mdw@git.distorted.org.uk Git - distorted-bits/blob - unlock-root

   1 #! /bin/sh
   2 ###
   3 ### unlock-root KEY-FILE
   4
   5 set -e
   6
   7 ## Fetch the argument.
   8 case $# in
   9   1) keyfile=$1 ;;
  10   *) echo >&2 "Usage: $0 KEY-FILE"; exit 16 ;;
  11 esac
  12
  13 ## Some preflight checks.
  14 if [ ! -x /usr/bin/gpg ]; then
  15   echo >&2 "$0: can't find GnuPG executable"
  16   exit 8
  17 fi
  18
  19 ## Arrange to have somewhere for the key token.
  20 mkdir -p /mnt/keys
  21
  22 ## Now we try to find a token.
  23 lastuuid=no-match
  24 prompt=t
  25 win=nil
  26 while :; do
  27
  28   ## Wait for a different device to be inserted.  The first time through,
  29   ## we'll accept any device.
  30   while :; do
  31
  32     ## If there's a token already inserted then go with that.
  33     if info=$(blkid -o full -t LABEL=keys); then
  34       eval DEVICE=$info
  35       case "$UUID" in
  36         "$lastuuid") ;;
  37         *) lastuuid=$UUID; break ;;
  38       esac
  39     else
  40       lastuuid=no-token
  41     fi
  42
  43     ## Otherwise we could be here for a while.
  44     case "$prompt" in
  45       t) echo >&2 -n "Waiting for key token..."; prompt=nil ;;
  46     esac
  47
  48     ## Wait for a bit.
  49     sleep 1
  50     udevadm settle
  51   done
  52
  53   ## Mount the device somewhere.
  54   mount -o ro -t ext2 UUID="$UUID" /mnt/keys
  55
  56   ## If we have the key file, then we're done.
  57   if [ -f /mnt/keys/"$keyfile".gpg ]; then
  58
  59     ## Update the eyecandy, such as it is.
  60     case "$prompt" in
  61       nil) >&2 echo " ok"; prompt=t ;;
  62     esac
  63
  64     ## Get GnuPG to decrypt the key.  The enormous `gpg' rune is taken from
  65     ## the cryptsetup `decrypt_gnupg' script.  The here-document prevents
  66     ## the key ending up in a ps(1) listing, though the expected use-case is
  67     ## to run this script from an initramfs so there won't be anyone
  68     ## watching.
  69     while :; do
  70       key=$(/lib/cryptsetup/askpass "Enter passphrase for key $1: ")
  71       case "$key" in "") break ;; esac
  72       if /usr/bin/gpg -q --batch --no-options --no-mdc-warning  \
  73                 --no-random-seed-file --no-default-keyring \
  74                 --keyring /dev/null --secret-keyring /dev/null \
  75                 --trustdb-name /dev/null --passphrase-fd 0 --decrypt \
  76                 /mnt/keys/"$keyfile".gpg <<EOF
  77 $key
  78 EOF
  79       then win=t; break; fi
  80     done
  81   fi
  82
  83   ## Unmount the filesystem.
  84   umount /mnt/keys
  85
  86   ## If we did anything, stop.
  87   case "$win" in t) break ;; esac
  88 done
  89
  90 ## Done.
  91 exit 0