Imported secret subkey unusable "ssb#"

[Ingo Klöcker]

On Sonntag, 18. April 2021 02:06:40 CEST anon85786376 via Gnupg-users wrote:
> When a batch mode key is created with "Subkey-Type: ECC" and "Subkey-Curve:
> Ed25519", the key is generated without errors and appears to function
> normally. However, importing the secret keys will yield an unusable secret
> subkey:
[...]
> $ gpg -K
> /home/me/.gnupg/pubring.kbx
> -----------------------------
> sec   rsa3072 2021-04-17 [SC]
>       1CB8F79F656BCD71BF9A89694C95665DD06F8126
> uid           [ unknown] testkey
> ssb#  ed25519 2021-04-17 [E]

I could reproduce the problem.

Note that the "#" next to the subkey indicates that the subkey is just a stub 
for a secret key.

I noticed that after importing there are (as expected) two new files in 
~/.gnupg/private-keys-v1.d, e.g.
82380E8EB005D76AE6A1E73FCDC82B374B8D9584.key
05E9DDE401B12A726DF0058FB4F62EACED979CC5.key

The names of those files should correspond to the keygrips of the primary key 
and the subkey. This is true for the primary key, but the keygrip of the 
subkey does not match.

$ gpg -K --with-keygrip FB489AAC37C42F19
sec   rsa3072/FB489AAC37C42F19 2021-04-18 [SC]
      92AB7959B2905BED251F522DFB489AAC37C42F19
      Keygrip = 82380E8EB005D76AE6A1E73FCDC82B374B8D9584
uid                 [ unknown] testkey
ssb#  ed25519/2C45A3D965A1FEFE 2021-04-18 [E]
      Keygrip = B1838BACC3F53C98C675146D7E929AB285C6E49C

This seems to be the problem. gpg looks for a file named 
B1838BACC3F53C98C675146D7E929AB285C6E49C.key which doesn't exist.

Please submit a bug report at https://dev.gnupg.org

Regards,
Ingo
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