sftpgo.json ; Configuration file - sftpd - host_key_algorithms

[Mistique8885]

Hi!
Here is an issue:
I want to restrict SFTPGo to specific algorithms only:

"host_certificates": [],
"host_key_algorithms": ["ecdsa-sha2-nistp256-cert-v01@openssh.com","ecdsa-sha2-nistp521-cert-v01@openssh.com"],
"kex_algorithms": [],

Expected:
Config loaded properly, only "ecdsa-sha2-nistp256-cert-v01@openssh.com","ecdsa-sha2-nistp521-cert-v01@openssh.com" are supported:

Result:
{"level":"info","time":"2023-07-03T21:08:13.774","sender":"service","message":"initializing SFTP server with config {Banner:JOPA Bindings:[{Address: Port:2022 ApplyProxyConfig:true}] MaxAuthTries:0 HostKeys:[] HostCertificates:[] HostKeyAlgorithms:[ecdsa-sha2-nistp256-cert-v01@openssh.com ecdsa-sha2-nistp521-cert-v01@openssh.com] KexAlgorithms:[] Ciphers:[aes256-gcm@openssh.com] MACs:[] TrustedUserCAKeys:[] RevokedUserCertsFile: LoginBannerFile: EnabledSSHCommands:[md5sum sha1sum sha256sum cd pwd scp] KeyboardInteractiveAuthentication:false KeyboardInteractiveHook: PasswordAuthentication:true FolderPrefix: certChecker:<nil> parsedUserCAKeys:[]}"}

When Client tries to connect we see in the log:
{"level":"debug","time":"2023-07-03T21:12:04.950","sender":"sftpd","message":"failed to accept an incoming connection: ssh: no common algorithm for host key; client offered: [ssh-ed25519 ssh-ed448 ecdsa-sha2-nistp256 ecdsa-sha2-nistp384 ecdsa-sha2-nistp521 rsa-sha2-512 rsa-sha2-256 ssh-rsa ssh-dss], server offered: []"}

Question:
How to properly limit SFTPGo with specific algo?
Thank you!

[dedit-lutwama]

@Mistique8885 - Were you able to setup SFTP and ssh into your sftpgo instance before applying the host_key_algorithms restrictions?

[Mistique8885]

Hi!
My main task is:
Ubuntu 14.04 can connect to the SFTPGo

I solved it with setting ENV var like this:
SFTPGO_SFTPD__HOST_KEY_ALGORITHMS='ssh-rsa,rsa-sha2-512-cert-v01@openssh.com,rsa-sha2-256-cert-v01@openssh.com,ecdsa-sha2-nistp256-cert-v01@openssh.com,ecdsa-sha2-nistp384-cert-v01@openssh.com,ecdsa-sha2-nistp521-cert-v01@openssh.com,ssh-ed25519-cert-v01@openssh.com,ecdsa-sha2-nistp256,ecdsa-sha2-nistp384,ecdsa-sha2-nistp521,rsa-sha2-512,rsa-sha2-256,ssh-ed25519'

It is 'ssh-rsa' + Default Algorithms