SSH Too many authentication failures

When i ssh into a server, i get following error

root@lab:~# ssh [email protected] -p 3333
Received disconnect from 14.18.58.78: 2: Too many authentication failures
root@lab:~#

I checked server log (/var/log/auth.log) and found following

Nov 13 19:06:42 lab sshd[32030]: error: maximum authentication attempts exceeded for root from 188.40.131.92 port 52956 ssh2 [preauth]
Nov 13 19:06:42 lab sshd[32030]: Disconnecting: Too many authentication failures [preauth]

This error happens when you have several SSH keys. When you try to connect to remote server, ssh client try to autenticate to remote server using SSH keys present on your computer. If you have several keys, ssh client make that much login attempts if the keys are valid for remote server you are trying to login.

ssh server deamon have a settings MaxAuthTries. Default value for this settings is 6. If number of invalid login attempt exceeds the value of MaxAuthTries, you will get above error.

You can see all SSH keys on your computer with

ssh-add -l

If you have many keys, consider removing some of the keys from agent using ssh-add command.

To fix this error edit file

vi /etc/ssh/sshd_config

Check if the file have entry for MaxAuthTries, if yes, increase its value. If no entry present in the server add it.

MaxAuthTries 8

Restart sshd service.

systemctl restart sshd

You can see how many login attemts you make using ssh -v option (verbose).

root@server12:~# ssh -v [email protected] -p 3333
OpenSSH_5.3p1, OpenSSL 1.0.1e-fips 11 Feb 2013
debug1: Reading configuration data /root/.ssh/config
debug1: Reading configuration data /etc/ssh/ssh_config
debug1: Applying options for *
debug1: Connecting to 174.138.58.78 [174.138.58.78] port 3333.
debug1: Connection established.
debug1: permanently_set_uid: 0/0
debug1: identity file /root/.ssh/identity type -1
debug1: identity file /root/.ssh/identity-cert type -1
debug1: identity file /root/.ssh/id_rsa type 1
debug1: identity file /root/.ssh/id_rsa-cert type -1
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_7.2p2 Ubuntu-4ubuntu2.8
debug1: match: OpenSSH_7.2p2 Ubuntu-4ubuntu2.8 pat OpenSSH*
debug1: Enabling compatibility mode for protocol 2.0
debug1: Local version string SSH-2.0-OpenSSH_5.3
debug1: SSH2_MSG_KEXINIT sent
debug1: SSH2_MSG_KEXINIT received
debug1: kex: server->client aes128-ctr hmac-sha1 none
debug1: kex: client->server aes128-ctr hmac-sha1 none
debug1: SSH2_MSG_KEX_DH_GEX_REQUEST(1024<2048<8192) sent
debug1: expecting SSH2_MSG_KEX_DH_GEX_GROUP
debug1: SSH2_MSG_KEX_DH_GEX_INIT sent
debug1: expecting SSH2_MSG_KEX_DH_GEX_REPLY
debug1: Host '[174.138.58.78]:3333' is known and matches the RSA host key.
debug1: Found key in /root/.ssh/known_hosts:139
debug1: ssh_rsa_verify: signature correct
debug1: SSH2_MSG_NEWKEYS sent
debug1: expecting SSH2_MSG_NEWKEYS
debug1: SSH2_MSG_NEWKEYS received
debug1: SSH2_MSG_SERVICE_REQUEST sent
debug1: SSH2_MSG_SERVICE_ACCEPT received
debug1: Authentications that can continue: publickey,password
debug1: Next authentication method: publickey
debug1: Offering public key: /home/boby/.ssh/id_rsa
debug1: Authentications that can continue: publickey,password
debug1: Offering public key: boby@hon-pc-01
debug1: Authentications that can continue: publickey,password
debug1: Offering public key: redbridgefinance-mumbai
debug1: Authentications that can continue: publickey,password
debug1: Offering public key: aws-eb
debug1: Authentications that can continue: publickey,password
debug1: Offering public key: aws-austin-boby
debug1: Authentications that can continue: publickey,password
debug1: Trying private key: /root/.ssh/identity
debug1: Offering public key: /root/.ssh/id_rsa
Received disconnect from 174.138.58.78: 2: Too many authentication failures
root@server12:~# 

See SSH