From ef309a681f4c761503e4cd4cc6884d7d6ef70436 Mon Sep 17 00:00:00 2001
From: Lennart Poettering <lennart@poettering.net>
Date: Thu, 30 Oct 2014 15:35:37 +0100
Subject: [PATCH] util: unify how we see srand()

---
 src/libsystemd-terminal/modeset.c |  2 +-
 src/shared/util.c                 | 53 +++++++++++++++++--------------
 src/shared/util.h                 |  1 +
 src/udev/cdrom_id/cdrom_id.c      |  2 +-
 src/udev/scsi_id/scsi_serial.c    |  2 +-
 5 files changed, 34 insertions(+), 26 deletions(-)

diff --git a/src/libsystemd-terminal/modeset.c b/src/libsystemd-terminal/modeset.c
index f5be38e4f..f0508d7a0 100644
--- a/src/libsystemd-terminal/modeset.c
+++ b/src/libsystemd-terminal/modeset.c
@@ -480,7 +480,7 @@ int main(int argc, char *argv[]) {
         log_parse_environment();
         log_open();
 
-        srand(time(NULL));
+        initialize_srand();
 
         r = parse_argv(argc, argv);
         if (r <= 0)
diff --git a/src/shared/util.c b/src/shared/util.c
index 1d67abe58..0f44eb5af 100644
--- a/src/shared/util.c
+++ b/src/shared/util.c
@@ -2521,8 +2521,36 @@ int dev_urandom(void *p, size_t n) {
         return 0;
 }
 
-void random_bytes(void *p, size_t n) {
+void initialize_srand(void) {
         static bool srand_called = false;
+        unsigned x;
+#ifdef HAVE_SYS_AUXV_H
+        void *auxv;
+#endif
+
+        if (srand_called)
+                return;
+
+        x = 0;
+
+#ifdef HAVE_SYS_AUXV_H
+        /* The kernel provides us with a bit of entropy in auxv, so
+         * let's try to make use of that to seed the pseudo-random
+         * generator. It's better than nothing... */
+
+        auxv = (void*) getauxval(AT_RANDOM);
+        if (auxv)
+                x ^= *(unsigned*) auxv;
+#endif
+
+        x ^= (unsigned) now(CLOCK_REALTIME);
+        x ^= (unsigned) gettid();
+
+        srand(x);
+        srand_called = true;
+}
+
+void random_bytes(void *p, size_t n) {
         uint8_t *q;
         int r;
 
@@ -2533,28 +2561,7 @@ void random_bytes(void *p, size_t n) {
         /* If some idiot made /dev/urandom unavailable to us, he'll
          * get a PRNG instead. */
 
-        if (!srand_called) {
-                unsigned x = 0;
-
-#ifdef HAVE_SYS_AUXV_H
-                /* The kernel provides us with a bit of entropy in
-                 * auxv, so let's try to make use of that to seed the
-                 * pseudo-random generator. It's better than
-                 * nothing... */
-
-                void *auxv;
-
-                auxv = (void*) getauxval(AT_RANDOM);
-                if (auxv)
-                        x ^= *(unsigned*) auxv;
-#endif
-
-                x ^= (unsigned) now(CLOCK_REALTIME);
-                x ^= (unsigned) gettid();
-
-                srand(x);
-                srand_called = true;
-        }
+        initialize_srand();
 
         for (q = p; q < (uint8_t*) p + n; q ++)
                 *q = rand();
diff --git a/src/shared/util.h b/src/shared/util.h
index 35584467c..aad9eb7fc 100644
--- a/src/shared/util.h
+++ b/src/shared/util.h
@@ -321,6 +321,7 @@ int make_console_stdio(void);
 
 int dev_urandom(void *p, size_t n);
 void random_bytes(void *p, size_t n);
+void initialize_srand(void);
 
 static inline uint64_t random_u64(void) {
         uint64_t u;
diff --git a/src/udev/cdrom_id/cdrom_id.c b/src/udev/cdrom_id/cdrom_id.c
index 7a4b98726..5fe3fb535 100644
--- a/src/udev/cdrom_id/cdrom_id.c
+++ b/src/udev/cdrom_id/cdrom_id.c
@@ -922,7 +922,7 @@ int main(int argc, char *argv[])
                 goto exit;
         }
 
-        srand((unsigned int)getpid());
+        initialize_srand();
         for (cnt = 20; cnt > 0; cnt--) {
                 struct timespec duration;
 
diff --git a/src/udev/scsi_id/scsi_serial.c b/src/udev/scsi_id/scsi_serial.c
index b3d20a3c2..933867159 100644
--- a/src/udev/scsi_id/scsi_serial.c
+++ b/src/udev/scsi_id/scsi_serial.c
@@ -861,7 +861,7 @@ int scsi_get_serial(struct udev *udev,
         int retval;
 
         memzero(dev_scsi->serial, len);
-        srand((unsigned int)getpid());
+        initialize_srand();
         for (cnt = 20; cnt > 0; cnt--) {
                 struct timespec duration;
 
-- 
2.30.2