uuid: Break code to read /dev/urandom into a new module.

This code is useful for seeding other random number generators, so we might
as well make it a separate source file.

6 files changed, 98 insertions, 28 deletions

diff --git a/PORTING b/PORTING
index 3b3e15052..5f88c940a 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 16b8d0218..eedb57213 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 000000000..b844d64ae
--- /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);
+    close(fd);
+
+    if (error) {
+        VLOG_ERR("%s: read error (%s)", urandom,
+                 error == EOF ? "unexpected end of file" : strerror(error));
+    }
+    return error;
+}
+
+/* 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 000000000..6d256e0b9
--- /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 9aaa91590..a1100f2fd 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 11736578b..c3a5e4ad5 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)