"No hostkey for host ***** found" when connecting to SFTP server with pysftp using private key

Question

So I am having many issues connecting to a remote server via SFTP. I have tried the normal way like below.

sftp = pysftp.Connection(host='Host',username='username',password='passwd',private_key=".ppk")

Which did not work. I got the following error:

SSHException: No hostkey for host ***** found.

I then tried the following:

cnopts = pysftp.CnOpts()
cnopts.hostkeys = None
s = pysftp.Connection(host='host', username='user', password='password', cnopts=cnopts)

Which also did not work. I got the following error:

BadAuthenticationType: ('Bad authentication type', ['publickey']) (allowed_types=['publickey'])

Also when I run the following:

client = paramiko.SSHClient()
client.set_missing_host_key_policy(paramiko.AutoAddPolicy())
client.connect("host",username = "username",password = "password")
ssh_session = client.get_transport().open_session()

I get the same error:

BadAuthenticationType: ('Bad authentication type', ['publickey']) (allowed_types=['publickey'])

Answer 1

Your are confusing a private key used for authentication and a host key used to verify an identify of a server. Both need to be taken care of, while all your code attempts take care of one of them only. See my article on SSH key pairs to understand the difference between the two kinds of keys involved in SSH.

So this should "work":

# Accept any host key (still wrong see below)
cnopts = pysftp.CnOpts()
cnopts.hostkeys = None
# And authenticate with a private key
sftp = pysftp.Connection(
  host='Host', username='user', password='passwd', private_key=".ppk", cnopts=cnopts)

But this code will actually blindly accept any host key (cnopts.hostkeys = None), what is a security flaw. For a correct approach, see Verify host key with pysftp.