

type mac struct{ macGeneric }

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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 poly1305 implements Poly1305 one-time message authentication code as
// specified in https://cr.yp.to/mac/poly1305-20050329.pdf.
//
// Poly1305 is a fast, one-time authentication function. It is infeasible for an
// attacker to generate an authenticator for a message without the key. However, a
// key must only be used for a single message. Authenticating two different
// messages with the same key allows an attacker to forge authenticators for other
// messages with the same key.
//
// Poly1305 was originally coupled with AES in order to make Poly1305-AES. AES was
// used with a fixed key in order to generate one-time keys from an nonce.
// However, in this package AES isn't used and the one-time key is specified
// directly.
package poly1305

import "crypto/subtle"

// TagSize is the size, in bytes, of a poly1305 authenticator.
const TagSize = 16

// Sum generates an authenticator for msg using a one-time key and puts the
// 16-byte result into out. Authenticating two different messages with the same
// key allows an attacker to forge messages at will.
func Sum(out *[16]byte, m []byte, key *[32]byte) {
h := New(key)
h.Write(m)
h.Sum(out[:0])
}

// Verify returns true if mac is a valid authenticator for m with the given key.
func Verify(mac *[16]byte, m []byte, key *[32]byte) bool {
var tmp [16]byte
Sum(&tmp, m, key)
return subtle.ConstantTimeCompare(tmp[:], mac[:]) == 1
}

// New returns a new MAC computing an authentication
// tag of all data written to it with the given key.
// This allows writing the message progressively instead
// of passing it as a single slice. Common users should use
// the Sum function instead.
//
// The key must be unique for each message, as authenticating
// two different messages with the same key allows an attacker
// to forge messages at will.
func New(key *[32]byte) *MAC {
m := &MAC{}
initialize(key, &m.macState)
return m
}

// MAC is an io.Writer computing an authentication tag
// of the data written to it.
//
// MAC cannot be used like common hash.Hash implementations,
// because using a poly1305 key twice breaks its security.
// Therefore writing data to a running MAC after calling
// Sum or Verify causes it to panic.
type MAC struct {
mac // platform-dependent implementation

finalized bool
}

// Size returns the number of bytes Sum will return.
func (h *MAC) Size() int { return TagSize }

// Write adds more data to the running message authentication code.
// It never returns an error.
//
// It must not be called after the first call of Sum or Verify.
func (h *MAC) Write(p []byte) (n int, err error) {
if h.finalized {
panic("poly1305: write to MAC after Sum or Verify")
}
return h.mac.Write(p)
}

// Sum computes the authenticator of all data written to the
// message authentication code.
func (h *MAC) Sum(b []byte) []byte {
var mac [TagSize]byte
h.mac.Sum(&mac)
h.finalized = true
return append(b, mac[:]...)
}

// Verify returns whether the authenticator of all data written to
// the message authentication code matches the expected value.
func (h *MAC) Verify(expected []byte) bool {
var mac [TagSize]byte
h.mac.Sum(&mac)
h.finalized = true
return subtle.ConstantTimeCompare(expected, mac[:]) == 1
}

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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 poly1305

import (
"crypto/rand"
"encoding/binary"
"encoding/hex"
"flag"
"testing"
"unsafe"
)

var stressFlag = flag.Bool("stress", false, "run slow stress tests")

type test struct {
in string
key string
tag string
state string
}

func (t *test) Input() []byte {
in, err := hex.DecodeString(t.in)
if err != nil {
panic(err)
}
return in
}

func (t *test) Key() [32]byte {
buf, err := hex.DecodeString(t.key)
if err != nil {
panic(err)
}
var key [32]byte
copy(key[:], buf[:32])
return key
}

func (t *test) Tag() [16]byte {
buf, err := hex.DecodeString(t.tag)
if err != nil {
panic(err)
}
var tag [16]byte
copy(tag[:], buf[:16])
return tag
}

func (t *test) InitialState() [3]uint64 {
// state is hex encoded in big-endian byte order
if t.state == "" {
return [3]uint64{0, 0, 0}
}
buf, err := hex.DecodeString(t.state)
if err != nil {
panic(err)
}
if len(buf) != 3*8 {
panic("incorrect state length")
}
return [3]uint64{
binary.BigEndian.Uint64(buf[16:24]),
binary.BigEndian.Uint64(buf[8:16]),
binary.BigEndian.Uint64(buf[0:8]),
}
}

func testSum(t *testing.T, unaligned bool, sumImpl func(tag *[TagSize]byte, msg []byte, key *[32]byte)) {
var tag [16]byte
for i, v := range testData {
// cannot set initial state before calling sum, so skip those tests
if v.InitialState() != [3]uint64{0, 0, 0} {
continue
}

in := v.Input()
if unaligned {
in = unalignBytes(in)
}
key := v.Key()
sumImpl(&tag, in, &key)
if tag != v.Tag() {
t.Errorf("%d: expected %x, got %x", i, v.Tag(), tag[:])
}
if !Verify(&tag, in, &key) {
t.Errorf("%d: tag didn't verify", i)
}
// If the key is zero, the tag will always be zero, independent of the input.
if len(in) > 0 && key != [32]byte{} {
in[0] ^= 0xff
if Verify(&tag, in, &key) {
t.Errorf("%d: tag verified after altering the input", i)
}
in[0] ^= 0xff
}
// If the input is empty, the tag only depends on the second half of the key.
if len(in) > 0 {
key[0] ^= 0xff
if Verify(&tag, in, &key) {
t.Errorf("%d: tag verified after altering the key", i)
}
key[0] ^= 0xff
}
tag[0] ^= 0xff
if Verify(&tag, in, &key) {
t.Errorf("%d: tag verified after altering the tag", i)
}
tag[0] ^= 0xff
}
}

func TestBurnin(t *testing.T) {
// This test can be used to sanity-check significant changes. It can
// take about many minutes to run, even on fast machines. It's disabled
// by default.
if !*stressFlag {
t.Skip("skipping without -stress")
}

var key [32]byte
var input [25]byte
var output [16]byte

for i := range key {
key[i] = 1
}
for i := range input {
input[i] = 2
}

for i := uint64(0); i < 1e10; i++ {
Sum(&output, input[:], &key)
copy(key[0:], output[:])
copy(key[16:], output[:])
copy(input[:], output[:])
copy(input[16:], output[:])
}

const expected = "5e3b866aea0b636d240c83c428f84bfa"
if got := hex.EncodeToString(output[:]); got != expected {
t.Errorf("expected %s, got %s", expected, got)
}
}

func TestSum(t *testing.T) { testSum(t, false, Sum) }
func TestSumUnaligned(t *testing.T) { testSum(t, true, Sum) }
func TestSumGeneric(t *testing.T) { testSum(t, false, sumGeneric) }
func TestSumGenericUnaligned(t *testing.T) { testSum(t, true, sumGeneric) }

func TestWriteGeneric(t *testing.T) { testWriteGeneric(t, false) }
func TestWriteGenericUnaligned(t *testing.T) { testWriteGeneric(t, true) }
func TestWrite(t *testing.T) { testWrite(t, false) }
func TestWriteUnaligned(t *testing.T) { testWrite(t, true) }

func testWriteGeneric(t *testing.T, unaligned bool) {
for i, v := range testData {
key := v.Key()
input := v.Input()
var out [16]byte

if unaligned {
input = unalignBytes(input)
}
h := newMACGeneric(&key)
if s := v.InitialState(); s != [3]uint64{0, 0, 0} {
h.macState.h = s
}
n, err := h.Write(input[:len(input)/3])
if err != nil || n != len(input[:len(input)/3]) {
t.Errorf("#%d: unexpected Write results: n = %d, err = %v", i, n, err)
}
n, err = h.Write(input[len(input)/3:])
if err != nil || n != len(input[len(input)/3:]) {
t.Errorf("#%d: unexpected Write results: n = %d, err = %v", i, n, err)
}
h.Sum(&out)
if tag := v.Tag(); out != tag {
t.Errorf("%d: expected %x, got %x", i, tag[:], out[:])
}
}
}

