From 587c3847da81aa7cfc3b3db2677c8586c94df13a Mon Sep 17 00:00:00 2001
From: Filippo Valsorda <filippo@golang.org>
Date: Wed, 22 May 2024 20:47:31 +0200
Subject: [PATCH] math/rand/v2: add ChaCha8.Read
Fixes #67059
Closes #67452
Closes #67498
Change-Id: I84eba2ed787a17e9d6aaad2a8a78596e3944909a
Reviewed-on: https://go-review.googlesource.com/c/go/+/587280
Reviewed-by: Roland Shoemaker <roland@golang.org>
Auto-Submit: Filippo Valsorda <filippo@golang.org>
Reviewed-by: Carlos Amedee <carlos@golang.org>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
---
api/next/67059.txt | 1 +
.../6-stdlib/99-minor/math/rand/v2/67059.md | 1 +
src/math/rand/rand.go | 1 +
src/math/rand/v2/chacha8.go | 66 ++++++-
src/math/rand/v2/chacha8_test.go | 161 +++++++++++++++++-
5 files changed, 228 insertions(+), 2 deletions(-)
create mode 100644 api/next/67059.txt
create mode 100644 doc/next/6-stdlib/99-minor/math/rand/v2/67059.md
diff --git a/api/next/67059.txt b/api/next/67059.txt
new file mode 100644
index 00000000000..c128585d14f
--- /dev/null
+++ b/api/next/67059.txt
@@ -0,0 +1 @@
+pkg math/rand/v2, method (*ChaCha8) Read([]uint8) (int, error) #67059
diff --git a/doc/next/6-stdlib/99-minor/math/rand/v2/67059.md b/doc/next/6-stdlib/99-minor/math/rand/v2/67059.md
new file mode 100644
index 00000000000..c66110c7a44
--- /dev/null
+++ b/doc/next/6-stdlib/99-minor/math/rand/v2/67059.md
@@ -0,0 +1 @@
+The new [ChaCha8.Read] method implements the [io.Reader] interface.
diff --git a/src/math/rand/rand.go b/src/math/rand/rand.go
index a8ed9c0cb7c..61ff5c1b387 100644
--- a/src/math/rand/rand.go
+++ b/src/math/rand/rand.go
@@ -474,6 +474,7 @@ func Shuffle(n int, swap func(i, j int)) { globalRand().Shuffle(n, swap) }
// Read, unlike the [Rand.Read] method, is safe for concurrent use.
//
// Deprecated: For almost all use cases, [crypto/rand.Read] is more appropriate.
+// If a deterministic source is required, use [math/rand/v2.ChaCha8.Read].
func Read(p []byte) (n int, err error) { return globalRand().Read(p) }
// NormFloat64 returns a normally distributed float64 in the range
diff --git a/src/math/rand/v2/chacha8.go b/src/math/rand/v2/chacha8.go
index 6b9aa727825..f9eaacf6017 100644
--- a/src/math/rand/v2/chacha8.go
+++ b/src/math/rand/v2/chacha8.go
@@ -4,12 +4,20 @@
package rand
-import "internal/chacha8rand"
+import (
+ "errors"
+ "internal/byteorder"
+ "internal/chacha8rand"
+)
// A ChaCha8 is a ChaCha8-based cryptographically strong
// random number generator.
type ChaCha8 struct {
state chacha8rand.State
+
+ // The last readLen bytes of readBuf are still to be consumed by Read.
+ readBuf [8]byte
+ readLen int // 0 <= readLen <= 8
}
// NewChaCha8 returns a new ChaCha8 seeded with the given seed.
@@ -22,6 +30,8 @@ func NewChaCha8(seed [32]byte) *ChaCha8 {
// Seed resets the ChaCha8 to behave the same way as NewChaCha8(seed).
func (c *ChaCha8) Seed(seed [32]byte) {
c.state.Init(seed)
+ c.readLen = 0
+ c.readBuf = [8]byte{}
}
// Uint64 returns a uniformly distributed random uint64 value.
