infra-docs-fpo/modules/sysadmin_guide/pages/sshaccess.adoc

= SSH Access Infrastructure SOP

== Contents

[arabic]
* <<_contact_information>>
* <<_introduction>>
* <<_ssh_configuration>>
* <<_ssh_agent_forwarding>>
* <<_troubleshooting>>

== Contact Information

Owner::
  sysadmin-main
Contact::
  #fedora-admin or admin@fedoraproject.org
Location::
  IAD2
Servers::
  All IAD2 and VPN Fedora machines
Purpose::
  Access via ssh to Fedora project machines.

== Introduction

This page will contain some useful instructions about how you can safely
login into Fedora IAD2 machines successfully using a public key
authentication. As of 2011-05-27, all machines require a SSH key to
access. Password authentication will no longer work. Note that this SOP
has nothing to do with actually gaining access to specific machines. For
that you MUST be in the correct group for shell access to that machine.
This SOP simply describes the process once you do have valid and
appropriate shell access to a machine.

== SSH configuration

First of all: (on your local machine):

....
vi ~/.ssh/config
....

[NOTE]
====
This file, and any keys, need to be chmod 600, or you will get a "Bad
owner or permissions" error. The .ssh directory must be mode 700.
====

then, add the following:

....
Host bastion.fedoraproject.org
  HostName bastion-iad01.fedoraproject.org
  User FAS_USERNAME (all lowercase)
  ProxyCommand none
  ForwardAgent no
Host *.iad2.fedoraproject.org *.qa.fedoraproject.org 10.3.160.* 10.3.161.* 10.3.163.* 10.3.165.* 10.3.167.* *.vpn.fedoraproject.org batcave01
  User FAS_USERNAME (all lowercase)
  ProxyCommand ssh -W %h:%p bastion.fedoraproject.org
....

How ProxyCommand works?

A connection is established to the bastion host:

....
+-------+            +--------------+
|  you  | ---ssh---> | bastion host |
+-------+            +--------------+
....

Bastion host establish a connction to the target server:

....
+--------------+          +--------+
| bastion host | -------> | server |
+--------------+          +--------+
....

Your client then connects through the Bastion and reaches the target
server:

....
+-----+                  +--------------+                +--------+
| you |                  | bastion host |                | server |
|     | ===ssh=over=bastion============================> |        |
+-----+                  +--------------+                +--------+
....

== PuTTY SSH configuration

You can configure Putty the same way by doing this:

[arabic, start=0]
. In the session section type _batcave01.fedoraproject.org_ port 22
. In Connection:Data enter your FAS_USERNAME
. In Connection:Proxy add the proxy settings

____
* ProxyHostname is bastion-iad01.fedoraproject.org
* Port 22
* Username FAS_USERNAME
* Proxy Command `plink %user@%proxyhost %host:%port`
____

[arabic, start=3]
. In Connection:SSH:Auth remember to insert the same key file for
authentication you have used on FAS profile

== SSH Agent forwarding

You should normally have:

....
ForwardAgent no
....

For Fedora hosts (this is the default in OpenSSH). You can override this
on a per-session basis by using '-A' with ssh. SSH agents could be
misused if you connect to a compromised host with forwarding on (the
attacker can use your agent to authenticate them to anything you have
access to as long as you are logged in). Additionally, if you do need
SSH agent forwarding (say for copying files between machines), you
should remember to logout as soon as you are done to not leave your
agent exposed.

== Troubleshooting

* 'channel 0: open failed: administratively prohibited: open failed'
+
____
If you receive this message for a machine proxied through bastion, then
bastion was unable to connect to the host. This most likely means that
tried to SSH to a nonexistent machine. You can debug this by trying to
connect to that machine from bastion.
____
* if your local username is different from the one registered in FAS,
please remember to set up a User variable (like above) where you
specify your FAS username. If that's missing SSH will try to login by
using your local username, thus it will fail.
* `ssh -vv` is very handy for debugging what sections are matching and
what are not.
* If you get access denied several times in a row, please consult with
#fedora-admin. If you try too many times with an invalid config your
IP could be added to denyhosts.
* If you are running an OpenSSH version less than 5.4, then the -W
option is not available. In that case, use the following ProxyCommand
line instead:
+
....
ProxyCommand ssh -q bastion.fedoraproject.org exec nc %h %p
....