-devrandom: make flag a no-op

Commit f3c777d5eaa682d878c638192311e52f9c204294 added the `-devrandom` option:

    commit f3c777d5eaa682d878c638192311e52f9c204294
    Author: @slackner
    Date:   Sun Nov 19 13:30:04 2017 +0100

    main: Add '-devrandom' commandline option

    Allows to use /dev/random for generating the master key instead of the
    default Go implementation. When the kernel random generator has been
    properly initialized both are considered equally secure, however:

    * Versions of Go prior to 1.9 just fall back to /dev/urandom if the
      getrandom() syscall would be blocking (Go Bug #19274)

    * Kernel versions prior to 3.17 do not support getrandom(), and there
      is no check if the random generator has been properly initialized
      before reading from /dev/urandom

    This is especially useful for embedded hardware with low-entroy. Please
    note that generation of the master key might block indefinitely if the
    kernel cannot harvest enough entropy.

We now require Go v1.13 and Kernel versions should have also moved on.
Make the flag a no-op.

https://github.com/rfjakob/gocryptfs/issues/596

2 files changed, 1 insertions, 36 deletions

diff --git a/internal/configfile/config_file.go b/internal/configfile/config_file.go
index c1f93af..951dce8 100644
--- a/internal/configfile/config_file.go
+++ b/internal/configfile/config_file.go
@@ -5,9 +5,7 @@ package configfile
 import (
 	"encoding/json"
 	"fmt"
-	"io"
 	"io/ioutil"
-	"log"
 	"syscall"
 
 	"os"
@@ -61,21 +59,6 @@ type ConfFile struct {
 	filename string
 }
 
-// randBytesDevRandom gets "n" random bytes from /dev/random or panics
-func randBytesDevRandom(n int) []byte {
-	f, err := os.Open("/dev/random")
-	if err != nil {
-		log.Panic("Failed to open /dev/random: " + err.Error())
-	}
-	defer f.Close()
-	b := make([]byte, n)
-	_, err = io.ReadFull(f, b)
-	if err != nil {
-		log.Panic("Failed to read random bytes: " + err.Error())
-	}
-	return b
-}
-
 // CreateArgs exists because the argument list to Create became too long.
 type CreateArgs struct {
 	Filename           string
@@ -84,7 +67,6 @@ type CreateArgs struct {
 	LogN               int
 	Creator            string
 	AESSIV             bool
-	Devrandom          bool
 	Fido2CredentialID  []byte
 	Fido2HmacSalt      []byte
 	DeterministicNames bool
@@ -136,12 +118,7 @@ func Create(args *CreateArgs) error {
 	}
 	{
 		// Generate new random master key
-		var key []byte
-		if args.Devrandom {
-			key = randBytesDevRandom(cryptocore.KeyLen)
-		} else {
-			key = cryptocore.RandBytes(cryptocore.KeyLen)
-		}
+		key := cryptocore.RandBytes(cryptocore.KeyLen)
 		tlog.PrintMasterkeyReminder(key)
 		// Encrypt it using the password
 		// This sets ScryptObject and EncryptedKey
diff --git a/internal/configfile/config_test.go b/internal/configfile/config_test.go
index 021b6c1..b8012d3 100644
--- a/internal/configfile/config_test.go
+++ b/internal/configfile/config_test.go
@@ -86,18 +86,6 @@ func TestCreateConfDefault(t *testing.T) {
 	}
 }
 
-func TestCreateConfDevRandom(t *testing.T) {
-	err := Create(&CreateArgs{
-		Filename:  "config_test/tmp.conf",
-		Password:  testPw,
-		LogN:      10,
-		Creator:   "test",
-		Devrandom: true})
-	if err != nil {
-		t.Fatal(err)
-	}
-}
-
 func TestCreateConfPlaintextnames(t *testing.T) {
 	err := Create(&CreateArgs{
 		Filename:       "config_test/tmp.conf",