SSH Disable Password Authentication

Question

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

/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

Answer 1

This is from a tutorial I have:

On your machine as root:

ssh-keygen -t rsa 

and leave passphrase empty

From your local machine: (and you will have to type in password)

ssh root@remotemachine mkdir -p .ssh

then:

cat .ssh/id_rsa.pub | ssh root@remotemachine 'cat >> .ssh/authorized_keys'

Now you can login without pw prompt

ssh root@remotemachine

link: http://www.linuxproblem.org/art_9.html should you have any problems!

Answer 2

here's a script to do this automatically

# only allow key based logins
sed -n 'H;${x;s/\#PasswordAuthentication yes/PasswordAuthentication no/;p;}' /etc/ssh/sshd_config > tmp_sshd_config
cat tmp_sshd_config > /etc/ssh/sshd_config
rm tmp_sshd_config 

Answer 3

I followed these steps(For mac).

in /etc/ssh/sshd_config

change this

#ChallengeResponseAuthentication yes #PasswordAuthentication yes

to

ChallengeResponseAuthentication no PasswordAuthentication no

Now generate rsa key: ssh-keygen -t rsa -P '' -f ~/.ssh/id_rsa (for me rsa key worked. dsa key did not worked).

Key will be generated in ~/.ssh/id_rsa along with ~/.ssh/id_rsa.pub

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

enter rm -rf authorized_keys(some time multiple key leads to 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

Answer 4

in /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

Answer 5

Run

service ssh restart

instead of

/etc/init.d/ssh restart

This might work.