This script turns the file given as argument to an image of an encrypted and ext4-formatted disk image file.
After this, you can do something like:
losetup /dev/loop0 /storage/diskimages/thefile cryptsetup luksOpen /dev/loop0 myfakedisk mount /dev/mapper/myfakedisk /path/to/mountpoint
And then close with
umount /path/to/mountpoint cryptsetup luksClose myfakedisk losetup -d /dev/loop0
The operation above and the script below must be run as root. This means that you can mess up things heavily, including wiping your disk if you don’t know what you’re doing, or because of a mistake of mine. Be sure you’ve proofread the script below, and that you know what you’re doing. Don’t blame me, even if I got the script wrong.
If you’ll ever think about modifying this script, please note that the most dangerous point is that the script will, for some reason, not be able to bind the image file to the loop device, because it’s bound to something else, but will go on anyhow. In that case, it will really wipe important data without any warning. Note the first “if” statement. That’s where the pudding lies.
#!/bin/bash # Usage (as root!): make_enc_ext4.sh imagefile myloop=`losetup -f` mymapper=temporary_$$ if losetup $myloop $1 ; then echo Using loop device $myloop echo ALL DATA IN $1 WILL BE LOST if ! cryptsetup luksFormat $myloop ; then echo Did not set up LUKS on image losetup -d $myloop exit 1; fi echo Now mapping the encrypted loop device. Enter the same passphrase if ! cryptsetup luksOpen $myloop $mymapper ; then echo Failed to map the image. Probably you entered the passphrase echo wrong. Just run this script again. losetup -d $myloop exit 1; fi echo $myloop is now mapped to $mymapper if ! mkfs.ext4 /dev/mapper/$mymapper ; then echo Failed to create an ext4 filesystem on the image cryptsetup luksClose $mymapper losetup -d $myloop exit 1; fi if ! tune2fs -c 0 -i 0 /dev/mapper/$mymapper ; then echo Failed to cancel automatic fsck on the disk fi cryptsetup luksClose $mymapper echo Done. You should now be able to do something like echo losetup $myloop $1 echo cryptsetup luksOpen $myloop myfakedisk echo mount /dev/mapper/myfakedisk /path/to/mountpoint echo Then close with echo cryptsetup luksClose myfakedisk echo losetup -d $myloop else echo Failed to set up loop device for file \"$1\" exit 1; fi losetup -d $myloop