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crypto: use /dev/[u]random as a final fallback random source

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If neither gcrypt or gnutls are available to provide a
cryptographic random number generator, fallback to consuming
bytes directly from /dev/[u]random.

Signed-off-by: Daniel P. Berrange <berrange@redhat.com>
This commit is contained in:
Daniel P. Berrange 2016-07-21 10:37:14 +01:00
parent e66b05e9ca
commit f3c8355c7a
2 changed files with 36 additions and 3 deletions
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64
crypto/random-platform.c Normal file
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@ -0,0 +1,64 @@
/*
* QEMU Crypto random number provider
*
* Copyright (c) 2015-2016 Red Hat, Inc.
*
* 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 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"
int qcrypto_random_bytes(uint8_t *buf G_GNUC_UNUSED,
size_t buflen G_GNUC_UNUSED,
Error **errp)
{
int fd;
int ret = -1;
int got;
/* TBD perhaps also add support for BSD getentropy / Linux
* getrandom syscalls directly */
fd = open("/dev/urandom", O_RDONLY);
if (fd == -1 && errno == ENOENT) {
fd = open("/dev/random", O_RDONLY);
}
if (fd < 0) {
error_setg(errp, "No /dev/urandom or /dev/random found");
return -1;
}
while (buflen > 0) {
got = read(fd, buf, buflen);
if (got < 0) {
error_setg_errno(errp, errno,
"Unable to read random bytes");
goto cleanup;
} else if (!got) {
error_setg(errp,
"Unexpected EOF reading random bytes");
goto cleanup;
}
buflen -= got;
buf += got;
}
ret = 0;
cleanup:
close(fd);
return ret;
}