Ssh – unexpected SSH input_userauth_request: invalid user

ssh

We have a user that suddenly cannot log in via SSH on a Linux box. The error output in /var/log/secure is:

Invalid user foo from xx.xx.xx.xx

input_userauth_request: invalid user foo

Some additional details:

The user has a shell correctly specified in /etc/passwd
The user has a home directory with the correct permissions
We made no changes to sshd_config, verified by the mod date
No changes to user's .bashrc or .bash_profile
The user cannot log in via password or key
I've restarted sshd, and restarted the box
The user's shell history shows no commands that might have caused this problem
Ditto for root (used by only one person)
VERBOSE output for sshd gives no other details
No other user has this problem

I've done an extensive search, and have not found where else to look to identify the problem — any insights would be greatly appreciated, thanks in advance.

Best Answer

A couple things you can check:

If you are using the AllowUsers directive make sure the IP/hostname matches what's defined in sshd_config.

If you are using hostnames instead of IP addresses with the AllowUsers directive verify the hostname reverses properly.

Related Solutions

Ssh – How to automate SSH login with password

Don't use a password. Generate a passphrase-less SSH key and push it to your VM.

If you already have an SSH key, you can skip this step… Just hit Enter for the key and both passphrases:

$ ssh-keygen -t rsa -b 2048
Generating public/private rsa key pair.
Enter file in which to save the key (/home/username/.ssh/id_rsa):
Enter passphrase (empty for no passphrase):
Enter same passphrase again:
Your identification has been saved in /home/username/.ssh/id_rsa.
Your public key has been saved in /home/username/.ssh/id_rsa.pub.

Copy your keys to the target server:

$ ssh-copy-id id@server
id@server's password:

Now try logging into the machine, with ssh 'id@server', and check-in:

.ssh/authorized_keys

Note: If you don't have .ssh dir and authorized_keys file, you need to create it first

to make sure we haven’t added extra keys that you weren’t expecting.

Finally, check to log in…

$ ssh id@server

id@server:~$

You may also want to look into using ssh-agent if you want to try keeping your keys protected with a passphrase.

SSH – Bad Owner or Permissions on ~/.ssh/config

I needed to have rw for user only permissions on config. This fixed it.

chmod 600 ~/.ssh/config

As others have noted below, it could be the file owner. (upvote them!)

chown $USER ~/.ssh/config

If your whole folder has invalid permissions here's a table of possible permissions:

Path	Permission
.ssh directory (code)	0700 (drwx------)
private keys (ex: `id_rsa`) (code)	0600 (-rw-------)
`config`	0600 (-rw-------)
public keys (*.pub ex: `id_rsa.pub`)	0644 (-rw-r--r--)
`authorized_keys` (code)	0644 (-rw-r--r--)
`known_hosts`	0644 (-rw-r--r--)

Sources:

openssh check-perm.c
openssh readconf.c
openssh ssh_user_config fix_authorized_keys_perms

Best Answer

Related Solutions

Ssh – How to automate SSH login with password

SSH – Bad Owner or Permissions on ~/.ssh/config

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