Add key format option

[afaranha]

I'd like to be able to choose the format of the key Im generating, for example: ssh-keygen -m PEM`, but I can't see how to do it on the library.
I was also trying other types of rsa keys (Maybe the default format would be the one I'm looking for), and it seems that they don't work:

https://github.com/ParallelSSH/ssh-python/blob/master/ssh/keytypes.pyx#L53-L60

key_type = keytypes.RSAKey()
print(key_type)

Outputs:
ssh-rsa

key_type = keytypes.RSA1Key()
print(key_type)

Outputs:
unknown

[enkore]

That's basically just the wrapper for an enum, see examples/keygen.py for how to use the ssh.key.generate API.

https://github.com/ParallelSSH/ssh-python/blob/master/examples/keygen.py

[afaranha]

Sorry if I wasn't clear when I opened the issue, but that enum if for the key type, not the key format, for example, using the terminal I can do this to generate a RSA key:

$ ssh-keygen -f test -t rsa
$ head test
-----BEGIN OPENSSH PRIVATE KEY-----

or

$ ssh-keygen -f test -t rsa -m PEM
$ head test
-----BEGIN RSA PRIVATE KEY-----

The key type is the same but the format is different.

https://man.openbsd.org/ssh-keygen.1

-m Specify a key format for key generation, the -i (import), -e (export) conversion options, and the -p change passphrase operation. The latter may be used to convert between OpenSSH private key and PEM private key formats. The supported key formats are: “RFC4716” (RFC 4716/SSH2 public or private key), “PKCS8” (PKCS8 public or private key) or “PEM” (PEM public key). By default OpenSSH will write newly-generated private keys in its own format, but when converting public keys for export the default format is “RFC4716”. Setting a format of “PEM” when generating or updating a supported private key type will cause the key to be stored in the legacy PEM private key format.

Do we have a way how to choose a different key format? On the generate function we can only pass the bits and the key type, not the key format.

[enkore]

Apologies. No, ssh_pki_export_privkey_file_format isn't wrapped by this library.