etc/ssh/sshd_config AllowAgentForwarding no To address that, add another configuration parameter to disable Agent forwarding on bastion SSH server: It contains no private information so that even if compromised, the attacker will find no useful information to access the private network So this contradicts to one of the key elements of a Bastion host: An attacker cannot obtain key material from the agent, however they can perform operations on the keys that enable them to authenticate using the identities loaded into the agent. Users with the ability to bypass file permissions on the remote host (for the agent's UNIX-domain socket) can access the local agent through the forwarded connection. Agent forwarding should be enabled with caution. This can also be specified on a per-host basis in a configuration file. A Enables forwarding of the authentication agent connection. The existence of this socket on the bastion host is problematic. $ env | grep -i ssh_auth SSH_AUTH_SOCK=/tmp/ssh-iOyEN3vXnp/agent.80756 $ ssh -A works as expected, without the need of any password.īut, before continue, lets check our environment variables on jump box running: Then we can access jump box, forwarding SSH agent: On our local client machine (at home), we can execute SSH agent and load our private key: Now our bastion host, that has the private IP /XX, is allowed to access the selected private servers. # firewall-cmd -new-zone=SSH_access -permanent # firewall-cmd -reload # firewall-cmd -zone=-add-service=SSH_access -permanent # firewall-cmd -zone=SSH-access -add-source=/XX -permanent # firewall-cmd -reload We will run some self-explanatory firewall-cmd commands: We now need to decide which of our private servers need to be managed from outside the organization and allow jump box to access them. If you have SELinux on enforcing mode ( of course you have!! - this will be an internet facing server) you also need to tell SELinux about the port ~]# semanage port -a -t ssh_port_t -p tcp 22222 and run systemctl reload rvice to reload the service. In order to generate and use SSH key pair, take a look on Using SSH Effectively.Īs for implementation, edit /etc/ssh/sshd_config modifying the following parameters: 22222) and relieve our server from 99.999% of the dump bots out there, scanning and probing known ports Configure openssh to listen to a random high port (eg.Completely disable password authentication and use only SSH keys.As we said, we need to make it more resistant than the default configuration. We will use a CentOS Linux release running OpenSSH_8.0p1 as our bastion host. Users will access internal servers as effortless as from internal network (or VPN).And we will do this without complicating the day-to-day experience of administrators. The scope of this article is to describe how we can implement all of the above 4 elements on an SSH bastion host and use it to access our private servers via SSH.
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |