So I am using RHEL 7. I have two servers with the following user accounts
root (obvious)
admin
I want the setup to work in the following manner.
passwordless SSH from server 1 to server 2 using the admin user, but the SSH initiation is done from the root user always.
We are not allowed to do ssh key exchange for the root user, but the app that we are working with uses root to ssh to the other nodes.
I hope I am making sense here :)
SSH using root user to server2, but internally it should use admin user's key and connect to server2 using admin user.
I have tried to confiure /etc/ssh/ssh_config file and added host/user config there, now I am able to run ssh server2 from root user and it connects to server2 using my defined admin user in the ssh_config file but it prompts for a password every time which I don't want.
Key exchange with admin is already done and tested to be working fine when I issue ssh as admin user.
Thanks in advance.
In the same file /etc/ssh/ssh_config you need to add the key to use, something like this:
Host srv2
User admin
IdentityFile /home/admin/.ssh/id_rsa
Related
I'm hosting my file server on GCP debian 10 virtual machine and I want to create passwordless user so people could publicly download files from his home directory.
So I created new user, removed his password with passwd -d username, changed /etc/ssh/sshd_config file so it would allow this exact user to login with empty password and set chroot jail, restarted ssh service.
Unfortunately, when I'm connection via ssh into this user it still prompts me with a password.
This setup was working on the old server, configs are definitly correct and user definitely does not have password. I guess google implemented some additionl protection that dosen't allow me to do what I want.
Maybe someone had already bumbed into the same problem before?
I reached the support and they said google doesn't support passwordless ssh connections.
We have a Linux Server with 2 users user1 and user2. We have to login from user1 to user2 via ssh such as:
ssh user2#<computer-name>
Both users are on the same server. However, user1 is an automated script where we cant type in manually the password and we dont want to store the password. Therefore, we want to use an ssh key (private to user2 and public to user1).
Thereby, the traffic should not go via the network as it has already a high load. The question is: will be the network connection automatically always via the localhost? If not how to force ssh to use only the localhost?
Are the two users both on the same server ?
If you are on the same OS, you can use to switch between users :
su user2
More details here : https://unix.stackexchange.com/questions/3568/how-to-switch-between-users-on-one-terminal
So I've a VM that has SSH login. In this machine I only want one user ( lets say admin) to be able to login in via SSH.
Ive changed the sshd_config and added the AllowUsers admin directive. The problem is that I can still login to the machine with the user user, for example.
The host is a Ubuntu server and I'm accessing it via vSphere Client.
Is there anything I'm missing here?
In ssh, it is possible to set up passwordless logins to a remote user, using only public key authentication. Out of curiosity, what is actually going on code-wise, when passwordless login has been set up?
Is the ssh-server daemon storing user passwords, and then applying them automatically, when they have authenticated a public key, or can the ssh-server, using some system-call magic, circumvent the password authentication procedure of a user account entirely?
The ssh server daemon is typically running as root (or another privileged user), and can thus simply spawn a login session running as whichever user is required. No password involved.
Other things that work in a similar manner are the -u flag for sudo, and the su command when already running as root.
The sshd (SSH daemon) process runs privileged on your server (e.g. root), so after it successfully completes authentication, it spawns a login shell as the user logging in.
You are starting from the point of assuming a password is a requirement for authentication. But it is really only one way there. On modern Linux the PAM subsystem controls authentication and authorization. You could make a PAM module that allowed you to login if you answered three questions correctly. Or know the right number. Or to be even more outlandish your "password" could be a music sequence entered over a MIDI device :-)
Something needs to tie your entered name with a Unix UID and then match that to an authentication mechanism. SSH is doing this by:
taking the name you provide and getting the "password entry" for it via PAM
using the "password entry" to locate the $HOME of the user
validate the SSH key in $HOME/.ssh/authorized_keys against the key sent in the authentication
If all of the above works, start a shell as the UID of the user
As you can see this process is not going around password authentication. Password authentication is simply one of the ways in the door. We are accustomed to this method via 'login' or ssh exposing a password prompt. But there are many ways. The core requirement is the program performing the authentication has root privileges.
Everyone already mentioned that sshd runs as a privileged daemon.
So how does passwordless public key authentication works?
When a user connects to sshd, by default unless configured otherwise, sshd will require the remote connection to present a key. In the absence of the key, sshd will attempt to ask for other methods of proof of identity of the remote user, one of which is interactive password.
Before one can start using passwordless public key authentication, one must register his public key. This usually involves copying public key to user's .ssh/authorized_keys file. There is a cli ssh-copy-id that can do exactly this.
How does private/public key authentication works then? When a user connects to ssh daemon, the ssh client will read the user's private key, usually stored in .ssh under different filenames such as id_rsa or identity or id_dsa. The ssh client will generate the public key from the private key and present the public key to sshd. The sshd daemon will compare the received public key against the user's authorized_keys. If a match is found, the connection is allowed. Then sshd will spawn a process and a shell and will drop the provileges to the user's privilege.
I need to allow certain users limited access to the lab server. The server is RHEL 5.6. However, I don't want to give them the root access. Basically, we have configured a LDAP server where all the users have centralized NFS and LDAP login from any of the client machines in the network. So, the LDAP users home area is located in /home/users in the server. I need to give access to only this folder to a certain user.
If I edit the visudo file and add the following line in the RHEL server, will I be able to accomplish what am looking for?
user1, %operator ALL= /home/users
When you are authenicating users with ldap and nfs mounted share, as such users of ldap or without ldap would be restricted to work in their home directory only.
Thanks & Regards,
Alok Thaker
Basically, as you giving all users access as users not as root hence all users will not have root access either using local authentication or remote authentication. I hope the users don't know your root password. :)
SUDO is used only when you want to give some users privilege to run the command as root like a normal user will not be able to do the command "service network restart" but if you allow the user have sudo privileges, he will be able to do it.