func testWrite(t *testing.T, unaligned bool) {
for i, v := range testData {
key := v.Key()
input := v.Input()
var out [16]byte

if unaligned {
input = unalignBytes(input)
}
h := New(&key)
if s := v.InitialState(); s != [3]uint64{0, 0, 0} {
h.macState.h = s
}
n, err := h.Write(input[:len(input)/3])
if err != nil || n != len(input[:len(input)/3]) {
t.Errorf("#%d: unexpected Write results: n = %d, err = %v", i, n, err)
}
n, err = h.Write(input[len(input)/3:])
if err != nil || n != len(input[len(input)/3:]) {
t.Errorf("#%d: unexpected Write results: n = %d, err = %v", i, n, err)
}
h.Sum(out[:0])
tag := v.Tag()
if out != tag {
t.Errorf("%d: expected %x, got %x", i, tag[:], out[:])
}
if !h.Verify(tag[:]) {
t.Errorf("%d: Verify failed", i)
}
tag[0] ^= 0xff
if h.Verify(tag[:]) {
t.Errorf("%d: Verify succeeded after modifying the tag", i)
}
}
}

func benchmarkSum(b *testing.B, size int, unaligned bool) {
var out [16]byte
var key [32]byte
in := make([]byte, size)
if unaligned {
in = unalignBytes(in)
}
rand.Read(in)
b.SetBytes(int64(len(in)))
b.ResetTimer()
for i := 0; i < b.N; i++ {
Sum(&out, in, &key)
}
}

func benchmarkWrite(b *testing.B, size int, unaligned bool) {
var key [32]byte
h := New(&key)
in := make([]byte, size)
if unaligned {
in = unalignBytes(in)
}
rand.Read(in)
b.SetBytes(int64(len(in)))
b.ResetTimer()
for i := 0; i < b.N; i++ {
h.Write(in)
}
}

func Benchmark64(b *testing.B) { benchmarkSum(b, 64, false) }
func Benchmark1K(b *testing.B) { benchmarkSum(b, 1024, false) }
func Benchmark2M(b *testing.B) { benchmarkSum(b, 2*1024*1024, false) }
func Benchmark64Unaligned(b *testing.B) { benchmarkSum(b, 64, true) }
func Benchmark1KUnaligned(b *testing.B) { benchmarkSum(b, 1024, true) }
func Benchmark2MUnaligned(b *testing.B) { benchmarkSum(b, 2*1024*1024, true) }

func BenchmarkWrite64(b *testing.B) { benchmarkWrite(b, 64, false) }
func BenchmarkWrite1K(b *testing.B) { benchmarkWrite(b, 1024, false) }
func BenchmarkWrite2M(b *testing.B) { benchmarkWrite(b, 2*1024*1024, false) }
func BenchmarkWrite64Unaligned(b *testing.B) { benchmarkWrite(b, 64, true) }
func BenchmarkWrite1KUnaligned(b *testing.B) { benchmarkWrite(b, 1024, true) }
func BenchmarkWrite2MUnaligned(b *testing.B) { benchmarkWrite(b, 2*1024*1024, true) }

func unalignBytes(in []byte) []byte {
out := make([]byte, len(in)+1)
if uintptr(unsafe.Pointer(&out[0]))&(unsafe.Alignof(uint32(0))-1) == 0 {
out = out[1:]
} else {
out = out[:len(in)]
}
copy(out, in)
return out
}

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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.

//go:build gc && !purego
// +build gc,!purego

package poly1305

//go:noescape
func update(state *macState, msg []byte)

// mac is a wrapper for macGeneric that redirects calls that would have gone to
// updateGeneric to update.
//
// Its Write and Sum methods are otherwise identical to the macGeneric ones, but
// using function pointers would carry a major performance cost.
type mac struct{ macGeneric }

func (h *mac) Write(p []byte) (int, error) {
nn := len(p)
if h.offset > 0 {
n := copy(h.buffer[h.offset:], p)
if h.offset+n < TagSize {
h.offset += n
return nn, nil
}
p = p[n:]
h.offset = 0
update(&h.macState, h.buffer[:])
}
if n := len(p) - (len(p) % TagSize); n > 0 {
update(&h.macState, p[:n])
p = p[n:]
}
if len(p) > 0 {
h.offset += copy(h.buffer[h.offset:], p)
}
return nn, nil
}

func (h *mac) Sum(out *[16]byte) {
state := h.macState
if h.offset > 0 {
update(&state, h.buffer[:h.offset])
}
finalize(out, &state.h, &state.s)
}

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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.

//go:build gc && !purego
// +build gc,!purego

#include "textflag.h"

#define POLY1305_ADD(msg, h0, h1, h2) \
ADDQ 0(msg), h0; \
ADCQ 8(msg), h1; \
ADCQ $1, h2; \
LEAQ 16(msg), msg

#define POLY1305_MUL(h0, h1, h2, r0, r1, t0, t1, t2, t3) \
MOVQ r0, AX; \
MULQ h0; \
MOVQ AX, t0; \
MOVQ DX, t1; \
MOVQ r0, AX; \
MULQ h1; \
ADDQ AX, t1; \
ADCQ $0, DX; \
MOVQ r0, t2; \
IMULQ h2, t2; \
ADDQ DX, t2; \
\
MOVQ r1, AX; \
MULQ h0; \
ADDQ AX, t1; \
ADCQ $0, DX; \
MOVQ DX, h0; \
MOVQ r1, t3; \
IMULQ h2, t3; \
MOVQ r1, AX; \
MULQ h1; \
ADDQ AX, t2; \
ADCQ DX, t3; \
ADDQ h0, t2; \
ADCQ $0, t3; \
\
MOVQ t0, h0; \
MOVQ t1, h1; \
MOVQ t2, h2; \
ANDQ $3, h2; \
MOVQ t2, t0; \
ANDQ $0xFFFFFFFFFFFFFFFC, t0; \
ADDQ t0, h0; \
ADCQ t3, h1; \
ADCQ $0, h2; \
SHRQ $2, t3, t2; \
SHRQ $2, t3; \
ADDQ t2, h0; \
ADCQ t3, h1; \
ADCQ $0, h2

// func update(state *[7]uint64, msg []byte)
TEXT ·update(SB), $0-32
MOVQ state+0(FP), DI
MOVQ msg_base+8(FP), SI
MOVQ msg_len+16(FP), R15

MOVQ 0(DI), R8 // h0
MOVQ 8(DI), R9 // h1
MOVQ 16(DI), R10 // h2
MOVQ 24(DI), R11 // r0
MOVQ 32(DI), R12 // r1

CMPQ R15, $16
JB bytes_between_0_and_15

loop:
POLY1305_ADD(SI, R8, R9, R10)

multiply:
POLY1305_MUL(R8, R9, R10, R11, R12, BX, CX, R13, R14)
SUBQ $16, R15
CMPQ R15, $16
JAE loop

bytes_between_0_and_15:
TESTQ R15, R15
JZ done
MOVQ $1, BX
XORQ CX, CX
XORQ R13, R13
ADDQ R15, SI

flush_buffer:
SHLQ $8, BX, CX
SHLQ $8, BX
MOVB -1(SI), R13
XORQ R13, BX
DECQ SI
DECQ R15
JNZ flush_buffer

ADDQ BX, R8
ADCQ CX, R9
ADCQ $0, R10
MOVQ $16, R15
JMP multiply

done:
MOVQ R8, 0(DI)
MOVQ R9, 8(DI)
MOVQ R10, 16(DI)
RET

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// Copyright 2018 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.

