cryptimg

#!/bin/bash

set -e

verify_img_name() {
    IMG_NAME=${1%.cryptimg.bin}
    IMG_FILE="$IMG_NAME.cryptimg.bin"
    [[ ! "$IMG_NAME" =~ ^[a-z0-9-]+$ ]] && echo "invalid name '$IMG_NAME'" && exit 1 || true
    case "$2" in
        exists) [ ! -f "$IMG_FILE" ] && echo "'$IMG_FILE' not found" && exit 1 || true ;;
        *) [ -f "$IMG_FILE" ] && echo "'$IMG_FILE' already exists" && exit 1 || true ;;
    esac
}

verify_size() {
    SIZE=$1
    [[ ! "$SIZE" =~ ^[0-9]+[MGT]$ ]] && echo "invalid size '$SIZE' (..M, ..G, ..T)" && exit 1 || true
}

luks_init() {
    IMG_UUID="$(cryptsetup luksUUID "$IMG_FILE").cryptimg"
    IMG_DEV="/dev/mapper/$IMG_UUID"
}

luks_open() {
    if [ ! -b "$IMG_DEV" ]; then
        if [ "$1" == "ro" ]; then
            sudo cryptsetup -r luksOpen "$IMG_FILE" "$IMG_UUID"
        else
            sudo cryptsetup luksOpen "$IMG_FILE" "$IMG_UUID"
        fi
    fi
}

luks_close() {
    if [ -b "$IMG_DEV" ]; then
        sudo cryptsetup luksClose "$IMG_UUID"
    fi
}

img_umount() {
    if [ -b "$IMG_DEV" ] && [ -d "$IMG_NAME" ]; then
        BK_DEVNO=$(mountpoint -qx "$IMG_DEV" || true)
        FS_DEVNO=$(mountpoint -qd "$IMG_NAME" || true)
        if [ -n "$BK_DEVNO" ] && [ "$BK_DEVNO" == "$FS_DEVNO" ]; then
            sudo umount "$IMG_DEV"
        fi
    fi
    if [ -d "$IMG_NAME" ]; then
        rmdir "$IMG_NAME" || true
    fi
}

img_mount() {
    if ! mountpoint -qd "$IMG_NAME"; then
        mkdir "$IMG_NAME"
        sudo mount "$IMG_DEV" "$IMG_NAME"
    fi
}

cmd_create() {
    verify_img_name "$1"
    verify_size "$2"

    echo "creating disk image..."
    fallocate -l "$SIZE" "$IMG_FILE"
    sudo cryptsetup -qy luksFormat "$IMG_FILE"

    echo "unlock to continue..."
    luks_init
    luks_open

    echo "creating ext4 filesystem..."
    sudo mkfs.ext4 "$IMG_DEV"

    echo "mounting..."
    img_mount

    echo "done"
}

cmd_mount() {
    verify_img_name "$1" exists
    luks_init
    luks_open "$2"
    img_mount
}

cmd_umount() {
    verify_img_name "$1" exists
    luks_init
    img_umount
    luks_close
}

cmd_dump() {
    verify_img_name "$1" exists
    cryptsetup luksDump "$IMG_FILE"
}

case "$1" in
    create) cmd_create $2 $3 ;;
    mount) cmd_mount $2 ;;
    mount-ro) cmd_mount $2 ro ;;
    umount) cmd_umount $2 ;;
    dump) cmd_dump $2 ;;
    *)
        echo "usage: ${0##*/} create <name> <size>"
        echo "       ${0##*/} mount <name>"
        echo "       ${0##*/} mount-ro <name>"
        echo "       ${0##*/} umount <name>"
        echo "       ${0##*/} dump <name>"
        ;;
esac