ssh Keyboard Authentication: when to enter Google Authenticator code

Question

These questions seem related:

• Duo Authentication Interactive Keyboard (No answer.)
• https://serverfault.com/questions/417209/enabled-password-auth-on-sshd-now-keyboard-interactive-auth-hangs (Bug. My system is up to date.)

I believe my circumstances are different enough to start a new thread.

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I have set up ssh to use PAM, with Google-Authenticator. I have added the necessary lines to both /etc/ssh/sshd_config and /etc/pam.d/sshd and have set up the Google Authenticator on both computers and the app. The public key of each system is copied on the other.

In /etc/ssh/sshd_config:

PasswordAuthentication no
ChallengeResponseAuthentication yes
AuthenticationMethods publickey,keyboard-interactive:pam

In /etc/pam.d/sshd:

#%PAM-1.0
auth     required  pam_securetty.so     #disable remote root
# require google authenticator
auth      required  pam_google_authenticator.so
# but not password
#auth      include   system-remote-login
account   include   system-remote-login
password  include   system-remote-login
session   include   system-remote-login

This is the output from ssh -vvv 192.IP.address.0:

OpenSSH_7.4p1, OpenSSL 1.0.2j  26 Sep 2016
...
debug3: send packet: type 20
debug1: SSH2_MSG_KEXINIT sent
debug3: receive packet: type 20
debug1: SSH2_MSG_KEXINIT received
debug2: local client KEXINIT proposal
debug2: KEX algorithms: ...
...
debug2: service_accept: ssh-userauth
...
debug1: Authentications that can continue: publickey
debug3: start over, passed a different list publickey
debug3: preferred publickey,keyboard-interactive,password
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: /home/trespaul/.ssh/id_rsa
debug3: send_pubkey_test
debug3: send packet: type 50
debug2: we sent a publickey packet, wait for reply
debug3: receive packet: type 60
debug1: Server accepts key: pkalg ssh-rsa blen 279
debug2: input_userauth_pk_ok
debug3: sign_and_send_pubkey
Enter passphrase for key '/home/trespaul/.ssh/id_rsa': 
debug3: send packet: type 50
debug3: receive packet: type 51
Authenticated with partial success.
debug1: Authentications that can continue: **keyboard-interactive**
debug3: **start over**, passed a different list keyboard-interactive
debug3: preferred publickey,keyboard-interactive,password
debug3: authmethod_lookup keyboard-interactive
debug3: remaining preferred: password
debug3: authmethod_is_enabled keyboard-interactive
debug1: Next authentication method: **keyboard-interactive**
debug2: userauth_kbdint
debug3: send packet: type 50
debug2: **we sent a keyboard-interactive packet**, wait for reply
debug3: receive packet: type 51
debug1: Authentications that can continue: keyboard-interactive
debug3: userauth_kbdint: disable: no info_req_seen
debug2: we did not send a packet, disable method
debug1: No more authentication methods to try.
Permission denied (keyboard-interactive).

Between that last two bolds / double stars ("next auth method is kbd interactive" and "we sent a packet"), I am not asked for my OTP. Why is this? What am I missing?

Extra info

I am on Arch. libpam-google-authenticator installed from AUR with make install etc.

Edit: Server log

journalctl on the server has the following:

systemd[1]: Started OpenSSH Per-Connection Daemon (10.0.0.5:38150).
sshd[1376]: PAM unable to dlopen(/usr/lib/security/pam_google_authenticator.so): /usr/lib/security/pam_google_authenticator.so: cannot open shared object file: No such file or directory
sshd[1376]: PAM adding faulty module: /usr/lib/security/pam_google_authenticator.so
sshd[1376]: error: PAM: Module is unknown for paul from 10.0.0.5
sshd[1376]: Connection closed by 10.0.0.5 port 38150 [preauth]

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Thanks.

Answer 1

libpam-google-authenticator installed from AUR with make install etc.

That's not how you install things from AUR.

An AUR package already has its own build & install instructions – the PKGBUILD file, which already copies the necessary files to their places and even makes a .pkg.tar.gz file with them. The proper way of building one is makepkg:

makepkg -sirc

will build, install, and clean up.

What if your download doesn't have a PKGBUILD in it? Then you downloaded the wrong file. The top-level package sources can be obtained from tthe link in the rightmost box,

Answer 2

So I solved this with

sudo cp '.../AUR Package/.libs/pam_google_authenticator.so' /usr/lib/security/pam_google_authenticator.so

The error was the missing .so file, implicating that something went wrong or I missed something during the installation.

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This however does not seem like best practice. If someone has a better, more elegant solution, please feel free to add as an answer.