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crypto: add "none" random provider

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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: Marek Marczykowski-Górecki <marmarek@invisiblethingslab.com>
Signed-off-by: Daniel P. Berrangé <berrange@redhat.com>
This commit is contained in:
Marek Marczykowski-Górecki 2020-05-20 15:20:23 +02:00 committed by Daniel P. Berrangé
parent 7d3660e798
commit b767d2578d
3 changed files with 51 additions and 1 deletions
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11
configure vendored
View File

@ -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

3
crypto/Makefile.objs
View File

@ -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

38
crypto/random-none.c Normal file
View File

@ -0,0 +1,38 @@
/*
* 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;
}