Commit b767d257 authored by Marek Marczykowski-Górecki's avatar Marek Marczykowski-Górecki Committed by Daniel P. Berrangé
Browse files

crypto: add "none" random provider 



In case of not using random-number needing feature, it makes sense to
skip RNG init too. This is especially helpful when QEMU is sandboxed in
Stubdomain under Xen, where there is very little entropy so initial
getrandom() call delays the startup several seconds. In that setup, no
random bytes are needed at all.

Signed-off-by: default avatarMarek Marczykowski-Górecki <marmarek@invisiblethingslab.com>
Signed-off-by: default avatarDaniel P. Berrangé <berrange@redhat.com>
parent 7d3660e7

configure

+11 −0
Original line number Diff line number Diff line
@@ -509,6 +509,7 @@ libpmem="" 
default_devices="yes"

plugins="no"

fuzzing="no"

rng_none="no"



supported_cpu="no"

supported_os="no"
@@ -1601,6 +1602,10 @@ for opt do 
  ;;

  --gdb=*) gdb_bin="$optarg"

  ;;

  --enable-rng-none) rng_none=yes

  ;;

  --disable-rng-none) rng_none=no

  ;;

  *)

      echo "ERROR: unknown option $opt"

      echo "Try '$0 --help' for more information"
@@ -1898,6 +1903,7 @@ disabled with --disable-FEATURE, default is enabled if available: 
  debug-mutex     mutex debugging support

  libpmem         libpmem support

  xkbcommon       xkbcommon support

  rng-none        dummy RNG, avoid using /dev/(u)random and getrandom()



NOTE: The object files are built at the place where configure is launched

EOF
@@ -6767,6 +6773,7 @@ echo "default devices $default_devices" 
echo "plugin support    $plugins"

echo "fuzzing support   $fuzzing"

echo "gdb               $gdb_bin"

echo "rng-none          $rng_none"



if test "$supported_cpu" = "no"; then

    echo
@@ -7744,6 +7751,10 @@ if test "$edk2_blobs" = "yes" ; then 
  echo "DECOMPRESS_EDK2_BLOBS=y" >> $config_host_mak

fi



if test "$rng_none" = "yes"; then

  echo "CONFIG_RNG_NONE=y" >> $config_host_mak

fi



# use included Linux headers

if test "$linux" = "yes" ; then

  mkdir -p linux-headers

crypto/Makefile.objs

+2 −1
Original line number Diff line number Diff line
@@ -35,5 +35,6 @@ crypto-obj-y += block-luks.o 


util-obj-$(CONFIG_GCRYPT) += random-gcrypt.o

util-obj-$(if $(CONFIG_GCRYPT),n,$(CONFIG_GNUTLS)) += random-gnutls.o

util-obj-$(if $(CONFIG_GCRYPT),n,$(if $(CONFIG_GNUTLS),n,y)) += random-platform.o

util-obj-$(if $(CONFIG_GCRYPT),n,$(if $(CONFIG_GNUTLS),n,$(CONFIG_RNG_NONE))) += random-none.o

util-obj-$(if $(CONFIG_GCRYPT),n,$(if $(CONFIG_GNUTLS),n,$(if $(CONFIG_RNG_NONE),n,y))) += random-platform.o

util-obj-y += aes.o init.o

crypto/random-none.c

0 → 100644
+38 −0
Original line number Diff line number Diff line 
/*

 * QEMU Crypto "none" random number provider

 *

 * Copyright (c) 2020 Marek Marczykowski-Górecki

 *                      <marmarek@invisiblethingslab.com>

 *

 * This library is free software; you can redistribute it and/or

 * modify it under the terms of the GNU Lesser General Public

 * License as published by the Free Software Foundation; either

 * version 2.1 of the License, or (at your option) any later version.

 *

 * This library is distributed in the hope that it will be useful,

 * but WITHOUT ANY WARRANTY; without even the implied warranty of

 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU

 * Lesser General Public License for more details.

 *

 * You should have received a copy of the GNU Lesser General Public

 * License along with this library; if not, see <http://www.gnu.org/licenses/>.

 *

 */



#include "qemu/osdep.h"



#include "crypto/random.h"

#include "qapi/error.h"



int qcrypto_random_init(Error **errp)

{

    return 0;

}



int qcrypto_random_bytes(void *buf,

                         size_t buflen,

                         Error **errp)

{

    error_setg(errp, "Random bytes not available with \"none\" rng");

    return -1;

}