// This file provides the generic implementation of Sum and MAC. Other files
// might provide optimized assembly implementations of some of this code.

package poly1305

import "encoding/binary"

// Poly1305 [RFC 7539] is a relatively simple algorithm: the authentication tag
// for a 64 bytes message is approximately
//
// s + m[0:16] * r⁴ + m[16:32] * r³ + m[32:48] * r² + m[48:64] * r mod 2¹³⁰ - 5
//
// for some secret r and s. It can be computed sequentially like
//
// for len(msg) > 0:
// h += read(msg, 16)
// h *= r
// h %= 2¹³⁰ - 5
// return h + s
//
// All the complexity is about doing performant constant-time math on numbers
// larger than any available numeric type.

func sumGeneric(out *[TagSize]byte, msg []byte, key *[32]byte) {
h := newMACGeneric(key)
h.Write(msg)
h.Sum(out)
}

func newMACGeneric(key *[32]byte) macGeneric {
m := macGeneric{}
initialize(key, &m.macState)
return m
}

// macState holds numbers in saturated 64-bit little-endian limbs. That is,
// the value of [x0, x1, x2] is x[0] + x[1] * 2⁶⁴ + x[2] * 2¹²⁸.
type macState struct {
// h is the main accumulator. It is to be interpreted modulo 2¹³⁰ - 5, but
// can grow larger during and after rounds. It must, however, remain below
// 2 * (2¹³⁰ - 5).
h [3]uint64
// r and s are the private key components.
r [2]uint64
s [2]uint64
}

type macGeneric struct {
macState

buffer [TagSize]byte
offset int
}

// Write splits the incoming message into TagSize chunks, and passes them to
// update. It buffers incomplete chunks.
func (h *macGeneric) Write(p []byte) (int, error) {
nn := len(p)
if h.offset > 0 {
n := copy(h.buffer[h.offset:], p)
if h.offset+n < TagSize {
h.offset += n
return nn, nil
}
p = p[n:]
h.offset = 0
updateGeneric(&h.macState, h.buffer[:])
}
if n := len(p) - (len(p) % TagSize); n > 0 {
updateGeneric(&h.macState, p[:n])
p = p[n:]
}
if len(p) > 0 {
h.offset += copy(h.buffer[h.offset:], p)
}
return nn, nil
}

// Sum flushes the last incomplete chunk from the buffer, if any, and generates
// the MAC output. It does not modify its state, in order to allow for multiple
// calls to Sum, even if no Write is allowed after Sum.
func (h *macGeneric) Sum(out *[TagSize]byte) {
state := h.macState
if h.offset > 0 {
updateGeneric(&state, h.buffer[:h.offset])
}
finalize(out, &state.h, &state.s)
}

// [rMask0, rMask1] is the specified Poly1305 clamping mask in little-endian. It
// clears some bits of the secret coefficient to make it possible to implement
// multiplication more efficiently.
const (
rMask0 = 0x0FFFFFFC0FFFFFFF
rMask1 = 0x0FFFFFFC0FFFFFFC
)

// initialize loads the 256-bit key into the two 128-bit secret values r and s.
func initialize(key *[32]byte, m *macState) {
m.r[0] = binary.LittleEndian.Uint64(key[0:8]) & rMask0
m.r[1] = binary.LittleEndian.Uint64(key[8:16]) & rMask1
m.s[0] = binary.LittleEndian.Uint64(key[16:24])
m.s[1] = binary.LittleEndian.Uint64(key[24:32])
}

// uint128 holds a 128-bit number as two 64-bit limbs, for use with the
// bits.Mul64 and bits.Add64 intrinsics.
type uint128 struct {
lo, hi uint64
}

func mul64(a, b uint64) uint128 {
hi, lo := bitsMul64(a, b)
return uint128{lo, hi}
}

func add128(a, b uint128) uint128 {
lo, c := bitsAdd64(a.lo, b.lo, 0)
hi, c := bitsAdd64(a.hi, b.hi, c)
if c != 0 {
panic("poly1305: unexpected overflow")
}
return uint128{lo, hi}
}

func shiftRightBy2(a uint128) uint128 {
a.lo = a.lo>>2 | (a.hi&3)<<62
a.hi = a.hi >> 2
return a
}

// updateGeneric absorbs msg into the state.h accumulator. For each chunk m of
// 128 bits of message, it computes
//
// h₊ = (h + m) * r mod 2¹³⁰ - 5
//
// If the msg length is not a multiple of TagSize, it assumes the last
// incomplete chunk is the final one.
func updateGeneric(state *macState, msg []byte) {
h0, h1, h2 := state.h[0], state.h[1], state.h[2]
r0, r1 := state.r[0], state.r[1]

for len(msg) > 0 {
var c uint64

// For the first step, h + m, we use a chain of bits.Add64 intrinsics.
// The resulting value of h might exceed 2¹³⁰ - 5, but will be partially
// reduced at the end of the multiplication below.
//
// The spec requires us to set a bit just above the message size, not to
// hide leading zeroes. For full chunks, that's 1 << 128, so we can just
// add 1 to the most significant (2¹²⁸) limb, h2.
if len(msg) >= TagSize {
h0, c = bitsAdd64(h0, binary.LittleEndian.Uint64(msg[0:8]), 0)
h1, c = bitsAdd64(h1, binary.LittleEndian.Uint64(msg[8:16]), c)
h2 += c + 1

msg = msg[TagSize:]
} else {
var buf [TagSize]byte
copy(buf[:], msg)
buf[len(msg)] = 1

h0, c = bitsAdd64(h0, binary.LittleEndian.Uint64(buf[0:8]), 0)
h1, c = bitsAdd64(h1, binary.LittleEndian.Uint64(buf[8:16]), c)
h2 += c

msg = nil
}

// Multiplication of big number limbs is similar to elementary school
// columnar multiplication. Instead of digits, there are 64-bit limbs.
//
// We are multiplying a 3 limbs number, h, by a 2 limbs number, r.
//
// h2 h1 h0 x
// r1 r0 =
// ----------------
// h2r0 h1r0 h0r0 <-- individual 128-bit products
// + h2r1 h1r1 h0r1
// ------------------------
// m3 m2 m1 m0 <-- result in 128-bit overlapping limbs
// ------------------------
// m3.hi m2.hi m1.hi m0.hi <-- carry propagation
// + m3.lo m2.lo m1.lo m0.lo
// -------------------------------
// t4 t3 t2 t1 t0 <-- final result in 64-bit limbs
//
// The main difference from pen-and-paper multiplication is that we do
// carry propagation in a separate step, as if we wrote two digit sums
// at first (the 128-bit limbs), and then carried the tens all at once.

h0r0 := mul64(h0, r0)
h1r0 := mul64(h1, r0)
h2r0 := mul64(h2, r0)
h0r1 := mul64(h0, r1)
h1r1 := mul64(h1, r1)
h2r1 := mul64(h2, r1)

// Since h2 is known to be at most 7 (5 + 1 + 1), and r0 and r1 have their
// top 4 bits cleared by rMask{0,1}, we know that their product is not going
// to overflow 64 bits, so we can ignore the high part of the products.
//
// This also means that the product doesn't have a fifth limb (t4).
if h2r0.hi != 0 {
panic("poly1305: unexpected overflow")
}
if h2r1.hi != 0 {
panic("poly1305: unexpected overflow")
}

m0 := h0r0
m1 := add128(h1r0, h0r1) // These two additions don't overflow thanks again
m2 := add128(h2r0, h1r1) // to the 4 masked bits at the top of r0 and r1.
m3 := h2r1

t0 := m0.lo
t1, c := bitsAdd64(m1.lo, m0.hi, 0)
t2, c := bitsAdd64(m2.lo, m1.hi, c)
t3, _ := bitsAdd64(m3.lo, m2.hi, c)

