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I am two servers A and B under the same firewall. I can login from server A to B using root account but I cannot login from B to A. My ssh keys are properly configured but I am not able to figure our what is wrong.

This is the verbose of when I try connect from server B to A.

root@web04:~# ssh -v -i.ssh/id_rsa root@11.11.11.4
OpenSSH_5.9p1 Debian-5ubuntu1.4, OpenSSL 1.0.1 14 Mar 2012
Warning: Identity file .ssh/id_rsa not accessible: No such file or directory.
debug1: Reading configuration data /etc/ssh/ssh_config
debug1: /etc/ssh/ssh_config line 19: Applying options for *
debug1: Connecting to 11.11.11.4 [11.11.11.4] port 22.
debug1: Connection established.
debug1: permanently_set_uid: 0/0
debug1: identity file /root/.ssh/id_rsa type -1
debug1: identity file /root/.ssh/id_rsa-cert type -1
debug1: read_keyfile_line: /root/.ssh/id_dsa.pub line 1 exceeds size limit
debug1: identity file /root/.ssh/id_dsa type -1
debug1: identity file /root/.ssh/id_dsa-cert type -1
debug1: identity file /root/.ssh/id_ecdsa type -1
debug1: identity file /root/.ssh/id_ecdsa-cert type -1
debug1: Remote protocol version 2.0, remote software version OpenSSH_5.9p1 Debian-5ubuntu1.4
debug1: match: OpenSSH_5.9p1 Debian-5ubuntu1.4 pat OpenSSH*
debug1: Enabling compatibility mode for protocol 2.0
debug1: Local version string SSH-2.0-OpenSSH_5.9p1 Debian-5ubuntu1.4
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 2c:37:bc:c8:47:07:53:07:9c:a8:f8:1d:12:a6:4a:a0
debug1: Host '11.11.11.4' is known and matches the ECDSA host key.
debug1: Found key in /root/.ssh/known_hosts:11
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
Ubuntu 12.04 LTS
-------------------------------------
UNAUTHORISED ACCESS IS PROHIBITED!!
-------------------------------------
debug1: Authentications that can continue: publickey,password
debug1: Next authentication method: publickey
debug1: Trying private key: /root/.ssh/id_rsa
debug1: Trying private key: /root/.ssh/id_dsa
debug1: read PEM private key done: type DSA
debug1: Authentications that can continue: publickey,password
debug1: Trying private key: /root/.ssh/id_ecdsa
debug1: Next authentication method: passwor
  • Did you check /etc/ssh/sshd_conf? There should be a PermitRootLogin parameter that is probably set to no – jesusbolivar Jul 2 '14 at 13:54
  • What do the server logs say? – Jenny D Jul 2 '14 at 13:54
  • 2
    Forbidding direct access to the root user via SSH is a best practice advised by most "securing your server" guides. You should SSH in as a normal user and use su/sudo when you need privileged access. – ceejayoz Jul 2 '14 at 13:54
  • Looks like your public key is corrupted: read_keyfile_line: /root/.ssh/id_dsa.pub line 1 exceeds size limit – Nathan C Jul 2 '14 at 14:14
5

Please check the Option "PermitRootLogin" in /etc/ssh/sshd_config is set to "yes".

Please note that this is usually set to "no" or "public-key" since logging in as root via SSH is widely considered an security problem.

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