I guess I have done everything right. Public/private keys, files permissions, etc.
There are 3 machines:
- ubuntu
- old_synology
- new_synology
- I start from ubuntu, ssh to old_synology without a password. It works.
- I ssh from old_synology to new_synology without a password. It works.
- I try to ssh from ubuntu to new_synology - it fails.
Connection from ubuntu port 41568 on new_synology port 1234
debug1: Client protocol version 2.0; client software version OpenSSH_7.6p1 Ubuntu-4ubuntu0.3
debug1: match: OpenSSH_7.6p1 Ubuntu-4ubuntu0.3 pat OpenSSH* compat 0x04000000
debug1: Local version string SSH-2.0-OpenSSH_7.4
debug1: Enabling compatibility mode for protocol 2.0
debug1: permanently_set_uid: 1024/100 [preauth]
debug1: ssh_sandbox_child: prctl(PR_SET_SECCOMP): Invalid argument [preauth]
debug1: list_hostkey_types: ssh-rsa,rsa-sha2-512,rsa-sha2-256,ecdsa-sha2-nistp256,ssh-ed25519 [preauth]
debug1: SSH2_MSG_KEXINIT sent [preauth]
debug1: SSH2_MSG_KEXINIT received [preauth]
debug1: kex: algorithm: curve25519-sha256 [preauth]
debug1: kex: host key algorithm: ecdsa-sha2-nistp256 [preauth]
debug1: kex: client->server cipher: chacha20-poly1305@openssh.com MAC: <implicit> compression: none [preauth]
debug1: kex: server->client cipher: chacha20-poly1305@openssh.com MAC: <implicit> compression: none [preauth]
debug1: expecting SSH2_MSG_KEX_ECDH_INIT [preauth]
debug1: rekey after 134217728 blocks [preauth]
debug1: SSH2_MSG_NEWKEYS sent [preauth]
debug1: expecting SSH2_MSG_NEWKEYS [preauth]
debug1: SSH2_MSG_NEWKEYS received [preauth]
debug1: rekey after 134217728 blocks [preauth]
debug1: KEX done [preauth]
debug1: userauth-request for user admin service ssh-connection method none [preauth]
debug1: attempt 0 failures 0 [preauth]
debug1: get user realname admin => admin
debug1: user admin matched 'User admin' at line 124
debug1: PAM: initializing for "admin"
debug1: PAM: setting PAM_RHOST to "ubuntu"
debug1: PAM: setting PAM_TTY to "ssh"
debug1: userauth-request for user admin service ssh-connection method publickey [preauth]
debug1: attempt 1 failures 0 [preauth]
debug1: userauth_pubkey: test whether pkalg/pkblob are acceptable for RSA SHA256:*** [preauth]
debug1: temporarily_use_uid: 1024/100 (e=0/0)
debug1: trying public key file /var/services/homes/admin/.ssh/authorized_keys
debug1: fd 4 clearing O_NONBLOCK
debug1: restore_uid: 0/0
Failed publickey for admin from ubuntu port 41568 ssh2: RSA SHA256:***
The obvious checks:
- ubuntu's public/private keys are valid because I can log in to old_synology
- new_synology's .ssh/* file permissions are correct because I can log in from old_synology
- ubuntu's public key is THE SAME in both synology's authorized_keys file.
Any ideas?