// Now we have the result as 4 64-bit limbs, and we need to reduce it
// modulo 2¹³⁰ - 5. The special shape of this Crandall prime lets us do
// a cheap partial reduction according to the reduction identity
//
// c * 2¹³⁰ + n = c * 5 + n mod 2¹³⁰ - 5
//
// because 2¹³⁰ = 5 mod 2¹³⁰ - 5. Partial reduction since the result is
// likely to be larger than 2¹³⁰ - 5, but still small enough to fit the
// assumptions we make about h in the rest of the code.
//
// See also https://speakerdeck.com/gtank/engineering-prime-numbers?slide=23

// We split the final result at the 2¹³⁰ mark into h and cc, the carry.
// Note that the carry bits are effectively shifted left by 2, in other
// words, cc = c * 4 for the c in the reduction identity.
h0, h1, h2 = t0, t1, t2&maskLow2Bits
cc := uint128{t2 & maskNotLow2Bits, t3}

// To add c * 5 to h, we first add cc = c * 4, and then add (cc >> 2) = c.

h0, c = bitsAdd64(h0, cc.lo, 0)
h1, c = bitsAdd64(h1, cc.hi, c)
h2 += c

cc = shiftRightBy2(cc)

h0, c = bitsAdd64(h0, cc.lo, 0)
h1, c = bitsAdd64(h1, cc.hi, c)
h2 += c

// h2 is at most 3 + 1 + 1 = 5, making the whole of h at most
//
// 5 * 2¹²⁸ + (2¹²⁸ - 1) = 6 * 2¹²⁸ - 1
}

state.h[0], state.h[1], state.h[2] = h0, h1, h2
}

const (
maskLow2Bits uint64 = 0x0000000000000003
maskNotLow2Bits uint64 = ^maskLow2Bits
)

// select64 returns x if v == 1 and y if v == 0, in constant time.
func select64(v, x, y uint64) uint64 { return ^(v-1)&x | (v-1)&y }

// [p0, p1, p2] is 2¹³⁰ - 5 in little endian order.
const (
p0 = 0xFFFFFFFFFFFFFFFB
p1 = 0xFFFFFFFFFFFFFFFF
p2 = 0x0000000000000003
)

// finalize completes the modular reduction of h and computes
//
// out = h + s mod 2¹²⁸
func finalize(out *[TagSize]byte, h *[3]uint64, s *[2]uint64) {
h0, h1, h2 := h[0], h[1], h[2]

// After the partial reduction in updateGeneric, h might be more than
// 2¹³⁰ - 5, but will be less than 2 * (2¹³⁰ - 5). To complete the reduction
// in constant time, we compute t = h - (2¹³⁰ - 5), and select h as the
// result if the subtraction underflows, and t otherwise.

hMinusP0, b := bitsSub64(h0, p0, 0)
hMinusP1, b := bitsSub64(h1, p1, b)
_, b = bitsSub64(h2, p2, b)

// h = h if h < p else h - p
h0 = select64(b, h0, hMinusP0)
h1 = select64(b, h1, hMinusP1)

// Finally, we compute the last Poly1305 step
//
// tag = h + s mod 2¹²⁸
//
// by just doing a wide addition with the 128 low bits of h and discarding
// the overflow.
h0, c := bitsAdd64(h0, s[0], 0)
h1, _ = bitsAdd64(h1, s[1], c)

binary.LittleEndian.PutUint64(out[0:8], h0)
binary.LittleEndian.PutUint64(out[8:16], h1)
}

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// Copyright 2019 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.

//go:build gc && !purego
// +build gc,!purego

package poly1305

//go:noescape
func update(state *macState, msg []byte)

// mac is a wrapper for macGeneric that redirects calls that would have gone to
// updateGeneric to update.
//
// Its Write and Sum methods are otherwise identical to the macGeneric ones, but
// using function pointers would carry a major performance cost.
type mac struct{ macGeneric }

func (h *mac) Write(p []byte) (int, error) {
nn := len(p)
if h.offset > 0 {
n := copy(h.buffer[h.offset:], p)
if h.offset+n < TagSize {
h.offset += n
return nn, nil
}
p = p[n:]
h.offset = 0
update(&h.macState, h.buffer[:])
}
if n := len(p) - (len(p) % TagSize); n > 0 {
update(&h.macState, p[:n])
p = p[n:]
}
if len(p) > 0 {
h.offset += copy(h.buffer[h.offset:], p)
}
return nn, nil
}

func (h *mac) Sum(out *[16]byte) {
state := h.macState
if h.offset > 0 {
update(&state, h.buffer[:h.offset])
}
finalize(out, &state.h, &state.s)
}

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// Copyright 2019 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.

//go:build gc && !purego
// +build gc,!purego

#include "textflag.h"

// This was ported from the amd64 implementation.

#define POLY1305_ADD(msg, h0, h1, h2, t0, t1, t2) \
MOVD (msg), t0; \
MOVD 8(msg), t1; \
MOVD $1, t2; \
ADDC t0, h0, h0; \
ADDE t1, h1, h1; \
ADDE t2, h2; \
ADD $16, msg

#define POLY1305_MUL(h0, h1, h2, r0, r1, t0, t1, t2, t3, t4, t5) \
MULLD r0, h0, t0; \
MULLD r0, h1, t4; \
MULHDU r0, h0, t1; \
MULHDU r0, h1, t5; \
ADDC t4, t1, t1; \
MULLD r0, h2, t2; \
ADDZE t5; \
MULHDU r1, h0, t4; \
MULLD r1, h0, h0; \
ADD t5, t2, t2; \
ADDC h0, t1, t1; \
MULLD h2, r1, t3; \
ADDZE t4, h0; \
MULHDU r1, h1, t5; \
MULLD r1, h1, t4; \
ADDC t4, t2, t2; \
ADDE t5, t3, t3; \
ADDC h0, t2, t2; \
MOVD $-4, t4; \
MOVD t0, h0; \
MOVD t1, h1; \
ADDZE t3; \
ANDCC $3, t2, h2; \
AND t2, t4, t0; \
ADDC t0, h0, h0; \
ADDE t3, h1, h1; \
SLD $62, t3, t4; \
SRD $2, t2; \
ADDZE h2; \
OR t4, t2, t2; \
SRD $2, t3; \
ADDC t2, h0, h0; \
ADDE t3, h1, h1; \
ADDZE h2

DATA ·poly1305Mask<>+0x00(SB)/8, $0x0FFFFFFC0FFFFFFF
DATA ·poly1305Mask<>+0x08(SB)/8, $0x0FFFFFFC0FFFFFFC
GLOBL ·poly1305Mask<>(SB), RODATA, $16

// func update(state *[7]uint64, msg []byte)
TEXT ·update(SB), $0-32
MOVD state+0(FP), R3
MOVD msg_base+8(FP), R4
MOVD msg_len+16(FP), R5

MOVD 0(R3), R8 // h0
MOVD 8(R3), R9 // h1
MOVD 16(R3), R10 // h2
MOVD 24(R3), R11 // r0
MOVD 32(R3), R12 // r1

CMP R5, $16
BLT bytes_between_0_and_15

loop:
POLY1305_ADD(R4, R8, R9, R10, R20, R21, R22)

multiply:
POLY1305_MUL(R8, R9, R10, R11, R12, R16, R17, R18, R14, R20, R21)
ADD $-16, R5
CMP R5, $16
BGE loop

bytes_between_0_and_15:
CMP R5, $0
BEQ done
MOVD $0, R16 // h0
MOVD $0, R17 // h1

flush_buffer:
CMP R5, $8
BLE just1

MOVD $8, R21
SUB R21, R5, R21

// Greater than 8 -- load the rightmost remaining bytes in msg
// and put into R17 (h1)
MOVD (R4)(R21), R17
MOVD $16, R22

