Ubuntu: SSH Permission denied (publickey)



Question:

I have tried searching previous questions for answers to my question but all of the answers that have been suggested previously haven't worked for me.

I am trying to connect to a linode (running ubuntu 12.04 LTS) from my local machine (also running ubnutu 12.04 LTS)

I have create a private and public key on my local machine and copied my public key to my linode's authorized_keys file. However whenever I try to ssh to my linode I get the error message "Permission denied (publickey).

Its not a problem with how ssh is set up on my linode because I can ssh to it from my Windows machine using key authentication.

In my .ssh directory on my local ubuntu machine I have my id_rsa and id_rsa.pub files. Do I need to create an authorized_keys file on my local machine?

EDIT: This is what I get when I run ssh -vvv -i id_rsa [youruser]@[yourLinode]

debug3: authmethod_lookup publickey  debug3: remaining preferred: keyboard-interactive,password  debug3: authmethod_is_enabled publickey  debug1: Next authentication method: publickey  debug1: Offering RSA public key: id_rsa  debug3: send_pubkey_test  debug2: we sent a publickey packet, wait for reply  debug1: Authentications that can continue: publickey  debug2: we did not send a packet, disable method  debug1: No more authentication methods to try.  Permission denied (publickey).  


Solution:1

PubKeyAuthentication

Set up your client

  1. Generate your key
    • ssh-keygen
  2. Configure ssh to use the key
    • vim ~/.ssh/config
  3. Copy your key to your server
    • ssh-copy-id -i /path/to/key.pub SERVERNAME

Your config file from step 2 should have something similar to the following:

Host SERVERNAME  Hostname ip-or-domain-of-server  User USERNAME  PubKeyAuthentication yes  IdentityFile ./path/to/key  

Troubleshooting

  1. use "-vvv" option
  2. Make sure the server has your PUBLIC key (.pub).
  3. Make sure your IdentiyFile points to your PRIVATE key.
  4. Make sure your .ssh directory has 700 and your files are 700 permissions (rwx------).
  5. tail -f /var/log/auth.log (on the server) and monitor errors when you attempt to login


Solution:2

Sometimes the issue comes from permissions and ownership. For instance, if you want to log in as root, /root, .ssh and authorized_keys must belong to root. Otherwise, sshd won't be able to read them and therefore won't be able to tell if the user is authorized to log in.

In your home directory:

chown -R your_user:your_user .ssh  

As for rights, go with 700 for .ssh and 600 for authorized_keys

chmod 700 .ssh  chmod 600 .ssh/authorized_keys  


Solution:3

You don't need authorized_keys on your client.

You must tell the ssh-client to actually use the key you generated. There are several ways to do that. Just for testing type ssh -vvv -i .ssh/id_rsa [youruser]@[yourLinode]. You will have to provide your passphrase every time you want to connect to the server.

If that worked you can add the key to the ssh-agent with ssh-add .ssh/id_rsa (you will have to provide the passphrase only once for this and it should work as long as you don't logout/reboot)


Solution:4

Also make sure that the user's home directory (on the server) actually belongs to the user ssh'ing into (was set to root:root in my case).

Should have been:

sudo chown username:username /home/username;  


Solution:5

The problem I had was it was using the wrong keys on the client. I had renamed id_rsa and id_rsa.pub to something else. You can either rename them back to their default, or when you issue the ssh command, use it like this

ssh -i ~/.ssh/private_key username@host  


Solution:6

Also check value of PasswordAuthentication in /etc/ssh/sshd_config and if it's no change it to yes. Don't forget to restart ssh service after that.


Solution:7

I ran into this issue recently with my web server.

I typically keep a list of authorized keys on all my servers in ~/.ssh/authorized_keys2. From my experience, sshd will look for ~/.ssh/authorized_keys or ~/.ssh/authorized_keys2 by default.

In the case of my webserver, the /etc/ssh/sshd_config had this line

AuthorizedKeysFile    %h/.ssh/authorized_keys  

instead of

AuthorizedKeysFile    %h/.ssh/authorized_keys2  

I applied the latter, restarted my ssh daemon, and solved my problem logging in with ssh using my pubkey.


