UnknownSec Bypass 403

: /etc/rcS.d/ [ drwxr-xr-x ]
name : S08urandom #! /bin/sh ### BEGIN INIT INFO # Provides: urandom # Required-Start: $local_fs $time # Required-Stop: $local_fs # Default-Start: S # Default-Stop: 0 6 # Short-Description: Save and restore random seed between restarts. # Description: This script saves the random seed between restarts. # It is called from the boot, halt and reboot scripts. ### END INIT INFO ## Assumption 1: We assume $SAVEDFILE is a file (or a symlink ## to a file) that resides on a non-volatile medium that persists ## across reboots. ## Case 1a: Ideally, it is readable and writeable. Its is unshared, ## i.e. its contents are unique to this machine. It is protected so ## that its contents are not known to attackers. ## Case 1b: Less than ideally, it is read-only. Its contents are ## unique to this machine and not known to attackers. SAVEDFILE=/var/lib/urandom/random-seed [ -c /dev/urandom ] || exit 0 PATH=/sbin:/bin if ! POOLBYTES=$(( ($(cat /proc/sys/kernel/random/poolsize 2>/dev/null) + 7) / 8 )) ; then POOLBYTES=512 fi . /lib/init/vars.sh . /lib/lsb/init-functions do_status () { if [ -f $SAVEDFILE ] ; then return 0 else return 4 fi } case "$1" in start|"") [ "$VERBOSE" = no ] || log_action_begin_msg "Initializing random number generator" # Seed the RNG with date and time. # This is helpful in the less-than-ideal case where $SAVEDFILE # is read-only. # The value of this is greatly reduced if $SAVEDFILE is missing, # or its contents are shared machine-to-machine or known to # attackers (since they might well know at what time this # machine booted up). ( date +%s.%N # Load and then save $POOLBYTES bytes, # which is the size of the entropy pool if [ -f "$SAVEDFILE" ] then cat "$SAVEDFILE" fi # Redirect output of subshell (not individual commands) # to cope with a misfeature in the FreeBSD (not Linux) # /dev/random, where every superuser write/close causes # an explicit reseed of the yarrow. ) >/dev/urandom # Write a new seed into $SAVEDFILE because re-using a seed # compromises security. Each time we re-seed, we want the # seed to be as different as possible. # Write it now, in case the machine crashes without doing # an orderly shutdown. # The write will fail if $SAVEDFILE is read-only, but it # doesn't hurt to try. umask 077 dd if=/dev/urandom of=$SAVEDFILE bs=$POOLBYTES count=1 >/dev/null 2>&1 ES=$? umask 022 [ "$VERBOSE" = no ] || log_action_end_msg $ES ;; stop) # Carry a random seed from shut-down to start-up; # Write it on shutdown, in case the one written at startup # has been lost, snooped, or otherwise compromised. # see documentation in linux/drivers/char/random.c [ "$VERBOSE" = no ] || log_action_begin_msg "Saving random seed" umask 077 dd if=/dev/urandom of=$SAVEDFILE bs=$POOLBYTES count=1 >/dev/null 2>&1 ES=$? [ "$VERBOSE" = no ] || log_action_end_msg $ES ;; status) do_status exit $? ;; restart|reload|force-reload) echo "Error: argument '$1' not supported" >&2 exit 3 ;; *) echo "Usage: urandom start|stop" >&2 exit 3 ;; esac :