// Find the offset to those bytes
SUB R5, R22, R22
SLD $3, R22

// Shift to get only the bytes in msg
SRD R22, R17, R17

// Put 1 at high end
MOVD $1, R23
SLD $3, R21
SLD R21, R23, R23
OR R23, R17, R17

// Remainder is 8
MOVD $8, R5

just1:
CMP R5, $8
BLT less8

// Exactly 8
MOVD (R4), R16

CMP R17, $0

// Check if we've already set R17; if not
// set 1 to indicate end of msg.
BNE carry
MOVD $1, R17
BR carry

less8:
MOVD $0, R16 // h0
MOVD $0, R22 // shift count
CMP R5, $4
BLT less4
MOVWZ (R4), R16
ADD $4, R4
ADD $-4, R5
MOVD $32, R22

less4:
CMP R5, $2
BLT less2
MOVHZ (R4), R21
SLD R22, R21, R21
OR R16, R21, R16
ADD $16, R22
ADD $-2, R5
ADD $2, R4

less2:
CMP R5, $0
BEQ insert1
MOVBZ (R4), R21
SLD R22, R21, R21
OR R16, R21, R16
ADD $8, R22

insert1:
// Insert 1 at end of msg
MOVD $1, R21
SLD R22, R21, R21
OR R16, R21, R16

carry:
// Add new values to h0, h1, h2
ADDC R16, R8
ADDE R17, R9
ADDZE R10, R10
MOVD $16, R5
ADD R5, R4
BR multiply

done:
// Save h0, h1, h2 in state
MOVD R8, 0(R3)
MOVD R9, 8(R3)
MOVD R10, 16(R3)
RET

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// Copyright 2018 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.

//go:build gc && !purego
// +build gc,!purego

package poly1305

import (
"golang.org/x/sys/cpu"
)

// updateVX is an assembly implementation of Poly1305 that uses vector
// instructions. It must only be called if the vector facility (vx) is
// available.
//
//go:noescape
func updateVX(state *macState, msg []byte)

// mac is a replacement for macGeneric that uses a larger buffer and redirects
// calls that would have gone to updateGeneric to updateVX if the vector
// facility is installed.
//
// A larger buffer is required for good performance because the vector
// implementation has a higher fixed cost per call than the generic
// implementation.
type mac struct {
macState

buffer [16 * TagSize]byte // size must be a multiple of block size (16)
offset int
}

func (h *mac) Write(p []byte) (int, error) {
nn := len(p)
if h.offset > 0 {
n := copy(h.buffer[h.offset:], p)
if h.offset+n < len(h.buffer) {
h.offset += n
return nn, nil
}
p = p[n:]
h.offset = 0
if cpu.S390X.HasVX {
updateVX(&h.macState, h.buffer[:])
} else {
updateGeneric(&h.macState, h.buffer[:])
}
}

tail := len(p) % len(h.buffer) // number of bytes to copy into buffer
body := len(p) - tail // number of bytes to process now
if body > 0 {
if cpu.S390X.HasVX {
updateVX(&h.macState, p[:body])
} else {
updateGeneric(&h.macState, p[:body])
}
}
h.offset = copy(h.buffer[:], p[body:]) // copy tail bytes - can be 0
return nn, nil
}

func (h *mac) Sum(out *[TagSize]byte) {
state := h.macState
remainder := h.buffer[:h.offset]

// Use the generic implementation if we have 2 or fewer blocks left
// to sum. The vector implementation has a higher startup time.
if cpu.S390X.HasVX && len(remainder) > 2*TagSize {
updateVX(&state, remainder)
} else if len(remainder) > 0 {
updateGeneric(&state, remainder)
}
finalize(out, &state.h, &state.s)
}

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// Copyright 2018 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.

//go:build gc && !purego
// +build gc,!purego

#include "textflag.h"

// This implementation of Poly1305 uses the vector facility (vx)
// to process up to 2 blocks (32 bytes) per iteration using an
// algorithm based on the one described in:
//
// NEON crypto, Daniel J. Bernstein & Peter Schwabe
// https://cryptojedi.org/papers/neoncrypto-20120320.pdf
//
// This algorithm uses 5 26-bit limbs to represent a 130-bit
// value. These limbs are, for the most part, zero extended and
// placed into 64-bit vector register elements. Each vector
// register is 128-bits wide and so holds 2 of these elements.
// Using 26-bit limbs allows us plenty of headroom to accommodate
// accumulations before and after multiplication without
// overflowing either 32-bits (before multiplication) or 64-bits
// (after multiplication).
//
// In order to parallelise the operations required to calculate
// the sum we use two separate accumulators and then sum those
// in an extra final step. For compatibility with the generic
// implementation we perform this summation at the end of every
// updateVX call.
//
// To use two accumulators we must multiply the message blocks
// by r² rather than r. Only the final message block should be
// multiplied by r.
//
// Example:
//
// We want to calculate the sum (h) for a 64 byte message (m):
//
// h = m[0:16]r⁴ + m[16:32]r³ + m[32:48]r² + m[48:64]r
//
// To do this we split the calculation into the even indices
// and odd indices of the message. These form our SIMD 'lanes':
//
// h = m[ 0:16]r⁴ + m[32:48]r² + <- lane 0
// m[16:32]r³ + m[48:64]r <- lane 1
//
// To calculate this iteratively we refactor so that both lanes
// are written in terms of r² and r:
//
// h = (m[ 0:16]r² + m[32:48])r² + <- lane 0
// (m[16:32]r² + m[48:64])r <- lane 1
// ^ ^
// | coefficients for second iteration
// coefficients for first iteration
//
// So in this case we would have two iterations. In the first
// both lanes are multiplied by r². In the second only the
// first lane is multiplied by r² and the second lane is
// instead multiplied by r. This gives use the odd and even
// powers of r that we need from the original equation.
//
// Notation:
//
// h - accumulator
// r - key
// m - message
//
// [a, b] - SIMD register holding two 64-bit values
// [a, b, c, d] - SIMD register holding four 32-bit values
// xᵢ[n] - limb n of variable x with bit width i
//
// Limbs are expressed in little endian order, so for 26-bit
// limbs x₂₆[4] will be the most significant limb and x₂₆[0]
// will be the least significant limb.

// masking constants
#define MOD24 V0 // [0x0000000000ffffff, 0x0000000000ffffff] - mask low 24-bits
#define MOD26 V1 // [0x0000000003ffffff, 0x0000000003ffffff] - mask low 26-bits

// expansion constants (see EXPAND macro)
#define EX0 V2
#define EX1 V3
#define EX2 V4

// key (r², r or 1 depending on context)
#define R_0 V5
#define R_1 V6
#define R_2 V7
#define R_3 V8
#define R_4 V9

// precalculated coefficients (5r², 5r or 0 depending on context)
#define R5_1 V10
#define R5_2 V11
#define R5_3 V12
#define R5_4 V13

// message block (m)
#define M_0 V14
#define M_1 V15
#define M_2 V16
#define M_3 V17
#define M_4 V18

// accumulator (h)
#define H_0 V19
#define H_1 V20
#define H_2 V21
#define H_3 V22
#define H_4 V23

// temporary registers (for short-lived values)
#define T_0 V24
#define T_1 V25
#define T_2 V26
#define T_3 V27
#define T_4 V28

GLOBL ·constants<>(SB), RODATA, $0x30
// EX0
DATA ·constants<>+0x00(SB)/8, $0x0006050403020100
DATA ·constants<>+0x08(SB)/8, $0x1016151413121110
// EX1
DATA ·constants<>+0x10(SB)/8, $0x060c0b0a09080706
DATA ·constants<>+0x18(SB)/8, $0x161c1b1a19181716
// EX2
DATA ·constants<>+0x20(SB)/8, $0x0d0d0d0d0d0f0e0d
DATA ·constants<>+0x28(SB)/8, $0x1d1d1d1d1d1f1e1d