@@ -35,12 +45,66 @@ func (c *ChaCha8) Uint64() uint64 {
}
}
+// Read reads exactly len(p) bytes into p.
+// It always returns len(p) and a nil error.
+//
+// If calls to Read and Uint64 are interleaved, the order in which bits are
+// returned by the two is undefined, and Read may return bits generated before
+// the last call to Uint64.
+func (c *ChaCha8) Read(p []byte) (n int, err error) {
+ if c.readLen > 0 {
+ n = copy(p, c.readBuf[len(c.readBuf)-c.readLen:])
+ c.readLen -= n
+ p = p[n:]
+ }
+ for len(p) >= 8 {
+ byteorder.LePutUint64(p, c.Uint64())
+ p = p[8:]
+ n += 8
+ }
+ if len(p) > 0 {
+ byteorder.LePutUint64(c.readBuf[:], c.Uint64())
+ n += copy(p, c.readBuf[:])
+ c.readLen = 8 - len(p)
+ }
+ return
+}
+
// UnmarshalBinary implements the encoding.BinaryUnmarshaler interface.
func (c *ChaCha8) UnmarshalBinary(data []byte) error {
+ data, ok := cutPrefix(data, []byte("readbuf:"))
+ if ok {
+ var buf []byte
+ buf, data, ok = readUint8LengthPrefixed(data)
+ if !ok {
+ return errors.New("invalid ChaCha8 Read buffer encoding")
+ }
+ c.readLen = copy(c.readBuf[len(c.readBuf)-len(buf):], buf)
+ }
return chacha8rand.Unmarshal(&c.state, data)
}
+func cutPrefix(s, prefix []byte) (after []byte, found bool) {
+ if len(s) < len(prefix) || string(s[:len(prefix)]) != string(prefix) {
+ return s, false
+ }
+ return s[len(prefix):], true
+}
+
+func readUint8LengthPrefixed(b []byte) (buf, rest []byte, ok bool) {
+ if len(b) == 0 || len(b) < int(1+b[0]) {
+ return nil, nil, false
+ }
+ return b[1 : 1+b[0]], b[1+b[0]:], true
+}
+
// MarshalBinary implements the encoding.BinaryMarshaler interface.
func (c *ChaCha8) MarshalBinary() ([]byte, error) {
+ if c.readLen > 0 {
+ out := []byte("readbuf:")
+ out = append(out, uint8(c.readLen))
+ out = append(out, c.readBuf[len(c.readBuf)-c.readLen:]...)
+ return append(out, chacha8rand.Marshal(&c.state)...), nil
+ }
return chacha8rand.Marshal(&c.state), nil
}
diff --git a/src/math/rand/v2/chacha8_test.go b/src/math/rand/v2/chacha8_test.go
index 2c55b479b25..50e83ea19a1 100644
--- a/src/math/rand/v2/chacha8_test.go
+++ b/src/math/rand/v2/chacha8_test.go
@@ -5,8 +5,13 @@
package rand_test
import (
+ "bytes"
+ "crypto/sha256"
+ "encoding/hex"
+ "io"
. "math/rand/v2"
"testing"
+ "testing/iotest"
)
func TestChaCha8(t *testing.T) {
@@ -25,6 +30,74 @@ func TestChaCha8(t *testing.T) {
}
}
+func TestChaCha8Read(t *testing.T) {
+ p := NewChaCha8(chacha8seed)
+ h := sha256.New()
+
+ buf := make([]byte, chacha8outlen)
+ if nn, err := p.Read(buf); err != nil {
+ t.Fatal(err)
+ } else if nn != len(buf) {
+ t.Errorf("Read short: got %d, expected %d", nn, len(buf))
+ }
+ h.Write(buf)
+ if got := h.Sum(nil); !bytes.Equal(got, chacha8hash) {
+ t.Errorf("transcript incorrect: got %x, want %x", got, chacha8hash)
