From 392fc41de86e865a16c5fa8fea20340eb673592b Mon Sep 17 00:00:00 2001
From: Andy Wang <cbeuw.andy@gmail.com>
Date: Sat, 13 Apr 2024 23:08:34 +0100
Subject: [PATCH] Move random utilities to common package

---
 internal/client/TLS.go    | 27 ++++-----------------------
 internal/common/crypto.go | 35 ++++++++++++++++++++++++++++++-----
 2 files changed, 34 insertions(+), 28 deletions(-)

diff --git a/internal/client/TLS.go b/internal/client/TLS.go
index 469ad28..5adcf0d 100644
--- a/internal/client/TLS.go
+++ b/internal/client/TLS.go
@@ -1,16 +1,11 @@
 package client
 
 import (
-	cryptoRand "crypto/rand"
+	"github.com/cbeuw/Cloak/internal/common"
 	utls "github.com/refraction-networking/utls"
 	log "github.com/sirupsen/logrus"
-	"math/big"
-	"math/rand"
 	"net"
 	"strings"
-	"time"
-
-	"github.com/cbeuw/Cloak/internal/common"
 )
 
 const appDataMaxLength = 16401
@@ -40,26 +35,12 @@ var topLevelDomains = []string{"com", "net", "org", "it", "fr", "me", "ru", "cn"
 // https://github.com/ProtonVPN/wireguard-go/commit/bcf344b39b213c1f32147851af0d2a8da9266883
 func randomServerName() string {
 	charNum := int('z') - int('a') + 1
-	size := 3 + randInt(10)
+	size := 3 + common.RandInt(10)
 	name := make([]byte, size)
 	for i := range name {
-		name[i] = byte(int('a') + randInt(charNum))
-	}
-	return string(name) + "." + randItem(topLevelDomains)
-}
-
-func randItem(list []string) string {
-	return list[randInt(len(list))]
-}
-
-func randInt(n int) int {
-	size, err := cryptoRand.Int(cryptoRand.Reader, big.NewInt(int64(n)))
-	if err == nil {
-		return int(size.Int64())
+		name[i] = byte(int('a') + common.RandInt(charNum))
 	}
-	//goland:noinspection GoDeprecation
-	rand.Seed(time.Now().UnixNano())
-	return rand.Intn(n)
+	return string(name) + "." + common.RandItem(topLevelDomains)
 }
 
 func buildClientHello(browser browser, fields clientHelloFields) ([]byte, error) {
diff --git a/internal/common/crypto.go b/internal/common/crypto.go
index 71b3f3f..c46ba89 100644
--- a/internal/common/crypto.go
+++ b/internal/common/crypto.go
@@ -6,6 +6,7 @@ import (
 	"crypto/rand"
 	"errors"
 	"io"
+	"math/big"
 	"time"
 
 	log "github.com/sirupsen/logrus"
@@ -52,8 +53,8 @@ func CryptoRandRead(buf []byte) {
 	RandRead(rand.Reader, buf)
 }
 
-func RandRead(randSource io.Reader, buf []byte) {
-	_, err := randSource.Read(buf)
+func backoff(f func() error) {
+	err := f()
 	if err == nil {
 		return
 	}
@@ -61,12 +62,36 @@ func RandRead(randSource io.Reader, buf []byte) {
 		100 * time.Millisecond, 300 * time.Millisecond, 500 * time.Millisecond, 1 * time.Second,
 		3 * time.Second, 5 * time.Second}
 	for i := 0; i < 10; i++ {
-		log.Errorf("Failed to get random bytes: %v. Retrying...", err)
-		_, err = randSource.Read(buf)
+		log.Errorf("Failed to get random: %v. Retrying...", err)
+		err = f()
 		if err == nil {
 			return
 		}
 		time.Sleep(waitDur[i])
 	}
-	log.Fatal("Cannot get random bytes after 10 retries")
+	log.Fatal("Cannot get random after 10 retries")
+}
+
+func RandRead(randSource io.Reader, buf []byte) {
+	backoff(func() error {
+		_, err := randSource.Read(buf)
+		return err
+	})
+}
+
+func RandItem[T any](list []T) T {
+	return list[RandInt(len(list))]
+}
+
+func RandInt(n int) int {
+	s := new(int)
+	backoff(func() error {
+		size, err := rand.Int(rand.Reader, big.NewInt(int64(n)))
+		if err != nil {
+			return err
+		}
+		*s = int(size.Int64())
+		return nil
+	})
+	return *s
 }