This is quite a mistery for me. I usually use passwordless RSA authentication to login into my remote *nix servers with ssh and sftp. Never had any problem until now.

I cannot connect to an Ubuntu 9.10 machine:

user@myclient$ ssh -i .ssh/Ganymede_key [email protected]
[...]
debug1: Host 'ganymede.server.com' is known and matches the RSA host key.
debug1: Found key in /home/user/.ssh/known_hosts:14
debug2: bits set: 494/1024
debug1: ssh_rsa_verify: signature correct
debug2: kex_derive_keys
debug2: set_newkeys: mode 1
debug1: SSH2_MSG_NEWKEYS sent
debug1: expecting SSH2_MSG_NEWKEYS
debug2: set_newkeys: mode 0
debug1: SSH2_MSG_NEWKEYS received
debug1: SSH2_MSG_SERVICE_REQUEST sent
debug2: service_accept: ssh-userauth
debug1: SSH2_MSG_SERVICE_ACCEPT received
debug2: key: .ssh/Ganymede_key (0xb96a0ef8)
debug2: key: .ssh/Ganymede_key ((nil))
debug1: Authentications that can continue: publickey,password,keyboard-interactive
debug1: Next authentication method: publickey
debug1: Offering public key: .ssh/Ganymede_key
debug2: we sent a publickey packet, wait for reply
debug1: Authentications that can continue: publickey,password,keyboard-interactive
debug1: Trying private key: .ssh/Ganymede_key
debug1: read PEM private key done: type RSA
debug2: we sent a publickey packet, wait for reply
debug1: Authentications that can continue: publickey,password,keyboard-interactive
debug2: we did not send a packet, disable method
debug1: Next authentication method: keyboard-interactive
debug2: userauth_kbdint
debug2: we sent a keyboard-interactive packet, wait for reply
debug2: input_userauth_info_req
debug2: input_userauth_info_req: num_prompts 1

Then it falls back to password authentication. If I disable password authentication on the remote machine my connection attempt just fails with a "Permission denied (publickey)." state.

Same thing for sftp from command line.

The "funny" thing is that the exact same RSA key works like a charm with a Filezilla sftp session instead:

12:08:00 Trace: Offered public key from "/home/user/.filezilla/keys/Ganymede_key"
12:08:00 Trace: Offer of public key accepted, trying to authenticate using it.
12:08:01 Trace: Access granted
12:08:01 Trace: Opened channel for session
12:08:01 Trace: Started a shell/command
12:08:01 Status: Connected to ganymede.server.com
12:08:02 Trace: CSftpControlSocket::ConnectParseResponse()
12:08:02 Trace: CSftpControlSocket::ResetOperation(0)
12:08:02 Trace: CControlSocket::ResetOperation(0)
12:08:02 Status: Retrieving directory listing...
12:08:02 Trace: CSftpControlSocket::SendNextCommand()
12:08:02 Trace: CSftpControlSocket::ChangeDirSend()
12:08:02 Command: pwd
12:08:02 Response: Current directory is: "/root"
12:08:02 Trace: CSftpControlSocket::ResetOperation(0)
12:08:02 Trace: CControlSocket::ResetOperation(0)
12:08:02 Trace: CSftpControlSocket::ParseSubcommandResult(0)
12:08:02 Trace: CSftpControlSocket::ListSubcommandResult()
12:08:02 Trace: CSftpControlSocket::ResetOperation(0)
12:08:02 Trace: CControlSocket::ResetOperation(0)
12:08:02 Status: Directory listing successful

Any thoughts?

M