Cfrgtkky

18.10 install. I'm asking about sshd_config (in /etc/ssh/)

How do I permit/authenticate sshd keys?

When I log in from another Ubuntu instance, password works fine. ssh-copy-id should have set up the keys in the proper files (verified permission on directory, key file, authorizedhosts file entries match) Attempts to ssh in still demanded password. No reference in auth.log to authentication attempt.

I uncommented/permitted one of the host keys in the existing sshd_config

I added the AuthenticationMethods publickey, password line.

(authenticationmethods did not previously exist in the file, or was commented out)

A subsequent attempt to connect was completely blocked.

When I examined the auth.log (debug1 level), I did not see any reference to a key validation had been made.

What do I need to configure in sshd_config in order that ssh key are usable?
What am i missing?

(I had expected that this would work out of the box)

Your sshd_config is missing many fields my working version has, mayge that's the problem.
Here's mine which does keylogin for me successfully, based on the sample in /usr/share/doc/openssh-client/examples/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

HostKey /etc/ssh/ssh_host_ed25519_key

#Privilege Separation is turned on for security

UsePrivilegeSeparation yes



# Lifetime and size of ephemeral version 1 server key

KeyRegenerationInterval 3600

ServerKeyBits 1024



# Logging

SyslogFacility AUTH

LogLevel INFO



# Authentication:

LoginGraceTime 120

PermitRootLogin without-password

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 yes