Use Content-Security-Policy: script nonce (#37232)

Fix #305

modules/util/util.go

@@ -6,11 +6,14 @@ package util
 import (
 	"bytes"
 	"crypto/rand"
+	"encoding/hex"
 	"fmt"
 	"math/big"
+	rand2 "math/rand/v2"
 	"slices"
 	"strconv"
 	"strings"
+	"sync"
 
 	"golang.org/x/text/cases"
 	"golang.org/x/text/language"
@@ -85,10 +88,39 @@ func CryptoRandomString(length int64) (string, error) {
 // CryptoRandomBytes generates `length` crypto bytes
 // This differs from CryptoRandomString, as each byte in CryptoRandomString is generated by [0,61] range
 // This function generates totally random bytes, each byte is generated by [0,255] range
+// TODO: it never fails, remove the "error" in the future
 func CryptoRandomBytes(length int64) ([]byte, error) {
 	buf := make([]byte, length)
-	_, err := rand.Read(buf)
-	return buf, err
+	if _, err := rand.Read(buf); err != nil {
+		panic(err) // this should never happen, "rand.Read" never fails
+	}
+	return buf, nil
+}
+
+var chaCha8RandPool = sync.OnceValue(func() *sync.Pool {
+	return &sync.Pool{
+		New: func() any {
+			var buf [32]byte
+			_, _ = rand.Read(buf[:])
+			return rand2.NewChaCha8(buf)
+		},
+	}
+})
+
+func FastCryptoRandomBytes(length int) []byte {
+	// ChaCha8 is about 20x times faster than system's crypto/rand.
+	// It is suitable for UUIDs, session IDs, etc
+	pool := chaCha8RandPool()
+	chaCha8Rand := pool.Get().(*rand2.ChaCha8)
+	defer pool.Put(chaCha8Rand)
+	buf := make([]byte, length)
+	_, _ = chaCha8Rand.Read(buf)
+	return buf
+}
+
+func FastCryptoRandomHex(length int) string {
+	buf := FastCryptoRandomBytes(length / 2)
+	return hex.EncodeToString(buf)
 }
 
 // ToLowerASCII returns s with all ASCII letters mapped to their lower case.