reencryption with multi keyslots in batch mode

[Frederic Hoerni <frederic.hoerni@canonical.com>]

Hello,

If we want to reencrypt a disk that has several keyslots (main and 
recovery keyslots), I believe the only way is to do it in interactive mode.

But in some cases, we would like to do this in batch mode. We could 
imagine a scenario like this:

1. Setup of the use case (no modification of cryptsetup needed so far)

# Initialize LUKS container
dd if=/dev/zero count=200 of=disk.img bs=1M
echo 0000 | sudo cryptsetup luksFormat --keyfile-size 4 \
                                        --key-file - \
                                        disk.img
# Add two keyslots
echo -n 0000x111111 | cryptsetup luksAddKey --key-file - \
                                             --keyfile-size 4 \
                                             disk.img
echo -n 0000222     | cryptsetup luksAddKey --key-file - \
                                             --keyfile-size 4 \
                                             disk.img


2. Reencryption (this step needs modification of cryptsetup)

echo -n 0000x111111222 | \
     sudo cryptsetup reencrypt --key-file - \
                               --keypipe-sizes "4,7,3" \
                               --batch-mode \
                               --force-offline-reencrypt \
                               disk.img

3. Verify all keyslots

for passphrase in 0000 x111111 222; do
     echo -n $passphrase | cryptsetup open disk.img --test-passphrase \
                                                    --key-file -
done

Do you have any on-going work in this direction?
Are you open to contribution for that? (I already have a proof of 
concept for the above scenario)
Do you have any particular caveat about developing this feature?

Thank you
Frederic