Getting "Ill-formed input" in ostree sign

[ganjiii3]

Hi!
I wanted to try composefs with the verification of the userspace by ostree-prepare-root, however I am not able to pass the ed25519 key to ostree sign .

I've generated the key using
openssl genpkey -algorithm ed25519 -out private.key
and took only the base64-encoded part, and tried to pass it using both --keys-file and <KEY-ID> arguments to ostree sign. In either way, I get:

OT: using fuse: 0
OT: using fuse: 0
error: Invalid ed25519 secret key: Ill-formed input: expected 48 bytes, got 64 bytes

While inspecting the code, I found that the outputs of validate_lenght function are probably swapped, but also that the comments suggest that the API accepts also keys in binary format. So I've tried OpenSSL key in DER format, getting output:

OT: using fuse: 0
OT: using fuse: 0
error: Invalid ed25519 secret key: Ill-formed input: expected 0 bytes, got 64 bytes

Could you please take a look? 😅 I'm using latest Fedora Kinoite 41, the output of ostree --version:

libostree:
 Version: '2024.9'
 Git: 14e29775963d44bc533715efcf2362d6051756de
 Features:
  - inode64
  - initial-var
  - libcurl
  - libsoup3
  - gpgme
  - composefs
  - ex-fsverity
  - libarchive
  - selinux
  - openssl
  - sign-ed25519
  - libmount
  - systemd
  - release
  - p2p

Resources I've been following:
https://ostreedev.github.io/ostree/composefs/
https://blogs.gnome.org/alexl/2024/01/15/testing-composefs-in-silverblue/
#2867

[prydom]

You can use this script I wrote, that I mostly sourced from OSTree's tests. In particular this test:

ostree/tests/libtest.sh

Lines 760 to 776 in 111a45f

	gen_ed25519_keys ()
	{
	# Generate private key in PEM format
	pemfile="$(mktemp -p ${test_tmpdir} ed25519_XXXXXX.pem)"
	openssl genpkey -algorithm ed25519 -outform PEM -out "${pemfile}"
	# Based on: http://openssl.6102.n7.nabble.com/ed25519-key-generation-td73907.html
	# Extract the private and public parts from generated key.
	ED25519PUBLIC="$(openssl pkey -outform DER -pubout -in ${pemfile} | tail -c 32 | base64)"
	ED25519SEED="$(openssl pkey -outform DER -in ${pemfile} | tail -c 32 | base64)"
	# Secret key is concantination of SEED and PUBLIC
	ED25519SECRET="$(echo ${ED25519SEED}${ED25519PUBLIC} | base64 -d | base64 -w 0)"
	echo "Generated ed25519 keys:"
	echo "public: ${ED25519PUBLIC}"
	echo " seed: ${ED25519SEED}"
	}

For some reason the sign command wants the concatenated private key seed and the public key rather then just the private key seed like e.g. Wireguard. It also doesn't want the PKCS#8 header that OpenSSL generates.

#!/usr/bin/bash
umask=$(umask)

pemfile=private.pem
umask 177
openssl genpkey -algorithm ed25519 -outform PEM -out "${pemfile}"

# Extract the private and public parts from generated key.
ED25519PUBLIC="$(openssl pkey -outform DER -pubout -in ${pemfile} | tail -c 32 | base64)"
ED25519SEED="$(openssl pkey -outform DER -in ${pemfile} | tail -c 32 | base64)"
# Secret key is concantination of SEED and PUBLIC
ED25519SECRET="$(echo ${ED25519SEED}${ED25519PUBLIC} | base64 -d | base64 -w 0)"

echo $ED25519SEED > secret.ed25519
echo $ED25519SECRET > secret_concatinated.ed25519
umask $umask
echo $ED25519PUBLIC > public.ed25519
rm -f $pemfile

echo "Generated ed25519 keys:"
echo "public: ${ED25519PUBLIC}"

[ganjiii3]

Thank you! I should have looked at the tests 😄