+ }
+
+ p.Seed(chacha8seed)
+ h.Reset()
+
+ buf = make([]byte, chacha8outlen)
+ if _, err := io.ReadFull(iotest.OneByteReader(p), buf); err != nil {
+ t.Errorf("one byte reads: %v", err)
+ }
+ h.Write(buf)
+ if got := h.Sum(nil); !bytes.Equal(got, chacha8hash) {
+ t.Errorf("transcript incorrect (one byte reads): got %x, want %x", got, chacha8hash)
+ }
+
+ p.Seed(chacha8seed)
+ h.Reset()
+
+ if n, err := p.Read(make([]byte, 0)); err != nil {
+ t.Errorf("zero length read: %v", err)
+ } else if n != 0 {
+ t.Errorf("Read zero length: got %d, expected %d", n, 0)
+ }
+
+ var n int
+ for n < chacha8outlen {
+ if IntN(2) == 0 {
+ out, err := p.MarshalBinary()
+ if err != nil {
+ t.Fatal(err)
+ }
+ if IntN(2) == 0 {
+ p = NewChaCha8([32]byte{})
+ }
+ if err := p.UnmarshalBinary(out); err != nil {
+ t.Fatal(err)
+ }
+ }
+ buf := make([]byte, IntN(100))
+ if n+len(buf) > chacha8outlen {
+ buf = buf[:chacha8outlen-n]
+ }
+ n += len(buf)
+ t.Logf("reading %d bytes", len(buf))
+ if nn, err := p.Read(buf); err != nil {
+ t.Fatal(err)
+ } else if nn != len(buf) {
+ t.Errorf("Read short: got %d, expected %d", nn, len(buf))
+ }
+ h.Write(buf)
+ }
+ if got := h.Sum(nil); !bytes.Equal(got, chacha8hash) {
+ t.Errorf("transcript incorrect: got %x, want %x", got, chacha8hash)
+ }
+}
+
func TestChaCha8Marshal(t *testing.T) {
p := NewChaCha8(chacha8seed)
for i, x := range chacha8output {
@@ -33,7 +106,7 @@ func TestChaCha8Marshal(t *testing.T) {
t.Fatalf("#%d: MarshalBinary: %v", i, err)
}
if string(enc) != chacha8marshal[i] {
- t.Fatalf("#%d: MarshalBinary=%q, want %q", i, enc, chacha8marshal[i])
+ t.Errorf("#%d: MarshalBinary=%q, want %q", i, enc, chacha8marshal[i])
}
*p = ChaCha8{}
if err := p.UnmarshalBinary(enc); err != nil {
@@ -45,6 +118,24 @@ func TestChaCha8Marshal(t *testing.T) {
}
}
+func TestChaCha8MarshalRead(t *testing.T) {
+ p := NewChaCha8(chacha8seed)
+ for i := range 50 {
+ enc, err := p.MarshalBinary()
+ if err != nil {
+ t.Fatalf("#%d: MarshalBinary: %v", i, err)
+ }
+ if string(enc) != chacha8marshalread[i] {
+ t.Errorf("#%d: MarshalBinary=%q, want %q", i, enc, chacha8marshalread[i])
+ }
+ *p = ChaCha8{}
+ if err := p.UnmarshalBinary(enc); err != nil {
+ t.Fatalf("#%d: UnmarshalBinary: %v", i, err)
+ }
+ p.Read(make([]byte, 1))
+ }
+}
+
func BenchmarkChaCha8(b *testing.B) {
p := NewChaCha8([32]byte{1, 2, 3, 4, 5})
var t uint64
@@ -54,11 +145,26 @@ func BenchmarkChaCha8(b *testing.B) {
Sink = t
}
+func BenchmarkChaCha8Read(b *testing.B) {
+ p := NewChaCha8([32]byte{1, 2, 3, 4, 5})
+ buf := make([]byte, 32)
+ b.SetBytes(32)
+ var t uint8
+ for n := b.N; n > 0; n-- {
+ p.Read(buf)
+ t += buf[0]
+ }
+ Sink = uint64(t)
+}
+
// Golden output test to make sure algorithm never changes,
// so that its use in math/rand/v2 stays stable.
