#!/bin/sh
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### BEGIN INIT INFO
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# Provides: urandom
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# Required-Start: $local_fs mountvirtfs
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# Required-Stop: $local_fs
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# Default-Start: S
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# Default-Stop: 0 6
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# Short-Description: Save and restore the random seed
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# Description: Save the random seed on shutdown and restore it on boot,
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# to ensure that the seed isn't predicable on startup
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# (because the boot process is predictable)
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### END INIT INFO
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test -c /dev/urandom || exit 0
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RANDOM_SEED_FILE=/var/lib/urandom/random-seed
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. /etc/default/rcS
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[ -f /etc/default/urandom ] && . /etc/default/urandom
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case "$1" in
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start|"")
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test "$VERBOSE" != no && echo "Initializing random number generator..."
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# Load and then save 512 bytes, which is the size of the entropy
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# pool. Also load the current date, in case the seed file is
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# empty.
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( date +%s.%N; [ -f "$RANDOM_SEED_FILE" ] && cat "$RANDOM_SEED_FILE" ) \
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>/dev/urandom
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rm -f "$RANDOM_SEED_FILE"
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umask 077
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dd if=/dev/urandom of=$RANDOM_SEED_FILE count=1 \
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>/dev/null 2>&1 || echo "urandom start: failed."
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umask 022
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;;
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stop)
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# Carry a random seed from shut-down to start-up;
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# see documentation in linux/drivers/char/random.c
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test "$VERBOSE" != no && echo "Saving random seed..."
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umask 077
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dd if=/dev/urandom of=$RANDOM_SEED_FILE count=1 \
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>/dev/null 2>&1 || echo "urandom stop: failed."
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;;
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*)
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echo "Usage: urandom {start|stop}" >&2
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exit 1
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;;
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esac
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exit 0
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