Salamander finalmask: Replace math/rand with crypto/rand in salt generation (#6228)

And https://github.com/XTLS/Xray-core/pull/6228#issuecomment-4612712100

Fixes https://github.com/XTLS/Xray-core/pull/6228#issuecomment-4599037015

transport/internet/finalmask/salamander/salamander.go

@@ -1,11 +1,11 @@
 package salamander
 
 import (
+	"crypto/rand"
 	"fmt"
-	"math/rand"
 	"sync"
-	"time"
 
+	"github.com/xtls/xray-core/common"
 	"golang.org/x/crypto/blake2b"
 )
 
@@ -21,8 +21,7 @@ var ErrPSKTooShort = fmt.Errorf("PSK must be at least %d bytes", smPSKMinLen)
 // the BLAKE2b-256 hash of a pre-shared key combined with a random salt.
 // Packet format: [8-byte salt][payload]
 type SalamanderObfuscator struct {
-	PSK     []byte
-	RandSrc *rand.Rand
+	PSK []byte
 
 	lk       sync.Mutex
 	keyInput []byte
@@ -37,7 +36,6 @@ func NewSalamanderObfuscator(psk []byte) (*SalamanderObfuscator, error) {
 	copy(keyInput, pskCopy)
 	return &SalamanderObfuscator{
 		PSK:      pskCopy,
-		RandSrc:  rand.New(rand.NewSource(time.Now().UnixNano())),
 		keyInput: keyInput,
 	}, nil
 }
@@ -47,8 +45,8 @@ func (o *SalamanderObfuscator) Obfuscate(in, out []byte) int {
 	if len(out) < outLen {
 		return 0
 	}
+	common.Must2(rand.Read(out[:smSaltLen]))
 	o.lk.Lock()
-	_, _ = o.RandSrc.Read(out[:smSaltLen])
 	key := o.keyLocked(out[:smSaltLen])
 	o.lk.Unlock()
 	for i, c := range in {

transport/internet/finalmask/sudoku/codec.go

@@ -2,7 +2,7 @@ package sudoku
 
 import (
 	"fmt"
-	"math/rand"
+	"math/rand/v2"
 )
 
 var perm4 = [24][4]byte{
@@ -67,7 +67,7 @@ func pickPaddingChance(rng *rand.Rand, pMin, pMax int) int {
 	if pMax == pMin {
 		return pMin
 	}
-	return pMin + rng.Intn(pMax-pMin+1)
+	return pMin + rng.IntN(pMax-pMin+1)
 }
 
 func (c *codec) shouldPad() bool {
@@ -77,7 +77,7 @@ func (c *codec) shouldPad() bool {
 	if c.paddingChance >= 100 {
 		return true
 	}
-	return c.rng.Intn(100) < c.paddingChance
+	return c.rng.IntN(100) < c.paddingChance
 }
 
 func (c *codec) currentTable() *table {
@@ -89,7 +89,7 @@ func (c *codec) currentTable() *table {
 
 func (c *codec) randomPadding(t *table) byte {
 	pool := t.layout.paddingPool
-	return pool[c.rng.Intn(len(pool))]
+	return pool[c.rng.IntN(len(pool))]
 }
 
 func (c *codec) encode(in []byte) ([]byte, error) {
@@ -112,8 +112,8 @@ func (c *codec) encode(in []byte) ([]byte, error) {
 			return nil, fmt.Errorf("sudoku encode table missing for byte %d", b)
 		}
 
-		hints := enc[c.rng.Intn(len(enc))]
-		perm := perm4[c.rng.Intn(len(perm4))]
+		hints := enc[c.rng.IntN(len(enc))]
+		perm := perm4[c.rng.IntN(len(perm4))]
 		for _, idx := range perm {
 			if c.shouldPad() {
 				out = append(out, c.randomPadding(t))

transport/internet/finalmask/sudoku/conn_tcp_packed.go

@@ -72,7 +72,7 @@ func (e *packedEncoder) maybePad(out []byte, layout *byteLayout) []byte {
 		return append(out, layout.paddingPool[0])
 	}
 	for {
-		b := layout.paddingPool[e.codec.rng.Intn(len(layout.paddingPool))]
+		b := layout.paddingPool[e.codec.rng.IntN(len(layout.paddingPool))]
 		if b != layout.padMarker {
 			return append(out, b)
 		}

transport/internet/finalmask/sudoku/table.go

@@ -7,10 +7,12 @@ import (
 	"fmt"
 	"math/bits"
 	"math/rand"
+	rand_v2 "math/rand/v2"
 	"sort"
 	"strings"
 	"sync"
-	"time"
+
+	"github.com/xtls/xray-core/common"
 )
 
 type table struct {
@@ -570,11 +572,8 @@ func sort4(in [4]byte) [4]byte {
 	return in
 }
 
-func newSeededRand() *rand.Rand {
-	seed := time.Now().UnixNano()
-	var seedBytes [8]byte
-	if _, err := crypto_rand.Read(seedBytes[:]); err == nil {
-		seed = int64(binary.BigEndian.Uint64(seedBytes[:]))
-	}
-	return rand.New(rand.NewSource(seed))
+func newSeededRand() *rand_v2.Rand {
+	var seedBytes [32]byte
+	common.Must2(crypto_rand.Read(seedBytes[:]))
+	return rand_v2.New(rand_v2.NewChaCha8(seedBytes))
 }