[ovs-dev] [PATCH 2/3] uuid: Break code to read /dev/urandom into a new module.
Ben Pfaff
blp at nicira.com
Thu Aug 12 18:12:20 UTC 2010
This code is useful for seeding other random number generators, so we might
as well make it a separate source file.
---
PORTING | 6 ++--
lib/automake.mk | 2 +
lib/entropy.c | 65 ++++++++++++++++++++++++++++++++++++++++++++++++++
lib/entropy.h | 24 ++++++++++++++++++
lib/uuid.c | 28 ++-------------------
lib/vlog-modules.def | 1 +
6 files changed, 98 insertions(+), 28 deletions(-)
create mode 100644 lib/entropy.c
create mode 100644 lib/entropy.h
diff --git a/PORTING b/PORTING
index 3b3e150..5f88c94 100644
--- a/PORTING
+++ b/PORTING
@@ -205,9 +205,9 @@ during a port:
Miscellaneous Notes
-------------------
-lib/uuid.c, used in OVSDB, assumes that it can obtain a high-quality
-random number seed at startup by reading from /dev/urandom. You may
-need to modify it if this is not true on your platform.
+lib/entropy.c assumes that it can obtain high-quality random number
+seeds at startup by reading from /dev/urandom. You will need to
+modify it if this is not true on your platform.
Questions
---------
diff --git a/lib/automake.mk b/lib/automake.mk
index 16b8d02..eedb572 100644
--- a/lib/automake.mk
+++ b/lib/automake.mk
@@ -40,6 +40,8 @@ lib_libopenvswitch_a_SOURCES = \
lib/dpif.h \
lib/dynamic-string.c \
lib/dynamic-string.h \
+ lib/entropy.c \
+ lib/entropy.h \
lib/fatal-signal.c \
lib/fatal-signal.h \
lib/flow.c \
diff --git a/lib/entropy.c b/lib/entropy.c
new file mode 100644
index 0000000..01a418f
--- /dev/null
+++ b/lib/entropy.c
@@ -0,0 +1,65 @@
+/* Copyright (c) 2008, 2009, 2010 Nicira Networks
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at:
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#include <config.h>
+
+#include "entropy.h"
+
+#include <errno.h>
+#include <fcntl.h>
+#include <unistd.h>
+
+#include "socket-util.h"
+#include "vlog.h"
+
+VLOG_DEFINE_THIS_MODULE(entropy)
+
+static const char urandom[] = "/dev/urandom";
+
+/* Initializes 'buffer' with 'n' bytes of high-quality random numbers. Returns
+ * 0 if successful, otherwise a positive errno value or EOF on error. */
+int
+get_entropy(void *buffer, size_t n)
+{
+ size_t bytes_read;
+ int error;
+ int fd;
+
+ fd = open(urandom, O_RDONLY);
+ if (fd < 0) {
+ VLOG_ERR("%s: open failed (%s)", urandom, strerror(errno));
+ return errno ? errno : EINVAL;
+ }
+ error = read_fully(fd, buffer, n, &bytes_read);
+ if (error) {
+ VLOG_ERR("%s: read error (%s)", urandom,
+ error == EOF ? "unexpected end of file" : strerror(error));
+ return error;
+ }
+ close(fd);
+
+ return 0;
+}
+
+/* Initializes 'buffer' with 'n' bytes of high-quality random numbers. Exits
+ * if an error occurs. */
+void
+get_entropy_or_die(void *buffer, size_t n)
+{
+ int error = get_entropy(buffer, n);
+ if (error) {
+ ovs_fatal(error, "%s: read error", urandom);
+ }
+}
diff --git a/lib/entropy.h b/lib/entropy.h
new file mode 100644
index 0000000..6d256e0
--- /dev/null
+++ b/lib/entropy.h
@@ -0,0 +1,24 @@
+/* Copyright (c) 2010 Nicira Networks
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at:
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#ifndef ENTROPY_H
+#define ENTROPY_H 1
+
+#include <stddef.h>
+
+int get_entropy(void *, size_t);
+void get_entropy_or_die(void *, size_t);
+
+#endif /* entropy.h */
diff --git a/lib/uuid.c b/lib/uuid.c
index 9aaa915..a1100f2 100644
--- a/lib/uuid.c
+++ b/lib/uuid.c
@@ -22,11 +22,10 @@
#include <fcntl.h>
#include <sys/time.h>
#include <sys/types.h>
-#include <unistd.h>
#include "aes128.h"
+#include "entropy.h"
#include "sha1.h"
-#include "socket-util.h"
#include "util.h"
static struct aes128 key;
@@ -181,27 +180,6 @@ error:
}
static void
-read_urandom(void *buffer, size_t n)
-{
- static const char urandom[] = "/dev/urandom";
- size_t bytes_read;
- int error;
- int fd;
-
- fd = open(urandom, O_RDONLY);
- if (fd < 0) {
- ovs_fatal(errno, "%s: open failed", urandom);
- }
- error = read_fully(fd, buffer, n, &bytes_read);
- if (error == EOF) {
- ovs_fatal(0, "%s: unexpected end of file", urandom);
- } else if (error) {
- ovs_fatal(error, "%s: read error", urandom);
- }
- close(fd);
-}
-
-static void
do_init(void)
{
uint8_t sha1[SHA1_DIGEST_SIZE];
@@ -213,7 +191,7 @@ do_init(void)
gid_t gid;
/* Get seed data. */
- read_urandom(random_seed, sizeof random_seed);
+ get_entropy_or_die(random_seed, sizeof random_seed);
if (gettimeofday(&now, NULL)) {
ovs_fatal(errno, "gettimeofday failed");
}
@@ -236,5 +214,5 @@ do_init(void)
aes128_schedule(&key, sha1);
/* Generate initial counter. */
- read_urandom(counter, sizeof counter);
+ get_entropy_or_die(counter, sizeof counter);
}
diff --git a/lib/vlog-modules.def b/lib/vlog-modules.def
index 1173657..c3a5e4a 100644
--- a/lib/vlog-modules.def
+++ b/lib/vlog-modules.def
@@ -29,6 +29,7 @@ VLOG_MODULE(dpif)
VLOG_MODULE(dpif_linux)
VLOG_MODULE(dpif_netdev)
VLOG_MODULE(dpctl)
+VLOG_MODULE(entropy)
VLOG_MODULE(ezio_term)
VLOG_MODULE(fail_open)
VLOG_MODULE(fatal_signal)
--
1.7.1
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