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Dave avatar Server

SSH refuses to allow specific user to login directly via ssh

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Dave

I have a specific user (Lets call them user through out this post) on a host that displays the following errors when trying to ssh via public key auth:

PTY allocation request failed on channel 0
Direct login access is disallowed

I can mitigate the first error by using ssh user@host "/bin/bash -i", but I am unable to get past the second error.

Things I have tried:

  • I can sudo -s (or sudo -i to the user as root on the host directly.
  • The user is locked down (passwd -l user), I unlocked and assigned a password to the user. Same problem. However I can su - user as any other user after the account is unlocked and a password is applied.
  • I checked /etc/ssh/sshd_config on the server, No entries for AllowUsers, AllowGroups, DenyUsers, DenyGroups.
  • I am able to ssh directly as root no problem.
  • I created a new user, and able to ssh directly to them as well.
  • Confirmed ssh key selection and authorized_keys are set properly, however I dont think this is a key issue.
  • /etc/passwd shows the user has /bin/bash set for their shell.
  • /etc/security/access.conf is completely commented out with no settings set.
  • restarted sshd many times.
  • There is no /etc/login.blocks file.
  • /var/log/secure, /var/log/messages, nor journalctl -fu sshd only show Session open then Session closed for user user
  • ssh user@host -vvvvvvv just shows the Direct login access is disallowed
  • rebooted the host.

Note: this is a rhel system that does not have its subscriptions enabled yet.

What gives? Why can I not access this

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Dave avatar Server
id flag
Dave

Figured it out. It was a script that someone wrote that was restricting access to the host. The script was being run after anyone connected to the user via ssh.

This was implemented in user's ~/.ssh/authorized_keys.

Here is the line that was showing in the file:

command="/home/user/script/that/was/causing/problems.sh", ssh-rsa ABC123hugepubliccipher==

After removing the command= section, users were then able to ssh in again.

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