var chacha8seed = [32]byte([]byte("ABCDEFGHIJKLMNOPQRSTUVWXYZ123456"))
+var chacha8outlen = 2976
+var chacha8hash, _ = hex.DecodeString("bfec3d418b829afe5df2d8887d1508348409c293b73758d7efd841dd995fe021")
+
var chacha8output = []uint64{
0xb773b6063d4616a5, 0x1160af22a66abc3c, 0x8c2599d9418d287c, 0x7ee07e037edc5cd6,
0xcfaa9ee02d1c16ad, 0x0e090eef8febea79, 0x3c82d271128b5b3e, 0x9c5addc11252a34f,
@@ -529,3 +635,56 @@ var chacha8marshal = []string{
"chacha8:\x00\x00\x00\x00\x00\x00\x00zK3\x9bB!,\x94\x9d\x975\xce'O_t\xee|\xb21\x87\xbb\xbb\xfd)\x8f\xe52\x01\vP\fk",
"chacha8:\x00\x00\x00\x00\x00\x00\x00{K3\x9bB!,\x94\x9d\x975\xce'O_t\xee|\xb21\x87\xbb\xbb\xfd)\x8f\xe52\x01\vP\fk",
}
+
+var chacha8marshalread = []string{
+ "chacha8:\x00\x00\x00\x00\x00\x00\x00\x00ABCDEFGHIJKLMNOPQRSTUVWXYZ123456",
+ "readbuf:\a\x16F=\x06\xb6s\xb7chacha8:\x00\x00\x00\x00\x00\x00\x00\x01ABCDEFGHIJKLMNOPQRSTUVWXYZ123456",
+ "readbuf:\x06F=\x06\xb6s\xb7chacha8:\x00\x00\x00\x00\x00\x00\x00\x01ABCDEFGHIJKLMNOPQRSTUVWXYZ123456",
+ "readbuf:\x05=\x06\xb6s\xb7chacha8:\x00\x00\x00\x00\x00\x00\x00\x01ABCDEFGHIJKLMNOPQRSTUVWXYZ123456",
+ "readbuf:\x04\x06\xb6s\xb7chacha8:\x00\x00\x00\x00\x00\x00\x00\x01ABCDEFGHIJKLMNOPQRSTUVWXYZ123456",
+ "readbuf:\x03\xb6s\xb7chacha8:\x00\x00\x00\x00\x00\x00\x00\x01ABCDEFGHIJKLMNOPQRSTUVWXYZ123456",
+ "readbuf:\x02s\xb7chacha8:\x00\x00\x00\x00\x00\x00\x00\x01ABCDEFGHIJKLMNOPQRSTUVWXYZ123456",
+ "readbuf:\x01\xb7chacha8:\x00\x00\x00\x00\x00\x00\x00\x01ABCDEFGHIJKLMNOPQRSTUVWXYZ123456",
+ "chacha8:\x00\x00\x00\x00\x00\x00\x00\x01ABCDEFGHIJKLMNOPQRSTUVWXYZ123456",
+ "readbuf:\a\xbcj\xa6\"\xaf`\x11chacha8:\x00\x00\x00\x00\x00\x00\x00\x02ABCDEFGHIJKLMNOPQRSTUVWXYZ123456",
+ "readbuf:\x06j\xa6\"\xaf`\x11chacha8:\x00\x00\x00\x00\x00\x00\x00\x02ABCDEFGHIJKLMNOPQRSTUVWXYZ123456",
+ "readbuf:\x05\xa6\"\xaf`\x11chacha8:\x00\x00\x00\x00\x00\x00\x00\x02ABCDEFGHIJKLMNOPQRSTUVWXYZ123456",
