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gluon-autoupdater: get random number from urandom

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The approach with awk's rand() wasn't really random between across
devices: When srand() was called without arguments, time() was used as
seed, which of course is the same on all devices when the script is
called via cron at HH:00:00.

This patch instead uses /dev/urandom as source of random (we don't need
cryptographically strong random numbers, so urandom is just fine) but
still uses awk for the comparison as busybox's ash cannot deal with
floats in $(())
This commit is contained in:
Jan-Philipp Litza 2014-01-19 16:43:25 +01:00
parent 74493b2ba5
commit 7cdf3708f0
1 changed files with 3 additions and 1 deletions
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package/gluon-autoupdater/files/usr/sbin/autoupdater
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@ -10,7 +10,9 @@ BRANCH=$(uci get autoupdater.settings.branch)
PROBABILITY=$(uci get autoupdater.${BRANCH}.probability) PROBABILITY=$(uci get autoupdater.${BRANCH}.probability)
if test "a$1" != "a-f"; then if test "a$1" != "a-f"; then
echo | awk "END{srand();exit rand() > $PROBABILITY}" # get one random byte from /dev/urandom, convert it to decimal and check
# against update_probability*255
hexdump -n1 -e '/1 "%d"' /dev/urandom | awk "{exit \$1 > $PROBABILITY * 255}"
if test $? -ne 0; then if test $? -ne 0; then
echo "No autoupdate this time. Use -f to override" echo "No autoupdate this time. Use -f to override"
exit 0 exit 0