what you will see is the current state of a problem I am trying to solve.
I restarted sshd before filling the body this question.
What I am trying to do:
- I need to use ssh keys with a yubikey combined to secure authentication to SSH.
- I need to disable clear text passwords.
Relevant parts of my /etc/ssh/sshd_config look like this:
ChallengeResponseAuthentication yes
UsePAM yes
PasswordAuthentication no
AuthenticationMethods publickey,keyboard-interactive
My /etc/pam.d/sshd looks like this:
# PAM configuration for the Secure Shell service
auth required pam_yubico.so id=16 debug authfile=/etc/authorized_yubikeys
# Standard Un*x authentication.
@include common-auth
# Disallow non-root logins when /etc/nologin exists.
account required pam_nologin.so
# Uncomment and edit /etc/security/access.conf if you need to set complex
# access limits that are hard to express in sshd_config.
# account required pam_access.so
# Standard Un*x authorization.
@include common-account
# SELinux needs to be the first session rule. This ensures that any
# lingering context has been cleared. Without this it is possible that a
# module could execute code in the wrong domain.
session [success=ok ignore=ignore module_unknown=ignore default=bad] pam_selinux.so close
# Set the loginuid process attribute.
session required pam_loginuid.so
# Create a new session keyring.
session optional pam_keyinit.so force revoke
# Standard Un*x session setup and teardown.
@include common-session
# Print the message of the day upon successful login.
# This includes a dynamically generated part from /run/motd.dynamic
# and a static (admin-editable) part from /etc/motd.
session optional pam_motd.so motd=/run/motd.dynamic
session optional pam_motd.so noupdate
# Print the status of the user's mailbox upon successful login.
session optional pam_mail.so standard noenv # [1]
# Set up user limits from /etc/security/limits.conf.
session required pam_limits.so
# Read environment variables from /etc/environment and
# /etc/security/pam_env.conf.
session required pam_env.so # [1]
# In Debian 4.0 (etch), locale-related environment variables were moved to
# /etc/default/locale, so read that as well.
session required pam_env.so user_readenv=1 envfile=/etc/default/locale
# SELinux needs to intervene at login time to ensure that the process starts
# in the proper default security context. Only sessions which are intended
# to run in the user's context should be run after this.
session [success=ok ignore=ignore module_unknown=ignore default=bad] pam_selinux.so open
# Standard Un*x password updating.
@include common-password
The only row added to /etc/pam.d/sshd is:
auth required pam_yubico.so id=16 debug authfile=/etc/authorized_yubikeys
Result:
$ ssh test -v
OpenSSH_7.6p1 Ubuntu-4ubuntu0.3, OpenSSL 1.0.2n 7 Dec 2017
debug1: Reading configuration data /home/dev/.ssh/config
debug1: /home/dev/.ssh/config line 1: Applying options for *
debug1: /home/dev/.ssh/config line 5: Applying options for dev
debug1: Reading configuration data /etc/ssh/ssh_config
debug1: /etc/ssh/ssh_config line 9: Applying options for *
debug1: Connecting to test [192.168.1.2] port 22.
debug1: Connection established.
debug1: identity file /home/dev/.ssh/id_rsa type 0
debug1: key_load_public: No such file or directory
debug1: identity file /home/dev/.ssh/id_rsa-cert type -1
debug1: Local version string SSH-2.0-OpenSSH_7.6p1 Ubuntu-4ubuntu0.3
debug1: Remote protocol version 2.0, remote software version OpenSSH_7.6p1 Ubuntu-4ubuntu0.3
debug1: match: OpenSSH_7.6p1 Ubuntu-4ubuntu0.3 pat OpenSSH* compat 0x04000000
debug1: Authenticating to test:22 as 'admin'
debug1: SSH2_MSG_KEXINIT sent
debug1: SSH2_MSG_KEXINIT received
debug1: kex: algorithm: [email protected]
debug1: kex: host key algorithm: ecdsa-sha2-nistp256
debug1: kex: server->client cipher: [email protected] MAC: <implicit> compression: none
debug1: kex: client->server cipher: [email protected] MAC: <implicit> compression: none
debug1: expecting SSH2_MSG_KEX_ECDH_REPLY
debug1: Server host key: ecdsa-sha2-nistp256 SHA256:K2vxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
Warning: Permanently added 'test,192.168.1.2' (ECDSA) to the list of known hosts.
debug1: rekey after 134217728 blocks
debug1: SSH2_MSG_NEWKEYS sent
debug1: expecting SSH2_MSG_NEWKEYS
debug1: SSH2_MSG_NEWKEYS received
debug1: rekey after 134217728 blocks
debug1: SSH2_MSG_EXT_INFO received
debug1: kex_input_ext_info: server-sig-algs=<ssh-ed25519,ssh-rsa,rsa-sha2-256,rsa-sha2-512,ssh-dss,ecdsa-sha2-nistp256,ecdsa-sha2-nistp384,ecdsa-sha2-nistp521>
debug1: SSH2_MSG_SERVICE_ACCEPT received
debug1: Authentications that can continue: publickey
debug1: Next authentication method: publickey
debug1: Offering public key: RSA SHA256:mAExxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx /home/dev/.ssh/id_rsa
debug1: Server accepts key: pkalg rsa-sha2-512 blen 535
Authenticated with partial success.
debug1: Authentications that can continue: keyboard-interactive
debug1: Next authentication method: keyboard-interactive
YubiKey for `admin':
**Password**
debug1: Authentication succeeded (keyboard-interactive).
Authenticated to test ([192.168.1.2]:22).
debug1: channel 0: new [client-session]
debug1: Requesting [email protected]
debug1: Entering interactive session.
debug1: pledge: network
debug1: client_input_global_request: rtype [email protected] want_reply 0
debug1: Sending environment.
debug1: Sending env LANG = en_US.UTF-8
Welcome to Ubuntu 18.04.5 LTS (GNU/Linux 4.15.0-112-generic x86_64)
admin@test:~$
The login works fine, but can you see the line **Password** above? It shouldn't be asking for it (as it's disabled in the sshd_config) and I don't understand why :/