// MULTIPLY multiplies each lane of f and g, partially reduced
// modulo 2¹³⁰ - 5. The result, h, consists of partial products
// in each lane that need to be reduced further to produce the
// final result.
//
// h₁₃₀ = (f₁₃₀g₁₃₀) % 2¹³⁰ + (5f₁₃₀g₁₃₀) / 2¹³⁰
//
// Note that the multiplication by 5 of the high bits is
// achieved by precalculating the multiplication of four of the
// g coefficients by 5. These are g51-g54.
#define MULTIPLY(f0, f1, f2, f3, f4, g0, g1, g2, g3, g4, g51, g52, g53, g54, h0, h1, h2, h3, h4) \
VMLOF f0, g0, h0 \
VMLOF f0, g3, h3 \
VMLOF f0, g1, h1 \
VMLOF f0, g4, h4 \
VMLOF f0, g2, h2 \
VMLOF f1, g54, T_0 \
VMLOF f1, g2, T_3 \
VMLOF f1, g0, T_1 \
VMLOF f1, g3, T_4 \
VMLOF f1, g1, T_2 \
VMALOF f2, g53, h0, h0 \
VMALOF f2, g1, h3, h3 \
VMALOF f2, g54, h1, h1 \
VMALOF f2, g2, h4, h4 \
VMALOF f2, g0, h2, h2 \
VMALOF f3, g52, T_0, T_0 \
VMALOF f3, g0, T_3, T_3 \
VMALOF f3, g53, T_1, T_1 \
VMALOF f3, g1, T_4, T_4 \
VMALOF f3, g54, T_2, T_2 \
VMALOF f4, g51, h0, h0 \
VMALOF f4, g54, h3, h3 \
VMALOF f4, g52, h1, h1 \
VMALOF f4, g0, h4, h4 \
VMALOF f4, g53, h2, h2 \
VAG T_0, h0, h0 \
VAG T_3, h3, h3 \
VAG T_1, h1, h1 \
VAG T_4, h4, h4 \
VAG T_2, h2, h2

// REDUCE performs the following carry operations in four
// stages, as specified in Bernstein & Schwabe:
//
// 1: h₂₆[0]->h₂₆[1] h₂₆[3]->h₂₆[4]
// 2: h₂₆[1]->h₂₆[2] h₂₆[4]->h₂₆[0]
// 3: h₂₆[0]->h₂₆[1] h₂₆[2]->h₂₆[3]
// 4: h₂₆[3]->h₂₆[4]
//
// The result is that all of the limbs are limited to 26-bits
// except for h₂₆[1] and h₂₆[4] which are limited to 27-bits.
//
// Note that although each limb is aligned at 26-bit intervals
// they may contain values that exceed 2²⁶ - 1, hence the need
// to carry the excess bits in each limb.
#define REDUCE(h0, h1, h2, h3, h4) \
VESRLG $26, h0, T_0 \
VESRLG $26, h3, T_1 \
VN MOD26, h0, h0 \
VN MOD26, h3, h3 \
VAG T_0, h1, h1 \
VAG T_1, h4, h4 \
VESRLG $26, h1, T_2 \
VESRLG $26, h4, T_3 \
VN MOD26, h1, h1 \
VN MOD26, h4, h4 \
VESLG $2, T_3, T_4 \
VAG T_3, T_4, T_4 \
VAG T_2, h2, h2 \
VAG T_4, h0, h0 \
VESRLG $26, h2, T_0 \
VESRLG $26, h0, T_1 \
VN MOD26, h2, h2 \
VN MOD26, h0, h0 \
VAG T_0, h3, h3 \
VAG T_1, h1, h1 \
VESRLG $26, h3, T_2 \
VN MOD26, h3, h3 \
VAG T_2, h4, h4

// EXPAND splits the 128-bit little-endian values in0 and in1
// into 26-bit big-endian limbs and places the results into
// the first and second lane of d₂₆[0:4] respectively.
//
// The EX0, EX1 and EX2 constants are arrays of byte indices
// for permutation. The permutation both reverses the bytes
// in the input and ensures the bytes are copied into the
// destination limb ready to be shifted into their final
// position.
#define EXPAND(in0, in1, d0, d1, d2, d3, d4) \
VPERM in0, in1, EX0, d0 \
VPERM in0, in1, EX1, d2 \
VPERM in0, in1, EX2, d4 \
VESRLG $26, d0, d1 \
VESRLG $30, d2, d3 \
VESRLG $4, d2, d2 \
VN MOD26, d0, d0 \ // [in0₂₆[0], in1₂₆[0]]
VN MOD26, d3, d3 \ // [in0₂₆[3], in1₂₆[3]]
VN MOD26, d1, d1 \ // [in0₂₆[1], in1₂₆[1]]
VN MOD24, d4, d4 \ // [in0₂₆[4], in1₂₆[4]]
VN MOD26, d2, d2 // [in0₂₆[2], in1₂₆[2]]

// func updateVX(state *macState, msg []byte)
TEXT ·updateVX(SB), NOSPLIT, $0
MOVD state+0(FP), R1
LMG msg+8(FP), R2, R3 // R2=msg_base, R3=msg_len

// load EX0, EX1 and EX2
MOVD $·constants<>(SB), R5
VLM (R5), EX0, EX2

// generate masks
VGMG $(64-24), $63, MOD24 // [0x00ffffff, 0x00ffffff]
VGMG $(64-26), $63, MOD26 // [0x03ffffff, 0x03ffffff]

// load h (accumulator) and r (key) from state
VZERO T_1 // [0, 0]
VL 0(R1), T_0 // [h₆₄[0], h₆₄[1]]
VLEG $0, 16(R1), T_1 // [h₆₄[2], 0]
VL 24(R1), T_2 // [r₆₄[0], r₆₄[1]]
VPDI $0, T_0, T_2, T_3 // [h₆₄[0], r₆₄[0]]
VPDI $5, T_0, T_2, T_4 // [h₆₄[1], r₆₄[1]]

// unpack h and r into 26-bit limbs
// note: h₆₄[2] may have the low 3 bits set, so h₂₆[4] is a 27-bit value
VN MOD26, T_3, H_0 // [h₂₆[0], r₂₆[0]]
VZERO H_1 // [0, 0]
VZERO H_3 // [0, 0]
VGMG $(64-12-14), $(63-12), T_0 // [0x03fff000, 0x03fff000] - 26-bit mask with low 12 bits masked out
VESLG $24, T_1, T_1 // [h₆₄[2]<<24, 0]
VERIMG $-26&63, T_3, MOD26, H_1 // [h₂₆[1], r₂₆[1]]
VESRLG $+52&63, T_3, H_2 // [h₂₆[2], r₂₆[2]] - low 12 bits only
VERIMG $-14&63, T_4, MOD26, H_3 // [h₂₆[1], r₂₆[1]]
VESRLG $40, T_4, H_4 // [h₂₆[4], r₂₆[4]] - low 24 bits only
VERIMG $+12&63, T_4, T_0, H_2 // [h₂₆[2], r₂₆[2]] - complete
VO T_1, H_4, H_4 // [h₂₆[4], r₂₆[4]] - complete

// replicate r across all 4 vector elements
VREPF $3, H_0, R_0 // [r₂₆[0], r₂₆[0], r₂₆[0], r₂₆[0]]
VREPF $3, H_1, R_1 // [r₂₆[1], r₂₆[1], r₂₆[1], r₂₆[1]]
VREPF $3, H_2, R_2 // [r₂₆[2], r₂₆[2], r₂₆[2], r₂₆[2]]
VREPF $3, H_3, R_3 // [r₂₆[3], r₂₆[3], r₂₆[3], r₂₆[3]]
VREPF $3, H_4, R_4 // [r₂₆[4], r₂₆[4], r₂₆[4], r₂₆[4]]

