Disable password authentication for SSH [closed]

I'm looking for a way to disable SSH clients from accessing the password prompt as noted here.

I am unable to disable the password: prompt for root login. I have change the sshd_config file to read:

ChallengeResponseAuthentication no PasswordAuthentication no UsePAM no 

and have also changed the permissions chmod 700 ~/.ssh and chmod 600 ~/.ssh/authorized_keys. What am I missing? Does this require I have a passphrase?

Verbose dump:

debug1: Authentications that can continue: publickey,password debug1: Next authentication method: publickey debug1: Offering RSA public key: /home/user/.ssh/id_rsa debug1: Authentications that can continue: publickey,password debug1: Trying private key: /home/user/.ssh/id_dsa debug1: Trying private key: /home/user/.ssh/id_ecdsa debug1: Next authentication method: password 

File /etc/ssh/sshd_config:

# Package generated configuration file # See the sshd_config(5) manpage for details # What ports, IPs and protocols we listen for Port 22 # Use these options to restrict which interfaces/protocols sshd will bind to #ListenAddress :: #ListenAddress 0.0.0.0 Protocol 2 # HostKeys for protocol version 2 HostKey /etc/ssh/ssh_host_rsa_key HostKey /etc/ssh/ssh_host_dsa_key HostKey /etc/ssh/ssh_host_ecdsa_key #Privilege Separation is turned on for security UsePrivilegeSeparation yes # Lifetime and size of ephemeral version 1 server key KeyRegenerationInterval 3600 ServerKeyBits 768 # Logging SyslogFacility AUTH LogLevel INFO # Authentication: LoginGraceTime 120 PermitRootLogin no StrictModes yes RSAAuthentication yes PubkeyAuthentication yes #AuthorizedKeysFile %h/.ssh/authorized_keys # Don't read the user's ~/.rhosts and ~/.shosts files IgnoreRhosts yes # For this to work you will also need host keys in /etc/ssh_known_hosts RhostsRSAAuthentication no # similar for protocol version 2 HostbasedAuthentication no # Uncomment if you don't trust ~/.ssh/known_hosts for RhostsRSAAuthentication #IgnoreUserKnownHosts yes # To enable empty passwords, change to yes (NOT RECOMMENDED) PermitEmptyPasswords no # Change to yes to enable challenge-response passwords (beware issues with # some PAM modules and threads) ChallengeResponseAuthentication no # Change to no to disable tunnelled clear text passwords #PasswordAuthentication no # Kerberos options #KerberosAuthentication no #KerberosGetAFSToken no #KerberosOrLocalPasswd yes #KerberosTicketCleanup yes # GSSAPI options #GSSAPIAuthentication no #GSSAPICleanupCredentials yes X11Forwarding yes X11DisplayOffset 10 PrintMotd no PrintLastLog yes TCPKeepAlive yes #UseLogin no #MaxStartups 10:30:60 Banner /etc/issue.net # Allow client to pass locale environment variables AcceptEnv LANG LC_* Subsystem sftp /usr/lib/openssh/sftp-server # Set this to 'yes' to enable PAM authentication, account processing, # and session processing. If this is enabled, PAM authentication will # be allowed through the ChallengeResponseAuthentication and # PasswordAuthentication. Depending on your PAM configuration, # PAM authentication via ChallengeResponseAuthentication may bypass # the setting of "PermitRootLogin without-password". # If you just want the PAM account and session checks to run without # PAM authentication, then enable this but set PasswordAuthentication # and ChallengeResponseAuthentication to 'no'. UsePAM no 

5 Answers

In file /etc/ssh/sshd_config

# Change to no to disable tunnelled clear text passwords #PasswordAuthentication no 

Uncomment the second line, and, if needed, change yes to no.

Then run

service ssh restart 

Here's a one-liner to do this automatically

sed -i -E 's/#?PasswordAuthentication yes/PasswordAuthentication no/' /etc/ssh/sshd_config 

The #? is an extended regular expression that matches the line whether it's commented or not. The -E switch enables extended regexp support for sed.

Run

service ssh restart 

instead of

/etc/init.d/ssh restart 

This might work.

I followed these steps (for Mac).

In /etc/ssh/sshd_config change

#ChallengeResponseAuthentication yes #PasswordAuthentication yes 

to

ChallengeResponseAuthentication no PasswordAuthentication no 

Now generate the RSA key:

ssh-keygen -t rsa -P '' -f ~/.ssh/id_rsa 

(For me an RSA key worked. A DSA key did not work.)

A private key will be generated in ~/.ssh/id_rsa along with ~/.ssh/id_rsa.pub (public key).

Now move to the .ssh folder: cd ~/.ssh

Enter rm -rf authorized_keys (sometimes multiple keys lead to an error).

Enter vi authorized_keys

Enter :wq to save this empty file

Enter cat ~/.ssh/id_rsa.pub >> ~/.ssh/authorized_keys

Restart the SSH:

sudo launchctl stop com.openssh.sshd sudo launchctl start com.openssh.sshd 

The one-liner to disable SSH password authentication:

sed -i 's/PasswordAuthentication yes/PasswordAuthentication no/g' /etc/ssh/sshd_config && service ssh restart