Mini Shell

#!/usr/bin/sh

command -v ask_for_password > /dev/null || . /lib/dracut-crypt-lib.sh

# loop_decrypt mnt_point keypath keydev device
#
# Decrypts symmetrically encrypted key to standard output.
#
# mnt_point - mount point where <keydev> is already mounted
# keypath - LUKS encrypted loop file path relative to <mnt_point>
# keydev - device on which key resides; only to display in prompt
# device - device to be opened by cryptsetup; only to display in prompt
loop_decrypt() {
    local mntp="$1"
    local keypath="$2"
    local keydev="$3"
    local device="$4"
    local key

    key="/dev/mapper/$(str_replace "loop-$keydev-$mntp-$keypath" '/' '-')"

    if [ ! -b "$key" ]; then
        local loopdev
        local opts
        loopdev=$(losetup -f "${mntp}/${keypath}" --show)
        opts="-d - luksOpen $loopdev ${key##*/}"

        ask_for_password \
            --cmd "cryptsetup $opts" \
            --prompt "Password ($keypath on $keydev for $device)" \
            --tty-echo-off

        [ -b "$key" ] || die "Failed to unlock $keypath on $keydev for $device."

        printf "%s\n" "cryptsetup luksClose \"$key\"" > "${hookdir}/cleanup/crypt-loop-cleanup-10-${key##*/}.sh"
        printf "%s\n" "losetup -d \"$loopdev\"" > "${hookdir}/cleanup/crypt-loop-cleanup-20-${loopdev##*/}.sh"
    fi

    cat "$key"
}