SSH Access Infrastructure SOP

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ISOP:SSHACCESS

Contents

Contact Information

Owner: sysadmin-main

Contact: #fedora-admin or admin@fedoraproject.org

Location: All fedora machines

Servers: All 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 internal machines successfully using a PubAuthKey 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.

Single host example

First of all: (on your local machine)

cd /home/user/.ssh
touch config && nano config

Note: You'll need to create an entry for every internal machine you plan to log in to, or create wildcard entries.

Note2: This example is valid only if you are trying to login into puppet01 to commit your changes to Infrastructure's Puppet tree. (see Note1)

then, edit it as it follows:

Host puppet01 puppet1 puppet01.fedoraproject.org
   Hostname %h (or if it doesn't resolve, go ahead to the troubleshooting section) 
   User FASUID (you don't need this if your local UID and your FAS one correspond)
   ProxyCommand ssh -q FASUID@bastion.fedoraproject.org /usr/bin/nc %h 22

WildCard setup example

You can also setup wildcards so you don't have to enter a entry as above for each host.

Host allyourlocalmachines bastion.fedoraproject.org (add here any host you ssh to that is NOT a Fedora machine as well as bastion)
   ProxyCommand none

Host *
   Hostname %h
   ProxyCommand ssh -q %u@bastion.fedoraproject.org /usr/bin/nc %h 22

This will match the first entry for those specific hosts you wish to go to directly, and pass all the rest via bastion. You may need to set:

export LOCALDOMAIN="fedoraproject.org vpn.fedoraproject.org phx2.fedoraproject.org"

In order to do simple 'ssh puppet01' type commands.

SSH Agent forwarding

You should normally have:

    ForwardAgent no

For Fedora hosts. You can override this on a 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:

  • 'nc: getaddrinfo: Name or service not known', replace Hostname %h with Hostname 10.5.126.23 (this is puppet's IP, so it will be different by machine to machine)
  • if your local UID is different from the one registered in FAS, please remember to set up a User variable (like above) where you specify your FAS UID. If that's missing SSH will try to login by using your local UID, thus it will fail.
  • If you can't resolve a hostname like 'puppet01' you may need the LOCALDOMAIN export above.
  • 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.