// zero out lane 1 of h
VLEIG $1, $0, H_0 // [h₂₆[0], 0]
VLEIG $1, $0, H_1 // [h₂₆[1], 0]
VLEIG $1, $0, H_2 // [h₂₆[2], 0]
VLEIG $1, $0, H_3 // [h₂₆[3], 0]
VLEIG $1, $0, H_4 // [h₂₆[4], 0]

// calculate 5r (ignore least significant limb)
VREPIF $5, T_0
VMLF T_0, R_1, R5_1 // [5r₂₆[1], 5r₂₆[1], 5r₂₆[1], 5r₂₆[1]]
VMLF T_0, R_2, R5_2 // [5r₂₆[2], 5r₂₆[2], 5r₂₆[2], 5r₂₆[2]]
VMLF T_0, R_3, R5_3 // [5r₂₆[3], 5r₂₆[3], 5r₂₆[3], 5r₂₆[3]]
VMLF T_0, R_4, R5_4 // [5r₂₆[4], 5r₂₆[4], 5r₂₆[4], 5r₂₆[4]]

// skip r² calculation if we are only calculating one block
CMPBLE R3, $16, skip

// calculate r²
MULTIPLY(R_0, R_1, R_2, R_3, R_4, R_0, R_1, R_2, R_3, R_4, R5_1, R5_2, R5_3, R5_4, M_0, M_1, M_2, M_3, M_4)
REDUCE(M_0, M_1, M_2, M_3, M_4)
VGBM $0x0f0f, T_0
VERIMG $0, M_0, T_0, R_0 // [r₂₆[0], r²₂₆[0], r₂₆[0], r²₂₆[0]]
VERIMG $0, M_1, T_0, R_1 // [r₂₆[1], r²₂₆[1], r₂₆[1], r²₂₆[1]]
VERIMG $0, M_2, T_0, R_2 // [r₂₆[2], r²₂₆[2], r₂₆[2], r²₂₆[2]]
VERIMG $0, M_3, T_0, R_3 // [r₂₆[3], r²₂₆[3], r₂₆[3], r²₂₆[3]]
VERIMG $0, M_4, T_0, R_4 // [r₂₆[4], r²₂₆[4], r₂₆[4], r²₂₆[4]]

// calculate 5r² (ignore least significant limb)
VREPIF $5, T_0
VMLF T_0, R_1, R5_1 // [5r₂₆[1], 5r²₂₆[1], 5r₂₆[1], 5r²₂₆[1]]
VMLF T_0, R_2, R5_2 // [5r₂₆[2], 5r²₂₆[2], 5r₂₆[2], 5r²₂₆[2]]
VMLF T_0, R_3, R5_3 // [5r₂₆[3], 5r²₂₆[3], 5r₂₆[3], 5r²₂₆[3]]
VMLF T_0, R_4, R5_4 // [5r₂₆[4], 5r²₂₆[4], 5r₂₆[4], 5r²₂₆[4]]

loop:
CMPBLE R3, $32, b2 // 2 or fewer blocks remaining, need to change key coefficients

// load next 2 blocks from message
VLM (R2), T_0, T_1

// update message slice
SUB $32, R3
MOVD $32(R2), R2

// unpack message blocks into 26-bit big-endian limbs
EXPAND(T_0, T_1, M_0, M_1, M_2, M_3, M_4)

// add 2¹²⁸ to each message block value
VLEIB $4, $1, M_4
VLEIB $12, $1, M_4

multiply:
// accumulate the incoming message
VAG H_0, M_0, M_0
VAG H_3, M_3, M_3
VAG H_1, M_1, M_1
VAG H_4, M_4, M_4
VAG H_2, M_2, M_2

// multiply the accumulator by the key coefficient
MULTIPLY(M_0, M_1, M_2, M_3, M_4, R_0, R_1, R_2, R_3, R_4, R5_1, R5_2, R5_3, R5_4, H_0, H_1, H_2, H_3, H_4)

// carry and partially reduce the partial products
REDUCE(H_0, H_1, H_2, H_3, H_4)

CMPBNE R3, $0, loop

finish:
// sum lane 0 and lane 1 and put the result in lane 1
VZERO T_0
VSUMQG H_0, T_0, H_0
VSUMQG H_3, T_0, H_3
VSUMQG H_1, T_0, H_1
VSUMQG H_4, T_0, H_4
VSUMQG H_2, T_0, H_2

// reduce again after summation
// TODO(mundaym): there might be a more efficient way to do this
// now that we only have 1 active lane. For example, we could
// simultaneously pack the values as we reduce them.
REDUCE(H_0, H_1, H_2, H_3, H_4)

// carry h[1] through to h[4] so that only h[4] can exceed 2²⁶ - 1
// TODO(mundaym): in testing this final carry was unnecessary.
// Needs a proof before it can be removed though.
VESRLG $26, H_1, T_1
VN MOD26, H_1, H_1
VAQ T_1, H_2, H_2
VESRLG $26, H_2, T_2
VN MOD26, H_2, H_2
VAQ T_2, H_3, H_3
VESRLG $26, H_3, T_3
VN MOD26, H_3, H_3
VAQ T_3, H_4, H_4

// h is now < 2(2¹³⁰ - 5)
// Pack each lane in h₂₆[0:4] into h₁₂₈[0:1].
VESLG $26, H_1, H_1
VESLG $26, H_3, H_3
VO H_0, H_1, H_0
VO H_2, H_3, H_2
VESLG $4, H_2, H_2
VLEIB $7, $48, H_1
VSLB H_1, H_2, H_2
VO H_0, H_2, H_0
VLEIB $7, $104, H_1
VSLB H_1, H_4, H_3
VO H_3, H_0, H_0
VLEIB $7, $24, H_1
VSRLB H_1, H_4, H_1

// update state
VSTEG $1, H_0, 0(R1)
VSTEG $0, H_0, 8(R1)
VSTEG $1, H_1, 16(R1)
RET

b2: // 2 or fewer blocks remaining
CMPBLE R3, $16, b1

// Load the 2 remaining blocks (17-32 bytes remaining).
MOVD $-17(R3), R0 // index of final byte to load modulo 16
VL (R2), T_0 // load full 16 byte block
VLL R0, 16(R2), T_1 // load final (possibly partial) block and pad with zeros to 16 bytes

// The Poly1305 algorithm requires that a 1 bit be appended to
// each message block. If the final block is less than 16 bytes
// long then it is easiest to insert the 1 before the message
// block is split into 26-bit limbs. If, on the other hand, the
// final message block is 16 bytes long then we append the 1 bit
// after expansion as normal.
MOVBZ $1, R0
MOVD $-16(R3), R3 // index of byte in last block to insert 1 at (could be 16)
CMPBEQ R3, $16, 2(PC) // skip the insertion if the final block is 16 bytes long
VLVGB R3, R0, T_1 // insert 1 into the byte at index R3

// Split both blocks into 26-bit limbs in the appropriate lanes.
EXPAND(T_0, T_1, M_0, M_1, M_2, M_3, M_4)

// Append a 1 byte to the end of the second to last block.
VLEIB $4, $1, M_4

// Append a 1 byte to the end of the last block only if it is a
// full 16 byte block.
CMPBNE R3, $16, 2(PC)
VLEIB $12, $1, M_4

