[Bug 1522190] Re: Permission denied (publickey) whereas the public key has been inserted into ~/.ssh/authorized_keys

[jean-christophe manciot]

We have a winner: setting usePAM to no generates the issue:
/etc/ssh/sshd_config
-------------------------------
...
usePAM no

ChallengeResponseAuthentication no
PasswordAuthentication no
PermitEmptyPasswords no
...

ssh -v  root at localhost
---------------------------------
...
debug1: Authentications that can continue: publickey
debug1: Next authentication method: publickey
debug1: Offering RSA public key: /root/.ssh/id_rsa
debug1: Authentications that can continue: publickey
debug1: Trying private key: /root/.ssh/id_dsa
debug1: Trying private key: /root/.ssh/id_ecdsa
debug1: Offering ED25519 public key: /root/.ssh/id_ed25519
debug1: Authentications that can continue: publickey
debug1: No more authentication methods to try.
Permission denied (publickey).

However, setting usePAM to yes makes the session work:
/etc/ssh/sshd_config
-------------------------------
...
use PAM yes

ChallengeResponseAuthentication no
PasswordAuthentication no
PermitEmptyPasswords no
...

ssh -v root at localhost
--------------------------------
...
debug1: Authentications that can continue: publickey
debug1: Next authentication method: publickey
debug1: Offering RSA public key: /root/.ssh/id_rsa
debug1: Server accepts key: pkalg ssh-rsa blen 279
Enter passphrase for key '/root/.ssh/id_rsa': 
debug1: Authentication succeeded (publickey).
Authenticated to localhost ([::1]:xxx).
debug1: channel 0: new [client-session]
debug1: Requesting no-more-sessions at openssh.com
debug1: Entering interactive session.
debug1: client_input_global_request: rtype hostkeys-00 at openssh.com want_reply 0
debug1: Sending environment.
debug1: Sending env LANG = en_US.UTF-8
Welcome to Ubuntu 15.10 (GNU/Linux 4.2.0-19-generic x86_64)
...

** Information type changed from Private Security to Public Security

** Summary changed:

- Permission denied (publickey) whereas the public key has been inserted into  ~/.ssh/authorized_keys
+ Permission denied (publickey) whereas the public key has been inserted into  ~/.ssh/authorized_keys: usePAM no issue

** Summary changed:

- Permission denied (publickey) whereas the public key has been inserted into  ~/.ssh/authorized_keys: usePAM no issue
+ Permission denied (publickey) whereas the public key has been inserted into  ~/.ssh/authorized_keys: "usePAM no" issue

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https://bugs.launchpad.net/bugs/1522190

Title:
  Permission denied (publickey) whereas the public key has been inserted
  into  ~/.ssh/authorized_keys: "usePAM no" issue

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