On Wed, Aug 01, 2018 at 01:44:32PM +0200, Michal Privoznik wrote: > The function is supposed to return up to 64bit long integer. In > order to do that it calls virRandomBytes() to fill the integer > with random bytes and then masks out everything but requested > bits. However, when doing that it shifts 1U and not 1ULL. So > effectively, requesting 32 random bis or more always return 0 > which is not random enough. > > Signed-off-by: Michal Privoznik <mprivozn(a)redhat.com&gt; > --- > src/util/virrandom.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/src/util/virrandom.c b/src/util/virrandom.c > index 01cc82a052..3c011a8615 100644 > --- a/src/util/virrandom.c > +++ b/src/util/virrandom.c > @@ -68,7 +68,7 @@ uint64_t virRandomBits(int nbits) > return 0; > } > > - ret &= (1U << nbits) - 1; > + ret &= (1ULL << nbits) - 1;

In virStorageBackendCreateIfaceIQN() the virRandomBits() is called in order to use random bits to generate random name for new interface. However, virAsprintf() is expecting 32 bits and we are requesting only 30. Signed-off-by: Michal Privoznik <mprivozn(a)redhat.com&gt; --- src/util/viriscsi.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/src/util/viriscsi.c b/src/util/viriscsi.c index 653b4fd932..f00aeb53a7 100644 --- a/src/util/viriscsi.c +++ b/src/util/viriscsi.c @@ -221,7 +221,7 @@ virStorageBackendCreateIfaceIQN(const char *initiatoriqn, if (virAsprintf(&temp_ifacename, "libvirt-iface-%08llx", - (unsigned long long)virRandomBits(30)) < 0) + (unsigned long long)virRandomBits(32)) < 0)

And here's the fix for the viriscsitest on big-endian machine like Daniel suggested. Bjoern -- IBM Systems Linux on Z & Virtualization Development ------------------------------------------------------------------------ IBM Deutschland Research & Development GmbH Schönaicher Str. 220, 71032 Böblingen Phone: +49 7031 16 1819 ------------------------------------------------------------------------ Vorsitzende des Aufsichtsrats: Martina Koederitz Geschäftsführung: Dirk Wittkopp Sitz der Gesellschaft: Böblingen Registergericht: Amtsgericht Stuttgart, HRB 243294

From d59b254294a90c5a9ca0fb6ad29465cd0950bb61 Mon Sep 17 00:00:00 2001 From: Bjoern Walk <bwalk(a)linux.ibm.com&gt; Date: Wed, 1 Aug 2018 14:48:47 +0200 Subject: [PATCH] util: virrandom: make virRandomBits endian-safe Make the generation of random bits in virRandomBits independent of the endianness of the running architecture. This also solves problems with the mocked random byte generation on big-endian machines. Suggested-by: Daniel P. Berrangé <berrange(a)redhat.com&gt; Signed-off-by: Bjoern Walk <bwalk(a)linux.ibm.com&gt; --- src/util/virrandom.c | 8 ++++---- 1 file changed, 4 insertions(+), 4 deletions(-) diff --git a/src/util/virrandom.c b/src/util/virrandom.c index 01cc82a0..a58ee97a 100644 --- a/src/util/virrandom.c +++ b/src/util/virrandom.c @@ -34,6 +34,7 @@ # include <gnutls/crypto.h> #endif +#include "virendian.h" #include "virrandom.h" #include "virthread.h" #include "count-one-bits.h" @@ -60,16 +61,15 @@ VIR_LOG_INIT("util.random"); */ uint64_t virRandomBits(int nbits) { - uint64_t ret = 0; + uint8_t ret[8]; - if (virRandomBytes((unsigned char *) &ret, sizeof(ret)) < 0) { + if (virRandomBytes(ret, sizeof(ret)) < 0) { /* You're already hosed, so this particular non-random value * isn't any worse. */ return 0; } - ret &= (1ULL << nbits) - 1; - return ret; + return virReadBufInt64LE(ret) & ((1ULL << nbits) - 1); }