g10: Allow receiving cleartext secret keys from agent
* g10/export.c (match_curve_skey_pk): New function, testing whether an OpenPGP public key and an S-expression use the same curve. * g10/export.c (cleartext_secret_key_to_openpgp): New function, filling in the secret key parameters of a PKT_public_key object from a corresponding cleartext S-expression. * g10/export.c, g10/main.h (receive_seckey_from_agent): Add cleartext parameter, enabling retrieval of the secret key, unlocked. * g10/export.c (do_export_stream): Send cleartext as 0, keeping current behavior. * g10/keygen.c (card_store_key_with_backup): Use cleartext=0 to ensure that smartcard backups are all passphrase-locked.
This sets up internal functionality to be capable of exporting
cleartext secret keys, but does not change any existing behavior.
- Signed-off-by: Daniel Kahn Gillmor <dkg@fifthhorseman.net>