+ "readbuf:\x04\"\xaf`\x11chacha8:\x00\x00\x00\x00\x00\x00\x00\x02ABCDEFGHIJKLMNOPQRSTUVWXYZ123456",
+ "readbuf:\x03\xaf`\x11chacha8:\x00\x00\x00\x00\x00\x00\x00\x02ABCDEFGHIJKLMNOPQRSTUVWXYZ123456",
+ "readbuf:\x02`\x11chacha8:\x00\x00\x00\x00\x00\x00\x00\x02ABCDEFGHIJKLMNOPQRSTUVWXYZ123456",
+ "readbuf:\x01\x11chacha8:\x00\x00\x00\x00\x00\x00\x00\x02ABCDEFGHIJKLMNOPQRSTUVWXYZ123456",
+ "chacha8:\x00\x00\x00\x00\x00\x00\x00\x02ABCDEFGHIJKLMNOPQRSTUVWXYZ123456",
+ "readbuf:\a(\x8dAٙ%\x8cchacha8:\x00\x00\x00\x00\x00\x00\x00\x03ABCDEFGHIJKLMNOPQRSTUVWXYZ123456",
+ "readbuf:\x06\x8dAٙ%\x8cchacha8:\x00\x00\x00\x00\x00\x00\x00\x03ABCDEFGHIJKLMNOPQRSTUVWXYZ123456",
+ "readbuf:\x05Aٙ%\x8cchacha8:\x00\x00\x00\x00\x00\x00\x00\x03ABCDEFGHIJKLMNOPQRSTUVWXYZ123456",
+ "readbuf:\x04ٙ%\x8cchacha8:\x00\x00\x00\x00\x00\x00\x00\x03ABCDEFGHIJKLMNOPQRSTUVWXYZ123456",
+ "readbuf:\x03\x99%\x8cchacha8:\x00\x00\x00\x00\x00\x00\x00\x03ABCDEFGHIJKLMNOPQRSTUVWXYZ123456",
+ "readbuf:\x02%\x8cchacha8:\x00\x00\x00\x00\x00\x00\x00\x03ABCDEFGHIJKLMNOPQRSTUVWXYZ123456",
+ "readbuf:\x01\x8cchacha8:\x00\x00\x00\x00\x00\x00\x00\x03ABCDEFGHIJKLMNOPQRSTUVWXYZ123456",
+ "chacha8:\x00\x00\x00\x00\x00\x00\x00\x03ABCDEFGHIJKLMNOPQRSTUVWXYZ123456",
+ "readbuf:\a\\\xdc~\x03~\xe0~chacha8:\x00\x00\x00\x00\x00\x00\x00\x04ABCDEFGHIJKLMNOPQRSTUVWXYZ123456",
+ "readbuf:\x06\xdc~\x03~\xe0~chacha8:\x00\x00\x00\x00\x00\x00\x00\x04ABCDEFGHIJKLMNOPQRSTUVWXYZ123456",
+ "readbuf:\x05~\x03~\xe0~chacha8:\x00\x00\x00\x00\x00\x00\x00\x04ABCDEFGHIJKLMNOPQRSTUVWXYZ123456",
+ "readbuf:\x04\x03~\xe0~chacha8:\x00\x00\x00\x00\x00\x00\x00\x04ABCDEFGHIJKLMNOPQRSTUVWXYZ123456",
+ "readbuf:\x03~\xe0~chacha8:\x00\x00\x00\x00\x00\x00\x00\x04ABCDEFGHIJKLMNOPQRSTUVWXYZ123456",
+ "readbuf:\x02\xe0~chacha8:\x00\x00\x00\x00\x00\x00\x00\x04ABCDEFGHIJKLMNOPQRSTUVWXYZ123456",
+ "readbuf:\x01~chacha8:\x00\x00\x00\x00\x00\x00\x00\x04ABCDEFGHIJKLMNOPQRSTUVWXYZ123456",
