From 3946a5529132c80793a9e5ee665a3cd6b0835310 Mon Sep 17 00:00:00 2001 From: Etienne CHAMPETIER Date: Mon, 27 Jun 2016 15:53:30 +0000 Subject: base-files: seed /dev/urandom This commit: 1) seed /dev/urandom with the saved seeds as early as possible (see /lib/preinit/81_urandom_seed) 2) save a seed at /etc/urandom.seed if it doesn't exists 3) save a new seed each boot at "system.@system[0].urandom_seed" (see /etc/init.d/urandom_seed) We use getrandom() so we are sure /dev/urandom pool is initialized 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 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 if after "urandom-seed: Seeding with ..." message Saving a new seed on each boot is disabled by default to avoid too much writes without user consent v2: log preinit messages to /dev/kmsg v3: use non generic function name for logging, as /lib/preinit/ files are all sourced together in /etc/preinit v4: after a lot of discussion on the ML, use a uci config param v5: config param is now the path of the seed Signed-off-by: Etienne CHAMPETIER Acked-by: Jo-Philipp Wich --- .../base-files/files/lib/preinit/81_urandom_seed | 24 ++++++++++++++++++++++ 1 file changed, 24 insertions(+) create mode 100644 package/base-files/files/lib/preinit/81_urandom_seed (limited to 'package/base-files/files/lib/preinit') 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 0000000000..10878f3dc2 --- /dev/null +++ b/package/base-files/files/lib/preinit/81_urandom_seed @@ -0,0 +1,24 @@ +#!/bin/sh + +log_urandom_seed() { + echo "urandom-seed: $1" > /dev/kmsg +} + +_do_urandom_seed() { + [ -f "$1" ] || { log_urandom_seed "Seed file not found ($1)"; return; } + [ -O "$1" -a -G "$1" -a ! -x "$1" ] || { log_urandom_seed "Wrong owner / permissions for $1"; return; } + + log_urandom_seed "Seeding with $1" + cat "$1" > /dev/urandom +} + +do_urandom_seed() { + [ -c /dev/urandom ] || { log_urandom_seed "Something is wrong with /dev/urandom"; return; } + + _do_urandom_seed "/etc/urandom.seed" + + SEED="$(uci -q get system.@system[0].urandom_seed)" + [ "${SEED:0:1}" == "/" -a "$SEED" != "/etc/urandom.seed" ] && _do_urandom_seed "$SEED" +} + +boot_hook_add preinit_main do_urandom_seed -- cgit v1.2.3