We have the following ssh hop setup:

    localhost -> hub -> server

hubuser@hub accepts the public key for localuser@localhost.

serveruser@server accepts the public key for hubuser@hub.

So we are issuing ssh -t hubuser@hub ssh serveruser@server for connecting to server.

The problem with this setup is we can not scp directly to the server.

I tried creating .ssh/config file like this:

    Host server
      user serveruser
      port 22
      hostname server
      ProxyCommand ssh -q hubuser@hub 'nc %h %p'

But I am not able to connect (yigit is localuser):

    $ ssh serveruser@server -v
    OpenSSH_6.1p1, OpenSSL 1.0.1c 10 May 2012
    debug1: Reading configuration data /home/yigit/.ssh/config
    debug1: /home/yigit/.ssh/config line 19: Applying options for server        debug1: Reading configuration data /etc/ssh/ssh_config
    debug1: Executing proxy command: exec ssh -q hubuser@hub 'nc server 22'
    debug1: permanently_drop_suid: 1000
    debug1: identity file /home/yigit/.ssh/id_rsa type 1000        debug1: identity file /home/yigit/.ssh/id_rsa-cert type -1
    debug1: identity file /home/yigit/.ssh/id_dsa type -1
    debug1: identity file /home/yigit/.ssh/id_dsa-cert type -1
    debug1: identity file /home/yigit/.ssh/id_ecdsa type -1
    debug1: identity file /home/yigit/.ssh/id_ecdsa-cert type -1
    debug1: Remote protocol version 2.0, remote software version OpenSSH_5.9p1 Debian-5ubuntu1
    debug1: match: OpenSSH_5.9p1 Debian-5ubuntu1 pat OpenSSH_5*
    debug1: Enabling compatibility mode for protocol 2.0        debug1: Local version string SSH-2.0-OpenSSH_6.1
    debug1: SSH2_MSG_KEXINIT sent
    debug1: SSH2_MSG_KEXINIT received
    debug1: kex: server->client aes128-ctr hmac-md5 none
    debug1: kex: client->server aes128-ctr hmac-md5 none        debug1: sending SSH2_MSG_KEX_ECDH_INIT
    debug1: expecting SSH2_MSG_KEX_ECDH_REPLY
    debug1: Server host key: ECDSA cb:ee:1f:78:82:1e:b4:39:c6:67:6f:4d:b4:01:f2:9f
    debug1: Host 'server' is known and matches the ECDSA host key.
    debug1: Found key in /home/yigit/.ssh/known_hosts:33
    debug1: ssh_ecdsa_verify: signature correct
    debug1: SSH2_MSG_NEWKEYS sent
    debug1: expecting SSH2_MSG_NEWKEYS
    debug1: SSH2_MSG_NEWKEYS received
    debug1: Roaming not allowed by server
    debug1: SSH2_MSG_SERVICE_REQUEST sent
    debug1: SSH2_MSG_SERVICE_ACCEPT received
    debug1: Authentications that can continue: publickey
    debug1: Next authentication method: publickey
    debug1: Offering RSA public key: /home/yigit/.ssh/id_rsa
    debug1: Authentications that can continue: publickey
    debug1: Trying private key: /home/yigit/.ssh/id_dsa
    debug1: Trying private key: /home/yigit/.ssh/id_ecdsa
    debug1: No more authentication methods to try.
    Permission denied (publickey).

Notice that it is trying to use the public key localuser@localhost for authenticating on server and fails since it is not the right one. Is it possible to modify the ProxyCommand so that the key for hubuser@hub is used for authenticating on server?