- Replace paramiko-based OpenSSH private key serialization with
cryptography's PrivateFormat.OpenSSH backend.
The old code relied on paramiko.RSAKey, paramiko.DSSKey, etc. to write
private keys, but Paramiko 5.1.0 removed DSSKey entirely and changed
constructor APIs, causing crashes.
- Add explicit fallback path in _load_ssh_private_with_paramiko that
guards against missing DSSKey (getattr paramiko 'DSSKey', append only
when present), modern private_key attribute vs legacy signing_key,
and Ed25519 PyNaCl key material conversion.
- Add two new test coverage methods:
test_ssh_private_roundtrip – round-trip RSA/DSA/EC/Ed25519
unencrypted and password-encrypted, verifying OpenSSH PEM header
and DER preservation.
test_ssh_private_paramiko_fallback – explicitly exercise the
Paramiko fallback for RSA and EC keys, confirming it still works
under locked Paramiko 5.1.0.
Also clean up the comment in load_key_bytes to reflect the new fallback
behavior rather than the old 'encrypted OpenSSH keys not supported' note.
- Encode EC coordinates and private d with curve-width (32/48/66 bytes) to satisfy RFC 7518,
preserving leading zero octets.
- Restrict JWK values to registered JOSE names: P-256, P-384, P-521, secp256k1.
Raise ValueError for unregistered curves (P-192, P-224, Brainpool).
- Add regression tests: deterministic coordinate/private-value widths, leading-zero
preservation, supported curve names, and rejection of unsupported curves.
- Mypy clean; all core and backend tests pass.
Replace the backtracking _PEM_BLOCK regex with a forward-only scanner
that indexes END markers by label, so repeated unterminated headers do
not cause the regex to rescan the remaining input.
Impact: 80 KiB payload went from 8.34 s to 0.001 s.
woggioni