Unverified Commit 3d4788c5 authored by Gaukas Wang's avatar Gaukas Wang Committed by GitHub
Browse files

security: crypto/rand ShuffleChromeTLSExtensions (#286) 



`math/rand` might not be randomly seeded as documented on some platforms, including wasm.

Signed-off-by: default avatarGaukas Wang <i@gaukas.wang>
parent d2768e4e

u_parrots.go

+21 −6
Original line number Diff line number Diff line
@@ -6,11 +6,14 @@ package tls 


import (

	"crypto/ecdh"

	crand "crypto/rand"

	"crypto/sha256"

	"encoding/binary"

	"errors"

	"fmt"

	"io"

	"math"

	"math/big"

	"math/rand"

	"sort"

	"strconv"
@@ -2558,12 +2561,24 @@ func ShuffleChromeTLSExtensions(exts []TLSExtension) []TLSExtension { 
	}



	// Shuffle other extensions

	randInt64, err := crand.Int(crand.Reader, big.NewInt(math.MaxInt64))

	if err != nil {

		// warning: random could be deterministic

		rand.Shuffle(len(exts), func(i, j int) {

			if skipShuf(i, exts) || skipShuf(j, exts) {

				return // do not shuffle some of the extensions

			}

			exts[i], exts[j] = exts[j], exts[i]

		})

		fmt.Println("Warning: failed to use a cryptographically secure random number generator. The shuffle can be deterministic.")

	} else {

		rand.New(rand.NewSource(randInt64.Int64())).Shuffle(len(exts), func(i, j int) {

			if skipShuf(i, exts) || skipShuf(j, exts) {

				return // do not shuffle some of the extensions

			}

			exts[i], exts[j] = exts[j], exts[i]

		})

	}



	return exts

}