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Error: User modify failed. Cannot modify user on other node: Authentication by SSH key failed!

255  Manu Chacko May 24, 2023  Common Errors & Troubleshooting

Error: User modify failed. Cannot modify user on other node: Authentication by SSH key failed!

Check the following on the slave/secondary node

1. The error ’User modify failed Cannot modify user on other node: Authentication by ssh key failed’ would occur when the Ezeelogin installed node has its public key missing in /root/.ssh/authorized_keys. To add the key, execute the following command 

root@gateway ~]# cat /usr/local/etc/ezlogin/id_clkey.pub >> /root/.ssh/authorized_keys

      Check if the key is back in the file.

root@gateway ~]# cat /root/.ssh/authorized_keys

Run the following command to check if you have enabled the recommended sshd settings in /etc/ssh/sshd_config

root@ez:/home# sshd -T | grep -i 'AllowTcpForwarding\|PermitRootLogin\|PubkeyAuthentication\|PasswordAuthentication\|pubkeyacceptedalgorithms\|Port'

port 22
permitrootlogin yes
pubkeyauthentication yes
passwordauthentication yes
gatewayports no
allowtcpforwarding yes
pubkeyacceptedalgorithms [email protected],[email protected],[email protected],[email protected],[email protected],[email protected],[email protected],[email protected],ssh-ed25519,ecdsa-sh

 

2. Also, make sure that the port sshd is listening on the servers is given as the gateway port in Settings->General->Miscellaneous->Gateway SSH port

3. Also, make sure PubkeyAuthentication is set to ’YES’ in your sshd_config (sshd configuration) file. In Centos/RHEL/Fedora it would be

root@gateway ~]# vi /etc/ssh/sshd_config

#set PubkeyAuthentication to yes

PubkeyAuthentication yes

root@gateway ~]# service sshd restart

4. Also, make sure root login is permitted on the gateway server.

     You can check this by doing

ssh root@localhost

and it should log you in else edit /etc/ssh/sshd_config and set  PermitRootLogin yes 

root@gateway ~]# vi /etc/ssh/sshd_config

#Add the following lines to the end of  /etc/ssh/sshd_config to allow root login from localhost only

Match Address 127.0.0.1

PermitRootLogin yes

PubkeyAuthentication yes

#Replace MASTER_NODE_IP with your master node Ezeelogin IP ADDRESS

Match Address MASTER_NODE_IP

PermitRootLogin yes

PubkeyAuthentication yes

root@gateway ~]# service sshd restart

     and make sure you are able to authenticate with the command 

ssh root@localhost

     Make sure you are able to login after entering the password.

If you have enabled Allow Or Deny SSH Access To A Particular User Or Group in sshd.conf, make sure that the user root is allowed

4. Also, make sure that the web user(apache, nobody, etc) that the webserver(apache/nginx) runs as is able to read the keys in the dir /usr/local/etc/ezlogin.

  Make sure to grant the read privileges to

chmod o r /usr/local/etc/ezlogin/id_clkey
chmod o r /usr/local/etc/ezlogin/id_clkey.pub
or
usermod -G <current_groupname_of_id_clkey_files> <webserver_user>

5. Find out which key type is used by the server by running the below command.

root@gateway ~]# ssh-keygen -l -f /usr/local/etc/ezlogin/id_key.pub

4096 SHA256:n4lmX53/gwkKB4+nSQ30hZXxXK+DRG1LPc7N1KN/1Ag ezlogin (RSA)

     Open /etc/ssh/sshd_config file and append below line to enable RSA key type.

root@gateway ~]# vim /etc/ssh/sshd_config

PubkeyAcceptedKeyTypes +ssh-rsa

root@gateway ~]# systemctl restart sshd

6. Check the log file /var/log/secure

root@gateway ~]# tail -f /var/log/secure

Refer below article if you get "userauth_pubkey: signature algorithm ssh-rsa not in PubkeyAcceptedAlgorithms"

https://www.ezeelogin.com/kb/article/userauth_pubkey-signature-algorithm-ssh-rsa-not-in-pubkeyacceptedalgorithms-518.html

6. Reset Ezeelogin cluster keys

How to reset cluster keys in Ezeelogin Master-slave Configuration?

 

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