// Finally, set up the coefficients for the final multiplication.
// We have previously saved r and 5r in the 32-bit even indexes
// of the R_[0-4] and R5_[1-4] coefficient registers.
//
// We want lane 0 to be multiplied by r² so that can be kept the
// same. We want lane 1 to be multiplied by r so we need to move
// the saved r value into the 32-bit odd index in lane 1 by
// rotating the 64-bit lane by 32.
VGBM $0x00ff, T_0 // [0, 0xffffffffffffffff] - mask lane 1 only
VERIMG $32, R_0, T_0, R_0 // [_, r²₂₆[0], _, r₂₆[0]]
VERIMG $32, R_1, T_0, R_1 // [_, r²₂₆[1], _, r₂₆[1]]
VERIMG $32, R_2, T_0, R_2 // [_, r²₂₆[2], _, r₂₆[2]]
VERIMG $32, R_3, T_0, R_3 // [_, r²₂₆[3], _, r₂₆[3]]
VERIMG $32, R_4, T_0, R_4 // [_, r²₂₆[4], _, r₂₆[4]]
VERIMG $32, R5_1, T_0, R5_1 // [_, 5r²₂₆[1], _, 5r₂₆[1]]
VERIMG $32, R5_2, T_0, R5_2 // [_, 5r²₂₆[2], _, 5r₂₆[2]]
VERIMG $32, R5_3, T_0, R5_3 // [_, 5r²₂₆[3], _, 5r₂₆[3]]
VERIMG $32, R5_4, T_0, R5_4 // [_, 5r²₂₆[4], _, 5r₂₆[4]]

MOVD $0, R3
BR multiply

skip:
CMPBEQ R3, $0, finish

b1: // 1 block remaining

// Load the final block (1-16 bytes). This will be placed into
// lane 0.
MOVD $-1(R3), R0
VLL R0, (R2), T_0 // pad to 16 bytes with zeros

// The Poly1305 algorithm requires that a 1 bit be appended to
// each message block. If the final block is less than 16 bytes
// long then it is easiest to insert the 1 before the message
// block is split into 26-bit limbs. If, on the other hand, the
// final message block is 16 bytes long then we append the 1 bit
// after expansion as normal.
MOVBZ $1, R0
CMPBEQ R3, $16, 2(PC)
VLVGB R3, R0, T_0

// Set the message block in lane 1 to the value 0 so that it
// can be accumulated without affecting the final result.
VZERO T_1

// Split the final message block into 26-bit limbs in lane 0.
// Lane 1 will be contain 0.
EXPAND(T_0, T_1, M_0, M_1, M_2, M_3, M_4)

// Append a 1 byte to the end of the last block only if it is a
// full 16 byte block.
CMPBNE R3, $16, 2(PC)
VLEIB $4, $1, M_4

// We have previously saved r and 5r in the 32-bit even indexes
// of the R_[0-4] and R5_[1-4] coefficient registers.
//
// We want lane 0 to be multiplied by r so we need to move the
// saved r value into the 32-bit odd index in lane 0. We want
// lane 1 to be set to the value 1. This makes multiplication
// a no-op. We do this by setting lane 1 in every register to 0
// and then just setting the 32-bit index 3 in R_0 to 1.
VZERO T_0
MOVD $0, R0
MOVD $0x10111213, R12
VLVGP R12, R0, T_1 // [_, 0x10111213, _, 0x00000000]
VPERM T_0, R_0, T_1, R_0 // [_, r₂₆[0], _, 0]
VPERM T_0, R_1, T_1, R_1 // [_, r₂₆[1], _, 0]
VPERM T_0, R_2, T_1, R_2 // [_, r₂₆[2], _, 0]
VPERM T_0, R_3, T_1, R_3 // [_, r₂₆[3], _, 0]
VPERM T_0, R_4, T_1, R_4 // [_, r₂₆[4], _, 0]
VPERM T_0, R5_1, T_1, R5_1 // [_, 5r₂₆[1], _, 0]
VPERM T_0, R5_2, T_1, R5_2 // [_, 5r₂₆[2], _, 0]
VPERM T_0, R5_3, T_1, R5_3 // [_, 5r₂₆[3], _, 0]
VPERM T_0, R5_4, T_1, R5_4 // [_, 5r₂₆[4], _, 0]

// Set the value of lane 1 to be 1.
VLEIF $3, $1, R_0 // [_, r₂₆[0], _, 1]

MOVD $0, R3
BR multiply

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// Copyright 2018 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.

//go:build !purego
// +build !purego

// Package subtle implements functions that are often useful in cryptographic
// code but require careful thought to use correctly.
package subtle // import "golang.org/x/crypto/internal/subtle"

import "unsafe"

// AnyOverlap reports whether x and y share memory at any (not necessarily
// corresponding) index. The memory beyond the slice length is ignored.
func AnyOverlap(x, y []byte) bool {
return len(x) > 0 && len(y) > 0 &&
uintptr(unsafe.Pointer(&x[0])) <= uintptr(unsafe.Pointer(&y[len(y)-1])) &&
uintptr(unsafe.Pointer(&y[0])) <= uintptr(unsafe.Pointer(&x[len(x)-1]))
}

// InexactOverlap reports whether x and y share memory at any non-corresponding
// index. The memory beyond the slice length is ignored. Note that x and y can
// have different lengths and still not have any inexact overlap.
//
// InexactOverlap can be used to implement the requirements of the crypto/cipher
// AEAD, Block, BlockMode and Stream interfaces.
func InexactOverlap(x, y []byte) bool {
if len(x) == 0 || len(y) == 0 || &x[0] == &y[0] {
return false
}
return AnyOverlap(x, y)
}

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// Copyright 2018 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.

//go:build purego
// +build purego

// Package subtle implements functions that are often useful in cryptographic
// code but require careful thought to use correctly.
package subtle // import "golang.org/x/crypto/internal/subtle"

// This is the Google App Engine standard variant based on reflect
// because the unsafe package and cgo are disallowed.

import "reflect"

// AnyOverlap reports whether x and y share memory at any (not necessarily
// corresponding) index. The memory beyond the slice length is ignored.
func AnyOverlap(x, y []byte) bool {
return len(x) > 0 && len(y) > 0 &&
reflect.ValueOf(&x[0]).Pointer() <= reflect.ValueOf(&y[len(y)-1]).Pointer() &&
reflect.ValueOf(&y[0]).Pointer() <= reflect.ValueOf(&x[len(x)-1]).Pointer()
}

// InexactOverlap reports whether x and y share memory at any non-corresponding
// index. The memory beyond the slice length is ignored. Note that x and y can
// have different lengths and still not have any inexact overlap.
//
// InexactOverlap can be used to implement the requirements of the crypto/cipher
// AEAD, Block, BlockMode and Stream interfaces.
func InexactOverlap(x, y []byte) bool {
if len(x) == 0 || len(y) == 0 || &x[0] == &y[0] {
return false
}
return AnyOverlap(x, y)
}

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// Copyright 2018 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 subtle_test

import (
"testing"

"golang.org/x/crypto/internal/subtle"
)

var a, b [100]byte

var aliasingTests = []struct {
x, y []byte
anyOverlap, inexactOverlap bool
}{
{a[:], b[:], false, false},
{a[:], b[:0], false, false},
{a[:], b[:50], false, false},
{a[40:50], a[50:60], false, false},
{a[40:50], a[60:70], false, false},
{a[:51], a[50:], true, true},
{a[:], a[:], true, false},
{a[:50], a[:60], true, false},
{a[:], nil, false, false},
{nil, nil, false, false},
{a[:], a[:0], false, false},
{a[:10], a[:10:20], true, false},
{a[:10], a[5:10:20], true, true},
}

func testAliasing(t *testing.T, i int, x, y []byte, anyOverlap, inexactOverlap bool) {
any := subtle.AnyOverlap(x, y)
if any != anyOverlap {
t.Errorf("%d: wrong AnyOverlap result, expected %v, got %v", i, anyOverlap, any)
}
inexact := subtle.InexactOverlap(x, y)
if inexact != inexactOverlap {
t.Errorf("%d: wrong InexactOverlap result, expected %v, got %v", i, inexactOverlap, any)
}
}

func TestAliasing(t *testing.T) {
for i, tt := range aliasingTests {
testAliasing(t, i, tt.x, tt.y, tt.anyOverlap, tt.inexactOverlap)
testAliasing(t, i, tt.y, tt.x, tt.anyOverlap, tt.inexactOverlap)
}
}