From 1d45cf4f91010b6664651f2d0dee9543508169f5 Mon Sep 17 00:00:00 2001
From: Kovid Goyal <kovid@kovidgoyal.net>
Date: Thu, 2 Feb 2023 06:04:17 +0530
Subject: [PATCH] Use crypto/rand rather than math/rand

Who knows how random math/rand actually is
---
 tools/cmd/icat/transmit.go  | 19 +++++++++++++++++--
 tools/utils/shm/shm.go      | 12 +++++++++---
 tools/utils/shm/shm_test.go |  2 +-
 3 files changed, 27 insertions(+), 6 deletions(-)

diff --git a/tools/cmd/icat/transmit.go b/tools/cmd/icat/transmit.go
index f95c89850..5db9ac49a 100644
--- a/tools/cmd/icat/transmit.go
+++ b/tools/cmd/icat/transmit.go
@@ -4,11 +4,13 @@ package icat
 
 import (
 	"bytes"
+	"crypto/rand"
+	"encoding/binary"
 	"errors"
 	"fmt"
 	"io"
 	"math"
-	"math/rand"
+	not_rand "math/rand"
 	"os"
 	"path/filepath"
 
@@ -202,6 +204,19 @@ func place_cursor(imgd *image_data) {
 	}
 }
 
+func next_random() (ans uint32) {
+	for ans == 0 {
+		b := make([]byte, 4)
+		_, err := rand.Read(b)
+		if err == nil {
+			ans = binary.LittleEndian.Uint32(b[:])
+		} else {
+			ans = not_rand.Uint32()
+		}
+	}
+	return ans
+}
+
 func transmit_image(imgd *image_data) {
 	defer func() {
 		for _, frame := range imgd.frames {
@@ -239,7 +254,7 @@ func transmit_image(imgd *image_data) {
 	}
 	if len(imgd.frames) > 1 {
 		for imgd.image_number == 0 {
-			imgd.image_number = rand.Uint32()
+			imgd.image_number = next_random()
 		}
 	}
 	place_cursor(imgd)
diff --git a/tools/utils/shm/shm.go b/tools/utils/shm/shm.go
index cd6e4d655..79a04a716 100644
--- a/tools/utils/shm/shm.go
+++ b/tools/utils/shm/shm.go
@@ -3,9 +3,11 @@
 package shm
 
 import (
+	"crypto/rand"
+	"encoding/base32"
 	"errors"
 	"fmt"
-	"math/rand"
+	not_rand "math/rand"
 	"os"
 	"strconv"
 	"strings"
@@ -42,8 +44,12 @@ func prefix_and_suffix(pattern string) (prefix, suffix string, err error) {
 }
 
 func next_random() string {
-	num := rand.Uint32()
-	return strconv.FormatUint(uint64(num), 16)
+	b := make([]byte, 8)
+	_, err := rand.Read(b)
+	if err != nil {
+		return strconv.FormatUint(uint64(not_rand.Uint32()), 16)
+	}
+	return base32.StdEncoding.WithPadding(base32.NoPadding).EncodeToString(b)
 }
 
 type MMap interface {
diff --git a/tools/utils/shm/shm_test.go b/tools/utils/shm/shm_test.go
index 8bb2952ba..6d6c2817e 100644
--- a/tools/utils/shm/shm_test.go
+++ b/tools/utils/shm/shm_test.go
@@ -3,10 +3,10 @@
 package shm
 
 import (
+	"crypto/rand"
 	"errors"
 	"fmt"
 	"io/fs"
-	"math/rand"
 	"os"
 	"reflect"
 	"testing"