initramfs cryptroot with keyscript and binary passphrase

[d4]

cryptsetup --key-file=-
is not the same as
cryptsetup --key-file=/dev/stdin

I use initramfs cryptroot script to set up an encrypted device early, and i have a keyscript that decrypts a keyfile and writes the decrypted key to stdout. (binary key 512 bytes long)

# /etc/crypttab was this before running update-initramfs -u #
swap /dev/disk/by-partlabel/swap /etc/key.enc cipher=aes-cbc-essiv:sha256,size=256,hash=sha256,swap,tries=1,keyscript=/etc/initramfs-tools/decrypt-key,precheck=un_blkid,noauto

But despite the decrypt-key keyscript workes fine inside the initramfs environment, and the decrypted key it produces is correct, cryptroot script failes with "unknown fs type" error.
I used keyscript manually to decrypt the key to a file, then call cryptsetup with --key-file=key.decrypted along with the appropirate options, and it successfully opened the drive with a valid fstype.

I've discovered that by replacing a part of the initramfs script "cryptroot"
$cryptkeyscript "$cryptkey" | $cryptcreate --key-file=- ;
to
$cryptkeyscript "$cryptkey" | $cryptcreate --key-file=/dev/stdin ;
fixed the problem. (/scripts/local-top/cryptroot around line 263)

I could reproduce the problem in initramfs environment with a /conf/conf.d/cryptroot like this:
target=swap,source=/dev/disk/by-partlabel/swap,key=/etc/key,cipher=aes-cbc-essiv:sha256,size=256,hash=sha256,tries=1,keyscript=/bin/cat
Where /etc/key is a 512 byte binary keyfile (already decrypted).
(try /bin/dd if /bin/cat is missing in your initramfs environment or ln -s /bin/busybox /bin/cat)

My Quick-Fix was:
cp /usr/share/initramfs-tools/scripts/local-top/cryptroot to /etc/initramfs-tools/scripts/local-top/cryptroot
Edit and replace --key-file=- with --key-file=/dev/stdin around line 263.
update-initramfs -u

Description: Ubuntu 14.04.1 LTS
Release: 14.04

Package: cryptsetup
Version: 2:1.6.1-1ubuntu1
Architecture: amd64

[Launchpad Janitor (janitor)]

Status changed to 'Confirmed' because the bug affects multiple users.