Solution:8

I my case, the client is ubuntu 14.04lts, the server was win 2012 server running cygwin. I was using 'ssh administrator@x.x.x.x', when the 2012 server directory in cygwin was /home/Administrator. So it was case sensitive, when I tried 'ssh Administrator@x.x.x.x' (note the capital A on Administrator) then it worked fine.

An error message like 'user not found' would have led me to the solution a lot quicker than 'Permission denied (publickey,keyboard-interactive)'.


Solution:9

I had the same issue when copying a regular user's (e.g. johndoe) public key from a cPanel Centos system over to an Ubuntu server on AWS. As suggested by gertvdijk above, I checked /var/log/auth.log and sure enough it said Authentication refused: bad ownership or modes for directory /home/johndoe. Turns out I had wrongly 777'ed /home/johndoe when trying to set /home/johndoe/public_html as the default virtualhost Document Root for apache2 (that's not needed for that task either).

See also the answers here and here

The server only needs to have the public key in .ssh/authorized_keys and the client (computer you're working on) needs to have the private key (.pem, or if using SFTP with Filezilla, .ppk)


Solution:10

For those Putty users like me who came to this thread, you may also get this error if you forgot to add user user@Ip !

Others being permission on key file chmod to 600)

ssh 1.1.1.1 -i /path/to/.pem file   Permission denied (publickey).`    ssh user@1.1.1.1 -i /path/to/.pem file   


Solution:11

This is what worked for me, the fix is not mine but I would rather write it down here in case someone else has the same problem.

The original author posted it here: digital-ocean-public-access-key-denied

sudo nano /etc/ssh/sshd_config  

Replace this

UsePAM yes  IgnoreUserKnownHosts no  PasswordAuthentication no  

With this

UsePAM no  IgnoreUserKnownHosts no  PasswordAuthentication yes  

Save the file and restart ssh

reload ssh  

ssh should work now asking for a password


Solution:12

I had the same problem as described in the question. The output from executing ssh -vvv -i id_rsa [youruser]@[yourLinode] on the client machine was similar to that described in the question. I checked all the file and directory permissions as advised in the other answers, and they were correct.

It turned out that when copying the generated file id_rsa.pub to the server machine, as file ~username/.ssh/authorized_keys, I'd accidentally omitted the word ssh-rsa from the start. Adding it solved the problem.


Solution:13

If all else failed, check that your login user belongs to the ssh's AllowedGroup. That is, your users is a member of the group shown at the following line in /etc/ssh/sshd_config on the server:

AllowGroups ssh #Here only users of 'ssh' group can login  


Solution:14

Another possible cause could be with the AllowedUsers configuration in /etc/ssh/sshd_conf. NOTE: the list is space delimited (not comma delimited) as I learned the hard way.

AllowUsers user1 user2 user3  


Solution:15

In my case the issue was caused by copying over an .ssh directory from an older machine. Turns out that my older SSH config was using DSA keys which have since been deprecated. Switching to a new pair of keys, this time RSA-based, solved the problem for me.


Solution:16

The following method might work if you can access machineA and machineB independently (e.g. from machineC).

If ssh-copy-id is not working, password authentication could be disabled. The following is a workaround.

Having machineA's public key in machineB's authorized keys (i.e. ~/.ssh/authorized_keys) will allow you to ssh from machineA. This also applies to scp.

After generating the key pairs using: ssh-keygen

On machineA, execute cat ~/.ssh/id_rsa.pub

Sample output:

ssh-rsa AAAAB3NzaSGMFZW7yB anask@mahineA

Copy the printed key (⌘ Command+C, or CRTL+C) then add it to the ~/.ssh/authorized_keys file on machineB.

For example, execute the following on machineB:

echo 'ssh-rsa AAAAB3NzaSGMFZW7yB anask@mahineA' >> ~/.ssh/authorized_keys


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