This commit:
1) seed /dev/urandom with a saved seed as early as possible
(using /lib/preinit/81_urandom_seed)
2) save a new seed using getrandom() so we are sure /dev/urandom
pool is initialized (using /etc/init.d/urandom_seed)
seed size is 512 bytes (ie /proc/sys/kernel/random/poolsize / 8)
it's the same size as in ubuntu 14.04 and all systemd systems
seed file is /etc/urandom.seed (need a writable path)
seeding /dev/urandom doesn't change entropy estimation, so we still have
"random: ubus urandom read with 4 bits of entropy available"
messages in the logs, but we can now ignore them
We could also add an urandom.seed at build time to improve first boot
Signed-off-by: Etienne CHAMPETIER <champetier.etie...@gmail.com>
---
package/base-files/files/etc/init.d/urandom_seed | 22 ++++++++++++++++++++++
.../base-files/files/lib/preinit/81_urandom_seed | 15 +++++++++++++++
2 files changed, 37 insertions(+)
create mode 100755 package/base-files/files/etc/init.d/urandom_seed
create mode 100644 package/base-files/files/lib/preinit/81_urandom_seed
diff --git a/package/base-files/files/etc/init.d/urandom_seed
b/package/base-files/files/etc/init.d/urandom_seed
new file mode 100755
index 0000000..d7c1f71
--- /dev/null
+++ b/package/base-files/files/etc/init.d/urandom_seed
@@ -0,0 +1,22 @@
+#!/bin/sh /etc/rc.common
+
+START=99
+
+SEED=/etc/urandom.seed
+
+error_exit() {
+ logger -t urandom_seed "$1"
+ exit 1
+}
+
+save_seed() {
+ touch $SEED.tmp || error_exit "touch failed"
+ chown root:root $SEED.tmp || error_exit "chown failed"
+ chmod 600 $SEED.tmp || error_exit "chmod failed"
+ getrandom 512 > $SEED.tmp || error_exit "getrandom failed"
+ mv $SEED.tmp $SEED || error_exit "mv failed"
+}
+
+boot() {
+ save_seed
+}
diff --git a/package/base-files/files/lib/preinit/81_urandom_seed
b/package/base-files/files/lib/preinit/81_urandom_seed
new file mode 100644
index 0000000..27ff587
--- /dev/null
+++ b/package/base-files/files/lib/preinit/81_urandom_seed
@@ -0,0 +1,15 @@
+#!/bin/sh
+
+do_urandom_seed() {
+ S=/etc/urandom.seed
+ U=/dev/urandom
+
+ [ -c $U ] || { echo "Something is wrong with $U"; return; }
+ [ -f $S ] || { echo "Seed file not found: $S"; return; }
+ [ -O $S -a -G $S -a ! -x $S ] || { echo "Wrong owner / permissions for
$S"; return; }
+
+ echo "Seeding $U with $S"
+ cat $S > $U
+}
+
+boot_hook_add preinit_main do_urandom_seed
--
1.9.1
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