+ "chacha8:\x00\x00\x00\x00\x00\x00\x00\x04ABCDEFGHIJKLMNOPQRSTUVWXYZ123456",
+ "readbuf:\a\x16\x1c-\xe0\x9e\xaa\xcfchacha8:\x00\x00\x00\x00\x00\x00\x00\x05ABCDEFGHIJKLMNOPQRSTUVWXYZ123456",
+ "readbuf:\x06\x1c-\xe0\x9e\xaa\xcfchacha8:\x00\x00\x00\x00\x00\x00\x00\x05ABCDEFGHIJKLMNOPQRSTUVWXYZ123456",
+ "readbuf:\x05-\xe0\x9e\xaa\xcfchacha8:\x00\x00\x00\x00\x00\x00\x00\x05ABCDEFGHIJKLMNOPQRSTUVWXYZ123456",
+ "readbuf:\x04\xe0\x9e\xaa\xcfchacha8:\x00\x00\x00\x00\x00\x00\x00\x05ABCDEFGHIJKLMNOPQRSTUVWXYZ123456",
+ "readbuf:\x03\x9e\xaa\xcfchacha8:\x00\x00\x00\x00\x00\x00\x00\x05ABCDEFGHIJKLMNOPQRSTUVWXYZ123456",
+ "readbuf:\x02\xaa\xcfchacha8:\x00\x00\x00\x00\x00\x00\x00\x05ABCDEFGHIJKLMNOPQRSTUVWXYZ123456",
+ "readbuf:\x01\xcfchacha8:\x00\x00\x00\x00\x00\x00\x00\x05ABCDEFGHIJKLMNOPQRSTUVWXYZ123456",
+ "chacha8:\x00\x00\x00\x00\x00\x00\x00\x05ABCDEFGHIJKLMNOPQRSTUVWXYZ123456",
+ "readbuf:\a\xea\xeb\x8f\xef\x0e\t\x0echacha8:\x00\x00\x00\x00\x00\x00\x00\x06ABCDEFGHIJKLMNOPQRSTUVWXYZ123456",
+ "readbuf:\x06\xeb\x8f\xef\x0e\t\x0echacha8:\x00\x00\x00\x00\x00\x00\x00\x06ABCDEFGHIJKLMNOPQRSTUVWXYZ123456",
+ "readbuf:\x05\x8f\xef\x0e\t\x0echacha8:\x00\x00\x00\x00\x00\x00\x00\x06ABCDEFGHIJKLMNOPQRSTUVWXYZ123456",
+ "readbuf:\x04\xef\x0e\t\x0echacha8:\x00\x00\x00\x00\x00\x00\x00\x06ABCDEFGHIJKLMNOPQRSTUVWXYZ123456",
+ "readbuf:\x03\x0e\t\x0echacha8:\x00\x00\x00\x00\x00\x00\x00\x06ABCDEFGHIJKLMNOPQRSTUVWXYZ123456",
+ "readbuf:\x02\t\x0echacha8:\x00\x00\x00\x00\x00\x00\x00\x06ABCDEFGHIJKLMNOPQRSTUVWXYZ123456",
+ "readbuf:\x01\x0echacha8:\x00\x00\x00\x00\x00\x00\x00\x06ABCDEFGHIJKLMNOPQRSTUVWXYZ123456",
+ "chacha8:\x00\x00\x00\x00\x00\x00\x00\x06ABCDEFGHIJKLMNOPQRSTUVWXYZ123456",
+ "readbuf:\a[\x8b\x12q҂<chacha8:\x00\x00\x00\x00\x00\x00\x00\aABCDEFGHIJKLMNOPQRSTUVWXYZ123456",
+}
--
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